Transcriptional Analysis And Functional Determination Of Phytophthora Sojae Genes Relevant To Anti-Oxidation During Compatible Interaction

Reactive oxygen burst and subsequent disarrangement of redox homeostasis are key responsive events that regulate plant-pathogen interaction. For the host, it represents one important defense strategy; for the pathogen, it stands as one obstacle which must be overcome to succeed in infection. Since little has been kwown about anti-oxidative mechanisms of phyto-pathogen, especially for Phytophthora sojae, it is necessary to study the pathogen's defense responses against oxidative burst during compatible interaction for detail elucidation on pathogenesis.By in situ and quantitative assays of H₂O₂ accumulation, oxidative burst was detected in soybean leaves infected by P. sojae during both compatible and incompatible interactions. According to the acquired rules of oxidative burst in infected soybean leaves, an in vitro system was established to challenge P. sojae by oxidative stress. Through bio-informatics screening among three compatible interaction libraries and one oxidative stress library, candidate genes of P. sojae were selected on account of their overlapping appearance under different treatments. RT-PCR analysis revealed that some of these genes were actually induced under oxidative stress in vitro, indicating their positive roles in anti-oxidation propitious to successful infection of P. sojae and enlightening further studies on their attractive mechanisms.Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a multifunctional protein well defined in eukaryotes, especially in mammalian and Saccharomyces cerevisiae. Using the method of suppression subtractive hybridization (SSH), we identified a P. sojae cDNA sequence coding GAPDH, which was up-regulated during early infection. There are three copies of PsGAPDH in P. sojae genome. Its amino acid sequence contains overall conserved domain of GADPH, homologous closest to GapC1 of Achlya bisexualis (oomycete) and adjacent to GapC2s of Odontella sinensis and Phaeodactylum tricornutum (diatom), on the C- II branch of subfamily GapC in phylogeny tree of GAPDH. RT-PCR analysis demonstrated that the transcriptional level of PsGAPDH was up-regulated throughout early infection. Heterogenous expression of PsGAPDH in the yeast tdh1-deleted...