Investigation of Mating Pheromone-Pheromone Receptor Specificity inLentinula edodes

Abstract

TheBmating-type locus ofLentinula edodes, a representative edible mushroom, is highly complex because of allelic variations in the mating pheromone receptors (RCBs) and the mating pheromones (PHBs) in both theB alpha andB beta subloci. The complexity of theBmating-type locus, fiveB alpha subloci with five alleles ofRCB1and ninePHBsand threeB beta subloci with 3 alleles ofRCB2and fivePHBs, has led us to investigate the specificity of the PHB-RCB interaction because the interaction plays a key role in non-self-recognition. In this study, the specificities of PHBs to RCB1-2 and RCB1-4 from theB alpha sublocus and RCB2-1 from theBbsublocus were investigated using recombinant yeast strains generated by replacingSTE2, an endogenous yeast mating pheromone receptor, with theL. edodesRCBs. Fourteen synthetic PHBs with C-terminal carboxymethylation but without farnesylation were added to the recombinant yeast cells and the PHB-RCB interaction was monitored by the expression of theFUS1gene-a downstream gene of the yeast mating signal pathway. RCB1-2 (B alpha 2) was activated by PHB1 (4.3-fold) and PHB2 (2.1-fold) from theB alpha 1sublocus and RCB1-4 (B alpha 4) was activated by PHB5 (3.0-fold) and PHB6 (2.7-fold) from theB alpha 2sublocus and PHB13 (3.0-fold) from theB alpha 5sublocus. In particular, PHB3 fromB beta 2and PHB9 fromB beta 3showed strong activation of RCB2-1 of theB beta 1sublocus by 59-fold. The RCB-PHB interactions were confirmed in the monokaryotic S1-10 strain ofL. edodesby showing increased expression ofclp1,a downstream gene of the mating signal pathway and the occurrence of clamp connections after the treatment of PHBs. These results indicate that a single PHB can interact with a non-self RCB in a sublocus-specific manner for the activation of the mating pheromone signal pathways inL. edodes.