Screening And Functional Analysis Of The Host Target Of Phytophthora Sojae Effector Avh238

Phytophthora sojae belongs to the Chromista Oomycetes Phytophthora, which is an aggressive pathogen causing root rot on soybean, is able to infect and kill soybean plants throughout much of the growing season. During the long-term interaction process between Phytophthora sojae and host plant, Phytophthora sojae deliver kinds of extracellular effectors into the plant cell to help itself promote infection, while plant generates resistance by resistance genes recognizing the effectors. So understanding the mechanism of plant disease resistance interfered by effects, and clearing pathogenic ways and the target site in the host plant, can effectively provide new ideas and direction of disease prevention and control strategies, and be of important significance to design and improve disease resistance.Most RxLR effectors go into plant cells freely, their targets of host cells maybe various components of plant defensing signal pathways. The effects are collaborative interaction to play maximum toxicity, regulate itself to infect plant cells, damage plant defense response, and cause diseases.Avh238plays an important role in the process of Phytophthora infecting host plant. On the functional analysis, Avh238can inhibit the Phytophthora elicitors INF1triggered PCD, and also can inhibit MKK1and NPK1mediated plant immune responses which are MAP kinases of PAMP downstream signaling pathways, it is the main member of destroying plant immune responses and promoting infection. so, according to research on the interaction between Avh238and host plant, we can apply important provement to reveal the way of Phytophthora sojae causing plant disease.The experiment is to screen the target of Avh238in the soybean library by using yeast two-hybrid assays and succeed to get one gene interact with Avh238.The positive clone is encoded by phenylalanine ammonia lyase (PAL) gene. As one of the most important enzymes in the phenylpropanoid pathway, the activity of PAL is related to the plant disease resistance closely. Silencing PAL leads to enhance the infecting capability of Phytophthora capsici.In order to evade the recognition of plant, there are rich sequence polymorphism in different species. we use different experiments in vitro and vivo to verify the interaction between Avh238P7076and PAL. We get consistent results that they can indeed interact with each other, which illustrate that the inter-specific variability does not affect the interaction between them. By constructing different mutants, we find the critical region in the interaction is consist of82-122amino acids of Avh238. Meanwhile, the interaction would be disrupted if deleting the phosphorylation sites of PAL including195-202amino acids. We speculated that Avh238perform its virulent function through inhibition of PAL’s phosphoric sites and destroy signaling pathways of disease resistance, followed by preventing the plant defense. PAL mediated signal pathway does not affect ETI triggered by Avh238from the P6497(race2) strains while expressing Avh238in the tobacco of silencing PAL. We hypothesized that the host toxicity target of Avh238is PAL. Avh238recoganized by plant can cause cell death and the medium way is through the MEK2and the Ga related pathways.