CONSTRUCTION OF AN SFII MACRORESTRICTION MAP OF THE CANDIDA-ALBICANS GENOME

The opportunistic fungal pathogen, Candida albicans, is diploid is usu ally isolated and has no apparent sexual cycle. Genetic analysis has t herefore been very difficult. Molecular genetics has yielded important information in the past few years, but it too is hampered by the lack of a good genetic map. Using the well-characterized strain 1006 and s train WO-1, which undergoes the white-opaque phenotypic transition, we have developed a genomic restriction map of C. albicans with the enzy me SfiI. There are approximately 34 SfiI restriction sites in the C. a lbicans genome. Restriction fragments were separated by pulsed-field e lectrophoresis and were assigned to chromosomes by hybridization of co mplete and partial digests with known chromosome-specific probes as we ll as by digestion of isolated chromosomes. Telomeric fragments were i dentified by hybridization with a telomere-specific probe (C. Sadhu, M . J. McEachern, E. P. Rustchenko-Bulgac, J. Schmid, D. R. Soll, and J. B. Hicks, J. Bacteriol. 173:842-850, 1991). WO-1 differs from 1006 in that it has undergone three reciprocal chromosomal translocations. An alysis of the translocation products indicates that each translocation has occurred at or near an SfiI site; thus, the SfiI fragments from t he two strains are similar or identical. The tendency for translocatio n to occur at or near SfiI sites may be related to the repeated sequen ce RPS 1, which contains four such sites and could provide homology fo r ectopic pairing and crossing over. The genome size of both strains i s about 16 to 17 megabases, in good agreement with previous determinat ions.