Mating Type and Morphogenesis in Ustilago violacea

Publisher Website
Google Scholar
Abstract
Conditions of low temperature and low nutrient (probably cation) levels activated the mating-type alleles (a1 and a2) in the anther smut fungus, U. violacea. The consequences of mating type activation were investigated in a1 and a2 haploids, a1a2 diploids, and a1 + a2 dikaryons (conjugated cells). The mating type locus was hypothesized to act as a master developmental switch, controlling entry into at least 3 distinct morphogenetic pathways: vegetative budding, conjugation and sexual differentiation. When the mating type alleles were inactivated by high temperatures and/or cations, the cells budded vegetatively. Cells with a single mating type allele became blocked in the G1 phase of vegetative growth and developed conjugation tubes after this allele was activated by the correct environmental conditions and by products from a nearby cell of opposite mating type. Cells carrying both mating type alleles (e.g., heterozygous a1a2 diploids) also became blocked in the G1 phase of vegetative growth, but could not initiate the conjugatative pathway; instead, they began to differentiate into spores. A comparison with the normal sequence of development of brandspores (teliospores) in the host established that the low temperature-induced differentiation of a1a2 cells represented a distorted and incomplete attempt to enter the sexual morphogenetic pathway. The possible reasons for this incomplete differentiation are discussed.
Keywords

This publication has 0 references indexed in Scilit: