Functional Characterization of MAT1 - 1 -Specific Mating-Type Genes in the Homothallic Ascomycete Sordaria macrospora Provides New Insights into Essential and Nonessential Sexual Regulators

Abstract

ABSTRACT Mating-type genes in fungi encode regulators of mating and sexual development. Heterothallic ascomycete species require different sets of mating-type genes to control nonself-recognition and mating of compatible partners of different mating types. Homothallic (self-fertile) species also carry mating-type genes in their genome that are essential for sexual development. To analyze the molecular basis of homothallism and the role of mating-type genes during fruiting-body development, we deleted each of the three genes, SmtA - 1 ( MAT1 - 1 - 1 ), SmtA - 2 ( MAT1 - 1 - 2 ), and SmtA - 3 ( MAT1 - 1 - 3 ), contained in the MAT1 - 1 part of the mating-type locus of the homothallic ascomycete species Sordaria macrospora . Phenotypic analysis of deletion mutants revealed that the PPF domain protein-encoding gene SmtA - 2 is essential for sexual reproduction, whereas the α domain protein-encoding genes SmtA - 1 and SmtA - 3 play no role in fruiting-body development. By means of cross-species microarray analysis using Neurospora crassa oligonucleotide microarrays hybridized with S. macrospora targets and quantitative real-time PCR, we identified genes expressed under the control of SmtA - 1 and SmtA - 2 . Both genes are involved in the regulation of gene expression, including that of pheromone genes.