Investigation of Mating Pheromone–Pheromone Receptor Specificity in Lentinula edodes

The B mating-type locus of Lentinula 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 the B&alpha
and B&beta
subloci. The complexity of the B mating-type locus, five B&alpha
subloci with five alleles of RCB1 and nine PHBs and three B&beta
subloci with 3 alleles of RCB2 and five PHBs, has led us to investigate the specificity of the PHB&ndash
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 the B&alpha
sublocus and RCB2-1 from the Bb sublocus were investigated using recombinant yeast strains generated by replacing STE2, an endogenous yeast mating pheromone receptor, with the L. edodes RCBs. Fourteen synthetic PHBs with C-terminal carboxymethylation but without farnesylation were added to the recombinant yeast cells and the PHB&ndash
RCB interaction was monitored by the expression of the FUS1 gene&mdash
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 the B&alpha
1 sublocus and RCB1-4 (B&alpha
4) was activated by PHB5 (3.0-fold) and PHB6 (2.7-fold) from the B&alpha
2 sublocus and PHB13 (3.0-fold) from the B&alpha
5 sublocus. In particular, PHB3 from B&beta
2 and PHB9 from B&beta
3 showed strong activation of RCB2-1 of the B&beta
1 sublocus by 59-fold. The RCB&ndash
PHB interactions were confirmed in the monokaryotic S1&ndash
10 strain of L. edodes by showing increased expression of clp1, 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 in L. edodes.