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Discovering genes involved in branching decisions in neurospora crassa Virag, Aleksandra

Abstract

The main objective of this study is to contribute to the understanding of branching in Neurospora crassa Shear & Dodge. Actin and actin-related proteins are present at hyphal tips and at sites where new branches emerge (Heath, 1990). Factors like cytochalasins (Allen et al, 1980) and cold conditions (Uyeda and Furuya, 1986) disrupt their distribution and the branching pattern and frequency. To reveal the role of actin and actin-related proteins in branch initiation and formation, mutants resistant to cytochalasin A (ccr) and sensitive to cold (cs) were obtained. Purified strains with single gene mutations were morphologically characterized. The ccr-100 strain is different from the wild type strain in several properties. It has different colony morphology, is predominantly dichotomously branched, has an increased branching frequency through development, and is cold sensitive. This mutant did not restore the wild type phenotype with the addition of calcium or cAMP to the medium, indicating that the mutation did not cause a deficiency in the calcium or cAMP content in hyphae. The cold sensitive mutant cs-43 has a decreased distance between branching sites, and the mutants cs-245, cs-466 and cs-611 have an increased distance between branching sites when compared to the wild type strain. The linkage tester strain alcoy was crossed to the mutant strains to map the mutated loci. The mutations of the cold sensitive strains were located throughout the genome, and the mutation of the selected cytochalasin A resistant strain ccr-100 was mapped to linkage group V. Further characterization of the obtained mutant strains will help to elucidate the role of specific gene products in branching events.

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