Identification of a Small Heat-Shock Protein Associated with a Ras-Mediated Signaling Pathway in Ectomycorrhizel Symbiosis

摘要

Initiation, development, and establishment of a functional ectomycorrhiza involve a series of biochemical events mediated by a number of genes from the fungus as well as the host plant. We have identified a heat-shock protein gene from Laccaria bicolor (Lbhsp) that appears to play a role in these events. The size and characteristics of Lbhsp suggest that it belongs to the family of small heat-shock proteins described in the literature. Nucleotide sequencing of an almost full length cDNA indicated that the Lbhsp mRNA is about 611 nucleotides long and codes for a single protein of approximately 17 kDa. Isolation and characterization of the Lbhsp gene showed that it was made up of three exons separated by two small introns. Southern analysis suggested that the L. bicolor genome contains at least two copies of the Lbhsp gene. Temporal expression analyses revealed that the gene is expressed when 4 to 12 hours after interaction with red pine roots. The yeast two-hybrid studies showed that the Lbhsp was closely associated with the ras gene (lbras) described earlier. The data suggest that Lbhsp may play a supporting role in ras-mediated mycorrhizal signaling pathways during various stages of ectomycorrhizal development.