A Preliminary Study On The Pathogenic Function Of RsIA＿NP8 Secreted By Rhizoctonia Solani AG1 IA

Rhizoctonia solani AG1 IA is a pathogen that causes rice sheath blight.In recent years,rice sheath blight,as one of the three major diseases that harm rice,has become the main disease of rice in China,especially in some areas of south China,causing huge loss to rice yield in China.AG1 IA,as the first strain of the genus Rhizoctonia whose genome was sequenced,can provide a good model for the study of its pathogenic mechanism in rice.Based on previous research,this paper screens and identifies predicted small secretory protein binding transcriptome data from Rhizoctonia solani AG1 IA,and uses the agrobacterium-mediated transient expression system,we performed functional studies on effectors in R.solani AG1 IA and found that,of 11 putative effectors tested,only RsIA＿NP8 caused necrosis in the leaves of Nicotiana benthamiana.The results showed that RsIA＿NP8,a small secreted protein,but it could not cause cell death after removing the signal peptide.The function of the signal peptide was verified to confirm that the signal peptide could function normally.Sequence homology analysis showed that RsIA＿NP8 was a conserved and unique gene in Rhizoctonia solani.We performed functional analysis of different deletion mutants and point mutants,and found that the RPT1 domain and the natural mutation site RsIA＿NP8-20are necessary for the function of causing cell death.The virus-mediated gene silencing（VIGS）method was used to verify that RsIA＿NP8 was dependent on SGT1 and HSP90,but not on SERK3 and RAR1.It was strongly induced during the infection of rice variety9311 by sheath blight,and was continuously up-regulated in the early stage of infection.In addition,when it is instantaneously expressed in N.benthamiana,it can enhances the expression of defense-associated genes in N.benthamiana and lead to the accumulation of H₂O₂ and callose deposition.The results of tobacco subcellular localization showed that RsIA＿NP8 gene was located in chloroplast.The yeast two-hybrid method was used to screen the host target protein of RsIA＿NP8,at present,1candidate target gene has been preliminarily obtained.