Preliminary Study Of Non-TAL Effectors In Xanthomonas Oryzae Pv.oryzicola GX01

The Bacterial leaf streak of rice(BLS)is one of the most destructive bacterial diseases in rice all over the world,which poses a great threat to the quality and yield of rice.Xanthomonas oryzae pv.oryzicola(Xoc)is the pathogen of BLS in rice.Type Ⅲ secretion system is widely distributed in Gram-negative bacterial species and most plant pathogenic bacteria,and plays a very important role in the pathogenicity of plant pathogenic bacteria.Type Ⅲ effectors from Xoc can be divided into two categories:transcription activator-like effectors(TALEs)and non-transcription activator-like effectors(non-TALEs).Studies have shown that non-tal effectors play an important role in the virulence and growth of pathogens on the host and they mainly regulate the immunity of plants by using their own molecular and biochemical functions.Xoc GX01 is a highly pathogenic strain isolated and screened from diseased rice fields in Hezhou,Guangxi.Our laboratory completed the whole genome sequencing and gene annotation of Xoc GX01.25 non-TAL effectors were annotated in Xoc GX01,and then 24 non-TAL effectors mutants were constructed.We found that XopN and AvrBs2 play a decisive role in the virulence of Xoc GX01,and found the interaction between XopN and rice protein OsZK.However,the specific functions of these 25 nonTAL effectors and the pathogenic molecular mechanism of XopN are still unclear.Therefore,we conducted a preliminary exploration of the non-TAL effector function in Xoc GX01 through a series of experiments on the basis of the previous research:(1)In this study,by detecting the reactive oxygen species and programmed cell death of rice leaves infected by different strains,we found nonTAL effectors XopAA,XopAB,XopAF,XopC2,XopI,XopL,XopN,XopO,XopQ,XopR,XopU,XopX,XopY,XopZ1 may induce the production of H2O2 in rice leaves and XopAJ,XopAF,XopAK,XopC2,XopP-1,XopV may inhibit the programmed cell death of rice leaves.(2)By constructing a segmented shortened fragment of OsZK,the interaction between XopN and the 1st to 6th WD40 domain of OsZK was verified through the yeast dual hybrid system.(3)We also analyzed the rice Nipponbare transcriptome of respectively infected with Xoc GX01 and GX01ΔxopN strains,and found that the expression of 199 genes have changed significantly.Transcriptome analysis showed that Xoc GX01 may inhibit the closure of rice stomata by using XopN to suppress calmodulin-like proteins,enabling Xoc GX01 to infect rice through the stomata.And XopN may be used to promote the photosynthesis of rice to meet its nutritional needs and thus successfully reproduce in rice.In conclusion,this study lays a foundation for the further study of functions of Xoc GX01 non-TAL effectors,and also provides clues for breeding BLS-resistant rice varieties.