Functional Characterization of a Gene Family Encoding Polygalacturonases in Phytophthora parasitica

Abstract

Phytophthora parasitica is an oomycete plant pathogen that causes severe disease in a wide variety of plant species. In our previous study, we discovered a multigene family encoding endopolygalacturonases (endoPG) in Phytophthora parasitica. Here, we screened the genomic library of Phytophthora parasitica for the genes encoding endoPG named pppg2 through pppg10, and analyzed their functions. Results obtained by real-time quantitative reverse transcriptase-polymerase chain reaction demonstrated that some of these genes are highly induced during plant infection, which suggests their important roles in the pathogenesis of Phytophthora parasitica. Analysis by in-gel activity assay of recombinant proteins obtained from Pichia pastoris indicated that each of these genes encodes a functional endoPG. Investigation of the function of pppg genes in planta by a Potato virus X agroinfection system in tobacco revealed that each pppg caused specific effects, varying from no symptoms to dwarfism, necrosis, leaf curl, silvery leaf, and cracks in leaf stalks. Appearance of these effects depends on the expression of a pppg protein with a normal active site in the apoplast. These results indicated that each pppg plays a distinct role in the decomposition of plant cell wall.

Functional analysis of Pcipg2 from the straminopilous plant pathogen Phytophthora capsici

“…, which were designed based on the conserved sequences of other pg genes (Götesson et al, 2002;Torto et al, 2002;Tyler et al, 2006;Wu et al, 2008;Yan and Liou, 2005). Pcipg genes were screened from the genomic library according to the procedure described, and minor adjustments made to the PCR reaction systems and parameters (Liu et al, 2000).…”

“…In P. cinna-momi, one large pg gene family with 19 members was identified (Götesson et al, 2002). Individual members of another pg gene family in P. parasitica have a specific role in decomposition of host plant cell wall (Wu et al, 2008), and 3 pg genes (Genbank: DQ415987, DQ415988, EF558847) and 21 Pg genes of Phytophthora capsici were downloaded from the Joint Genome Institute (http://genome.jgi-psf.org/PhycaF7/PhycaF7. home.html).…”

“…P. capsici can deploy an array of host cell wall modifying enzymes during pathogenesis, and PGs are important parts of that array (Jia et al, 2009). Although some pg genes have been identified from several Phytophthora species (Götesson et al, 2002;Torto et al, 2002;Tyler et al, 2006;Wu et al, 2008), the roles of PGs genes in the pathogenesis have not been conducted in P. capsici.…”

Molecular characterization and functional analysis of the Nep1-like protein-encoding gene from Phytophthora capsici

“…Studies have shown that some NLP genes -for example, 2 orthologous genes (MpNEP1 and MpNEP2) in Moniliophthora perniciosa -cause no changes in plants and show different characteristics when applied to plants (Garcia et al, 2007). These findings are reminiscent of a study that showed that eight Pg genes caused four types of significantly different changes (Wu et al, 2008). This phenomenon suggests that members of a gene family can have diversified functions.…”

“…Mature phcnlp1 (with predicted signal peptides removed) was introduced into PVX pGR106 (Wu et al, 2008). Test plants were observed for up to 10 dpi for the development of symptoms.…”