Internuclear Genetic Transfer in Vegetative Dikaryons of SCHIZOPHYLLUM COMMUNE: I. Di-Mon Mating Analysis.

A series of hemi-compatible dikaryon x monokaryon (di-mon) matings was designed to determine whether there was any genetic interaction between the dikaryotic nuclei. One of the nuclei in each dikaryon was known to carry a recessive gene (mnd) that promoted the development of an abnormal growth form, mound. Dikaryons containing both mnd( +) and mnd nuclei produced mosaic colonies that consisted of three distinct kinds of hyphae: mound, fruiting body, and vegetative (devoid of any multihyphal structure). When dikaryotic hyphae from each of these morphological regions were used in di-mon matings, the genetic and developmental characteristics of the selected nuclear types were examined in the resulting derived dikaryons. The results showed that fruiting-body and vegetative cells contained the expected mnd and mnd(+) nuclei. Dikaryotic mound hyphae, however, contained only mnd nuclei. In a manner as yet unresolved, but clearly dependent on the presence of the mnd allele, the mnd( +) allele of a wild nucleus was altered to, or acquired, the mnd allele. A number of hypotheses were considered to explain the genetic event(s) that generates [mnd + mnd*] dikaryotic cells from [mnd(+) + mnd] cells, but none was found to be entirely satisfactory.