Preliminary Functional Analysis Of OsWRKY70 Gene To Bacterial Blight And Brown Planthopper In Rice

Under natural conditions,rice are always invaded by various pathogens and suffered by pests,such as Xanthomonas oryzae pv.oryzae(Xoo),Magnaporthe oryzae,and Brown Planthopper(BPH),Chilo suppressalis(SSB),etc.The plant immune defense response signal pathway was activated After induced by pathogens and pests,the related resistance genes are expressed,and transcription factors play a very important regulatory role in this process.In this paper,we screened the defense-related OsWRKY70 transcription factor in rice,and conducted a preliminary analysis of its mechanism of action in the rice pathogen and pest resistance pathway:Based on the rice genome data in NCBI,the partial promoter and CDS sequences of OsWRKY70 were amplified from Oryza sativa L.ssp.japonica cv.Nipponbare.respectively,and the OsWRKY70::GUS and OsWRKY70-pCAMBI1300 UR expression vectors were constructed,using Agrobacterium-mediated transgenic technology to obtain the corresponding transgenic rice plants.OsWRKY70 is localized in the nucleus,and the results of dual luciferase experiments show that OsWRKY70 transcription factor can activate the expression of OsWRKY70 gene and has transcriptional activation activity.After exogenous hormone treatment,gibberellic acid(GA)could significantly induce the expression of OsWRKY70,Jasmonic acid(JA),salicylic acid(SA),Kinetin(KT),Abscisic acid(ABA),and Ethephon(ET)could slightly inhibit the expression of OsWRKY70,and KT inhibited the expression more obviously.OsWRKY70 was highly expressed in leaves and roots of rice Nipponbare,but lower in florets,flag leaves and stems;in the chemical histostaining analysis of OsWRKY70::GUS transgenic plants,The reporter gene of GUS is specifically expressed in rice meristems such as root tips,leaves,mature embryos,and florets.OsWRKY70 is a gene that is widely expressed in multiple tissues of rice and may be involved in various growth and development processes of rice plants.By analyzing the transcriptome data of OsWRKY70 overexpression transgenic plants OE6 and Nipponbare,there were 748 differentially expressed genes,359 genes were up-regulated and 389 genes were down-regulated,and GO and KEGG analysis were performed on DEGs.Through the analysis,we found that OsWRKY70 plays an important role in the growth and development of rice and the defense against pathogens and pests.By analyzing the induced expression of OsWRKY70 under the treatment of bacterial blight,it was found that the expression of OsWRKY70 was significantly induced within 12-36 h after inoculation.In the experimental treatment of OsWRKY70 overexpression plants in the field,the results showed that the lesion length of wild-type Nipponbare was significantly longer than that of OsWRKY70 overexpression plants.OsWRKY70 may positively regulate the resistance of rice to bacterial blight.Further analysis found that the expression levels of PR genes(OsPR1 a,OsPR1 b,OsPR10a)were all up-regulated in OsWRKY70 overexpressing plants.The expression of OsWRKY70 gene could be induced by brown planthopper damage treatment.There was no difference in the background level of OsHI-LOX between OsWRKY70 overexpression plants and wild-type Nipponbare,but OsHI-LOX was significantly induced in OsWRKY70 overexpression plants compared with Nipponbare after brown planthopper infestation treatment.Through dual luciferase experiments,it was found that OsWRKY70 transcription factor can activate the expression of OsHI-LOX gene.The results showed that OsWRKY70 may negatively regulate the resistance to brown planthopper in rice by inducing the expression of OsHI-LOX gene.In conclusion,OsWRKY70 may positively regulate the resistance of rice to bacterial blight and negatively regulate the resistance of rice to brown planthopper.OsWRKY70 has a regulatory role in the resistance response to bacterial infection and brown planthopper damage.