Submitted to: Biomed Central (BMC) Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/2014
Publication Date: 5/8/2014
Citation: Feng, B., Sun, B., Lv, R., Fu, L., Wang, H., Zhu, J., Wu, Q., Tooley, P.W., Zhang, X. 2014. The necrosis-inducing Phytophthora protein gene family of Phytophthora capsici is involved in pathogenicity. Biomed Central (BMC) Plant Biology. 14:126. Interpretive Summary: Phytophthora capsici is a very important pathogen of peppers worldwide, causing heavy losses in many regions of the world where peppers are grown. The pathogen produces a protein, called NPP, which is toxic to many plant species. Specialized genetic techniques were used to study the genes in P. capsici which code for this protein. At least 18 different forms for NPP were identified within P. capsici. Further, we studied the symptoms these selected forms of NPP caused on the host plants. Twelve forms of NPP were able to cause different symptoms in host plant species, and they were found to have distinct biological functions in different plant species. The results of these experiments have shed light on the process of pathogen virulence on peppers conditioned by genes for the NPP protein in P. capsici.
Technical Abstract: Phytophthora capsici is one of the most important pathogens limiting vegetable production worldwide. Necrosis-inducing Phytophthora protein (NPP), ocurring in phylogenetically distant organisms, is phytotoxic for dicotyledonous plants, but the mechanism of action has not been established. A gene family containing at least 18 NPP genes isolated from P. capsici was characterized in vitro and in vivo using agroinfection and stable gene silencing techniques. Agroinfection analysis of 12 selected genes on two plant species revealed varied disease symptoms. Site-directed mutation of PcNPP1 indicated that four residues were involved in the predicted active site, and agroinfection with mutant genes shed light on the putative enzyme activity of this protein. Q-PCR analysis of seven stable transformants showed that ten genes were silenced to different degrees, and that multiple gene silencing occurred simultaneously in the mutant strains. NPP silencing in P. capsici failed to cause phenotypic changes, but did impair the virulence of P. capsici on pepper plants. These results suggest that P. capsici NPPs may play a role in this host-pathogen interaction, appearing to influence virulence and avirulence functions.