Screening And Functional Analysis Of Phytophthora Capsici RxLR Effectors

Pepper Phytophthora blight,caused by the pathogenic oomycetes Phytophthora capsici,is one of the most devastating diseases of crops worldwide and causes enormous losses on economy.It can infect pepper,tomato,eggplant,cucumber,pumpkin,melon and so on.It has caused huge economic losses around the world.P.capsici is one of the pathogenic oomycetes which are classified in the kingdom Protoctista and are related to heterokont,biflagellate,golden-brown alage while fungi from a separate kingdom and are evolutionarily related animals.The evolution distance mades Phytophthora a specific plant infection mechanism.Phytophthora capsici,a causual agent of pepper,secretes a repertoire of highly divergent RxLR effectors into plant cells to suppress host immunity system during infection.RxLR effectors contain conserved RxLR-Deer bipartite motifs required for translocation into host cells and the C-terminal domains interacting with plant resistance proteins.Large-scale investigatation of RxLR effectors from P.capsici demonstrated that most of them are capable of suppressing P AMP(Pathogen Associated Molecular Patterns)and/or effector triggered immunities.The functional analysis of RxLR effectors genes of P.capsici provides new insight into the biological characterisitic and molecular pathological mechanism of the oomycetes,which leads to the prospects for sustainable control of pepper Phytophthora blight.A total of 321 RxLR effectors are predicted in the genome of Phytophthora capsici LT1534 by using bioinformatics analysis via computer prediction algorithms.These effectors may be required for virulence in the interaction between host and pathogen.To identify whether these RxLR effectors play a role in manipulating plant immunity,66 predicted RxLR effectors are screened and functional assayed by using a PVX-based high-throughout transient plant expression system in Nicotiana benthamiana.The results showed that 3 effectors,Avh 108、Avh110 and Avh121,can block the programmed cell deathInduced by protein BAX in N.benthamiana and trigger cell death in N.benthamiana,suggesting that P.capsici RxLR effectors play an import role in pathogenicity.We used RNAi and the system of genetics transformation technology of P.capsici to study the influence of effector Avh121 to host plant.The results showed that hyphae become malformation and zoospore vitality become lower in the RNAi silence mutant of Avh121.The pathogenicity also became significantly weaker in the mutant comparing to the wild type LT1534.All the results demonstrate that the effector Avh121 has influence in P.capsici infected host.