title: Pheromones are essential for male fertility and sufficient to direct chemotropic polarized growth of trichogynes during mating in Neurospora crassa.
abstract: Neurospora crassa is a self-sterile filamentous fungus with two mating types, mat A and mat a. Its mating involves chemotropic polarized growth of female-specific hyphae (trichogynes) toward male cells of the opposite mating type in a process involving pheromones and receptors. mat A cells express the ccg-4 pheromone and the pre-1 receptor, while mat a strains produce mRNA for the pheromone mfa-1 and the pre-2 receptor; MFA-1 and CCG-4 are the predicted ligands for PRE-1 and PRE-2, respectively. In this study, we generated Deltaccg-4 and Deltamfa-1 mutants and engineered a mat a strain to coexpress ccg-4 and its receptor, pre-2. As males, Deltaccg-4 mat A and Deltamfa-1 mat a mutants were unable to attract mat a and mat A trichogynes, respectively, and consequently failed to initiate fruiting body (perithecial) development or produce meiotic spores (ascospores). In contrast, Deltaccg-4 mat a and Deltamfa-1 mat A mutants exhibited normal chemotropic attraction and male fertility. Deltaccg-4 Deltamfa-1 double mutants displayed defective chemotropism and male sterility in both mating types. Heterologous expression of ccg-4 enabled mat a males to attract mat a trichogynes, although subsequent perithecial differentiation did not occur. Expression of ccg-4 and pre-2 in the same strain triggered self-stimulation, resulting in formation of barren perithecia with no ascospores. Our results indicate that CCG-4 and MFA-1 are required for mating-type-specific male fertility and that pheromones (and receptors) are initial determinants for sexual identity during mate recognition. Furthermore, a self-attraction signal can be transmitted within a strain that expresses a pheromone and its cognate receptor.
authors.affiliation: Department of Plant Pathology, 1415 Boyce Hall, 900 University Avenue, University of California, Riverside, CA 92521, USA.
authors.forename: Hyojeong
authors.initials: H
authors.lastname: Kim
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Borkovich
mesh_terms: D004271:DNA, Fungal; D005298:Fertility; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D049770:Genes, Mating Type, Fungal; D005818:Genetic Engineering; D005819:Genetic Markers; D016678:Genome; D008024:Ligands; D009492:Neurospora crassa / Q000166:cytology / Q000235:genetics* / Q000254:growth & development* / Q000502:physiology; D016366:Open Reading Frames; D010675:Pheromones / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D010957:Plasmids; D012333:RNA, Messenger / Q000378:metabolism; D043563:Receptors, Pheromone / Q000235:genetics / Q000502:physiology; D017384:Sequence Deletion; D014170:Transformation, Genetic
chemical_list: D004271:DNA, Fungal; D005819:Genetic Markers; D008024:Ligands; D010675:Pheromones; D012333:RNA, Messenger; D043563:Receptors, Pheromone