Analysis Of The Roles Of Xa5 And ROS1a Genes In The Control Of Resistance To Bacterial Leaf Streak In Rice

Bacterial leaf streak(BLS),caused by Xanthomonas oryzae pv.Oryzicole(Xoc),is a bacterial disease in rice.Studies have indicated that BLS resistance is quantitatively inherited in rice.Our lab previously cloned a major QTL for BLS resistance(qBlsr5a)and found that the functional gene of the QTL LOC_Os05g01710 is xa5,a major resistance gene to bacterial leaf blight.However,the mechanism of xa5 controlling BLS resistance is still unclear.In addition,our lab found that the expression of demethylase genes OsROS1 a and OsROS1 c significantly responded to Xoc infection,implying that they are probably related to BLS resistance.But this needs to be verified.In this study,the roles of xa5 and OsROS1 a in BLS resistance were investigated.The main results were as follows:(1)Identification of BLS resistance was performed on Xa5-RNAi lines and their wild-type control Minhui-86(MH86).The results showed that the former had significantly shorter lesion length than the latter,confirming that xa5 is really the functional gene of qBlsr5 a.(2)The transcriptional responses of Xa5-RNAi plants and MH86 to Xoc infection(9 h after inoculation)were analyzed by RNA-Seq.A total of 3115 and 157 differentially expressed genes(DEGs)were identified inXa5-RNAi plants and MH86,respectively,indicating that the response of the former was much stronger than that of the latter.GO analysis showed that the DEGs in the Xa5-RNAi plants were mainly enriched in the biology processes of “programmed cell death”,“defense response”,“cell death”,“apoptotic process” etc.In addition,genes for HSP,cytochrome P450,PR and some transcription factors such as WRKY,MYB and bHLH,etc.were significant upregulated.These results suggested that Xa5 might probably affect BLS resistance by directly or indirectly regulating the expression of these genes.(3)Five OsROS1a-RNAi plants were obtained by constructing the RNAi vector and transferring it into the japonica variety Nipponbare.The OsROS1a-RNAi plants showed normal vegetative growth and fertility,with increased plant height and decreased tiller number in comparison with the wild-type Nipponbare.These results suggested that the gene negatively regulates plant height but positively regulates tiller number.(4)Inoculation test showed that the OsROS1a-RNAi lines had significantly higher BLS resistance than wild type,suggesting that the gene negetively regulates BLS resistance.