Study On The Function Of Rxlr Effector AVH94in Phytophthora Sojae

Bioinformatics analysis indentifyied almost400candidate RxLR effector genes in the genomes of Phytophthora sojae. These effectors can be delivered into the plant cytoplasm, block plant disease resistance, improve the ability of pathogen infection, and some effector proteins also have the eliciting function. However, their targets have not been deeply researched.Mitogen-activated protein kinases(MAPKs) are the serine/threonine protein kinases in eukaryotes, they can be phosphorylated by MAPKKs and become activated, and then transfer signals by phosphorylating the serine or threonine residue of the substrate protein. MAPKs and other molecules together constitute the MAPK cascades, and this signal cascades is important for both basis resistance and R gene-mediated resistance. In the previous studies in our laboratory, we found that p. sojae effector Avh94(PsAvh94) can suppress the HR induced by NbMKKl. Thus, we speculated that this suppression is because of the interaction between PsAvh94and NbMKK1. In this article, we confirmed the interaction between them by yeast two hybrid (Y2H), GST-pull down and bimolecular fluorescence complementation (BiFC. Through futher research we silenced NbMKK1by agrobacterium-mediated PVX system and found that it become more sensitive to P. capsici. Overexpressing PsAvh94, we get the same results. Thus, we concluded PsAvh94can promote the infection of Phytophthora, And this promotion may be achieved by blocking the plant MAPK signaling pathway, then interfering with the host defense response.To further study the two functions of PsAvh94, we first predicted the structure of Avh94and NbMKK1, and as a basis designed a series of mutant. The study on NbMKK1mutants shows that NbMKK1deletion mutants can’t trigger HR in Nicotiana benthamiana, and also could not interact with the Avh94. When the ATP binding site was mutanted, we get the mutant NbMKK1K88R, which aboished the bility of inducing HR, could still interact with Avh94. This implied that he ATP binding site is not the critical sites of the interaction. On the study of Avh94, we found that the W domain is critical for both suppression and interaction function, in contrast, the RxLR motif had no effect on these two functions. And we also found that the mutant which can not interact with NbMKKl also can not suppress the cell death triggered by NbMKK1. It demonstrated these two functions is related, and it is also suggests that Avh94suppress plant immunity by blocking the MAPK signaling pathway...