Characterization of agglutinin-like sequence genes from non-albicans Candida and phylogenetic analysis of the ALS family

The ALS (agglutinin-like sequence) gene family of Candida albicans encodes cell-surface glycoproteins implicated in adhesion of the organism to host s urfaces. Southern blot analysis with ALS-specific probes suggested the pres ence of ALS gene families in C. dubliniensis and C. tropicalis; three parti al ALS genes were isolated from each organism. Northern blot analysis demon strated that mechanisms governing expression of ALS genes in C. albicans an d C. dublininsis are different. Western blots with an anti-Als serum showed that cross-reactive proteins are linked by beta1,6-glucan in the cell wall of each non-albicans Candida, suggesting similar cell wall architecture an d conserved processing of Als proteins in these organisms. Although and ALS family is present in each organism, phylogenetic analysis of the C. albica ns. C. dubliniensis, and C. tropicalis ALS genes indicated that, within eac h species, sequence diversification in extensive and unique ALS sequences h ave arisen. Phylogenetic analysis of the ALS and SAP (secreted aspartyl pro teinase) families show that the ALS family is younger than the SAP family. ALS genes in C. albicans, C. dubliniensis, and C. tropicalis tend to be loc ated on chromosomes that also encode genes from the SAP family, yet the two families have unexpectedly different evolutionary histories. Homologous re combination between the tandem repeat sequences present in ALS genes could explain the different histories for co-localized genes in a predominantly c lonal organism like C. ablicans.