Identification Of New Genes Conferring Susceptibility To Bacterial Leaf Streak In Rice(Oryza Sativa L.)

Rice（Oryza sativa L.）is a staple food for one third of world’s population and its production faces constant threats from biotic stresses.Among biotic stresses,bacterial diseases,bacterial leaf blight（BLB）and bacterial leaf streak（BLS）are devastating diseases conferring significant yield losses to rice production.BLB is caused by the vascular pathogen Xanthomonas oryzae pv.oryzae（Xoo）,while the etiological agent of BLS is a mesophyll invader named Xanthomonas oryzae pv.oryzicola（Xoc）.The identification and utilization of resistance genes against these bacterial diseases offer an efficient and environmentally sustainable solution to mitigate yield losses in rice production.Unfortunately,resources for resistance genes are scarce,and implied resistance has become ineffective over time.Pathogenomics of Xoo and Xoc largely depends on targeting susceptibility（S）genes in the rice genome.The transcriptional activation of S genes by bacterial virulent Transcription activator-like effectors（TALEs）often serves as a bootstrap for transporting nutrients to leaves,which are then hijacked by pathogenic bacteria for their proliferation and survival in planta.In the present dissertation we reported genome editing the S gene Os SULTR3;6 provides resistance against Xoc,identifies four hypervirulent strains（HVS）of Xoc,reports the presence of distinct TALEs in HVS and identification of natural variation resistant allele from a 3000-rice germplasm.Salient findings of experiments are following:The effector binding element（?EBE）and knockout mutant（?CDS）plants confer resistance againstXoc strains that dependent on Tal BF for virulence.Four virulent strains（AHB4-205,YNB01-3,JSB5-2,HNB16-100）remained virulent and were subjected to whole genome sequencing.Designer TALEs were used to induce sulfate and molybdate transporter genes,revealing new potential susceptibility supporter genes.Os SULTR3;5,Os SULTR2;1,Os SULTR1;1,and Os SULTR5;1 contribute to susceptibility to BLS when artificially induced in TALE dependent manner.Indica III cultivars exhibit a unique deletion in the entire?EBE_{Tal BF} region,with only 47 out of nearly4500 genomic sequenced cultivars showing this variation.Inoculation of these cultivars with Xoc strain RS105 demonstrates significantly enhanced resistance compared to Nipponbare.Haplotype network analysis of Os SULTR3;6 revealed four distinct haplotypes groups.Interestingly,99%of?EBE_{Tal BF}cultivars belong to the Indica-III subspecies,originating from the Southeast Asian region,including Myanmar,Thailand,Laos,Indonesia,and Malaysia.The hypervirulent Xoo strain NE-8,isolated from northeastern China,evolved recently from Korean and Japanese strains（K3a and JP01）,with a complete genome and plasmid.The plasmid encodes the essential Vir B gene,suggesting a significant role of genetic plasmids in transferring material among diverse Xoo strains,particularly through the Type IV secretion system.