The A alpha multiallelic mating-type genes of Schizophyllum commune
Ullrich, R.; Giasson, L.S.echt, C.; Stankis, M.; Novotny, C.
UCLA symposia on molecular and cellular biology 25(125): 271-288
Sexual development in Schizophyllum is regulated by four multiallelic mating-type (MAT) genes: Aalpha, Abeta, Balpha and Bbeta. There are nine Aalpha alleles in the worldwide population; we have cloned three of these alleles. Aalpha 4 was isolated by walking the chromosome from PAB1 in a cosmid library made from an Aalpha 4 strain. Aalpha 1 Aalpha 3 were isolated by using various fragments of insert DNA from an Aalpha 4-containing cosmid to probe cosmid libraries made from Aalpha 1 and Aalpha 3 strains, respectively. The isolated cosmids activate A-regulated development when transformed into recipients carrying alternative Aalpha alleles. Mating-type transformants were screened microscopically for A-activated development and were confirmed by mating tests and genetic analyses of progeny. The identity of Aalpha 1 and Aalpha 4 has been confirmed by Southerns and transformations in which the activation of A-regulated development is dependent upon the specific Aalpha alleles of the recipient and the transforming DNA. Aalpha 1 and Aalpha 4 have been subcloned to 2.8 and 1.2 kb fragments respectively. When transformed into wild-type recipients, these short fragments activate A-regulated developmental events. The transforming alleles are active in trans. Aalpha 1 and Aalpha 4 probes: hybridize only to Aalpha 1 and Aalpha 4 DNA respectively, do not hybridize to DNA from other Aalpha strains (even at low stringency), and do not hybridize to the DNA of the Abeta, Balpha or Bbeta loci. The simplest interpretation of these results is that there is only one Aalpha allele per haploid genome. Aalpha alleles map to the same region of the chromosome, but are embedded within a 4-6 kb region of heterogeneous, allele-specific sequence.