A molecular analysis of fungal mating type genes

• Main Author: Nixon, Julie
• Published: University of Edinburgh 1997
• Subjects: 579.5
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.660023

This work is concerned with the molecular analysis of ascomycete mating type genes of various <I>Sordaria</I> species. Work previously published has reported the cloning and characterisation of mating type genes from several <I>Neurospora </I>species. In heterothallic species the genotype at the mating type locus (mtA or mta) determines the mating type. Homothallic species, which proceed through the sexual cycle without the need to mate, have no obvious mating types but molecular analysis has been used to demonstrate the presence of mating type genes in species with this life cycle. <I>Neurospora </I>species and <I>Sordaria </I>species both belong to the Sordariaceae and are closely related. Several λ clones containing putative <I>Sordaria</I> mating type genes from heterothallic and homothallic species had been isolated previously using <I>N. crassa </I>mtA and mta probes. In this study the mtA-1 gene of the heterothallic species <I>S. sclerogenia </I>was subcloned from a λ clone and sequenced. The equivalent gene from <I>S. equina </I>(a homothallic species containing only the mtA sequence) was also subcloned and sequenced. A λ clone for the species <I>S. fimicola</I> was found to hybridise with both the mtA and mta probes. <I>S. fimicola </I>is a homothallic species containing mtA and mta in the same nucleus. On using the lambda clone it was found that the mtA and mta genes are linked in this species. All the <I>Sordaria</I> mtA-1 genes contained putative DNA binding domains, α domains. The mta-1 gene sequenced from <I>s. fimicola </I>contained a putative HMG box. The <I>S. equina</I> mtA-1 gene was expressed in a sterile <I>N. crassa </I>mta mutant and was found to restore mating type function to the mutant. The mtA-1 gene did not however confer homothallic behaviour on the recipient mutant. <I>S. equina </I>and <I>S. sclerogenia </I>contain a 59bp common region following on from the mtA-1 gene which is conserved in both these species and in <I>Neurospora </I>species. A variable region continues on from the common region in <I>S. equina </I>and <I>S. sclerogenia </I>and in <I>Neuropora </I>species.