A Conserved Host Target Of Oomycete Avr3a Family Effectors Positively Regulates Plant Resistance To Phytophthora

Oomycetes are a group of eukaryotes that are morphologically and structurally similar to filamentous fungi,their true phylogenetic affinity is with diatoms and brown algae in the kingdom Straminipila.Oomycetes are diverse,occupying a number of niches,most of which are plant parasites,and often result in severe losses in crop production,posing a serious threat to human activities and the ecological environment.Phytophthora infestans,P.sojae and P.capsici are notorious pathogens of potato,soybean and pepper,respectively.Phytophthora pathogens secrete numorous effector proteins with a RXLR motif to play a virulence role in promoting infection.Therefore,improved understanding on the modulation mechanism of RXLR effector proteins is essential for developing novel strategies for the prevention and control of plant diseases.Avr3a is an important RXLR effector protein in P.infestans,being relatively conserved across several Phytophthora species,including P.capsici and P.sojae.Avr3 a effector proteins from these Phytophthora species form Avr3 a family effector proteins.Arabidopsis thaliana cinnamyl alcohol dehydrogenase 7(At CAD7)was identified in our previous research as a target of the Avr3 a family effector proteins.In this research,I focus on the interaction between Avr3 a family members and other members of the CAD family proteins and the function of CAD5.The following results were obtained:(1)Multiple approaches with three different compatible pathosystms Arabidopsis-P.capsici,N.benthamiana-P.capsici,and N.benthamiana-P.infestans consistently showed that CAD5(At CAD5 in A.thaliana and its ortholog Nb CAD5 in N.benthamiana)proteins interact with Avr3 a family effector proteins.The three different interaction assays include Yeast two-hybrid system(Y2H),bimolecular fluorescence complementarity(Bi FC),and co-immunoprecipitation(Co-IP).(2)At CAD5 overexpression in A.thaliana and pathogenicity assays showed that At CAD5 is a positive regulator of plant immunity to P.capsici.(3)RNA silencing of the orthologous Nb CAD5 in N.benthamiana by virus induced gene silencing(VIGS)and pathogenicity assays with P.capsici and P.infestans further showed that CAD5 is a positive regulator of plant immunity to Phytophthora pathogens.