Transcriptional regulation of morphogenesis in Candida albicans
ALS3 encodes a hypha-specific cell wall protein of the Agglutinin-Like Sequence family of adhesins. The first aim of this project was to define the region of the ALS3 promoter required for its hypha-specific activation. Previous work in our laboratory defined a region of 190 bp between -496 and -306 that is important for ALS3 activation. Furthermore, two sequences that bind the transcriptional repressor Nrgl (NREs), were shown to be required for repression under yeast inducing conditions. In this study, the importance of these NREs for ALS3 repression was confirmed. Between the two studies, eight 13-68 bp overlapping sequences of the ALS3 promoter were placed upstream of the basal -306 to +4 region of ALS3 promoter (previously shown to cause no activation). None of these induced expression of the reporter. Further deletions downstream from -471, or upstream from -321 disrupted the hypha-specific regulation of ALS3. These results suggest that no short region or known response element, in isolation, is sufficient for hypha-specific activation of ALS3. During this study an efficient Streptococcus thermophilus lacZ reporter was developed for C. albicans. This was adopted to enable a high throughput mutagenesis screen on the ALS3 promoter. Another aim of this study was to contribute to the annotation of the C. albicans genome sequence with the EU Galar Fungail Consortium. This was achieved by annotating 6.5% (401 ORFs) of the predicted open reading frames annotated by the Consortium as a whole. These data were used by Christophe d'Enfert to design whole genome C. albicans microassays and to generate the database CandidaDB (http://genolist.pasteur.fr/CandidaDB/). Protocols for the use of these microarrays and for transcript profiling data analysis were established. Validation of the microarrays was carried out by the transcript profiling of cells which had undergone a temperature shift from 25°C to 37°C. This showed the up-regulation of some heat shock and stress response genes, as expected.