Heterokaryosis in Neurospora sitophila.

ETEROKARYOSIS has been extensively used as a major tool in formal genetic analysis of both Mendelian and non-Mendelian genes and in establishing gene-enzyme relationships. So far it is the only way to perform genetic anslysis of somatic cells in tissue culture (EPHRUSSI 1965; MINTZ and BAKER 1967). These aspects of heterokaryosis have been reviewed elsewhere ( JINKS 1965; FINCHAM 1966; DAVIS 1966). Heterokaryosis was first described in Neurospora by DODGE (1935) and later its genetic control was reported by GARNJOBST (1953). In Neurospora crassa stable heterokaryons are formed between two strains only when they are isogenic with respect to C, D, E , and the mating-type loci (WILSON and GARNJOBST 1966). During the present investigation the different strains of N . sitophila were found to form stable heterokaryons provided these strains had similar genetic backgrounds. However when strains of different genetic backgrounds (such as WHITEHOUSE and DODGE) were tested, they failed to form heterokaryons. Genetic evidence is presented for the presence of a gene controlling heterokaryon formation in N . sitophila. It was also found that in N . sitophila strains of opposite mating type form stable heterokaryons. Thus unlike N . crassa, the mating-type locus of N . sitophila was found to have no control over heterokaryon formation. This paper describes these aspects of heterokaryosis in Neurospora.