Roles of P-body factors in Candida albicans filamentation and stress response

Hyphal growth is strongly associated with virulence in the human fungal pathogen Candida albicans . While hyphal transcriptional networks have been the subject of intense study, relatively little is known about post-transcriptional regulation. Previous work reported that P Body (PB) factors Dhh1 and Edc3 were required for virulence and filamentation, suggesting an essential role for post-transcriptional regulation of these processes. However, the molecular roles of these factors have not been determined. To further study the function of PB factors in filamentation, we generated homozygous deletions of DHH1 and EDC3 in the prototrophic strain SC5314 using CRISPR-Cas9. Homozygous dhh1 deletion strongly impaired growth and altered filamentation, in addition to exhibiting unusual colony morphology in response to heat stress.

Using RNA-seq, we found DHH1 deletion disrupts the regulation of thousands of genes under both yeast and hyphal growth conditions. This included upregulation of many stress response genes in the absence of stress, similar to deletion of the S. cerevisiae DHH1 homolog. In contrast, we found EDC3 was not required for heat tolerance or filamentation. These results support a model in which DHH1 , but not EDC3 , represses hyphal stress response transcripts in yeast and remodels the transcriptome during filamentation. Our paper supports distinct requirements for specific mRNA decay factors, bolstering evidence for post-transcriptional regulation of filamentation in C. albicans .

Author summary

In the dimorphic fungal pathogen C. albicans , the hyphal phenotype corresponds with pathogenicity. While transcriptional control of hyphal growth has been extensively studied, comparatively little is known about post-transcriptional regulation of this significant morphological shift. PB factors are associated with mRNA decay and translational repression. Here we investigate the roles of two PB factors in growth, filamentation, and gene expression. Although deletion of PB factor EDC3 did not impact growth or filamentation, dhh1Δ/Δ had greatly impaired growth and heat tolerance as well as unusual hyphal phenotypes. Additionally, we found that the transcriptomes of dhh1Δ/Δ yeast and hyphae were highly dysregulated. The extensive transcriptomic impacts of the absence of Dhh1 correlated with our phenotypic findings. Stress-associated genes were induced under non-stress conditions and the filamentation response was blunted under physiologically relevant in vitro conditions. We demonstrate that mRNA decay factors play distinct roles in regulating C. albicans morphology and that Dhh1 contributes to environmentally appropriate expression of the stress response and hyphal growth.