The Function Of Transcription Factor OsMYC2 And Its Effect On Rice Resistance To Brown Planthopper

The transcription factor myelocytomatosis proteins(MYCs)are activating transcription factors in the response pathway of jasmonic acid(JA)in plants.They are widely found in animals and plants.MYC2 belongs to the family of bHLH and it is the most thoroughly studied of the current MYC transcription factors.With the deep study of plant resistance to biotic stress,the defense function of MYC2 has been reported.It was found that the exogenous ABA enhanced the expression of MYC2,a transcription factor in Arabidopsis,and improved insect resistance.In our previous study,we found that exogenous ABA treatment enhanced rice resistance to BPH.Does exogenous ABA treatment affect the expression of OsMYC2,thus affecting rice resistance to BPH?In this paper,we screened out rice transcription factor OsMYC2,analyzed its structure and function by bioinformatics,and further constructed a recombinant vector for directional mutation of OsMYC2 by CRISPR/cas9 technology.The vector was used to genetically transform rice ZH11,the transformed plants were screened and identified,and the mutant plants of rice gene were obtained.We detected the resistance of mutant to BPH,and studied transcriptome analysis in rice after BPH feeding,which provide a new exploration for rice control.The results are as follows:1.The screening,spatiotemporal expression and bioinformatics analysis of transcription factor OsMYC2After ABA treatment for 12 h and 48 h,the expression of OsMYC2 increased significantly compared with the control group,and OsMYC2 decreased compared with the control after ABA treatment for 24 h.The spatiotemporal expression of OsMYC2 was further detected,and it was found that OsMYC2 was expressed in the measured rice tissues at different stages,and the highest expression was found in the leaf sheaths at seedling stage,followed by the leaves at tillering stage.The expressions of leaf sheaths at seedling stage and leaves at tillering stage were significantly higher than other tissues at the same time.Domain analysis,tertiary structure prediction,phylogenetic tree construction and homologous alignment of protein sequences were completed,and the structure and evolutionary information of OsMYC2 were understood.2.Construction of osmyc2 mutants by CRISPR/cas9 and over expressed plantsThe rice osmyc2 mutants was constructed by using CRISPR/Cas9 technology,five hybrid lines and one homozygous line were found by T0 generation sequencing,but the homozygous mutants did not receive the seeds.After T1 generation seeds were propagated,T2 generation seeds were harvested and identified again.Line 1 mutant with 1 bp base change and line 2 mutant with 7 bp base reduction were screened out.The overexpressed osmyc2 strain rice was constructed.3.Identification of insect resistance with osmyc2 mutantAfter feeding on BPH,the mutants had higher average damage level and greater function loss index than the control,the N4 wave time of Line 1 and Line 2 in phloem was significantly longer than that of the control,Line 1 was more attractive to BPH.After feeding on BPH,Indole-3-aceticacid(IAA),Zeatin(ZT)and Salicylic acid(SA),which are related to the tolerance of rice,decreased significantly,and 1-aminocyclopropane-l-carboxylic acid(ACC),which is related to the avoidance of WT,increased significantly,but there was no significant change in the two mutants before and after BPH feeding,indicating that the transcription factor OsMYC2 may be a positive regulator of rice regulation and defense against BPH.4.Transcriptome analysis of osmyc2 mutant after BPH feedingThe analysis of transcriptome data showed that there were 1088,1150 and 1428 genes differentially expressed in WT,Linel and Line2 after BPH treatment,respectively.Comparison among rice lines,there were 3114 and 646 genes differentially expressed in Linel and line2 compared with WT,and 3071 and 1267 genes differentially expressed in Line1+BPH and Line2+BPH compared with WT+BPH.The enrichment analysis of GO and KEGG pathway showed that OsMYC2 was involved in phenylpropane metabolism pathway,and could positively regulate defense related metabolites such as flavonoids and lignin,and also participate in terpenoid metabolism pathway,and positively regulate diterpenoid metabolites.In addition,we found that many disease resistant genes were differentially expressed in knock-out mutants,which indicated that OsMYC2 is an important factor in the regulation of defense response of rice related genes was a regulation induced rice related genes form important factors of defense response.