Genome
One of the most important features of the C. albicans genome is the occurrence of numeric and structural chromosomal rearrangements as means of generating genetic diversity, named chromosome length polymorphisms (contraction/expansion of repeats), reciprocal translocations, chromosome deletions and trisomy of individual chromosomes. These karyotypic alterations lead to changes in the phenotype, which is an adaptation strategy of this fungus. These mechanisms will be better understood with the complete analysis of the C. albicans genome.
The C. albicans genome for strain SC5314 was sequenced at the Stanford DNA Sequencing and Technology Center. The genome of the WO1 strain was sequenced by the Broad Institute of MIT and Harvard.
The sequencing of the C. albicans genome and subsequently of the genomes of several other medically relevant Candida species has profoundly and irreversibly changed the way Candida species are now investigated and understood. The C. albicans genome sequencing effort was launched in October 1996. Successive releases of the sequencing data and genome assemblies have occurred in the last 10 years, culminating in the release of the diploid assembly 19, which provided a haploid version of the genome along with data on allelic regions in the genome. A refined assembly 20 with the eight assembled C. albicans chromosomes was released in the summer of 2006. Importantly, the availability of sequencing data prior to the completion of the genome sequence has made it possible to start C. albicans postgenomics early on. In this regard, genome databases have been made available to the research community, providing different forms of genome annotation. These have been merged in a community-based annotation hosted by the Candida Genome Database. The availability of the genome sequence has paved the way for the implementation of postgenomic approaches to the study of C. albicans: macroarrays and then microarrays have been developed and used to study the C. albicans transcriptome; proteomics has also been developed and complements transcriptional analyses; furthermore, systematic approaches are becoming available to study the contribution of each C. albicans gene in different contexts. Other Candida genome sequences have been, or are being, determined: C. glabrata, C. dubliniensis, C. parapsilosis, C. guilliermondii, C. lusitaniae, and C. tropicalis. These species will soon enter the postgenomic era, as well, and provide interesting comparative data. The genome sequences obtained for the different Candida species along with those of nonpathogenic hemiascomycetes provide a wealth of knowledge on the evolutionary processes that shaped the hemiascomycete group, as well as those that may have contributed to the success of different Candida species as pathogens.
An unusual feature of the Candida genus is that in many of its species (including C. albicans and C. tropicalis, but not, for instance, C. glabrata) the CUG codon, which normally specifies leucine, specifies serine in these species. This is an unusual example of a departure from the universal genetic code, and most such departures are in start codons or, for eukaryotes, mitochondrial genetic codes. This alteration may, in some environments, help these Candida species by inducing a permanent stress response, a more generalized form of the heat shock response.
The genome of C. albicans is highly dynamic, and this variability has been used advantageously for molecular epidemiological studies and population studies in this species. The genome sequence has allowed for identifying the presence of a parasexual cycle (no meiotic division) in C. albicans. This parasexual cycle is under the control of mating-type loci and switching between white and opaque phenotypes. Investigating the role the mating process plays in the dynamics of the C. albicans population or in other aspects of C. albicans biology and pathogenicity will undoubtedly represent an important focus for future research. A similar lack of meiosis was found in Saccharomyces cerevisiae altered to use the same genetic code as C. albicans.
Read more about this topic: Candida Albicans