Expression and functional analysis of polygalacturonase gene Pcipg5 from the plant pathogen Phytophthora capsici
As one of the cell wall-degrading enzymes, polygalacturonase involves in pathogenicity and virulence in a number of host pathogen interactions. In the polygalacturonase multigene family of Phytophthora capsici, Pcipg5 was screened from the genomic library. The Pcipg5 gene contains three putative active sites (179Asp, 200Asp, 201Asp) and one potential N-glycosylation site (252Asn). PCIPG5, four active-site mutagenesis proteins and N-glycosylation mutation were expressed in Pichia pastoris and purified by Ni-NTA Purification System. Pcipg5 functions were determined by Western blot, RT-PCR and Northern blot. Transmission electron microscopy discovery individually in treated pepper leaves was used to determine the virulence of PCIPG5. The results show that Pcipg5 can encode a pathogenesis-related protein during P. capsici infection of pepper leaves and degrade cell walls to produce necrotic lesions in treated pepper leaves. Meanwhile, the N-glycosylation mutagenesis protein decreased the activity compared with PCIPG5. It indicates that the existence N-glycosylation site in PCIPG5 plays a partial role in the activity of this enzyme.
Key words: Phytophthora capsici, Pcipg5, host-pathogen interactions, N-glycosylation.