Characterization of the Mutants mtb-4A, mtb-4B and Double Mutant in the Filamentous Fungus Neurospora crassa.

Callejas-Negrete O. A1, Plamann M. 3, Mouriño-Pérez R. R.1, R.W. Roberson.2, S. Bartnicki-Garcí­a.1.

Author address: 

Department of Microbiology, CICESE, Ensenada, Mexico, 2Department of Cellular and Molecular Biosciences, Arizona State University, Tempe, AZ, 3School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri.


The mtb-4A and mtb4-B genes of Neurospora crassa have a high identity with the nudF gene of Aspergillus nidulans, the pac1 gene of Saccharomyces cerevisiae and the human gene lis1. The proteins encoded by these genes appear to interact with the dynein/dynactin complex at the plus end of microtubules (Mts) and are required for proper nuclear distribution, in regulating Mts dynamics and cell growth. In A. nidulans, lack of NUDF may cause dynein to be kept at its inactive state and inhibit its transport of bound cargo, resulting in an over-accumulation at the plus end. The mammalian homolog of NUDF, LIS1, is product of a gene whose mutations cause brain malformation characterized by a disorganization of the neurons by a nuclear migration defect. We studied the effect of the lack of mtb-4A and mtb-4B during polarity establishment in Neurospora crassa. The lacks of mtb-4A and mtb-4B genes affect cell growth. The growth rate of mtb-4A mutant and double mutant mtb-4A;mtb-4B were 62% and 75% less than the wt, in contrast to mtb-4B mutant that had the same growth rate as the WT. Conidia production was affected in the mutants the strongest affect was in the double mutant (99% conidial production reduction). Branching rate in mtb-4A mutant and double mutant mtb-4A;mtb-4B were 3- folds higher than the WT (p mtb-4B mutant showed similar branching rate than the WT. The biomass production was the same in all mutants. The mutation in the mtb-4A and mtb-4B gene in N. crassa are not essential but in mtb-4A affects strongly the growth rate, increase the frequency of branching and reduce the production of conidia, although mtb-4B mutation does not affect the phenotype and growth rate, the lack of both mtb-4A and mtb-4B have a synergic effect.

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Full conference title: 

26th Fungal Genetics Conference
    • Fungal Genetics Conference 26th (2005)