Comparative expression analysis of Phytophthora sojae polysaccharide lyase family 3 (pectate lyase) genes during infection of the soybean Glycine max

Abstract

Abstract Phytophthora sojae is an important plant pathogen affecting soybean crops worldwide. The specific mechanisms this pathogen uses to penetrate the host cell and initiate infection have not been fully elucidated. However, a greater understanding of the molecular mechanisms that facilitate these processes will be critical to the development of novel strategies to control this devastating agricultural pathogen. It is likely that, to initiate infection, P. sojae uses an appressorium-like structure to break through the plant cell wall. It is also presumed that the pathogen relies on enzymatic activity to weaken the cell wall. The polysaccharide lyase (PL) enzyme superfamily, particularly the PL family 3 (PL3), has been hypothesized to play an important role in the process of host cell penetration by contributing to the degradation of the structural polysaccharides of the cell wall. To investigate this hypothesis, we have scanned the revised version of the annotated P. sojae genome for the presence of putative PL3-coding genes and conducted an extensive sequence analysis of all gene models found. In addition, we have quantified the relative expression of each gene in P. sojae during infection of susceptible (Williams) and resistant (Williams 82) soybean cultivars over a 48 h time period. Twelve PL3-coding gene models were identified and initial results indicate that during infection of the Williams cultivar, several of these genes experience significant up-regulation during the first 48 h of infection. An increase in transcriptional activity is also observed during infection of Williams 82; however, this expression pattern is distinct from that observed in the Williams cultivar. These results provide evidence regarding the potential involvement of PL-coding genes in the early pathogenic processes of P. sojae and suggest that this pathogen expresses genes differentially, depending on whether infection is occurring on a resistant or a susceptible soybean cultivar.

Keywords

• Phytophthora sojae
• Glycine max
• Polysaccharide lyases
• Soybean
• Williams
• Cell wall-degrading enzymes