Endosporium huanghuai EPI7 protein as well as coding gene and application thereof

Abstract

The invention belongs to the technical field of gene engineering, and discloses a glomus huanghuai EPI7 protein, a coding gene and application thereof, the amino acid sequence of the glomus huanghuai EPI7 protein is shown as SEQ ID NO.2, and the nucleotide sequence of nucleic acid or the gene for coding the EPI7 protein is shown as SEQ ID NO.1. The invention further discloses a preparation method of the glomus huanghuai EPI7 protein. The invention proves that the glomus huanghuai EPI7 protein plays an important role in the process of improving the disease resistance of plants through cloning of the glomus huanghuai EPI7 protein gene and transient expression of tobacco.

Description

Technical Field

[0001] This invention belongs to the field of genetic engineering technology, specifically relating to an EPI7 protein of *Cyclocarya paliurus*, its encoding gene, and its applications. Background Technology

[0002] Effector proteins are a class of virulence molecules secreted by pathogens during the infection of host plants. They can disrupt the immune system of plant cells, thereby promoting pathogen infection. *Hylocoria huanghuaiensis* (… Globisporangium huanghuaiense As a plant pathogenic oomycete, *Oomycetes* secretes various effector proteins during host infection. These proteins interact with different targets within the host, interfering with the plant's immune response or altering its metabolic pathways, thereby promoting pathogen infection and colonization. However, once these effector proteins are recognized by the host's immune receptors, they activate the plant's defense response, limiting the spread of the pathogen. Thus, effector proteins play a dual role in the pathogen-host interaction: influencing both the pathogenicity of the pathogen and regulating the expression of plant resistance. In-depth research into the function and mechanism of action of effector proteins not only helps to elucidate the pathogenic mechanisms of pathogens and the immune response mechanisms of plants, but also provides an important theoretical basis for designing durable and efficient disease control strategies based on the host-pathogen interaction.

[0003] EPI-type effector proteins are a class of secretory functional proteins in oomycetes with conserved Kazal-type domains. They promote pathogen infection by targeting and inhibiting the activity of host pathogenesis-related proteases and interfering with plant immune signal transduction. However, some EPI proteins can be recognized by plant-specific receptors as elicitors, rapidly triggering hypersensitive necrosis (HR) response and activating systemic immune response, thus having the potential to be developed into plant immune inducers. Summary of the Invention

[0004] Objectives of the Invention: The first objective of this invention is to provide an EPI effector protein from *Hypersensitive phytoreceptor* that can induce a hypersensitive response (HR) in plants. The second objective is to provide the nucleic acid or gene encoding the aforementioned *Hypersensitive phytoreceptor* EPI effector protein. The third objective is to provide an expression cassette, recombinant expression vector, transgenic cell line, or transgenic recombinant bacteria containing the aforementioned nucleic acid or gene, as well as methods for constructing the recombinant expression vector and transgenic recombinant bacteria. The fourth objective is to provide applications of the aforementioned *Hypersensitive phytoreceptor* EPI effector protein, nucleic acid or gene, expression cassette, recombinant expression vector, transgenic cell line, or transgenic recombinant bacteria.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: The present invention relates to the EPI7 protein of *Hylocereus huanghuaiense*, wherein the amino acid sequence of the EPI7 protein of *Hylocereus huanghuaiense* is shown in SEQ ID NO.2.

[0006] The present invention relates to the nucleic acid or gene encoding the above-mentioned Huanghuai cysticercus EPI7 protein, wherein the nucleotide sequence of the nucleic acid or gene is shown in SEQ ID NO.1.

[0007] The present invention relates to an expression cassette, recombinant expression vector, transgenic cell line, or transgenic recombinant bacterium containing the above-mentioned *Cyclocarya paliurus* EPI7 protein.

[0008] The present invention discloses a method for constructing a recombinant expression vector, wherein the expression vector is obtained by introducing the gene encoding the EPI7 protein of *Hylocereus huanghuaiense* into the plant expression vector pCAMBIA1300-FLAG.

[0009] The nucleotide sequences of the primers used in the construction of the expression vector are shown in SEQ ID NO.3~4.

[0010] The transgenic recombinant bacteria of the present invention are obtained by inserting the above-mentioned recombinant expression vector into Escherichia coli and screening for transgenic recombinant bacteria.

[0011] The *E. coli* strain is a DH5α competent cell.

[0012] The present invention relates to the application of the above-mentioned Huanghuai coccidioidomycete EPI7 protein, nucleic acid or gene, expression cassette, recombinant expression vector, transgenic cell line or transgenic recombinant bacteria in the preparation of reagents for inducing plant allergic reactions.

[0013] The above-mentioned Huanghuai Cyclocystis EPI7 protein, nucleic acid or gene, expression cassette, recombinant expression vector, transgenic cell line or transgenic recombinant bacteria of the present invention are used in the preparation of plant resistance reagents.

[0014] The improvement of plant resistance refers to improving the plant's resistance to infection by Phytophthora capsici.

[0015] Beneficial effects: Compared with existing technologies, this invention has the following significant advantages: Through extensive screening, this invention obtained a gene EPI7 derived from *Hylocereus huanghuaiense* that can trigger a plant hypersensitive response (HR). This gene triggers plant immunity and induces disease resistance in plants, which is of great significance for developing environmentally friendly disease resistance strategies. Attached Figure Description

[0016] Figure 1 : EPI7 Phenotypic diagram of the HR effect in gene-induced plants.

[0017] Figure 2EPI7 triggers HR to induce plant resistance. Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0019] Example 1: Amplification and sequencing of the EPI effector protein gene EPI7 1. Experimental strains The tested strain was *Cyclocarya huanghuai* ( Globisporangium huanghuaiense The strain was preserved by the Green Control Laboratory of Jiangsu Vocational College of Agriculture and Forestry. The strain was preserved on 10% V8 solid slant at a temperature of 10℃.

[0020] 2. Preparation of seedlings for testing *Nicotiana benthamiana* Ben's tobacco ( Nicotiana benthamiana It is placed in a plant growth chamber with 16 hours of light and 8 hours of darkness and 70% relative humidity.

[0021] 3. Extraction of *Cyclocarya paliurus* from the Huanghuai region ( Globisporangium huanghuaiense RNA was extracted, and cDNA of the target gene was obtained. Hyphae of *Cyclocarya paliurus* were collected, flash-frozen in liquid nitrogen, and then cooled and ground in a mortar. Total RNA was extracted from *Cyclocarya paliurus* according to the recommended method of the Novizan Total RNA Extraction Kit (catalog number: R711-01). cDNA was synthesized according to the method provided by the Novizan RNA Reverse Transcription Kit (catalog number: R212-01). Using the above cDNA as a template, PCR amplification was performed with the corresponding forward and reverse primers (SEQ ID NO. 3~4). The primer sequences are shown in Table 1.

[0022] Table 1 Primer Sequences Name Sequence 5’ - 3’ PyhuEPI7-F GACGAGCTGTACAAGGGTACCATGAAGCTCCTGTCCTCCTCCA PyhuEPI7-R GCGGACTCTAGTTCATCTAGAGAGCATCAGACTCACAACAGCACT The PCR reaction system consisted of: 12.5 μL high-fidelity enzyme; 0.5 μL primer; 0.5 μL template; and sterile water to a final volume of 25 μL.

[0023] The PCR reaction program was as follows: 95℃ pre-denaturation for 5 min; 95℃ denaturation for 15 s, 55℃ annealing for 15 s, 72℃ extension for 30 s, 30 cycles; 72℃ extension for 4 min; and storage at 12℃.

[0024] The amplified PCR products were subjected to 1% agarose gel electrophoresis and observed under UV light. PCR products showing the target band were sent to Nanjing Qingke Biotechnology Co., Ltd. for sequencing. After confirmation by sequencing, the obtained sequence was found to be the nucleotide sequence of the EPI protein gene. This EPI protein gene is derived from *Cyclocarya paliurus* (Huanghuai). Globisporangium huanghuaiense EPI protein gene EPI7 The EPI7The nucleotide sequence of the gene is shown in SEQ ID NO.1. The amino acid sequence of the protein encoded by the EPI7 gene is shown in SEQ ID NO.2.

[0025] SEQ ID NO.1 ATGAAGCTCCTGTCCTCCTCCAGCGTGCTCGCCGTCTCAGCGCTCGCCATCTCAGCGTCGCTCGCGCCACAACCTACCACGGCAGCCGATTCGTGCGGCAGCGGCGCGTGCCTGAGCAACTACGACCCCGTCTGCGGCTCGGACGGCAAGACGTACTCGAACGCCTGCGAGCTCACGCGCGCCAAGTGCACCAACACGTCTCTTACTCAAAAGAACACGGGCGAGTGCTCCAGCGGCAGCAGCTCGACTGGCACCGGCACTTGCGCGCAGGAGTTTGCGTGCACGTCCAAGTACGATCCGGTGTGCGGCTCGGACGGCAAGACGTACACCAACGCGTGCGAGCTCAAGCGCGCCACGTGCGCGAACCCATCAGTGGTCCTGAAGAGCACGGGCGAGTGCCCCGGCAGCAGCAGCAGCGCGACTGGCTCCACCGGAGGTAGCGGTAGCGCCACCGTCTGCAAGATCAAGGCGTGCACCAAGGAGTACAAGCCCGTGTGCGGCTCGGACAACAAGACGTACGCCAACAAGTGCACGTTCACGAACGCGCAGTGCGAGACCCCAGCACTGACGCTCAAGGCCGAGGTCGCGTGCGAAGGTGACGATGTCAACGACAGCGATGGCTCGTCGAGCGTGGGTCGCGATGCGCAGGTGTCATCAGGAAGCAGTGACGACGACGCATGTGTGACGATGTGCACGAAGGAGTACACTCCTGTGTGCGGCTCGAACGACCTCACGTACGAGAACCCGTGTCTGCTCAAGAACGCGCAGTGCAGCAACGCGACGCTCACGAAGGTGTCGGACAGCGCGTGTCCGACTGCTGCGCCTGCGACGGGCTCGACTGCGAATCCGACAGCTGCTGTTGGGATTCAAGTGGCAGCGCTCGCGGTGCTCAGTGCTGTTGTGAGTCTGATGCTCTAG SEQ ID NO.2 MKLLSSSSSVLAVSALAISASLAPQPTTAADSCGSGACLSNYDPVCGSDGKTYSNACELTRAKCTNTSLTQKNTGECSSGSSSTGTGTCAQEFACTSKYDPVCGSDGKTYTNACELKRATCANPSVVLKSTGECPGSSSSATGSTGGSGSATVC KIKACTKEYKPVCGSDNKTYANKCTFTNAQCETPALTLKAEVACEGDDVNDSDGSSSVGRDAQVSSGSSDDDACVTMCTKEYTPVCGSNDLTYENPCLLKNAQCSNATLTKVSDSACPTAAPATGSTANPTAAVGIQVAALAVLSAVVSLML* Example 2: Functional Verification of EPI7 1. Construct the pCAMBIA1300-FLAG:EPI7 expression vector The empty vector plasmid pCAMBIA1300-FLAG (BIOVECTOR China Plasmid Vector Strain Cell Line Gene Preservation Center) was digested with KpnⅠ and SalⅠ. The target fragment EPI7 (SEQ ID NO.1) was ligated to the vector using the homologous recombinase from Novizan to obtain the pCAMBIA1300-FLAG:EPI7 recombinant vector. The pCAMBIA1300-FLAG:GFP and pCAMBIA1300-FLAG:INF1 vectors were already constructed in the laboratory using conventional methods disclosed in existing technologies (refer to Chen R, Ma D, Bao Y, et al. Joint application of plant immunity-inducing elicitors and fungicides to control Phytophthora diseases[J]. Phytopathology Research, 2024, 6(1):15.DOI:10.1186 / s42483-024-00233-0.).

[0026] The reaction system is as follows: 1 μL 10×CE II reaction buffer; 2 μL PCR purified product of EPI7; 1 μL of the above-digested pCAMBIA1300-FLAG empty vector; 5 μL homologous recombinase; and sterile water to a final volume of 10 μL.

[0027] The above reaction system was reacted at 37 ℃ for 30 min. The ligation product was then transformed into 100 μL of *E. coli* DH5α competent cells, incubated at 42 ℃ for 1 min, and placed on ice for 2 min. After completion, 700 μL of fresh LB broth was added, and the cells were incubated at 37 ℃ with shaking for 1 h. After incubation, the cells were centrifuged at 5000 rpm for 3 min. 100 μL of the bacterial culture was plated onto a solid LB agar plate containing 50 mg / mL kanamycin, and incubated upside down at 37 ℃ for 16 h. Single colonies were then picked for colony PCR identification. The identified positive transformants were sequenced; if correct, the pCAMBIA1300-FLAG:EPI7 expression vector was obtained.

[0028] 2. Transformation of expression vector into Agrobacterium and functional verification 2.1. Agrobacterium was transformed with expression vectors pCAMBIA1300-FLAG:GFP, pCAMBIA1300-FLAG:INF1, and pCAMBIA1300-FLAG:EPI7. Add 30 ng of pCAMBIA1300-FLAG:GFP, pCAMBIA1300-FLAG:INF1, and pCAMBIA1300-FLAG:EPI7 expression vectors to 100 μL of Agrobacterium GV3101 competent cells, respectively. Incubate on ice for 5 min, freeze in liquid nitrogen for 5 min, incubate at 37℃ for 5 min, and place on ice for 5 min. After incubation, add 700 μL of fresh LB broth and incubate at 28℃ with shaking for 2 h. After incubation, centrifuge at 5000 rpm for 3 min. Retain 100 μL of bacterial culture and plate it onto a solid LB agar plate containing 50 mg / mL kanamycin and 25 mg / mL rifampicin. Incubate upside down at 28℃ for 48 h. Pick single colonies for colony PCR to obtain positive transformants.

[0029] 2.2 Transient expression of pCAMBIA1300-FLAG:GFP, pCAMBIA1300-FLAG:INF1, and pCAMBIA1300-FLAG:EPI7 proteins in Nicotiana benthamiana. Tobacco Benedict ( Nicotiana benthamiana The plants were placed in a plant growth chamber with 16 hours of light and 8 hours of darkness and 70% relative humidity. After 30 days, leaves from the same part were used for gene expression experiments.

[0030] The positive transformants were placed in LB liquid medium and cultured at 28°C with shaking for 30 h. The bacterial culture was collected, centrifuged at 8000 rpm for 2 min, and washed three times with 10 mM MgCl2. Finally, the bacterial culture was diluted with 10 mM MgCl2 to an OD 600 value of 0.3. Bacterial cultures containing pCAMBIA1300-FLAG:GFP, pCAMBIA1300-FLAG:INF1, and pCAMBIA1300-FLAG:EPI7 were mixed 1:1 with Agrobacterium GV3101 culture (OD 600 = 0.3) containing the plant gene silencing repressor p19 protein of tomato dwarf virus (which can significantly enhance the transient expression efficiency of the target gene). All gene combinations were injected into leaves of *Tobacco Benedict* using a 1 mL syringe, ensuring 100 μL of each combination was injected. Leaf phenotype was observed for 7 days to determine if a significant hazard ratio (HR) was observed. Each combination was repeated in five replicates, and the experiment was repeated three times. The results are shown below. Figure 1 As shown in the figure, the pCAMBIA1300-FLAG:GFP group served as the negative control, while the pCAMBIA1300-FLAG:INF1 group served as the positive control. It is evident that the EPI7 gene can elicit an HR response.

[0031] 2.3 Detection of resistance to Nicotiana benthamiana with transient expression of pCAMBIA1300-FLAG:EPI7 protein Leaves expressing the confirmed protein were cut and placed in a filter paper-insulated tray. Holes were punched along the edge of the *Phytophthora capsici* LT263 agar plate using a 7 mm punch, and the fungal discs were placed symmetrically on either side of the *N. benthamiana* leaves, mycelial side down. The trays were placed in a 25°C incubator in the dark for 36 h. The leaves were then removed and irradiated with UV light. The areas that darkened in color were the *Phytophthora capsici* infection areas. The area of ​​the infection area was measured with a ruler. Leaves expressing pCAMBIA1300-FLAG:GFP protein served as controls. The effect of EPI7 protein on resistance in *N. benthamiana* was compared. Results are as follows: Figure 2 As shown, Figure 2 The left image shows a Tobacco Benedict leaf infected with Phytophthora capsici. The area of ​​the Phytophthora capsici infection zone, where pCAMBIA1300-FLAG:EPI7 protein was injected, is 125 mm². 2 In the control group, the infection area of ​​Phytophthora capsici was 221 mm². 2 ; Figure 2 The right side shows the statistical results of lesion area for 15 replicates of Agrobacterium-induced disease resistance phenotypes, which ultimately verified that the EPI7 protein from *Hylocereus huanghuaiensis* significantly improved the resistance of *Nicotiana benthamiana* to *Phytophthora capsici*.

Claims

1. An EPI7 protein from *Cyclocarya paliurus*, characterized in that, The amino acid sequence of the EPI7 protein of *Cyclocystis huanghuaiensis* is shown in SEQ ID NO.

2.

2. The nucleic acid or gene encoding the EPI7 protein of *Cyclocarya paliurus* as described in claim 1, characterized in that, The nucleotide sequence of the nucleic acid or gene is shown in SEQ ID NO.

1.

3. An expression cassette, recombinant expression vector, transgenic cell line, or transgenic recombinant bacterium containing the nucleic acid or gene of the Huanghuai Coccidioidomyces EPI7 protein as described in claim 2.

4. The method for constructing the recombinant expression vector according to claim 3, characterized in that, The expression vector was obtained by introducing the gene encoding the EPI7 protein of *Hylocereus huanghuaiense* into the plant expression vector pCAMBIA1300-FLAG.

5. The construction method according to claim 4, characterized in that, The nucleotide sequences of the primers used in the construction of the expression vector are shown in SEQ ID NO.3~4.

6. The transgenic recombinant bacteria according to claim 3, characterized in that, The recombinant expression vector described in claim 3 was inserted into Escherichia coli, and transgenic recombinant bacteria were obtained by screening.

7. The transgenic recombinant bacteria according to claim 6, characterized in that, The Escherichia coli were DH5α competent cells.

8. The use of the EPI7 protein of *Cyclocarya paliurus* as described in claim 1, the nucleic acid or gene as described in claim 2, the expression cassette, recombinant expression vector, transgenic cell line, or transgenic recombinant bacteria as described in claim 3 in the preparation of reagents for inducing plant allergic reactions.

9. The application of the EPI7 protein of *Hylocereus huanghuaiense* as described in claim 1, the nucleic acid or gene as described in claim 2, the expression cassette, recombinant expression vector, transgenic cell line, or transgenic recombinant bacteria as described in claim 3 in the preparation of reagents to enhance plant resistance.

10. The application according to claim 9, characterized in that, The improvement of plant resistance refers to enhancing the plant's resistance to infection by Phytophthora capsici.

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