Expression of alpha tubulin during the dimorphic transition of Paracoccidioides brasiliensis

In this study we analyzed the expression of (alpha-tubulin during the dimorphic transition of the human-pathogenic fungus Paracoccidioides brasiliensis. The alpha-tubulin from P. brasiliensis was recognized by a commercially available anti-tubulin antibody and was developmentally regulated during the dimorphic form transition. We detected at least two alpha-tubulin isoforms in the mycelial state and only one isoform in the yeast forms. This finding suggests specific roles for the alpha-tubulin isoforms in P. brasiliensis's yeast and mycelial forms.

Isolation and characterization of alpha-tubulin genes from Septoria tritici and Rhynchosporium secalis, and comparative analysis of fungal alpha-tubulin sequences

The alpha-tubulin genes from Septoria tritici and Rhynchosporium secalis have been cloned and sequenced. The predicted amino acid sequence and intron structure showed strong homology with other known filamentous fungal alpha-tubulins. Comparison of sixteen fungal alpha-tubulin sequences based on amino acid sequence homology and intron structure identified five groups of proteins. Group 1 consists of filamentous fungi, including S. tritici and R. secalis, the dimorphic fungus Histoplasma capsulatum, and Pneumocystis carinii. Group 2 includes two divergent isoforms from Neurospora crassa and Aspergillus nidulans. Group 3 includes the yeast Saccharomyces cerevisiae and the dimorphic fungus Candida albicans. Group 4 contains the single yeast Schizosaccharomyces pombe. Group 5 includes the only Basidiomycete, Schizophyllum commune. This analysis supports the classification of P carinii as a primitive Ascomycete. The presence of an additional glycine residue between the second and third amino acid found only in Group 2 proteins may indicate a functionally distinct fungal isotype. Implications in terms of structure-function relationships for alpha-tubulin molecules are discussed.

Nuclear movement in filamentous fungi

One of the most striking features of eukaryotic cells is the organization of specific functions into organelles such as nuclei, mitochondria, chloroplasts, the endoplasmic reticulum, vacuoles, peroxisomes or the Golgi apparatus. These membrane-surrounded compartments are not synthesized de novo but are bequeathed to daughter cells during cell division. The successful transmittance of organelles to daughter cells requires the growth, division and separation of these compartments and involves a complex machinery consisting of cytoskeletal components, mechanochemical motor proteins and regulatory factors. Organelles such as nuclei, which are present in most cells in a single copy, must be precisely positioned prior to cytokinesis. In many eukaryotic cells the cleavage plane for cell division is defined by the location of the nucleus prior to mitosis. Nuclear positioning is thus absolutely crucial in the unequal cell divisions that occur during development and embryogenesis. Yeast and filamentous fungi are excellent organisms for the molecular analysis of nuclear migration because of their amenability to a broad variety of powerful analytical methods unavailable in higher eukaryotes. Filamentous fungi are especially attractive models because the longitudinally elongated cells grow by apical tip extension and the organelles are often required to migrate long distances. This review describes nuclear migration in filamentous fungi, the approaches used for and the results of its molecular analysis and the projection of the results to other organisms.