Inducibility studies with the arbuscular mycorrhizal fungus Glomus mosseae 3-phosphoglycerate kinase (PGK) gene promoter.

Abstract

Arbuscular mycorrhizal (AM) fungi are a multifaceted group of mutualistic symbionts that are common to terrestrial ecosystems. The role of AM fungi within processes related to carbon (C) dynamics of the plant-root-soil system are of global significance. An understanding of the C metabolism of AM fungi within the symbiotic and asymbiotic stages of their lifecycle is a necessary pre-requisite to understanding the mechanisms of C movement. This investigation studies the regulation of the Glomus mosseae (Gm) 3-phosphoglycerate kinase ( PGK) gene promoter by different C sources. The suitability of studying the GmPGK promoter (P(GmPGK)) within Saccharomyces cerevisiae was confirmed by complementation of a S. cerevisiae pgk (-) mutant with an expression vector carrying the P(GmPGK) driving the expression of the S. cerevisiae PGK gene. The inducibility of the P(GmPGK) to different C sources was studied by creating a P(GmPGK)-luciferase fusion, which was introduced into a S. cerevisiae expression vector and used to transform S. cerevisiae. The P(GmPGK)-luciferase fusion was tested for expression within S. cerevisiae by RT-PCR analysis and was shown to be expressing the luciferase gene. C upshift studies were completed to evaluate the inducibility of this promoter by different C sources. The sources raffinose, glycerol and glucose significantly induced the P(GmPGK), whereas the sources galactose, succinate and sucrose had the lowest transcriptional responses. Semi-quantitative RT-PCR was used to establish gene expression patterns of GmPGK during spore germination; and up-regulation of the GmPGK gene was observed.