Cyanobacterium of coral origin, its use in agricultural formulations and method for increasing the heat tolerance of corals

Abstract

The present application relates to the technical field of coral symbiotic cyanobacteria and cyanobacteria application, and specifically discloses a coral-derived cyanobacterium, an agricultural preparation, and an application and a method for improving the heat tolerance of corals. Synechococcus The present application discloses a coral-derived cyanobacterium GXU02, which is classified and named as: CCTCC NO: M 2026250, and is preserved in the China Center for Type Culture Collection (CCTCC). The present application isolates a cyanobacterium from the cross-petal coral, which provides good research materials for studying the function of marine cyanobacteria and the symbiotic relationship between the algae and corals, and has application potential in the development of preparations for crop growth promotion and stress resistance, and in the artificial modification of corals and the repair of coral reef ecosystems. The cyanobacterium of the present application can promote plant growth and improve stress resistance; inoculation of the cyanobacterium of the present application can improve the heat tolerance of corals, effectively alleviate the crisis of coral heat whitening, and open up a new idea and method for the cultivation of heat-resistant seedlings for the repair of coral reef ecosystems based on the recombination of symbiotic organisms.

Description

Technical Field

[0001] This invention relates to the field of coral symbiotic algae and coral reef ecological restoration technology, and particularly to the application of a coral-derived cyanobacteria in agricultural formulations and methods for improving the heat tolerance of corals. Background Technology

[0002] Coral reef ecosystems are among the most biodiverse and vital ecosystems in the ocean, providing habitats, feeding grounds, and breeding grounds for numerous marine organisms. They also play an irreplaceable role in coastal protection, fisheries resource maintenance, and marine carbon cycling, possessing immense ecological and economic value. However, due to global warming, the continuous rise in ocean surface temperatures has become the primary environmental stressor threatening coral survival. This sustained increase in water temperature leads to widespread coral bleaching and death, thereby damaging the health and sustainability of coral reef ecosystems.

[0003] Although there is evidence that corals possess a certain degree of adaptability, for example, during coral bleaching, some coral species, such as those in the genus *Ceratophyllum*, exhibit resilience. Favites colemani and the genus *Rhododendron* Montipora digitata Under heat stress, the levels of antioxidant proteins and chaperone proteins significantly increase. Furthermore, massive corals are more resistant to temperature changes than branching corals. However, the natural evolutionary cycle of corals is long, and their evolutionary speed is insufficient to keep pace with environmental changes. Strengthening artificial intervention is an important direction for coral reef restoration. Currently, methods to improve coral heat tolerance mainly include: heat acclimatization, which exposes corals to sub-lethal high temperatures to induce physiological adaptation, but this method may lead to baseline physiological changes such as tissue paleness and reduced photosynthetic efficiency; and sexual reproduction and selective breeding, which selects naturally heat-tolerant parents for reproduction to inherit heat tolerance traits, but the selection cycle is long, and improved heat tolerance may be accompanied by drawbacks such as slower growth rates.

[0004] Reef-building corals are typical sessile marine symbiotic organisms. Their symbiotic system includes algae, bacteria, archaea, fungi, protozoa, and viruses, collectively forming the coral holobiont. The photosynthetic products provided by this symbiotic system meet over 90% of the coral's nutritional needs. Through the synergistic effects of its components, this holobiont maintains the coral's physiological homeostasis and environmental adaptability. The algae living in symbiosis with corals include zooxanthellae, zoochlorophyll, and zoocyanobacteria. Over long periods of evolution, these coral-symbiotic algae have formed a mutually beneficial symbiotic relationship with the coral host, jointly influencing coral growth, development, and reef-building capacity. When seawater temperatures exceed the coral's tolerance threshold, the symbiotic relationship between the coral and its endosymbiotic photosynthetic algae is disrupted, leading to significant algal loss or inhibited photosynthetic function, resulting in coral bleaching. Among these algae, cyanobacteria are another important photosynthetic microorganism in the coral holobiont, besides zooxanthellae, and are among the potential beneficial microorganisms for corals. Existing research has shown that cyanobacteria are second only to zooxanthellae in abundance in some coral symbiotic microbiomes, and in some coral symbionts, cyanobacteria even account for more than 50% of the total bacteria. Current technologies mostly focus on basic research on the functions of cyanobacteria, lacking a system for screening, culturing, and verifying the effects of symbiotic cyanobacteria, which makes it impossible to translate the potential benefits of cyanobacteria into practical solutions for protecting coral reef ecosystems. Summary of the Invention

[0005] To address the above shortcomings, this invention provides a method for improving the heat tolerance of corals using a coral-derived cyanobacteria, offering a practical approach for research on the symbiotic relationship between corals and cyanobacteria, and for protecting coral populations and maintaining the stability and function of coral reef ecosystems. The specific technical solution is as follows: A coral-derived cyanobacteria, GXU02, is classified and named as follows: Synechococcus sp., accession number: CCTCC NO: M 2026250, depositary institution: China Center for Type Culture Collection. This invention relates to a coral symbiotic cyanobacteria (sp., accession number: CCTCC NO: M 2026250, deposited at: China Center for Type Culture Collection). Synechococcus sp. GXU02) from Weizhou Island Cross Peony Coral ( Pavona decussata It was isolated and identified as [the type of organism] by whole-genome sequencing. Synechococcus A potential new species of the genus, named Synechococcus sp.GXU02.

[0006] On the other hand, the present invention also provides a microbial preparation, wherein the active ingredient in the microbial preparation includes the aforementioned cyanobacteria.

[0007] The cyanobacteria or microbial preparations of the present invention have application potential in areas such as artificial modification of corals, restoration of coral reef ecosystems, and novel algal materials.

[0008] On the other hand, the present invention also provides the application of the above-mentioned cyanobacteria or microbial agents in the prevention and / or restoration of coral thermal bleaching.

[0009] On the other hand, the present invention also provides the application of the above-mentioned cyanobacteria or microbial preparations in improving the heat tolerance of corals and / or in the cultivation of heat-resistant coral seedlings.

[0010] On the other hand, the present invention also provides the application of the above-mentioned cyanobacteria or microbial preparations in the preparation of agricultural formulations.

[0011] Preferably, in the above applications, the agricultural preparation is used for plant cultivation and planting, and has the effects of promoting plant growth and improving stress resistance.

[0012] Preferably, in the above applications, the agricultural formulation is applied by foliar spraying or root application.

[0013] On the other hand, the present invention also provides a method for improving the heat tolerance of corals, including inoculating the above-mentioned cyanobacteria or the above-mentioned microbial preparations into corals for cultivation, thereby improving the tolerance of corals.

[0014] Preferably, the above-mentioned method for stabilizing and improving the heat tolerance of corals through symbiotic cyanobacteria recombination specifically includes the following steps: (1) Preliminary preparations: Select healthy corals in good growth condition and place them in the culture system for cultivation, so that the corals can adapt to the environment in the culture system; (2) Preparation of cyanobacterial cell suspension: First, cyanobacteria are inoculated into a culture medium for cultivation, and the algal cells are collected by centrifugation. Then, they are resuspended in sterile seawater to obtain a cyanobacteria cell suspension. (3) Co-incubation of corals and cyanobacteria: Cyanobacterial cell suspensions were inoculated into the coral culture system for co-culture. After inoculation, the culture was carried out at 26°C for 24-36 h, and then the temperature was increased to 32°C at a rate of 1°C per day.

[0015] Preferably, in the above-mentioned method for stabilizing and improving the heat tolerance of corals through symbiotic cyanobacteria recombination, the culture conditions in step (1) are: water temperature 26℃, salinity 32‰, and pH 8.2.

[0016] Preferably, in the above-mentioned method for stabilizing and improving the heat tolerance of corals through symbiotic cyanobacteria recombination, in step (2), the cell density in the cyanobacteria cell suspension is 1.0 × 10⁻⁶. 5 ~10 8 cells / mL.

[0017] Preferably, in the above-mentioned method for stabilizing and improving the heat tolerance of corals through symbiotic cyanobacteria recombination, step (3) specifically involves: placing the *Sinocyclocheilus 'Citrus aurantiacus'* in a culture bottle, adding the cell suspension obtained in step (2) to the coral surface, and adding artificial seawater to the culture bottle to completely submerge the coral; after the coral and algal cell suspension have been placed in the culture bottle for 45 min, transferring them back to a beaker, and adding seawater to the beaker to achieve a final concentration of cyanobacteria of 1.0 × 10⁻⁶ in the seawater. 4 ~10 7 cells / mL; after inoculation with cyanobacteria, the cells were co-cultured at 26°C for 24 h, and then the temperature was increased to 32°C at a rate of 1°C per day.

[0018] Preferably, in the above-mentioned method for stabilizing and improving the heat tolerance of corals through symbiotic cyanobacteria recombination, the final concentration of cyanobacteria in seawater is 1.0 × 10⁻⁶. 5 ~10 6 cells / mL.

[0019] Preferably, in the above-mentioned method for improving the heat tolerance of corals through symbiotic cyanobacteria recombination, in step (2), the centrifugation speed is 7000~8000 rpm and the time is 5~10 min.

[0020] Preferably, in the above-mentioned method for stabilizing and improving the heat tolerance of corals through symbiotic cyanobacteria recombination, the coral is the yellow coral.

[0021] The method of the present invention for improving the heat tolerance of corals involves inoculating them with cyanobacteria (… Synechococcus This process, using sp. GXU02, enables the effective recombination of coral symbionts, thereby stabilizing and improving the heat resistance of corals. Transplanting modified heat-resistant corals can effectively alleviate the coral bleaching crisis and stabilize coral population diversity.

[0022] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention isolates cyanobacteria from the cruciform coral. These cyanobacteria provide excellent research material for studying the functions of marine cyanobacteria and their symbiotic relationship with corals. They also have application potential in the development of growth-promoting and stress-resistant agricultural microbial agents, as well as in the artificial modification of corals, restoration of coral reef ecosystems, and the development of novel algal materials.

[0023] 2. This invention achieves effective reorganization of the coral symbiosis by inoculating the coral with this cyanobacteria, thereby improving the heat tolerance of the coral host and effectively alleviating the coral heat bleaching crisis. This method directly targets the root cause of coral heat bleaching by introducing beneficial symbiotic cyanobacteria to physiologically enhance the coral's resistance to high-temperature stress, with clear and verifiable effects. This invention focuses on improving the coral's inherent heat resistance, representing a proactive protection strategy. Compared to post-event restoration, it enhances the resilience of coral reef ecosystems to climate change from the source. This has long-term and significant ecological value for protecting coral populations and maintaining the stability and function of coral reef ecosystems.

[0024] 3. The cyanobacteria of the present invention can be used to prepare agricultural microbial preparations that promote growth and enhance stress resistance. By spraying the leaves or applying the cyanobacteria preparations of the present invention to the roots, plant growth can be promoted and plant stress resistance can be improved.

[0025] 4. This invention transforms beneficial microbiome research into practical application technology, opening up new ideas and methods for cultivating heat-resistant seedlings for coral reef ecological restoration based on symbiotic recombination, and has important reference value for developing similar protection technologies for other coral species. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 The following diagrams illustrate the cyanobacteria coating, purification, and cultivation processes of this invention: (A) Coating diagram; (B) Diagram of community morphology formed after solid plate separation and purification; (C) Diagram of cyanobacteria culture medium. Figure 2 The following are transmission electron microscope (TEM) and scanning electron microscope (SEM) images of cyanobacteria in this invention: (A) TEM image; (B) SEM image; Figure 3 The phylogenetic tree of cyanobacteria constructed based on the 16S rRNA gene sequence in this invention is shown below. Note: The numbers at the branch points represent the Bootstrap values ​​of the phylogenetic trees constructed by the maximum likelihood method (ML), neighbor-joining method (NL), and maximum parsimony method (MP), respectively, with 1000 confidence tests. Prochlorococcus marinus MIT 9313 is an outgroup, indicated in bold. Synechococcus sp. GXU02 is the algal strain studied in this paper. The number in parentheses is the accession number of the algal strain sequence in NCBI; the scale bar is the branch length of the sequence difference. Figure 4COG functional annotation of the cyanobacterial genome in this invention; Figure 5 This is a statistical graph of KEGG functional annotation of cyanobacterial genomes in this invention; Figure 6 This is a statistical graph of GO functional annotation of cyanobacterial genomes in this invention; Figure 7 The figures show the growth curves of cyanobacteria under different temperature stresses in Example 2 of this invention; Note: Significance between the experimental group and the control group is indicated by... express( : P <0.05; : P <0.01; : P <0.001).

[0028] Figure 8 The cyanobacteria in Example 2 of this invention under different temperature stresses Fv / Fm Note: Significance between the experimental group and the control group is expressed as... express( : P <0.05; : P <0.01; : P <0.001); Figure 9 The SOD activity of cyanobacteria in Example 2 of this invention after being cultured at different temperatures for 16 days; Note: Different letters indicate significant differences between groups ( P <0.05), if there are repeated letters, there is no significant difference, and a>b>c>d; Figure 10 The GSH content of cyanobacteria in Example 2 of this invention after culturing at different temperatures for 16 days; Note: Different letters indicate significant differences between groups ( P <0.05), if there are repeated letters, there is no significant difference, and a>b>c>d; Figure 11 The MDA content of cyanobacteria in Example 2 of this invention after culturing at different temperatures for 16 days; different letters indicate significant differences between groups ( P <0.05), if there are repeated letters, there is no significant difference, and a>b>c>d; Figure 12 The graph shows the phenotypic changes of *Sinocyclocheilus 'Citrus aurantiacus'* in different treatment groups cultured at 26°C in Example 3 of this invention: T26 represents a culture temperature of 26°C; Lo, Me, and Hi represent cyanobacterial inoculum concentrations of 3.65%. 10 4cells / mL, 1.66 10 5 cells / mL and 1.14 10 6 cells / mL; Ck represents the control group without cyanobacteria inoculation; Figure 13 The graph shows the phenotypic changes of *Sinocyclocheilus 'Citrus aurantiacus'* in different treatment groups cultured at 32°C in Example 3 of this invention: T32 represents a culture temperature of 32°C; Lo, Me, and Hi represent cyanobacterial inoculum concentrations of 3.65%. 10 4 cells / mL, 1.66 10 5 cells / mL and 1.14 10 6 cells / mL; Ck represents the control group without cyanobacteria inoculation; Figure 14 This refers to the treatment of *Sinocyclocheilus 'Orange' corals under different temperatures and inoculation concentrations in different treatment groups in Example 3 of this invention. Fv / Fm Changes; T26 and T32 represent culture temperatures of 26℃ and 32℃, respectively; Lo, Me, and Hi represent cyanobacterial inoculum concentrations of 3.65%. 10 4 cells / mL, 1.66 10 5 cells / mL and 1.14 10 6 cells / mL; Ck represents the control group without cyanobacteria inoculation. D0 and D21 represent coral samples on day 0 and 21, respectively; significance levels between the high-temperature inoculation group and the T32_Ck control group are shown in Figure 1. express( : P <0.05; : P <0.01; : P <0.001); Figure 15 For embodiment 32 of this invention, fluorescence in situ hybridization of cyanobacteria in Coral simonii tissue was performed: (A) Fluorescence in situ hybridization of the T32_Ck control group on day 21; (B) Fluorescence in situ hybridization of the T32_Me inoculated group on day 21; T32 represents the culture temperature of 32℃; Me represents the cyanobacteria inoculation concentration of 1.66. 10 5 cells / mL; Ck represents the control group without cyanobacteria inoculation; Figure 16The following are the changes in the density of yellow algae in *Sinocyclocheilus 'Citrus aurantiacus'* polyps under different temperatures and inoculation concentrations in Example 3 of this invention: (A) Changes in the density of yellow algae in the group cultured at room temperature; (B) Changes in the density of yellow algae in the group under high temperature stress; T26 and T32 represent culture temperatures of 26℃ and 32℃, respectively; Lo, Me, and Hi represent cyanobacterial inoculation concentrations of 3.65%. 10 4 cells / mL, 1.66 10 5 cells / mL and 1.14 10 6 cells / mL; Ck represents the control group without cyanobacteria inoculation; different letters indicate significant differences between groups ( P <0.05), if there are repeated letters, there is no significant difference, and a>b>c>d; Figure 17 The community composition of symbiotic cyanobacteria of *Sinocyclocheilus simonii* at the genus level in Example 3 of this invention is as follows: Note: T26 and T32 represent culture temperatures of 26℃ and 32℃, respectively; Lo, Me, and Hi represent cyanobacterial inoculum concentrations of 3.65%. 10 4 cells / mL, 1.66 10 5 cells / mL and 1.14 10 6 cells / mL; Ck represents the control group without cyanobacteria inoculation; Figure 18 The image shows Arabidopsis thaliana seedlings on day 28 in Example 4 of this invention. The left side represents the cyanobacteria group, and the right side represents the control group. Detailed Implementation

[0029] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Unless otherwise defined, all technical terms used below have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of the present invention. Unless otherwise specifically stated, all raw materials, reagents, instruments, and equipment used in the present invention are commercially available or can be prepared by existing methods.

[0030] The coral symbiotic cyanobacteria of the present invention ( Synechococcus sp. GXU02) from Weizhou Island Cross Peony Coral ( Pavona decussata It was isolated and identified as [the type of organism] by whole-genome sequencing. Synechococcus A potential new species of the genus, tentatively named Synechococcussp. GXU02. Scanning electron microscopy revealed that this algal strain is spherical or rod-shaped (approximately 500 nm in diameter) and forms aggregated structures through filamentous extracellular polymers, suggesting that it may enhance its environmental adaptability through colonization within host tissues. Physiological experiments showed that the strain maintained high activity at 35°C.

[0031] Cyanobacteria can participate in the response of corals to environmental stress through various pathways, such as: scavenging reactive oxygen species accumulated in corals under heat stress by synthesizing antioxidants to reduce oxidative damage; and regulating the structure of coral symbiotic microbiome and maintaining community stability through their own heat resistance.

[0032] The reagents used in the following examples are: Superoxide Dismutase (SOD) kit (Nanjing Jiancheng Bioengineering Institute, Nanjing), Malondialdehyde (MDA) assay kit (Nanjing Jiancheng Bioengineering Institute, Nanjing), Reduced Glutathione (GSH) content assay kit (Solepro, Beijing), Plant DNA Extraction Kit (OMEGA, USA), and BG-11 medium (Guangyu Biotechnology Co., Ltd., Shanghai).

[0033] BG-11 medium composition and usage: 1.5 g / L NaNO3, 0.075 g / L MgSO4·7H2O, 0.04 g / L K2HPO4, 0.036 g / L CaCl2·2H2O, 0.006 mg / L Citric acid, 0.006 mg / L FeC6H5O7·NH4OH, 0.001 g / L EDTANa2, 0.02 g / L Na2CO3, 2.86 mg / L H3BO3, 1.86 mg / L MnCl2·4H2O, 0.22 mg / L ZnSO4·7H2O, 0.39 mg / L Na2MoO4·2H2O, 0.08 mg / L CuSO4·5H2O, 0.05 mg / L Co(NO3)2·6H2O. Before use, filter the seawater through a 0.22 μm filter membrane, sterilize it with high-pressure steam at 121℃ for 20 min, cool it to room temperature, add the concentrate according to the concentration ratio, and then use it directly.

[0034] The *Pterocarya crus-galli* and *Sinocyclocheilus 'Citrus'* corals used in the experiment were both sourced from the coral reef area of ​​Weizhou Island. Using scuba diving, and equipped with chisels, hammers, baskets, and other sampling tools, a suitable number of *Sinocyclocheilus 'Citrus' individuals (approximately 30) were collected at a depth of about 5 meters. (30 cm). The samples were kept with water at ~25℃ and placed in an indoor coral culture system for controlled culture within 24 hours.

[0035] The coral culture system consists of 60 60 The system consists of a 40cm aquarium, a heater / cooler, a variable frequency heater, a variable frequency wavemaker, a protein skimmer, a water replenisher, and a full-spectrum coral lamp. The functions of each component are as follows: the heater / cooler and heater work together to control the system temperature, keeping the temperature error within 0.1℃; the wavemaker simulates ocean wave conditions for the corals, promoting seawater circulation and supplying sufficient dissolved oxygen; the protein skimmer reduces ammonia nitrogen levels in the system, separates organic matter from the water, increases dissolved oxygen, and maintains stable water quality and pH; the water replenisher compensates for water evaporation and maintains stable salinity; and the coral lamp provides the spectrum required for coral growth, simulating natural light conditions. Before introducing corals collected from Xinye into the aquarium, the aquarium must be prepared with live rock and artificial sea salt using a bottom filter to establish a complete nitrification system. After introducing the corals, the culture conditions are adjusted to: water temperature 26℃, salinity 32‰, and pH 8.2. One-third of the seawater in the culture system is replaced weekly to maintain the aquatic environment. The corals are used for subsequent experiments after one month of stable culture.

[0036] The 16S rDNA sequence of cyanobacteria (SEQ ID NO:1) is as follows:

[0037] Example 1: Isolation, purification, culture and identification of cyanobacteria The specific steps for the isolation, purification, cultivation, and identification of cyanobacteria are as follows: Appropriately cut tissue from *Ariocarpus cruciformis* into 2 mL EP tubes, thoroughly mince it with scissors, add 1 mL of sterile seawater and mix well. Spread 100 μL of the supernatant onto BG-11 solid medium. After single colonies grow, pick single colonies and streak them on plates for purification at least three times. The purified algal strains are then cultured in BG-11 liquid medium. All culture operations were performed in a 25℃ artificial climate chamber with 60% RH, 1000 PPM CO2, 4000 Lux light, and a 12-hour photoperiod. Spreading, purification, and liquid culture were performed as follows. Figure 1 As shown.

[0038] Transmission and scanning electron microscopy results are as follows Figure 2 As shown, this algal strain is spherical or rod-shaped, approximately 500 nm in diameter and 1000 nm in length, and aggregates through filamentous extracellular polymers. A thin, clearly defined cell wall is visible on the outermost layer of the cell, closely adhering to the cell membrane on its inner side; together, they form the outer barrier of the cell, maintaining cell shape and controlling the entry and exit of substances. The cytoplasm contains numerous flattened, cascaded membrane structures, namely thylakoids, which are the sites of photosynthesis in cyanobacteria. These membranes are bound to photosynthetic pigments such as chlorophyll and phycobiliproteins, appearing as granular or patchy structures with high electron density under an electron microscope. The central region of the cell lacks the nuclear membrane of eukaryotes, and instead displays filamentous structures with uneven electron density; these are the nucleoids of the cyanobacteria, containing circular double-stranded DNA.

[0039] Whole genome sequencing was performed on the cyanobacterium. Cyanobacterial DNA extraction was performed according to the instructions of the Plant DNA Extraction Kit (OMEGA, USA). After DNA extraction, the samples were tested, and qualified DNA samples were transported to Megagene Corporation on dry ice for DNA library construction and high-throughput sequencing.

[0040] For cyanobacteria Synechococcus sp. GXU02 16S rRNA BLAST homology search of the gene sequence showed that it was similar to... Synechococcus sp. MLCB showed the highest sequence similarity, reaching 97.87%. Phylogenetic tree ( Figure 3 The analysis results show that Synechococcus sp. GXU02 clusters in Synechococcus Belongs to branches, and with Synechococcussp. MLCB exhibits the closest phylogenetic relationship. In the phylogenetic trees constructed using maximum likelihood (ML), neighbor-join (NJ), and maximum parsimony (MP) methods, the support rates for this clustering relationship are 84%, 85%, and 77%, respectively. Preliminary inference suggests that this cyanobacterium is... Synechococcus A potential new species of the genus, named Synechococcus sp. GXU02.

[0041] COG functional annotation of cyanobacterial genomes, such as... Figure 4 As shown, the encoded proteins are richest in functional categories related to energy production and conversion, indicating that this algae possesses a highly active energy metabolism capacity. Furthermore, functional proteins related to amino acid transport and metabolism, coenzyme transport and metabolism, translation, ribosomal structure and biogenesis, and cell wall / membrane / envelope biogenesis also constitute a significant proportion. These results demonstrate that the cyanobacteria of this invention possess strong functional potential in maintaining basic life activities, constructing cell structures, and adapting to the external environment.

[0042] KEGG gene function annotation of cyanobacterial genomes ( Figure 5 The results showed that the largest number of genes annotated were related to amino acid biosynthesis, indicating that this cyanobacterium has a strong ability in amino acid synthesis. In addition, functional genes involved in ribosome assembly, purine metabolism, porphyrin and chlorophyll metabolism, photosynthesis, and carbon metabolism were also widely present, indicating their high potential activity in key life processes such as protein synthesis, genetic material construction, light capture, and carbon source utilization. Notably, genes encoding ABC transporters also accounted for a significant proportion, suggesting that this algae may possess strong material transport and environmental adaptation capabilities.

[0043] Further GO gene functional annotation of the cyanobacterial genome ( Figure 6The results showed that the cyanobacterial genes were mainly enriched in two major categories: biological processes and molecular functions. In terms of biological processes, genes related to metabolic processes and cellular processes accounted for a high proportion, indicating that this cyanobacterium possesses strong life activities and metabolic regulation capabilities. In terms of molecular functions, the annotation proportion of genes related to binding activity and catalytic activity was relatively large, showing that its gene products are widely involved in enzymatic reactions and substance recognition processes. In addition, genes related to antioxidant activity also accounted for a certain proportion, suggesting that this algae may have a strong ability to regulate redox balance, which helps it cope with environmental stress.

[0044] Example 2: Temperature Tolerance Test of Cyanobacteria Using 25℃ as the control temperature and 20℃, 30℃, and 35℃ as stress temperatures, cyanobacteria were cultured in a 25℃ carbon dioxide-based artificial climate chamber until OD (October Optimum). 730 After reaching a concentration of 0.3, the solution was aliquoted into 250 mL Erlenmeyer flasks, with three biological replicates. The flasks were then transferred to artificial climate chambers at 20°C, 25°C, 30°C, and 35°C for incubation, with 60% RH, 1000 PPM CO2, 4000 Lux illumination, and a 12-hour photoperiod. The algal solution was shaken twice daily, morning and evening. On days 2, 4, 6, 8, 10, 12, 14, and 16 of the temperature stress period, 2 mL of the algal solution was collected, and the absorbance at 730 nm was measured using a UV spectrophotometer.

[0045] On days 2, 4, 6, 8, 10, 12, 14, and 16 of temperature stress, after the algal solution was treated in the dark for 30 minutes, the maximum photon yield of the algal solution was measured using a continuous fluorescence spectrometer (WALZ, Germany). Fv / Fm The measurements were performed. The algal cells were shaken well before measurement. The probe was placed vertically at the bottom of the conical flask. The damping and gain settings were 1 and 2, respectively. Each sample was measured nine times, and the average value was taken.

[0046] Determination of oxidative stress levels in cyanobacteria: Superoxide dismutase (SOD) activity in cyanobacteria was detected using a superoxide dismutase (SOD) kit; GSH content in cyanobacteria was detected according to the instructions of a reduced glutathione (GSH) content assay kit; and MDA content in cyanobacteria was detected using a malondialdehyde (MDA) assay kit.

[0047] Figure 7 The growth curves of cyanobacteria cultured at different temperatures, and the initial OD of the cyanobacteria. 730Approximately 0.30 ± 0.01, after 16 days of culture, the OD of the control group at 25℃ was... 730 =0.93±0.02, while after culturing at 30℃ and 35℃ for 16 days, its OD 730 All were significantly higher than the control group. However, the OD730 of the 20℃ low-temperature stress group on day 16 was only 0.75±0.02, significantly lower than the control group. P <0.01). Compared with the control group at room temperature (25℃), the culture conditions at 30℃ and 35℃ significantly promoted the growth of cyanobacteria.

[0048] Blue algae Fv / Fm It reflects the maximum photochemical quantum yield of photosystem II (PSII) and is an important factor in measuring cyanobacterial photosynthesis under varying temperature conditions. Figure 8 The cyanobacteria in Example 2 of this invention under different temperature stresses Fv / Fm As shown in the figure, after 16 days of different temperature stresses, the cyanobacteria at 30℃ exhibited the highest [percentage]. Fv / Fm The temperature was significantly higher than that of the 25℃ control group ( P <0.05), while cyanobacteria cultured at 35℃ Fv / Fm Only slightly higher than the control group. This indicates that a temperature of 30℃ can increase the growth of cyanobacteria. Synechococcus The photosynthetic efficiency of sp. GXU02. And the photosynthetic efficiency of cyanobacteria under 20℃ low-temperature stress. Fv / Fm Significant decrease ( P <0.05), resulting in light suppression.

[0049] When cyanobacteria were cultured for 16 days, their superoxide dismutase (SOD) activity showed significant differences at different temperatures, such as... Figure 9 As shown. Superoxide dismutase (SOD) is one of the core antioxidant enzymes in cyanobacteria, capable of scavenging superoxide anion free radicals and protecting cells from oxidative damage. When cyanobacteria... Synechococcus When the culture temperature of sp. GXU02 was increased to 35℃, which exceeds the optimal growth temperature, the SOD activity increased significantly compared with the control group. This indicates that the cyanobacteria activated the enzymatic antioxidant system and enhanced SOD synthesis to cope with the oxidative stress caused by temperature.

[0050] Reduced glutathione (GSH) plays a crucial role in cyanobacteria, extensively participating in cellular redox homeostasis, detoxification, and iron metabolism. For example... Figure 10 As shown, after 16 days of cultivation, the GSH content in the 25℃ control group was 26.84±0.91 μg / mgprot. In the heated cultivation groups, the GSH content of cyanobacteria was the highest at 30℃, reaching 45.81±0.76 μg / mgprot, which was significantly higher than that in the control group. P<0.05), and the GSH content of cyanobacteria also increased to 34.59±1.46 μg / mgprot under 35℃ conditions, but the difference was not significant compared with the control group. The content of reduced glutathione in cyanobacteria was the highest at 30℃, which may be the combined result of the synergistic dynamic changes of SOD in the antioxidant system under the optimal growth conditions.

[0051] Malondialdehyde (MDA) is a typical product of membrane lipid peroxidation and is often used to measure the intensity of membrane lipid peroxidation. For example... Figure 11 As shown, after 16 days of cultivation at different temperatures, the MDA content of cyanobacteria within the temperature range of 25℃-35℃ did not differ significantly. However, the MDA content of cyanobacteria under 20℃ low-temperature stress was significantly higher than that of the 25℃ control group, suggesting that low-temperature stress led to an increase in ROS levels, resulting in exacerbated oxidative damage. This may be because the activity of antioxidant enzymes in cyanobacteria, such as superoxide dismutase (SOD), is insufficient at low temperatures to effectively remove excessive ROS, thus failing to completely counteract oxidative stress, leading to increased cell membrane damage and lipid peroxidation. In conclusion, cyanobacteria can maintain a good physiological state at high temperatures and have a strong adaptability to high temperatures.

[0052] Example 3 A method for stabilizing and improving the heat tolerance of corals through symbiotic cyanobacteria recombination includes the following steps: Using *Coral simonii* as the test case, healthy coral samples were divided into 4-5 cm pieces and placed in a 26℃ coral culture system for 15 days to acclimatize. Culture conditions were adjusted to: water temperature 26℃, salinity 32‰, and pH 8.2; this was continued until all coral pieces showed uniform color and stable condition before use. Eight 5 L beakers were placed in the culture system, fixed with supports, and each was filled with 4 L of artificial seawater. Nine coral pieces were randomly placed in each beaker, and the beakers were equipped with electric pumps and aeration. Then, cyanobacteria were introduced... Synechococcus sp. GXU02 cells were divided into three different final concentrations (Lo: 3.65). 10 4 cells / mL, Me: 1.66 10 5 cells / mL, Hi: 1.14 10 6 (cells / mL) were inoculated into a beaker; the specific inoculation method is as follows: (1) First, inoculate the cyanobacteria into BG-11 medium and culture until the cyanobacterial cell density is about 1×10⁻⁶. 7 After obtaining the cells / mL concentration, the corresponding volumes were taken out as 14.60 mL, 66.40 mL, and 456 mL, respectively. The algal solution was centrifuged at 8000 rpm for 5 min, the culture medium was discarded, and the solution was washed three times with sterile seawater and resuspended to 10 mL to obtain the cyanobacterial cell suspension. (2) Place the yellow coral in a 250 mL culture bottle, add the cell suspension obtained in step (1) to the surface of the coral, add artificial seawater to the culture bottle, and make up to 100 mL so that the coral is completely submerged; (3) After the coral and cell suspensions were placed in the culture flasks for 45 min, they were transferred back to the beakers. The beakers were then brought to a final volume of 4 L of seawater, and the electric pump and aeration were turned on. After inoculation, 20% of the seawater was replaced every 24 h to maintain water quality.

[0053] The experimental groups are shown in Table 1. In eight beakers, three groups were inoculated with cyanobacteria and cultured at 26℃ (T26_Lo, T26_Me, T26_Hi); three groups were subjected to temperature stress after inoculation (T32_Lo, T32_Me, T32_Hi); one group was a control group without inoculation and cultured at 26℃ (T26_Ck); and one group was a control group without inoculation and subjected to temperature stress (T32_Ck). The temperature stress group was cultured at 26℃ for 24 hours after cyanobacteria inoculation. The temperature was increased to 32℃ daily at a rate of 1℃. The first sampling was conducted on day 7 (D7), the end of the temperature increase; the second sampling was conducted on day 14 (D14); and the third sampling was conducted on day 21 (D21). Three corals were randomly selected from each sample. All samples were used for subsequent testing.

[0054] Table 1 Experimental group design Indicator Testing: Adopting a coral phenotype, with maximum photon yield Fv / Fm A comprehensive assessment of coral health was conducted. Underwater cameras were used to photograph the corals under the same light source conditions at each stage of phenotypic change, avoiding frequent photography that could negatively impact the corals. Maximum photon yield was also assessed. Fv / Fm Measurement method: After treating the corals in the dark for 30 min, the maximum photon production of the corals was measured using a continuous fluorescence analyzer (WALZ, Germany). Fv / Fm The measurements were performed. During measurement, the probe was inserted vertically into the coral block at a distance of 2-3 cm below the liquid surface. The electrical signal damping and gain were set to 1 and 2, respectively. Nine measurements were taken for each sample group, and the average value was recorded.

[0055] Coral FISH fluorescence in situ hybridization method: (1) Probe design: Based on the target gene sequence to be hybridized, specific oligonucleotide probes are designed and synthesized, and labeled with a corresponding fluorescein, namely 5-carboxyfluorescein (FAM), which emits green fluorescence. (Cyanobacteria) Synechococcus The DNA probe for sp. GXU02 is: 5′-FAM-TCGTTCTCGATGGTGGAATCCTCCGCATAGATCTCGT-3′.

[0056] (2) Tissue fixation: After the coral tissue was cleaned, it was immediately placed in a fixative solution prepared with DEPC water for 12 h.

[0057] (3) Decalcification treatment: The fixed coral sample is transferred to an EP tube, and 1 mL of decalcification solution is added for decalcification. The decalcification solution is replaced every 24 h until the coral calcium carbonate skeleton is completely removed.

[0058] (4) Dehydration and sectioning: The coral tissue was dehydrated by gradient alcohol and then embedded in paraffin. Subsequently, the paraffin was sectioned by a microtome, and the sections were picked up by a spreader and baked in an oven at 62°C for 2 hours.

[0059] (5) Dewaxing paraffin sections to water: Immerse the sections in xylene I (15 min), xylene II (15 min), anhydrous ethanol I (5 min), anhydrous ethanol II (5 min), 85% ethanol (5 min), and 75% ethanol (5 min) in sequence, and finally wash with DEPC water.

[0060] (6) Digestion: The slides were boiled in the repair solution for 15 min and allowed to cool naturally. The target area was circled with a gene pen, and proteinase K (20 ug / mL) was added and digested at 37℃ for 5 min. Then, the slides were rinsed with pure water and washed three times with PBS for 5 min each time.

[0061] (7) Hybridization: Add pre-hybridization solution to coral tissue and incubate at 37°C for 1 h. After removing the pre-hybridization solution, add hybridization solution containing probe (5 ng / uL) and place in an incubator to hybridize overnight at 37°C.

[0062] (8) Washing after hybridization: After removing the hybridization solution, wash with 2×SSC (37℃, 10 min), 1×SSC (37℃, 2×5 min) and 0.5×SSC (room temperature, 10 min) in sequence. If there are many non-specific hybridization signals, formamide can be added for additional washing.

[0063] (9) DAPI counterstaining of the nucleus: Add 2 ug / mL DAPI staining solution to the slide under light-protected conditions, incubate for 8 minutes, wash and then add anti-fluorescence quenching mounting medium to mount the slide.

[0064] (10) Microscopic observation and image acquisition: The slides were observed and photographed using an upright fluorescence microscope. Blue fluorescence was observed when the ultraviolet excitation wavelength was 330-380 nm and the emission wavelength was 420 nm; green fluorescence was observed when the FAM probe was excited at a wavelength of 465-495 nm and the emission wavelength was 515-555 nm.

[0065] Measurement of coral symbiotic zooxanthellae density: The density of zooxanthellae symbiotic with corals was measured using the foil wrapping method. Coral tissue was detached from the skeleton using sterile seawater with a dental scaler, and the tissue was dispersed using a homogenizer. The homogenate volume was recorded. Subsequently, the zooxanthellae density in the homogenate was determined using flow cytometry. Before measurement, the algae solution was thoroughly vortexed. The sample flow rate was 3 μL / s, and the measurement time was 60 s. Each sample was measured 9 times, and the average value was taken. For the measurement of the coral skeleton surface area, a standard curve was established using foil surface area x and weight y, as shown in formula (1). The coral skeleton was tightly wrapped in foil, and the surface area of ​​the coral was obtained by unfolding it. The weight of the foil was weighed and substituted into the standard curve to obtain the coral surface area. Finally, the zooxanthellae density (cells / cm²) was obtained by calculating the ratio of the number of zooxanthellae to the sample surface area. 2 The calculation formula is as follows (2), and the average value is taken after 9 measurements for each group of samples.

[0066] y=0.0042x+0.0005, R2=0.9995 (1) ρ_zooxanthellae = (ρ_homogeneous) V homogenate) / X coral (2) ρ 虫黄藻 Coral polyp and xanthophyll density (cells / cm) 2 ), ρ 匀浆 The density of zooxanthellae in the homogenate (cells / mL), V 匀浆 X is the volume of homogenate (mL). 珊瑚 Coral surface area (cm²) 2 ).

[0067] Experimental results: (1) Changes in coral phenotype Figure 12 and Figure 13 Phenotypic images of each group of *Sinocyclocheilus* corals, along with cyanobacteria. Synechococcus With the inoculation of sp. GXU02 and changes in the culture environment, the coral color in the 26℃ culture group showed a significant change on day 9 of the experiment. After 9-21 days of culture, the corals adapted to the environmental changes, their color deepened, and their overall condition continued to improve. Especially on day 21, the color and condition of the corals inoculated with different concentrations of cyanobacteria were better than those in the 26℃ control group. Under high-temperature stress at 32℃, the coral color also changed significantly on day 9 of the experiment, and with the extension of stress time, the coral color gradually changed from dark brown to light brown. On day 21, it was clearly observed that the color and overall condition of the corals in the cyanobacteria-inoculated groups were significantly better than those in the 32℃ control group, with the 1.66 concentration showing the most significant improvement. 10 5 The corals in the cells / mL cyanobacteria inoculation group had the deepest color and the best health.

[0068] (2) Maximum photon production of corals Fv / FmChanges The effect of cyanobacteria inoculation on Fv / Fm Porites lutea is as Figure 14 shown. As can be seen from the figure, there is no significant difference between groups under normal temperature conditions ( Fv / Fm P>0.05), P remaining between 0.57±0.02 and 0.60±0.03. When stressed at 32°C, Porites lutea Fv / Fm was greatly affected. When the experiment reached day 21, the 32°C control group (T32_Ck) Fv / Fm decreased to 0.40±0.07, a 34.43% decrease compared with the initial state (D0). In contrast, the cyanobacteria inoculation groups Fv / Fm were 0.45±0.05 to 0.48±0.04, significantly higher than the control group ( Fv / Fm P<0.05), and only decreased by 19.90 - 23.91% compared with the initial state. P <0.05),

[0069] (3) Fluorescence in situ hybridization to trace algal cells The results of fluorescence in situ hybridization (see Figure 15 ) showed that no fluorescence of cyanobacteria Synechococcus sp. GXU02 was detected in the coral samples collected on day 21 of the experiment in the T32_Ck control group, while fluorescence of cyanobacteria was still detected in the T32_Me inoculation group after high temperature stress, indicating initial colonization in the coral tissue. The green dots pointed to by the red arrows are cyanobacteria labeled with FAM fluorescein.

[0070] (4) Changes in the density of Symbiodinium in corals As Figure 16 shown, under normal temperature conditions, when the experiment reached day 21, the density of Symbiodinium in the corals of the cyanobacteria inoculation group was (2.39±0.11) × 6 -(2.57±0.19) × 6 cells / cm 2 , significantly higher than the density of Symbiodinium in the 26°C control group (1.90±0.16) × 6 cells / cm 2 ( P P<0.05), and cyanobacteria inoculation promoted a 25.79% - 35.26% increase in the density of Symbiodinium in corals. Under high temperature stress conditions, the density of Symbiodinium in the corals of the cyanobacteria inoculation group was (3.25±0.08) × 5 -(5.74±0.36) × 5 cells / cm 2The density of zooxanthellae was significantly higher than that of the control group at 32℃ (2.22±0.11). 10 5 cells / cm 2 ( P <0.05), the zooxanthellae density in the 32℃ control group was only 38.68-68.31% of that inoculated group. This indicates that cyanobacterial inoculation significantly promoted the increase of zooxanthellae density in *Sinocyclocheilus 'Cephalotaxus fortunei'* and effectively alleviated coral heat stress, of which 1.66... 10 5 The cells / mL cyanobacteria inoculation group showed the best results, with significantly higher densities of coral polyps and xanthophyll compared to other groups.

[0071] (5) Community composition of symbiotic cyanobacteria of *Sinocyclocheilus 'Citrus ... Further analysis of cyanobacteria Synechococcus The effects of sp. GXU02 inoculation on the symbiotic cyanobacterial community of *Porphyra tenera* are shown in […]. Figure 17 Data showed that 13 genera of cyanobacteria were detected in coral samples collected up to day 21 of the experiment. Among them, under high-temperature stress, the T32_Me group (inoculum concentration 1.66) showed the highest concentration. 10 5 (cells / mL) and T32_Hi group (inoculation concentration 1.14) 10 6 Cyanobacteria were detected (cells / mL) Synechococcus sp. GXU02, with relative abundances of 50.00% and 61.11%, respectively. This indicates that it is a cyanobacterial species. Synechococcus sp. GXU02 was able to initially colonize the microbial tissues of coral reefs.

[0072] In summary, this invention is based on exogenous inoculation of cyanobacteria. Synechococcus sp. GXU02 enhances the heat tolerance of *Sinocyclocheilus 'Orange'*, effectively improves the heat bleaching phenotype of *Sinocyclocheilus 'Orange'*, maintains coral population diversity, and constructs a new type of heat-resistant *Sinocyclocheilus 'Orange'*.

[0073] Example 4 An agricultural formulation, wherein cyanobacteria are cultured to OD according to Example 1. 730 =1.0, to obtain the cyanobacteria culture medium, and then dilute the cyanobacteria culture medium to OD. 730 =0.2-0.3, to obtain the agricultural formulation. The agricultural formulation is then used in plant cultivation.

[0074] Experimental Methods: Seedlings were raised in plug trays using a substrate of peat moss, perlite, and vermiculite in a 3:1:1 weight ratio. Three coated Arabidopsis seeds were sown per hole. The substrate moisture content was maintained at 60%-70%, and the temperature at 25-28℃. After germination, thinning was performed, retaining only the strongest seedlings. The first application of an agricultural preparation was carried out when the Arabidopsis seedlings had 3-4 true leaves, at 9:00 AM, when the leaves began to have strong absorption capacity. Subsequent applications were made on days 7, 14, and 21 after the first application, for a total of four applications. Each application consisted of 5 mL of foliar spray and 15 mL of root spray per Arabidopsis plant. A control group was sprayed with a culture solution without pure culture medium. The characteristics of the Arabidopsis seedlings were assessed after day 28. The specific testing methods are as follows: Chlorophyll content determination: Take 0.1 g of fresh, undamaged leaves, cut them into small pieces, and place them in a pre-cooled mortar. Add a small amount of quartz sand and calcium carbonate powder, then add 2 mL of 95% ethanol. Grind into a homogenate under ice bath conditions. Transfer the homogenate to a 10 mL centrifuge tube, and rinse the mortar 2-3 times with 95% ethanol (1-2 mL each time). Combine the washings in the centrifuge tube, and finally bring the volume to 10 mL with 95% ethanol. Centrifuge at 4000 r / min for 10 min, and collect the supernatant. If the supernatant is turbid, filter it before measurement. Using 95% ethanol as a blank control, measure the absorbance of the extract at wavelengths of 665 nm and 649 nm using a spectrophotometer. Calculate the total chlorophyll content (mg / g) according to the following formula: Chlorophyll a = (13.95 × A665 - 6.88 × A649) × V × 10⁻³ / W (3) Chlorophyll b = (24.96 × A649 - 7.32 × A665) × V × 10⁻³ / W (4) Total chlorophyll = chlorophyll a + chlorophyll b (5) Where V represents the final volume of the extract (10 mL) and W represents the fresh weight of the leaves (0.1 g).

[0075] Maximum photochemical efficiency Fv / Fm Measurement: After Arabidopsis seedlings were treated in the dark for 30 min, the maximum photon yield of Arabidopsis was measured using a continuous fluorescence spectrometer (WALZ, Germany). Fv / Fm The measurement was performed. The probe was held vertically 2-3 cm from the blade, with the electrical signal damping and gain set to 1 and 2 respectively. Nine measurements were taken for each sample group, and the average value was recorded.

[0076] Proline content determination: Take 0.1 g of fresh leaves, cut them into small pieces, put them in a mortar, add 1 mL of 3% sulfosalicylic acid solution, and grind them into a homogenate in an ice bath. Transfer the homogenate to a 10 mL centrifuge tube, add 2 mL of 3% sulfosalicylic acid solution to rinse the mortar, and combine the two tubes to a total volume of 3 mL. Place the centrifuge tube in a 100℃ water bath for 10 min, remove and cool, then centrifuge at 4000 r / min for 10 min and collect the supernatant. Take 2 mL of the supernatant, add 2 mL of glacial acetic acid and 2 mL of acidic ninhydrin reagent, mix well, heat in a 100℃ water bath for 30 min, and remove and cool to room temperature. Add 4 mL of toluene to the colorimetric solution, shake thoroughly to extract, allow to stand and separate into layers, take the upper toluene phase, use toluene as a blank control, and measure the absorbance at 520 nm using a spectrophotometer. Calculate the proline content using the standard curve method. Prepare proline standard solutions of 0, 2, 4, 6, 8, and 10 μg / mL. After color development and extraction following the steps described above, determine A. 520 A standard curve was plotted with proline concentration on the x-axis and absorbance on the y-axis, yielding the regression equation y = 0.042x + 0.008. The proline content was then calculated using the following formula: Proline (μg / g fresh weight) = (C×V×N) / W (6) Wherein, C: proline concentration (μg / mL) obtained from the standard curve; V: extraction volume (mL, 4 mL here); N: extraction dilution factor (1 if undiluted); W: leaf fresh weight.

[0077] Determination of malondialdehyde (MDA) content: Take 0.1 g of fresh leaves, cut them into small pieces, place them in a pre-cooled mortar, add 2 mL of 5% TCA solution, and grind them into a homogenate in an ice bath. Transfer the homogenate to a 10 mL centrifuge tube, rinse the mortar with 1 mL of 5% TCA, combine the homogenates to a total volume of 3 mL, and vortex to mix. Centrifuge at 8000 r / min for 10 min, collect the supernatant, and discard the precipitate. Take 2 mL of the supernatant, add 2 mL of 0.67% TBA solution, mix well, and heat in a 100℃ water bath for 15 min. Immediately remove and cool to room temperature in an ice bath. After cooling, centrifuge again at 8000 r / min for 5 min, collect the supernatant, and measure the absorbance at wavelengths of 532 nm and 600 nm using 2 mL of 5% TCA + 2 mL of 0.67% TBA as a blank control. Calculate the MDA content (nmol / g fresh weight) using the following formula.

[0078] MDA = (A 532 -A 600 )×V×N×10 9 ) / ε×W×1000 Where V: total volume of extract (mL, here 3 mL); N: dilution factor (1 for undiluted); ε: molar absorptivity of MDA-TBA adduct (1.56 × 10⁻⁶). 5 L / mol / cm); W: Fresh weight of leaf (g, here 0.1 g).

[0079] Experimental results: See photos of Arabidopsis seedlings after 28 days. Figure 18 The left side represents the cyanobacteria group, and the right side represents the control group. Standard growth indicators were as follows: the cyanobacteria group had 10 rosette leaves, while the control group had 6; the rosette diameter was 5.8 cm in the cyanobacteria group and 4.5 cm in the control group; the plant height was 18 cm in the cyanobacteria group and 11 cm in the control group.

[0080] In terms of physiological indicators, the chlorophyll content in the cyanobacteria-sprayed group was 1.42 mg / g fresh weight, while that in the control group was 1.15 mg / g fresh weight, showing a significant increase of 23.5% in the experimental group. Maximum photon yield... Fv / Fm The proline content in the cyanobacteria-treated group reached 0.80, while that in the control group reached 0.75, showing a significant increase of 6.7% after cyanobacteria spraying. The proline content in the cyanobacteria-treated group reached 95 μg / g fresh weight, a significant increase of 35.7% compared to the 70 μg / g fresh weight in the control group. The superoxide dismutase (SOD) activity in the cyanobacteria-treated group reached 210 U / mg protein, a significant increase of 31.3% compared to the 160 U / mg protein in the control group. Meanwhile, the malondialdehyde (MDA) content after cyanobacteria spraying was only 4.2 nmol / g fresh weight, compared to 6.5 nmol / g fresh weight in the control group, indicating a significant decrease of 35.4% in the degree of membrane peroxidation in Arabidopsis seedlings. These results indicate that cyanobacteria treatment promotes Arabidopsis growth and not only stimulates proline synthesis to regulate osmosis and protect structures, but also effectively activates the plant's endogenous antioxidant enzyme system, reducing oxidative damage at its source. This comprehensively enhances the plant's stress resistance, stabilizes its physiological metabolism, and ultimately provides a guarantee for maintaining growth (promoting growth).

[0081] Table 2. Comparison of agronomic traits of Arabidopsis seedlings in the cyanobacteria group and the control group. The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A cyanobacterial species derived from coral, characterized in that, The cyanobacteria GXU02 from which the coral originated is classified and named as follows: Synechococcus sp., accession number: CCTCC NO: M 2026250, deposited by: China Center for Type Culture Collection.

2. A microbial preparation, characterized in that, The active ingredient in the microbial preparation includes the cyanobacteria described in claim 1.

3. The application of the cyanobacteria as described in claim 1 or the microbial preparation as described in claim 2 in the prevention and / or restoration of coral thermal bleaching.

4. The application of the cyanobacteria as described in claim 1 or the microbial preparation as described in claim 2 in improving the heat tolerance of corals and / or in the cultivation of heat-resistant coral seedlings.

5. The application of the cyanobacteria as described in claim 1 or the microbial preparation as described in claim 2 in the preparation of agricultural formulations.

6. A method for stabilizing and improving the heat tolerance of corals through symbiotic cyanobacteria recombination, characterized in that, This includes inoculating corals with the cyanobacteria described in claim 1 or the microbial preparation described in claim 2 to improve the corals' tolerance.

7. The method for stabilizing and improving coral heat tolerance through symbiotic cyanobacteria recombination according to claim 6, characterized in that, Specifically, the following steps are included: (1) Preliminary preparations: Select healthy corals in good growth condition and place them in the culture system for cultivation, so that the corals can adapt to the environment in the culture system; (2) Preparation of cyanobacterial cell suspension: First, cyanobacteria are inoculated into a culture medium for cultivation, and the algal cells are collected by centrifugation. Then, they are resuspended in sterile seawater to obtain a cyanobacteria cell suspension. (3) Co-incubation of corals and cyanobacteria: Cyanobacterial cell suspensions were inoculated into the coral culture system for co-culture. After inoculation, the culture was carried out at 26°C for 24-36 hours, and then the temperature was increased to 32°C at a rate of 1°C per day.

8. The method for stabilizing and improving coral heat tolerance through symbiotic cyanobacteria recombination according to claim 7, characterized in that, In step (2), the cell density in the cyanobacterial cell suspension is 1.0 × 10⁻⁶. 5 ~10 8 cells / mL.

9. The method for stabilizing and improving coral heat tolerance through symbiotic cyanobacteria recombination according to claim 7, characterized in that, In step (3), specifically: the yellow coral is placed in a culture bottle, the cell suspension obtained in step (2) is dripped onto the surface of the coral, and artificial seawater is added to the culture bottle to completely submerge the coral; after the coral and algal cell suspension are placed in the culture bottle for 45 min, they are transferred back to a beaker, and seawater is added to the beaker to make the final concentration of cyanobacteria in the seawater 1.0 × 10⁻⁶. 4 ~10 7 cells / mL; after inoculation with cyanobacteria, the cells were co-cultured at 26°C for 24 h, and then the temperature was increased to 32°C at a rate of 1°C per day.

10. The method for stabilizing and improving coral heat tolerance through symbiotic cyanobacteria recombination according to any one of claims 6 to 9, characterized in that, The coral in question is the yellow coral.

Images