Cellular distribution of COT1 kinase in Neurospora crassa

The Neurospora crassa cot-1 gene encodes a Ser/Thr protein kinase, which is involved in hyphal elongation. Many vacuoles, abnormally shaped mitochondr ia, and nuclei, along with differences in the structure of the cell wall an d hyphal septa, were observed in hyphae of the cot-l mutant shortly after a shift to the restrictive temperature. Immunolocalization experiments indic ated that COT1 was associated with the cytoplasmic membrane; COT1 was also detected in the cytoplasm, The membrane-associated COT1 was absent from the cot-1 mutant when shifted to the restrictive temperature, as was a lower m olecular weight isoform of COT1, We propose that COT1 may be involved in se veral cellular processes, and the spatial and temporal regulation of COT1 a ctivity involves trafficking of the kinase within the fungal cell and its p ossible interaction with additional proteins. (C) 2000 Academic Press.