Candida albicans is a pathogenic fungus able to change morphology in response to variations in its growth environment. Simple inoculation of stationary cells into fresh medium at 37 degrees C, without Show more
Candida albicans is a pathogenic fungus able to change morphology in response to variations in its growth environment. Simple inoculation of stationary cells into fresh medium at 37 degrees C, without any other manipulations, appears to be a powerful but transient inducer of hyphal formation; this process also plays a significant role in classical serum induction of hyphal formation. The mechanism appears to involve the release of hyphal repression caused by quorum-sensing molecules in the growth medium of stationary-phase cells, and farnesol has a strong but incomplete role in this process. We used DNA microarray technology to study both the resumption of growth of Candida albicans cells and molecular regulation involving farnesol. Maintaining farnesol in the culture medium during the resumption of growth both delays and reduces the induction of hypha-related genes yet triggers expression of genes encoding drug efflux components. The persistence of farnesol also prevents the repression of histone genes during hyphal growth and affects the expression of putative or demonstrated morphogenesis-regulating cyclin genes, such as HGC1, CLN3, and PCL2. The results suggest a model explaining the triggering of hyphae in the host based on quorum-sensing molecules. Show less
G1 cyclins coordinate environmental conditions with growth and differentiation in many organisms. In the pathogen Candida albicans, differentiation of hyphae is induced by environmental cues but in a Show more
G1 cyclins coordinate environmental conditions with growth and differentiation in many organisms. In the pathogen Candida albicans, differentiation of hyphae is induced by environmental cues but in a cell cycle-independent manner. Intriguingly, repressing the G1 cyclin Cln3p under yeast growth conditions caused yeast cells to arrest in G1, increase in size, and then develop into hyphae and pseudohyphae, which subsequently resumed the cell cycle. Differentiation was dependent on Efg1p, Cph1p, and Ras1p, but absence of Ras1p was also synthetically lethal with repression of CLN3. In contrast, repressing CLN3 in environment-induced hyphae did not inhibit growth or the cell cycle, suggesting that yeast and hyphal cell cycles may be regulated differently. Therefore, absence of a G1 cyclin can activate developmental pathways in C. albicans and uncouple differentiation from the normal environmental controls. The data suggest that the G1 phase of the cell cycle may therefore play a critical role in regulating hyphal and pseudohyphal development in C. albicans. Show less