Functional Characterization Of The Effector Pst27791 In Puccinia Striiformis F.sp. Tritici

Wheat(Triticum aestivum L.)is an important crop for most families in China and even the world with a long history and its production quality plays an important role in ensuring world food security.Stripe rust,caused by Puccinia striiformis f.sp.tritici(Pst),is one of the most important diseases in wheat worldwide.At present,the main methods of preventing and controlling stripe rust in production are using chemical reagents or planting resistant varieties.However,stripe rust has the characteristics of rapid occurrence and frequent variation,which makes the disease resistance of wheat varieties are easy to be weakened or even lost.Previous studies have indicated that when wheat is infected by stripe rust,it secretes effectors into the wheat mesophyll cells through the haustorium,so as to regulate the host’s defense response.Therefore,it is of great significance for disease control to accelerate the research on the functions and pathogenesis of the effectors of wheat stripe rust.In this study,a candidate effector gene Pst27791 was screened from the transcriptome data of wheat leaves challenged by Pst.The full-length c DNA of Pst27791 were obtained by RT-PCR.The characteristics of the amino acid sequence encoded by the effector were analyzed.Yeast secretion system,agrobacterium mediated transient overexpression technology,real-time quantitative PCR,subcellular localization,type III secretion system(T3SS),virus-induced gene silencing technology(VIGS)and yeast two-hybrid screening were used to investigate the function of this gene.Sequence analysis indicated that the signal peptide was located in the N-terminal 1-17 amino acids of Pst27791 and its secretion function was proved by the yeast assay.Transient expression of Pst27791 in Nicotiana benthamiana can inhibit programmed cell death(PCD)induced by Bax.q RT-PCR assay showed that Pst27791 was up-regulated at the early stage of infection and reached its peak at 24 h.Subcellular localization analysis showed that Pst27791 was mainly distributed in chloroplasts of wheat protoplast.By secreting effector proteins into wheat leaves through the bacterial type III secretory system,it was found that the effector could inhibit the accumulation of callose,reactive oxygen species and necrosis in wheat.Transient silencing of Pst27791 could inhibit the growth and development of stripe rust and significantly decrease the spore production.Finally,three candidate targets from wheat were obtained by yeast double hybridization.The three candidate genes encoded cathepsin B,pyruvate dehydrogenase E1 and protein phosphatase 1,respectively.In summary,our results showed that the effector Pst27791 can suppress the host immunity and plays a virulence role in the infection of Pst.