Molecular cloning and expression studies of two divergent alpha-tubulin genes in Neurospora crassa

Three alpha-tubulin isoforms were previously detected in Neurospora crassa. We have cloned and analysed two alpha-tubulin cDNAs, Tub alpha A and Tub alpha B that encode polypeptides of 453 and 451 amino acids, respectively. The encoded amino acids exhibit an unusual divergence of 35%. This is the highest divergence ever observed between alpha-tubulins from the same species. The expression of the two genes is developmentally regulated. We did not detect any transcription of the Tub alpha A gene in dormant macroconidia and during the first 30 min of development even though the alpha-tub A protein is already present in the early stage of germination. In contrast, the Tub alpha B gene is continuously transcribed during the vegetative cycle and the expression profile of the protein follows the ones of its mRNA.