J. Ruiz-herrera et al., Carboxin-resistant mutant of Ustilago maydis is impaired in its pathogenicity for Zea mays, CURR MICROB, 39(5), 1999, pp. 291-294
We analyzed the pathogenicity of chitin synthetase (chs) disruptants of Ust
ilago maydis obtained with the carboxin-resistant or the hygromycin-resista
nt cassettes. We found that only chitin synthetase (chs) mutants obtained b
y gene disruption with:the carboxin resistance cassette lost their virulenc
e to maize (Zea mays) seedlings. Carboxin is a systemic fungicide that inhi
bits respiration by preventing the oxidation of succinate. We demonstrated
that carboxin-resistant transformants were affected in the levels of succin
ate dehydrogenase and respiratory activities when compared with hygromycin-
resistant disruptants. We propose that loss of virulence in the carboxin-re
sistant transformants is owing to loss of respiratory fitness, which probab
ly represents an important component of virulence in this fungus.