Identification of orthologous modules from Candida albicans expression data.
We used a set of gene expression profiles measuring the response of C. albicans to 3 environmental stresses in lieu of the S. pombe profiles, to perform the same analysis of conserved orthologous modules. We first constructed a set of C. albicans transcriptional modules independently of the S. cerevisiae profiles, and then identified S. cerevisiae – C. albicans orthologous modules. Since the C. albicans gene expression data set was very small (consisting of 3 time courses with 3 time points in each), we expected to find only a limited set of very general conserved stress responses. Interestingly, in concordance with previous reports, we couldn't find an orthologous C. albicans RP module. When we specifically examined the expression pattern of the C. albicans RP genes in this dataset, we observed only some reduction of some of the RPs, in contrast to the typically uniform and strong reduction of RPs under stress in S. cerevisiae and S. pombe. Thus, the regulatory mechanism of RPs in C. albicans underwent a significant functional modification with respect to what seems to be the ancestral mechanism in the Ascomycota phylum. Other stress-related modules, most notably the ribosomal biogenesis module, do show significant conservation with the S. cerevisiae ones.
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