Molecular alteration in a Neurospora crassa morphological mutant and its phenocopy.

Abstract

A procedure using ion exchange chromatography has been developed to detect alterations in a polysaccharide produced by Neurospora crassa. The polysaccharide, isolated from medium that has supported the growth of a culture, is highly responsive to the 3-methyl-2-benzothiazolinone hydrazone assay, indicating a high hexosamine content. The substance elaborated by wild-type N. crassa can be fractionated into two components that appear by rechromatography to be closely related. When isolated from mutants of the peak (pk) locus, the corresponding polysaccharide cannot be resolved into two components. Instead, a single component is consistently found. This variant chromatographic pattern cosegregates with morphological effects of the pk allele after crosses with the wild type. The polysaccharide isolated from a wild-type culture that has been induced by sorbose to phenocopy the hyphal characteristics of pk mutants elutes from the ion exchange column in a manner similar to the corresponding polysaccharide from the pk mutants.Neurospora crassa may undergo two distinct developmental phases. One phase involves the asexual production of conidia that germinate to produce a mycelial mat producing more conidia. The second, the sexual developmental phase, consists of protoperithecia production, fertilization of the protoperithecia, and then maturation of the perithecia, or fruiting bodies. Perithecia maturation includes differentiation of the perithecial wall and internal development of asci containing ascospores. By use of appropriate mutants, loci that regulate development of one phase only (1, 2) as well as loci regulating both phases (3) have been identified. A number of loci of the second type regulate morphology of both asci and vegetative hyphae. Mutations at these various loci offer the potential for dissecting ascus development and providing insight into the relationship of the zygote to the developing ascus. Full utilization of these mutants to study development requires some knowledge of their molecular function. No consistent molecular alteration that can be directly related to alterations in morphology has been previously detected for mutations at any of these loci. The careful examination of a molecular component of Neurospora now reveals a consistent molecular alteration for members of one set of allelic mutants.Reissig and Glasgow (4) reported the isolation of a growthregulating substance both from purified hyphal wall of Neurospora and from medium that had supported a culture. They found no difference between the materials from the two sources. The substance was found to be composed primarily of 2-amino-2-deoxygalactose, with several neutral sugars and amino acids as minor components. A portion of the 2-amino-2-deoxygalactose residues was found to be N-acetylated.Originally referred to as MP (for mucopolysaccharide), the designation was later changed to galactosaminoglycan (5).Mycelial morphology in Neurospora is determined in part by the frequency and location of branching and by growth rate. The galac...

Induction of Cellular Efflux by a Galactosamine Polymer from Neurospora crassa

“…The difference in N-substitution may reflect simply a strain difference or the fact that the differing growth conditions lead to differing Nacetylation levels of the polymer which in turn lead to alterations in hyphal morphology. Springer & Srb (1978) have correlated such alterations with the N-acetyl content of galactosaminoglycan.…”

“…The biological role of the polymer isolated from N. crassa may involve the regulation of growth H d hyphal morphology (Reissig & Glasgow, 1971 ;Springer & Srb, 1978). The polymer has been shown to adsorb to the cell surface of this fungus and to elicit alterations in both membrane permeability and viability (Glasgow & Reissig, 1974).…”

Chromosomal loci of Neurospora crassa

“…Increased activity of Lglutamine:D-fructose-6-phosphate amidotrans-ferase was observed in crude extracts of one pk strain but not in nine others; increased activity for this enzyme was also found in cl (see below) and in four other nonallelic morphological mutants (899). Hexoseaminoglycan consists of a single component on medium without sorbose, in contrast to two components for the wild type (1003). Antigenic surface mucopolyoside (281).…”