Cloning and characterization of a symbiosis-related gene from an ectomycorrhizal fungus Laccaria bicolor

An in vitro system for a Laccaria bicolor x Pinus resinosa interaction was used to identify and clone a symbiosis-regulated gene from L. bicolor emplo ying the mRNA differential display technique (DDRT-PCR). The DDRT-PCR ident ified several cDNAs that are differentially expressed as early as 6 h into the interaction. One such cDNA was used to screen a L. bicolor cDNA library enriched for mRNAs expressed during early interaction with red pine seedli ngs. Characterization of a cDNA clone, PF6.2, showed that it contained a 15 51 bp insert coding for a protein of 433 amino acids. Sequence analysis of the PF6.2 cDNA revealed the presence of several evolving repeats in the pro tein. To confirm this, the gene corresponding to PF6.2 was isolated and seq uenced. The PF6.2 gene consisted of seven exons interrupted by six relative ly small introns. Although the amino-acid sequence of the PF6.2 did not sho w significant overall similarity to any previously characterized proteins, of several direct repeats it contained a feature similar to other proteins involved in signal transduction through protein-protein interaction. Northe rn analysis showed that the PF6.2 mRNA was detectable in the fungus 6 h aft er interaction and continued to be expressed in established ectomycorrhizas , suggesting that it plays an important role in the formation and maintenan ce of the symbiosis. (C) 1998 Published by Elsevier Science B.V. All rights reserved.