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A/a incompatibility in Neurospora crassa : novel suppressors and nuclear incompatibility Vellani, Trina Sehar


The sexual functions of the mating type gene (mt) of Neurospora crassa include specification of mating identity (Shear and Dodge, 1927) and perithecial maturation (Griffiths and DeLange, 1978; Staben and Yanofsky, 1990). The gene also acts as a vegetative incompatibility locus, so that A + a heterokaryons (Beadle and Coonradt, 1944) or A/a duplication strains (Newmeyer and Taylor, 1967) grow poorly or not at all. An intriguing question regarding the mating type gene is this: How does it control both the switch between somatic and meiotic events and heterokaryon incompatibility? Several research groups (Glass, et al., 1990; Staben and Yanofsky, 1990) are presently studying the sexual functions of the mating type genes. I present a study of the incompatibility function. Two experiments were performed. The first was a search for new suppressors of mating type-associated incompatibility, which resulted in the identification of seven new suppressors, none of which was allelic with the one known suppressor, tol. The second was the comparison of growth rates of a mating type mutant (fertile, heterokaryon compatible) in a mixed mating type heterokaryon and in a mixed mating type duplication to determine whether or not cytoplasmic incompatibility is separable from nuclear incompatibility. The results obtained suggest that the mating type mutant, am33, eliminates heterokaryon incompatibility without eliminating nuclear incompatibility. The search for suppressors was attempted in order to define more of the genes involved in A/a incompatibility. The analysis of heterokaryon versus nuclear incompatibility was done to investigate the cellular interactions involved in A/a incompatibility.

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