Phytophthora capsici sterol reductase PcDHCR7 has a role in mycelium development and pathogenicity

The de novo biosynthesis of sterols is critical for the majority of eukaryotes; however, some organisms lack this pathway, including most oomycetes. Phytophthora spp. are sterol auxotrophic but, remarkably, have retained a few genes encoding enzymes in the sterol biosynthesis pathway. Here, we show that PcDHCR7, a gene in Phytophthora capsici predicted to encode Delta 7-sterol reductase, displays multiple functions. When expressed in Saccharomyces cerevisiae, PcDHCR7 showed the Delta 7-sterol reductase activity. Knocking out PcDHCR7 in P. capsici resulted in loss of the capacity to transform ergosterol into brassicasterol, which means PcDHCR7 has the Delta 7-sterol reductase activity in P. capsici itself. This enables P. capsici to transform sterols recruited from the environment for better use. The biological characteristics of Delta PcDHCR7 transformants were compared with those of the wild-type strain and a PcDHCR7 complemented transformant, and the results showed that PcDHCR7 plays a key role in mycelium development and pathogenicity of zoospores. Further analysis of the transcriptome indicated that the expression of many genes changed in the Delta PcDHCR7 transformant, which involve in different biological processes. It is possible that P. capsici compensates for the defects caused by the loss of PcDHCR7 by remodelling its transcriptome.

Automated summary

This study reveals the critical role of the PcDHCR7 gene in sterol biosynthesis, mycelium development, and pathogenicity in Phytophthora capsici. The loss of PcDHCR7 leads to changes in gene expression and potentially compensatory modulation of the transcriptome.