Molecular analysis of the pheromone and pheromone receptor genes of Ustilago hordei

Cell-cell signaling is an integral part of the sexual and disease cycles of the smut fungi, which must mate to be pathogenic. This study reports the c loning and characterization of the pheromone genes Uhmfal and Uhmfa2 from M AT-1 and MAT-2 mating types of U. hordei, respectively, and the pheromone r eceptor gene Uhpra2 from MAT-2 cells. Similar to other fungal pheromone gen es, Uhmfal and Uhmfa2 encode precursor peptides. Uhpra2 encodes a protein w ith sequence similarity to the 7-transmembrane class of G-protein coupled r eceptors. Deletion of Uhmfal and Uhpra1, and their subsequent replacement, confirmed the role of these genes in initiation of the sexual cycle. Uhmfal and Uhwfa2 were differentially expressed in various cell types and when op posite mating-type cells were grown together. The predicted mature pheromon es of each mating type were synthesized, and each specifically induced conj ugation tube formation in cells of the opposite mating type. (C) 1999 Elsev ier Science B.V. All rights reserved.