The cAMP phosphodiesterase encoded by CaPDE2 is required for hyphal development in Candida albicans

Abstract

The cAMP-dependent pathway, which regulates yeast-to-hypha morphogenesis in Candida albicans, is controlled by changes in cAMP levels determined by the processes of synthesis and hydrolysis. Both low-and high-affinity cAMP phosphodiesterases are encoded in the C. albicans genome. CaPDE2, encoding the high-affinity cAMP phosphodiesterase, has been cloned and shown to be toxic in Saccharomyces cerevisiae upon overexpression under pGAL1, but functional under the moderate pMET3. Deletion of CaPDE2 causes elevated cAMP levels and responsiveness to exogenous cAMP, higher sensitivity to heat shock, severe growth defects at 42 6C and highly reduced levels of EFG1 transcription. In vitro in hypha-inducing liquid medium CaPDE2, deletion prohibits normal hyphal, but not pseudohyphal growth. On solid medium capde2 mutants form aberrant hyphae, with fewer branches and almost no lateral buds, which are deficient in hypha-to-yeast reversion. The phenotypic defects of capde2 mutants show that the cAMP-dependent pathway plays specific roles in hyphal and pseudohyphal development, its regulatory role however, being greater in liquid than on solid medium in vitro. The increased expression of CaPDE2 after serum addition correlates well with a drop in cAMP levels following the initial rise in response to the hyphal inducer. These results suggest that Capde2p mediates a desensitization mechanism by lowering basal cAMP levels in response to environmental stimuli in C. albicans.

Deletion of PDE2, the gene encoding the high‐affinity cAMP phosphodiesterase, results in changes of the cell wall and membrane in Candida albicans

“…• C and impaired for growth at 42 • C (Jung and Stateva, 2003). In the current investigation, their sensitivity to SDS and Calcofluor white (CFW), was tested.…”

“…Cells were pelleted (OD 600 = 200), resuspended in 8 ml dH 2 O and divided into four equal aliquots, two were used for the determination of the cell dry weight and the others processed as described (Carotti et al, 2002). The conditions for serum hyphal induction prior to cell wall analysis of hyphae, were as described previously (Jung and Stateva, 2003).…”

“…• C and reduces levels of transcription of EFG1 (Jung and Stateva, 2003). In liquid media, PDE2 deletion inhibits normal hyphal, but not pseudohyphal, growth under most standard inducing conditions.…”

“…Two phosphodiesterase-encoding genes PDE1 and PDE2 have been found in the fungal pathogen C. albicans (Bahn et al, 2003;Hoyer et al, 1994;Jung and Stateva, 2003). Mutants lacking PDE1 are not yet available; however, hetero-and homozygous pde2 null mutants have been generated and characterized (Bahn et al, 2003;Jung and Stateva, 2003).…”

“…Mutants lacking PDE1 are not yet available; however, hetero-and homozygous pde2 null mutants have been generated and characterized (Bahn et al, 2003;Jung and Stateva, 2003). Deletion of PDE2 elevates intracellular cAMP levels, increases responsiveness to exogenous cAMP and sensitivity to heat shock, causes growth defects at 42…”