Double chitin synthetase mutants from the corn smut fungus Ustilago maydis

• Published in: The New phytologist Vol. 146; no. 2; pp. 335 - 341
• Main Authors: CHAVEZ-ONTIVEROS, JEANETT, MARTINEZ-ESPINOZA, ALFREDO D., RUIZ-HERRERA, JOSE
• Format: Journal Article
• Language: English
• Published: Cambridge, UK Cambridge University Press 01.05.2000; Blackwell
• Subjects: Biological and medical sciences; cell wall; Cell walls; Chitin; chitin synthetase mutants; Corn; corn smut; Fundamental and applied biological sciences. Psychology; Fungal plant pathogens; Fungi; maize virulence; Microbial genetics; Mycelium; Phytopathology. Animal pests. Plant and forest protection; Ustilago; Variation, races, biotypes, parasitic specialization, genetics; Virulence; Yeasts; chitin synthetase mutants; maize virulence; corn smut; cell wall; Monocotyledones; Zea mays; Plant pathogen; Enzyme; Transferases; Genetic variant; Virulence; Glycosyltransferases; Basidiomycetes; Concentration; Chitin synthase; Cereal crop; Stress; Fungi; Pathogenicity; Sensitivity resistance; Gramineae; Angiospermae; Hexosyltransferases; Spermatophyta; Thallophyta
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1046/j.1469-8137.2000.00635.x

Using genetic crosses between single chs mutants of Ustilago maydis inoculated into maize (Zea mays) seedlings, two classes of double mutants affected in genes coding for chitin synthetases were isolated: chs3/chs4, and chs4/chs5. Analysis of the mutants showed almost no change in their phenotype compared with wild-type strains. Growth rate, effect of stress conditions, dimorphic transition and mating were not affected. The only salient differences were increased sensitivity to osmotics at acid pH, and decrease in chitin synthetase activity, especially when measured with CO2+, and in chitin content. Most significant was a decrease in virulence, although this appeared to be due a factor unrelated to CHS genes. These data can be taken as further evidence that multigenic control of chitin synthetase in fungi operates as a safety mechanism to guarantee fungal viability in changing and hostile environmental conditions.