Corn gene ZmSCRM2 and application

Abstract

The invention belongs to the field of plant molecular biology, and relates to a corn gene ZmSCRM2 and application, and the nucleotide sequence of the corn gene ZmSCRM2 is shown as SEQ ID NO.3. The invention also relates to a preparation method of the corn gene ZmSCRM2. The invention provides the corn gene ZmSCRM2 which has important practical significance for cultivating new varieties of crops with strong stress resistance and agricultural production, and the application of the corn gene ZmSCRM2.

Description

Technical Field

[0001] The invention belongs to the field of plant molecular biology, relates to a gene and an application thereof, and in particular to a corn gene ZmSCRM2 and an application thereof. Background Art

[0002] Corn is an important food crop, cash crop and feed crop in my country and even in the world. Stomata are important "gateways" for plants to exchange gases with the outside world. Unlike other epidermal cells, stomatal guard cells have unevenly thickened and repeatedly retractable cell walls. The opening and closing of stomata give leaves more efficient photosynthesis and water use efficiency, making plants more adaptable to extreme growth environments. The latest research results show that increasing WUE by regulating stomatal development and stomatal movement has become an important way to enhance plant drought resistance. Therefore, studying the stomata of Poaceae plants, especially understanding the structure, development process and regulatory network of the stomatal complex of corn and rice, has important application value in creating new varieties of drought-resistant and heat-resistant crops.

[0003] In monocots such as corn, there are few studies on the molecular mechanisms that regulate stomatal development and morphology, and in-depth exploration and excavation are urgently needed. Unlike dicot stomata, monocot stomata, especially grass stomata, have typical subsidiary cells (SC). Through this unique stomatal complex, monocots can respond quickly to changes in the external environment, greatly improving photosynthesis and water use efficiency. In grass plants represented by Brachypodium distachyon, rice (Oryza sativa L.) and corn, the cell lines in the process of stomatal development mainly include 6 types: stomatal initiation cell row (Stomatal file), GMC, GC, SLGC, subsidiary mother cell (SMC) and SC. A part of the cells with stem cell activity in the early leaf primordium acquire the fate of stomatal cells, and through unequal division, produce GMC and a large cell; the large cell differentiates into SLGC, and GMC induces the epidermal cells on both sides to differentiate into SMC; SMC undergoes an unequal division to produce SC and a large cell, and the large cell develops into epidermal cells; then GMC undergoes an equal division to form a pair of GC, and GC and SC eventually differentiate to form a mature four-cell stomatal complex.

[0004] Studying stomatal development is of great significance for revealing basic theoretical scientific issues such as maintaining stem cell activity, cell division and differentiation, and improving crop stress resistance and yield. At present, little is known about the genetic regulation mechanism of stomatal development in monocotyledonous plants, especially in food crops such as corn. Summary of the invention

[0005] In order to solve the above technical problems existing in the background technology, the present invention provides a corn gene ZmSCRM2 and its application for breeding new crop varieties with strong stress resistance and having important practical significance for agricultural production.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A corn gene ZmSCRM2, characterized in that: the nucleotide sequence of the corn gene ZmSCRM2 is shown as SEQ ID NO.3.

[0008] Mutants based on the maize gene ZmSCRM2 were obtained as described previously.

[0009] The above mutants are allelic mutants of the corn gene ZmSCRM2 or allelic mutants obtained by editing the ZmSCRM2 gene using CRISPR-Cas9.

[0010] When the above-mentioned mutants are allelic mutants of the corn gene ZmSCRM2, the allelic mutants are zmscrm2-1 and zmscrm2-2; when the mutants are allelic mutants obtained after gene editing of ZmSCRM2 using CRISPR-Cas9, the mutants are 569-1, 569-2 and 569-3.

[0011] A biological material, characterized in that: the biological material comprises corn gene ZmSCRM2 or a mutant.

[0012] The above-mentioned biological material is an expression box, an expression vector, a cloning vector or an engineering bacterium.

[0013] The use of the corn gene ZmSCRM2 as described above, or the mutant as described above, or the biological material as described above in regulating plant stomatal development, improving plant stomatal density, plant drought resistance, or cultivating new drought-tolerant plant varieties.

[0014] The above plants are monocots.

[0015] The plant mentioned above is corn.

[0016] The plant drought-resistant substance or new drought-resistant plant variety seeds obtained based on the application as described above.

[0017] The advantages of the present invention are:

[0018] The present invention uses forward genetics to isolate a single gene recessive mutant, which has stomatal development defects, extremely significantly reduced stomatal density and index, breaks the arrangement pattern of one epidermal cell per stoma, and enhances the drought resistance of the plant. After a large number of experiments, the candidate gene was located and cloned, which encodes a scream-like bHLH leucine zipper protein. Therefore, the candidate gene was named ZmSCRM2 (INDUCER OF CBF EXPRESSION 2). This study genetically proved for the first time that ZmSCRM2 regulates maize stomatal development. Therefore, the present invention uses the mutant zmscrm2-1 as a research entry point to analyze the new mechanism of ZmSCRM2 regulating maize stomatal development and drought resistance. The research results will provide novel clues and a solid foundation for the study of stomatal cell fate determination in Gramineae, and provide useful guidance for the breeding of new high-yield and stress-resistant maize varieties. The present invention cloned the key gene ZmSCRM2 for stomatal morphology in corn, and for the first time analyzed the molecular mechanism of ZmSCRM2 regulating the division and differentiation of stomatal accessory cells and guard cells and the biological function of enhancing drought resistance. The present invention reveals the molecular regulatory mechanism of corn stomatal development, provides novel clues and a solid foundation for clarifying the cell fate determination and efficient water utilization of stomata in corn and other grass plants, and for cultivating new varieties of crops with strong stress resistance, which has important practical significance for agricultural production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The zmscrm2-1 mutant has abnormal stomatal phenotype;

[0020] Figure 2 This is the linkage map of the ZmSCRM2 candidate gene;

[0021] Figure 3 It is a loss-of-function mutant obtained by ZmSCRM2 gene editing;

[0022] Figure 4 is the stomatal development pattern of zmscrm2 mutant;

[0023] Figure 5 is the effect of ZmSCRM2 gene mutation on corn ears and kernels;

[0024] Figure 6 The effect of zmscrm2 mutant on drought stress tolerance. DETAILED DESCRIPTION

[0025] The present invention provides a corn gene ZmSCRM2 and its application, specifically: the present invention obtains different types of functional loss mutants by editing the ZmSCRM2 gene, deeply analyzes the editing sequence differences and gene structure, identifies excellent haplotypes, and analyzes the functions of candidate genes. The spatiotemporal expression pattern of ZmSCRM2 protein in the process of stomatal development is observed by GFP labeling, and its role in the process of stomatal division and the response of stomatal movement to drought stress are studied. The resequencing data of LY49 and zmscrm2-1 are analyzed to develop molecular markers that are closely linked to ZmSCRM2 and can be used for molecular-assisted selection of drought-resistant breeding.

[0026] In addition, the maize gene ZmSCRM2 allele variant plants provided by the present invention have different responses to external drought stress. Therefore, the drought resistance of overexpression and loss-of-function mutant strains is identified, and the superior haplotype (such as 569-1, see Figure 5 as well as Figure 6 ), hybridized and backcrossed with maize inbred lines of different genetic backgrounds, and created new germplasm materials with significantly improved drought resistance through backcrossing breeding (BC-MAS) and molecular marker detection.

[0027] The drought resistance of transgenic materials and the yield agronomic traits of transgenic materials were identified in experimental fields in arid areas, and the stability and genetic effects of the ZmSCRM2 superior haplotype under different genetic backgrounds were identified, providing new genes and new germplasm resources for the genetic improvement of corn drought resistance.

[0028] The following is a detailed description of the maize gene ZmSCRM2 and its application provided by the present invention in conjunction with the accompanying drawings:

[0029] 1 Research Materials

[0030] The pollen of the maize backbone inbred line LY49 was mutagenized with different concentrations of EMS to obtain the M1 generation of plants for self-pollination. The M2 offspring was screened and isolated to obtain the mutant strain zmscrm2-1 with stomatal development defects. The stomatal development defects, stomatal density and index were significantly reduced. Both M3 and M4 were stably inherited. The present invention uses the zmscrm2-1 mutant as the research entry point. zmscrm2-2 is a ZmSCRM2 allele mutant (genetic background is B73) ordered from the domestic EMS mutagenesis mutation library MEMD; 569-1, 569-2 and 569-3 are allele mutants of different mutation types obtained by using CRISPR-Cas9 gene editing ZmSCRM2 and transforming B104 (same as B73).

[0031] 2 Research methods, key technical means and related results

[0032] 2.1) Screening for maize mutants with stomatal development defects

[0033] The present invention screened out a stomatal development defect mutant in the EMS-induced offspring material by using the tooth synthetic resin imprinting technique, and annotated the mutant as zmscrm2-1 (inducer ofcbfexpression2-1) according to the name of the located candidate gene. Figure 1 , is the stomatal abnormality phenotype of zmscrm2-1 mutant, among which, Figure 1 A is the phenotype of wild-type LY49 and zmscrm2-1 plants; Figure 1 B and Figure 1 C is the stomatal arrangement of leaves of LY49 and zmscrm2-1 seedling plants. Figure 1 In panel C, the green asterisks mark abnormal cells that failed to develop and form stomata normally; scale bar = 100 μm. Figure 1 D shows the different types of abnormal stomata in the zmscrm2-1 mutant, among which Type A represents normal stomata, Type B lacks one side of the accessory cell stomata, Type C lacks both sides of the accessory cell stomata, Type D lacks the accessory cells and the guard cell development is arrested, Type E lacks the accessory cells and the guard cell division is abnormal, and Type F indicates guard cells that cannot mature normally; scale bar = 50 μm. Figure 1 E is the reduced plant height of zmscrm2-1; Figure 1 F is the reduced chlorophyll content in zmscrm2-1; Figure 1 G is the stomatal density and Figure 1 H is the decrease in stomatal index; Figure 1 I is the frequency statistics and analysis of different types of abnormal stomata in zmscrm2. Data are mean ± standard deviation. T-Text was used for significance analysis (**P < 0.01, ***P < 0.001). In the control LY49, the stomata were arranged in a linear pattern, with one epidermal long cell between each stomata. Mature stomata were composed of two "dumbbell-shaped" guard cells (GC) and two "triangular" secondary guard cells (SC) on both sides ( Figure 1 B and Figure 1 Compared with the control, the stomatal density and stomatal index of the mutant leaves were significantly reduced, and a variety of stomatal abnormalities were produced, mainly including: single SC deletion ( Figure 1 D's Type B), 2 SC deletions ( Figure 1 D's Type C), GMC developmental arrest ( Figure 1 Type D of D), GMC divides multiple times to form small cell clusters ( Figure 1 D's Type E) and GC cannot specialize to form mature stomata ( Figure 1 Type F of D). Statistics of pores of different shapes show that Figure 1 Type D has the highest abnormal frequency ( Figure 1 D and Figure 1 I), indicating that this gene functions at all stages of stomatal development and mainly regulates GMC differentiation ( Figure 1 B. Figure 1 C and Figure 1 D). In addition, the mutant had reduced plant height and ear height at the seedling and mature stages, yellow leaves, and reduced total chlorophyll content ( Figure 1 A, Figure 1 E and Figure 1 F).

[0034] 2.2) Construction of BC2F2 genetic segregation population

[0035] In the previous study, the F1 generation phenotypes were all wild type after the zmscrm2-1 positive and negative cross test, and the stomatal defect phenotype of the F2 offspring was basically in line with Mendel's law of segregation of 3:1 (wild type: mutant). The results showed that the mutation was caused by a single gene recessive mutation. zmscrm2-1 was backcrossed with the inbred line LY49 for 2 generations, the mutant gene was purified, and the zmscrm2-1 BC2 material was obtained. The BC2 offspring were used for phenotypic identification and genetic population construction. zmscrm2-1 was hybridized with another ecotype inbred line B73, and the F1 generation was selfed again to construct a BC2F2 large segregation population. The zmscrm2-1 homozygous strain was isolated from the F2 generation for locating the candidate gene ZmSCRM2.

[0036] Phenotypic analysis of the forward and reverse hybridization of zmscrm2-1 with LY49 and B73 showed that all F1 plants were wild-type. The F2 genetic population was constructed by selfing of F1. Among the F2 plants, 3500 offspring were counted. The separation of plants with normal stomatal development and plants with stomatal defect phenotypes was basically 3:1. The chi-square test results showed that the zmscrm2-1 mutant gene was a single gene recessive genetic variation. The results are shown in Table 1.

[0037] Table 1 Segregation ratio of wild-type plants and mutant phenotype plants in F2 population

[0038]

[0039]

[0040] 2.3) Preliminary localization of candidate gene ZmSCRM2

[0041] The maize genome is about 2.3G, so the genomic DNA of the parents, mutants and controls were sequenced in a simple and efficient pooled manner in combination with the second-generation genome sequencing technology. According to the BSA extreme trait pooled sequencing principle, the plant DNA of the parents (3 plants) and the offspring wild type and mutants (50-100 plants of each offspring) were extracted, and the library was sequenced with a sequencing depth of 30×. After obtaining the sequencing results, the B73 genome sequence was used as a reference. For each SNP, the empirical Bayesian method was used to estimate the conditional probability that there was no recombination between the SNP marker and the gene in the mutant library, given the specific count of the SNP allele. The SNP-index in the interval was significantly higher than the expected SNP site, which was determined as a candidate gene site, and the candidate gene ZmSCRM2 was preliminarily determined to be located near the peak site of chromosome 4.

[0042] See also Figure 2 , is the linkage map of the ZmSCRM2 candidate gene, where Figure 2 A is the result of BSA-seq linkage analysis of candidate genes, and the blue dots are SNP-index or InDel-index; Figure 2 B is the fine positioning of candidate genes in the Bin 4.04 interval; Figure 2 C is a simplified diagram of the alignment of the zmscrm2-1 candidate gene with the B73 reference genome sequence. The red line indicates a single base mutation, and the white area represents the CDS sequence 635-654bp, where there is a 19-base deletion, resulting in a frameshift mutation. In order to clone the mutant gene, the BSA-seq principle was used to sequence the F2 progeny and parental DNA, and the SNP and InDel association analysis was performed using the MutMap method (github.com / YuSugihara / MutMap). The sequencing results gave the candidate gene interval range ( Figure 2 A).

[0043] 2.4) Fine mapping of candidate gene ZmSCRM2

[0044] By combining whole-genome high-throughput sequencing technology with map-based cloning technology, using SSR, InDel, RFLP and other molecular markers (Markers) from different types of DNA libraries in the positioning area, PCR amplification was used to identify the homozygous genotype of the offspring and calculate the chromosome recombination exchange rate. The smaller the exchange rate, the tighter the linkage between the mutant gene and the marker, and the closer the candidate gene is to the marker with a low exchange rate. Genetic mapping and physical mapping methods were used to locate the candidate gene at a specific position on the chromosome. Combined with the shared information of the maize genome database, all genes in the interval were sequenced and verified, and the changes in the gene sequences of LY49 and zmscrm2-1 were detected.

[0045] Further fine positioning located the candidate gene mutation site between umc1607 and umc2206 on chromosome 4 (e.g. Figure 2 B). Develop new molecular markers, separate and identify the genotypes of about 2,100 F2 phenotype homozygous mutants, and finely locate the candidate gene between markers M122 and M125, about 1.6Mb. All genes in the interval were sequenced, and it was found that in zmscrm2-1, the gene numbered Zm00001d049294 (the nucleotide sequence of Zm00001d049294 is shown in SEQ ID NO.1) had a 19bp base deletion in the first exon, causing a frameshift mutation ( Figure 2 C, as indicated by a black arrow), the amino acid sequence encoded by the gene numbered Zm00001d049294 is shown in SEQ ID NO.2. This gene encodes Scream-like bHLH transcription factor 2, so the candidate gene was determined and named ZmSCRM2. The nucleotide sequence of ZmSCRM2 is shown in SEQ ID NO.3. The amino acid sequence encoded by the candidate gene ZmSCRM2 is shown in SEQ ID NO.4.

[0046] 2.5) Obtaining zmscrm2-2 allele mutants and identifying phenotypes

[0047] Using reverse genetics, an allelic variant mutant was obtained from the domestic MEMD (Maize EMS induced Mutant Database) mutant library and named zmscrm2-2. The mutation form is that the 1009th base of the CDS sequence of the ZmSCRM2 gene changes from C to T, resulting in the 337th amino acid changing from R (arginine) to W (tryptophan). The phenotype of zmscrm2-2 is similar to that of zmscrm2-1, with defects in the stomatal development pattern, and the plants also show yellow leaves throughout the seedling stage. zmscrm2-2 was hybridized with zmscrm2-1, and the phenotype of the F1 representative was detected. The yellow phenotype and stomatal development defect phenotype of the plant were consistent with those of the parents. Therefore, genetic evidence shows that the abnormal stomatal development is indeed caused by the mutation of the ZmSCRM2 gene.

[0048] 2.6) Elucidate the biological function of the candidate gene ZmSCRM2

[0049] The candidate gene ZmSCRM2 was edited using CRISPR / Cas 9 technology to construct a target gene editing vector and its overexpression vector, which were genetically transformed into maize inbred lines (B104 was used as the transgenic maize receptor material, and the maize genetic transformation vector was completed by Beijing Bomeixingao Technology Co., Ltd.), and 15 offspring materials including positive transgenic lines 569-1, 569-2 and 569-3 were obtained. The homozygous phenotype was identified, and the stomatal development was abnormal, and the stomatal density was significantly lower than that of the control. Therefore, the biological function of the candidate gene ZmSCRM2 in regulating stomatal development was determined. Different strains of transgenic offspring were treated with external drought stress to screen transgenic lines with enhanced drought resistance. Molecular biological research methods such as genetics, cytology, and transcriptomics were used to clarify the relationship between the candidate gene ZmSCRM2 regulating stomatal development, water use efficiency and drought resistance.

[0050] The present invention uses CRISPR-Cas9 tools to create gene-edited mutant materials and obtain 20 transgenic offspring strains. The transformation material is the inbred line B104. The transgenic offspring are phenotypically identified and genotypically tested. The transgenic strains have rich site variations, and the base fragments near ATG are missing, resulting in frameshift mutations ( Figure 3 A). Three homozygous plant progenies, 569-1, 569-2 and 569-3, were selected for phenotype identification. The yellowing and stomatal defect phenotypes of the plants were similar to those of zmscrm2-1 and zmscrm2-2. The stomatal density and stomatal index decreased to varying degrees, and the number of stomatal rows decreased significantly ( Figure 3 B to Figure 3 H). Therefore, the genetic evidence of the same phenotype in the hybrid F1 generation and the similar phenotype of the allelic mutant created by gene editing fully prove that ZmSCRM2 plays a vital role in regulating the stomatal morphology of maize. Figure 3 , is a loss-of-function mutant obtained by ZmSCRM2 gene editing, in which, Figure 3 A is the location of the ZmSCRM2 gene editing target site and the genotype sequencing of allelic mutants 569-1, 569-2, and 569-3; Figure 3 B is wild type corn and Figure 3 C to Figure 3 E is the stomatal distribution diagram of the leaves of the allelic mutant offspring of gene editing. Scale bar = 100 μm. Figure 3 F is the reduced stomatal density in the gene-edited offspring; Figure 3 G is the reduction of stomatal index in gene-edited offspring; Figure 3 H is the statistics and analysis of the number of stomatal rows, and the data are mean ± standard deviation. T-Text was used for significance analysis (*P < 0.05, **P < 0.01, ***P < 0.001).

[0051] 2.7) Observation of cell morphological changes in zmscrm2 mutants

[0052] In order to trace how the stomatal development defects of zmscrm2 mutants are generated, the stomatal development process was observed. In the control material B73, the stomatal primordium cells first undergo an unequal division to produce early guard mother cells (GMCs). After the GMCs mature, they induce the secondary mother cells (SMCs) on the side to undergo unequal division to produce SCs. Subsequently, the GMCs undergo an unequal division to produce GCs, which further differentiate into mature stomata ( Figure 4 A and Figure 4 B) Stomatal cells in zmscrm2-1 and zmscrm2-2 can undergo unequal division to form early GMCs ( Figure 4 C and Figure 4 D i-ii), but there is an obvious defect in the process of GMC inducing adjacent SMCs to divide and form SCs, and most SMCs fail to divide normally, resulting in the loss of some SCs ( Figure 4 C and Figure 4 ii-iii in D, indicated by arrows); subsequently, during the process of GMC equal division to form GC, most of the stomata of zmscrm2-1 and zmscrm2-2 remained stagnant at the GMC stage ( Figure 4 C and Figure 4 In addition, during GC maturation, some GCs in zmscrm2-1 and zmscrm2-2 were stagnant and could not form normal pore structures ( Figure 4 C and Figure 4 D iv-v, indicated by arrows), therefore, it is inferred that ZmSCRM2 plays a key role in the formation of SC and GC in stomata. Figure 4 , is the stomatal development diagram of zmscrm2 mutant, where Figure 4 A is a diagram of the stomatal development model of monocotyledonous plants. The stomatal development process of monocotyledonous plants is divided into five stages: i is the cells in the protodermis stage determine the identity of the stomatal lineage cells; ii is the stomatal lineage cells undergo an unequal division and develop into GMCs; iii is the GMC recruits the adjacent SMCs to undergo unequal division to form SCs, a three-cell complex of the stoma; iv is the GMC undergoes equal division to produce two GCs, a four-cell complex; v is the formation of small holes in the middle of the guard cells, and the stomatal development matures, refer to (Raissig et al., 2016) Figure 4 B is wild type and Figure 4 C and Figure 4 D is the stomatal development process of zmscrm2 mutant.

[0053] 2.8) Using the BC-MAS method to evaluate the breeding value of superior haplotypes

[0054] The drought resistance of alleles of candidate gene ZmSCRM2 at different sites was detected, and the best haplotypes with the strongest drought resistance were selected. The haplotypes were introduced into different genetic background materials (such as maize variety Xianyu 335 maternal inbred line PH6WC, Zhengdan 958 maternal inbred line Zheng 58, etc.) using the BC-MAS method to analyze the genetic effect of ZmSCRM2 and evaluate the application value of alleles in drought resistance breeding. Figure 5 The stomatal density of zmscrm2-1 and zmscrm2-2 was significantly reduced, and the leaves were very yellow, which was a strong phenotypic mutation, resulting in the undesirable traits of smaller ears and grains in the mutants ( Figure 5 B and Figure 5 C); while the allelic mutants 569-1 and 569-2 created by CRISPR–Cas9 gene editing had similar phenotypes of leaf yellowing and reduced stomatal density, but had no significant effect on the cob and grain traits, belonging to the weak mutation type ( Figure 5 A). The characteristics of the ear of natural pollination were counted. Compared with the control, there was no significant difference in the weight of a single ear and the number of rows of the 569-1 and 569-2 edited offspring mutants ( Figure 5 D and Figure 5 E). Therefore, ZmSCRM2 may be an important gene resource for breeding new drought-resistant maize varieties. Figure 5 middle, Figure 5 A is the naturally pollinated ears of zmscrm2 gene-edited mutants 569-1, 569-2 and 569-3 in the B104 background, scale bar = 10 cm. Figure 5 B) and B73 background ( Figure 5 C) The kernels of zmscrm2 mutants are smaller, scale bar = 5 cm. Figure 5 D) and ear row number ( Figure 5 E) There was no significant change, and the significance analysis was performed using t-text.

[0055] The stomatal density and index of zmscrm2 were significantly reduced, and it was speculated that the stomatal phenotype may be closely related to plant drought resistance. Therefore, in order to further explore whether ZmSCRM2 regulation of stomatal development is related to adverse stress, zmscrm2-1, zmscrm2-2 and gene-edited homozygous plants 569-1, 569-2 and 569-3 were subjected to drought treatment. The results showed that zmscrm2-1 and its allelic variant mutants showed stronger tolerance to drought stress ( Figure 6AC). The reduction in stomatal density may lead to reduced water loss in plants, weakened transpiration and photosynthesis, and enhanced drought resistance of plants. The physiological indicators of the control group and mutants under drought stress, such as transpiration rate, net photosynthetic rate, and stomatal conductance, were measured. Compared with the control group, it was found that the transpiration rate of the zmscrm2 allele mutant was reduced, and the difference was extremely significant ( Figure 6 D); The leaves of zmscrm2 mutants turned yellow, the chloroplast content was significantly reduced, and the net photosynthetic rate of alleles was reduced, with significant differences ( Figure 6 E); stomatal conductance also decreased significantly ( Figure 6 F). Therefore, the ZmSCRM2 gene not only affects stomatal development, resulting in a decrease in stomatal density and stomatal index, but also improves the plant's tolerance to drought stress. This will provide an important theoretical basis, excellent germplasm and gene resources for breeding new drought-resistant corn varieties in production. Figure 6 , is that the tolerance of zmscrm2 mutant to drought stress is significantly enhanced, among which, Figure 6 A to Figure 6 C respectively shows that under drought stress, different alleles of zmscrm2 mutants are more drought tolerant than the wild type. The transpiration rate ( Figure 6 D) Net photosynthetic rate ( Figure 6 E) and stomatal conductance ( Figure 6 F). Data are mean ± SD. T-Text was used for significance analysis (*P < 0.05, **P < 0.01, ***P < 0.001).

Claims

1. A maize gene ZmSCRM2, characterized in that: The nucleotide sequence of the corn gene ZmSCRM2 is shown in SEQ ID NO.

3.

2. A mutant obtained based on the maize gene ZmSCRM2 according to claim 1.

3. The mutant according to claim 2, characterized in that: The mutant is an allelic mutant of the corn gene ZmSCRM2 or an allelic mutant obtained by editing the ZmSCRM2 gene using CRISPR-Cas9.

4. The mutant according to claim 3, characterized in that: When the mutant is an allelic mutant of the corn gene ZmSCRM2, the allelic mutants are zmscrm2-1 and zmscrm2-2; when the mutant is an allelic mutant obtained by gene editing ZmSCRM2 using CRISPR-Cas9, the mutants are 569-1, 569-2 and 569-3.

5. A biomaterial, characterized in that: The biological material comprises the mutant according to claim 2 or 3 or 4.

6. The biomaterial according to claim 5, characterized in that: The biological material is an expression cassette, an expression vector, a cloning vector or an engineering bacterium.

7. Use of the maize gene ZmSCRM2 according to claim 1, or the mutant according to any one of claims 2 to 5, or the biological material according to claim 6 in regulating plant stomatal development, improving plant stomatal density, plant drought resistance, or cultivating new drought-tolerant plant varieties.

8. The use according to claim 7, characterized in that: The plant is a monocot.

9. The use according to claim 8, characterized in that: The plant is corn.

10. Plant drought-resistant substances or seeds of new drought-resistant plant varieties obtained based on the application of claim 7, 8 or 9.

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