The sidA Gene of Aureobasidium thailandense and its Phylogenetic Relationship among those of Aureobasidium Species

Abstract

The full length sequence of the sidA gene coding for L-ornithine-N5-monooxygenase, the key enzyme in the siderophore biosynthetic pathway, from Aureobasidium thailandense NRRL 58539 was assembled from gDNA and cDNA. Its open reading frame was 1,458 bp long and encoded a protein consisting of 485 amino acid residues with a calculated mass at 55.2 kDa and isoelectric point at 7.34. The deduced protein contained K_oxygenase, FADPNR, and FAD/NAD(P)-binding domains and also three possible N-linked glycosylation sites. When A. thailandense NRRL 58539 sidA and its deduced protein were compared with those of Aureobasidium pullulans species complex, the nucleotide and amino acid sequence identities were found at 72–77% and 77–85%, respectively. Phylogenetic analysis of sidA using maximum likelihood and Bayesian inference placed the A. thailandense on a distinct clade from other Aureobasidium species. The low pairwise dN/dS ratios suggested that the sidA gene was subjected to a strong purifying selection, which was likely due to the pressure of function preservation. In addition, the sidA gene showed great potential as a supplemental locus for phylogenetic analysis of the black yeasts in the genus Aureobasidium.