Phytophthora Sojae Effector AVH331Could Suppress Mapk Based Plant Defense Signal Pathway

Phytophthora sojae causes destructive disease of soybean in the world. Oomycetes, including Phytophthora, are evolutionarily very distant from fungi and fall within the kingdom Stramenopiles, despite they share similar growth habits with filamentus fungus. Common fungicide applied in fungi can’t be used for controlling oomycetes diseases. Molecular dissection of the pathogenicity mechanism of P. sojae will contribute to develop novel disease control strategies.Function screen for phytophthora sojae effectors that could suppress plant disease resistance. Bioinformatic analysis of the draft genome sequences of P. sojae has identified an extraordinarily large superfamily of RxLR effectors (>350), and these effector are presumed to contribute to virulence. Here we carry out high-throughput screenings to identify the virulence effect of30RxLR effectors which were highly expressed during infection. First, we co-transfected these effectors with FRK1promoter-luciferase reporter gene in plant protoplasts. Next, we Analysis FRK1-LUC activity and show that sixteen effectors could suppress FRK1-LUC activity. Furthermore, we generate estrogen-triggered transgenic plants expressing effectors-FLAG on Arabidopsis to obtain evidence that three effectors Avr4/6、Avr3c、Avh331could significantly increase the colonization of plant pathogen.Avh331could suppress phytophthora elicitor induced basal defense and increase the colonization of phytophthora pathogen. We generate estrogen triggered transgenic plants expressing effectors-FLAG on Arabidopsis to obtain evidence that Avh331has the most powerful virulence to increase the colonization of plant pathogen. We further demonstrate that expressing Avh331in transgenic plant could increase the colonization of a Phytophthora pathogen. In the final part of this chapter we showed that Phytophthora elicitor could activate MAPK signal pathway to induce ROS (reactive oxygen species) burst and callose deposition, whereas Avh331could suppress Phytophthora elicitor induced ROS burst and callose deposition, suggesting that Avh331could suppress Phytophthora elicitor induced basal defense to increase the colonization of an oomycete pathogen.Avh331could suppress flg22induced plant disease resistance and increase the colonization of bacteria pathogen. We inoculate Pseudomonas syringae pv. tomato in Avh331expressing plant to obtain evidence that Avh331couldn’t significantly increase the colonization of bacteria pathogen, whereas expressing Avh331in transgenic plant could increase the colonization of Pseudomonas syringae pv. tomato DC3000hrcC mutant. It has been reported that Flg22is a PAMP of Pseudomonas syringae pv. tomato DC3000and could induce ROS burst and callose deposition in Arabidopsis through MAPK pathway. Here we show that Avh331could suppress flg22induced ROS burst and callose deposition, suggesting that Avh331could increase the colonization of bacteria pathogens by manipulating MAPK signal pathway.Effector Avh331could act downstream of MAPK pathway to suppress plant disease resistance. In the first half of this chapter, we show that Avh331could suppress the expression of resistance maker genes downstream of MAPK pathway elicited by flg22or elicitor, whereas Avh331dosen’t directly suppress MAPK kinase activity, suggesting that Avh331could act downstream of MAPK pathway to suppress plant basal defense. This hypothesis was reinforced by our confirmation that Avh331could suppress Phytophthora elicitor INF1induced basal defense through MAPK pathway. In the second half of this chapter, we clone several plant kinase:NtMEK2、SIPK、NPK1to obtain evidence that express NtMEK2DD、SIPK、NPK1could induce ROS burst and HR response, and co-express Avh331with these kinase could retain NtMEK2DD, SIPK, NPK1induced ROS burst and HR response. These results suggest that Avh331could manipulate MAPK signal pathway to increase the colonization of palnt pathogen in two independent plant-microbe interacting systems.