An Ashbya gossypii cts2 mutant deficient in a sporulation-specific chitinase can be complemented by Candida albicans CHT4

The Candida albicans genome encodes four chitinases, CHT1, CHT2, CHT3 and CHT4. All four C. albicans chitinase-encoding genes are non-essential. The corresponding proteins belong to two groups in which Cht1, Cht2 and Cht3 are more similar to Saccharomyces cerevisiae Cts1, while Cht4 is more similar to ScCts2. In the filamentous fungus Ashbya gossypii, a CTS2 homolog (ACL166w) was identified as the sole chitinase gene. The AgCts2 is 490 aa in length and shows 42.3% overall identity to ScCts2 (511 aa) and 33.2% identity to CaCht4 (388 aa). The A. gossypii cts2 deletion mutant showed no growth retardation or vegetative morphogenetic defects. However, upon sporulation Agcts2 mutants revealed a defect in spore formation. Expression of AgCts2 using a lacZ reporter gene was only found in the centre of a mycelium corresponding to the sporogenous part of a colony. The mutant spore phenotype of Agcts2 could be complemented by either AgCTS2, the S. cerevisiae CTS2, or the C. albicans CHT4 gene when expressed by either the AgCTS2 or the AgTEF1 promoter.