Functional Characterization Of DLT In Rice Disease Resistance And Mechanism Of Rice Susceptibility Genes Hijacked By TALE-carrying Xanthomonas Oryzae

Rice,as a staple food for more than half of the population,is one of the three major food crops in the world.Rice diseases,such as leaf blight,rice blast,rice false smut,and sheath blight,cause a certain threat to the normal growth and harvest of rice.Especially in recent years,the increasingly serious rice false smut,not only affects the rice yield,but also produces harmful toxins to human and animals,and poses a certain threat to food security.Therefore,it is of great theoretical significance and practical value for rice breeding to excavate excellent disease-related genetic resources continuously.It’s reported that GRAS family members had important functions in rice plant architecture.DLT,a special member of GRAS family,has been reported to play an important role in regulating the angle of the leaves of the plant,but it is very little known in plant disease resistance.The mutant dlt-1 increased the rice susceptibility to the false smut significantly,cytological examination showed that the filaments of mutant dlt-1 were observed to be infected easily and quickly.The programmed cell death（PCD）related genes,the secondary wall synthesis related genes and the pathogenesis-related protein（PR）genes were induced after inoculation with the Villosiclava virens（Vv）.Overexpression of DLT enhanced the resistance to rice false smut than the wild type.The above results indicated that DLT gene positively regulate the resistance of rice to the false smut,which might be achieved by regulating the expression of genes related to cell wall synthesis and immunity.DLT also negatively regulated the leaf blight,bacterial stripe and rice blast.Through yeast two hybrid screening,we found that DLT interacted with HTA713,one of the histone variants H2A.Z.This interaction was in the nucleus verified with BIFC experiment.Knock-down and knock-out of the HTA713 enhanced rice resistance to the bacterial blight and rice blast.Overexpression of this gene significantly enhanced the susceptibility to the bacterial blight and rice blast.dlt/HTA713-oe and DLT-oe/hta713 hybrid materials showed resistance to Xanthomonas oryzae pv.oryzae between male parent and female parent.These results suggest that DLT together with HTA713 negatively regulated the leaf blight and rice blast.In addition,DLT also together with HTA713 positively regulated the rice false smut.After analyzing the CHIP-seq data and RNA-seq data,it’s found that WRKY transcription factor,glycosyl hydrolase and glucosyltransferase play an important role in the response of rice false smut.Many Xanthomonas bacteria use transcription activator-like effector（TALE）proteins to activate plant disease susceptibility（S）genes,and this activation contributes to disease.We recently reported that rice basal transcription factor IIA gamma subunit,Os TFIIAγ5,is hijacked by TALE-carrying Xanthomonas oryzae infecting the rice.In this study,We found that most of the amino acid mutations in the Os TFIIAγ5 gene encoding region of the 3024 rice varieties were at the thirty-ninth amino acids from valine（V）to glutamate（E）(Os TFIIAγ5^V39E).Complementation and overexpression of Os TFIIAγ5^V39D,Os TFIIAγ5^V39A,Os TFIIAγ5^V39L,Os TFIIAγ5^V39Qenhanced rice susceptibility to Xoo and Xoc in wild type IRBB5.Cs TFIIAγcan interact with the TALE of Xoo and overexpression of Cs TFIIAγsignificantly enhanced rice susceptibility to Xoo and Xoc in IRBB5.Overexpression of Cs TFIIAγ^V39E had no influence to rice resistance.The results suggested that Os TFIIAγ5^V39E is the core mutant site for escaping the hijack of TALE,This mechanism has guiding significance for rice resistance.At the same time,TAL effector gene of Xanthomonas bacteria has the same mechanism in other crops,which has reference value for another crops resistance and breeding.