MUTATIONS OF THE a MATING-TYPE GENE IN NEUROSPORA CRASSA

A. J. F. Griffiths ¹ and A. M. DeLange ¹

¹ Department of Botany, The University of British Columbia, Vancouver V6T 1W5, Canada

In Neurospora, the mating-type locus controls both mating ( A + a is fertile) and heterokaryosis (A + a is incompatible). The two alleles appear stable: no novel fertility reactions have ever been reported, and attempts to separate fertility and heterokaryon incompatibility functions by recombination have been unsuccessful. In the present approach the locus was studied through a mutational analysis of heterokaryon incompatibility function. A selection system was used that detects vigorous (A + a) heterokaryotic colonies against a background of inhibited growth. Twenty-five mutants of an a strain were produced following mutagenic treatment with UV and NG: 15 were viable as homokaryons and 10 were not. All but one were infertile, but most showed an abortive mating reaction involving the production of barren, well-developed perithecia with A and (surprisingly) a testers. None of the mutants complement each other to restore fertility. Seven mutants have been mapped to the mating-type locus region of chromosome 1. Restoration of fertility was used to detect revertants, and these were found in five out of the eight mutants tested. (A dose response was observed). In four cases incompatibility was fully restored and in one case it was not.—The results suggest two positive actions of the locus when in heterozygous (A/a) combination (the stimulation of some stage of ascus production and the inhibition of vegetative heterokaryosis), and one positive action in homozygous combination (the production of a perithecial inhibitor).

This article has been cited by other articles:

				K. Dementhon, G. Iyer, and N. L. Glass VIB-1 Is Required for Expression of Genes Necessary for Programmed Cell Death in Neurospora crassa Eukaryot. Cell, December 1, 2006; 5(12): 2161 - 2173. [Abstract] [Full Text] [PDF]

				A. Fleissner, S. Sarkar, D. J. Jacobson, M. G. Roca, N. D. Read, and N. L. Glass The so Locus Is Required for Vegetative Cell Fusion and Postfertilization Events in Neurospora crassa Eukaryot. Cell, May 1, 2005; 4(5): 920 - 930. [Abstract] [Full Text] [PDF]

				D. W. Lee, K.-Y. Seong, R. J. Pratt, K. Baker, and R. Aramayo Properties of Unpaired DNA Required For Efficient Silencing in Neurospora crassa Genetics, May 1, 2004; 167(1): 131 - 150. [Abstract] [Full Text] [PDF]

				A. Pandey, M. G. Roca, N. D. Read, and N. L. Glass Role of a Mitogen-Activated Protein Kinase Pathway during Conidial Germination and Hyphal Fusion in Neurospora crassa Eukaryot. Cell, April 1, 2004; 3(2): 348 - 358. [Abstract] [Full Text] [PDF]

				D. W. Lee, R. J. Pratt, M. McLaughlin, and R. Aramayo An Argonaute-Like Protein Is Required for Meiotic Silencing Genetics, June 1, 2003; 164(2): 821 - 828. [Abstract] [Full Text] [PDF]

				H. Kim, R. L. Metzenberg, and M. A. Nelson Multiple Functions of mfa-1, a Putative Pheromone Precursor Gene of Neurospora crassa Eukaryot. Cell, December 1, 2002; 1(6): 987 - 999. [Abstract] [Full Text] [PDF]

				Q. Xiang, C. Rasmussen, and N. L. Glass The ham-2 Locus, Encoding a Putative Transmembrane Protein, Is Required for Hyphal Fusion in Neurospora crassa Genetics, January 1, 2002; 160(1): 169 - 180. [Abstract] [Full Text] [PDF]

				S. J. Saupe Molecular Genetics of Heterokaryon Incompatibility in Filamentous Ascomycetes Microbiol. Mol. Biol. Rev., September 1, 2000; 64(3): 489 - 502. [Abstract] [Full Text] [PDF]

				P. K. T. Shiu and N. L. Glass Molecular Characterization of tol, a Mediator of Mating-Type-Associated Vegetative Incompatibility in Neurospora crassa Genetics, February 1, 1999; 151(2): 545 - 555. [Abstract] [Full Text]

				A. V.-B. Ferreira, Z. An, R. L. Metzenberg, and N. L. Glass Characterization of mat A-2, mat A-3 and {Delta}matA Mating-Type Mutants of Neurospora crassa Genetics, March 1, 1998; 148(3): 1069 - 1079. [Abstract] [Full Text] [PDF]

				N. Glass, S. Vollmer, C Staben, J Grotelueschen, R. Metzenberg, and C Yanofsky DNAs of the two mating-type alleles of Neurospora crassa are highly dissimilar Science, July 29, 1988; 241(4865): 570 - 573. [Abstract] [PDF]