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

Abstract

The de novo biosynthesis of sterols is critical for eukaryotes, however, some organisms lack this pathway including most oomycetes. Phytophthora spp. are sterol auxotroph but remarkably, have retained a few genes encoding enzymes in the sterol biosynthesis pathway. Here we investigated the function of PcDHCR7, a gene in Phytophthora capsici predicted to encode the Δ7-sterol reductase. When expressed in Saccharomyces cerevisiae, PcDHCR7 showed a Δ7-sterol reductase activity. Knocking out PcDHCR7 in P. capsici resulted in loss of the capacity to transform ergosterol into brassicasterol, which means PcDHCR7 has a Δ7-sterol reductase activity in P. capsici itself. This enables P. capsici to transform sterols recruited from the environment for better use. Biological characteristics were compared between wild-type isolate and PcDHCR7 knock-out transformants. The results indicated that PcDHCR7 plays a key role in mycelium development and pathogenicity of zoospores in P. capsici.

The mysterious route of sterols in oomycetes

“…For example, PAU : PleasenotethatasperPLOSstyle; iftwodifferentspeciessharethesamegenus hytophthora cactorum seems to have a preference for taking up Δ 5 sterols over Δ 5,7 sterols and tends to transform Δ 5,7 sterols into Δ 5 ones [21], probably mediated by DHCR7. This is corroborated by our recent study, which showed that DHCR7 in P. capsici is indeed responsible for reducing the double bond at that position [17]. When comparing different sterols or sterol mixtures, some stand out in showing higher activities than others.…”

“…For DHCR7 in Phytophthora capsici, we have evidence that this is indeed the case. It can indeed convert ergosterol into brassicasterol, and this modification seems to be essential for the completion of the asexual life cycle under certain conditions [17]. For producing zoospores in vitro, P. capsici requires medium supplemented with sterols.…”

“…For producing zoospores in vitro, P. capsici requires medium supplemented with sterols. CRISPR/Cas-9-mediated knock-out of DHCR7 resulted in strains that no longer responded to ergosterol; unlike the wild-type strain, they could hardly form zoospores on medium supplemented with ergosterol [17].…”

Anti-Fungal Activity of Moutan cortex Extracts against Rice Sheath Blight (Rhizoctonia solani) and Its Action on the Pathogen’s Cell Membrane

“…cortex had genus selectivity and had a high antifungal effect on Rhizoctonia, Fusarium, Colletotrichum, and Botryosphaeria, but the antifungal effect on Phytophthora, Alternaria , and Botrytis was poor. We speculated that the reason for this difference may be the different contents of the cell wall or cell membrane structural components in different species, leading to the different difficulties of antifungal drugs entering the cells, for example, Phytophthora, most of which are ergosterol-deficient, so they are less sensitive to agents targeting cell membranes . Compared with other reported extracts of plants, the ethanol extract of M.…”

The Mevalonate Pathway Is Important for Growth, Spore Production, and the Virulence of Phytophthora sojae

“…However, two enzymes (ERG3 and DHCR7) that function in the last steps of sterol biosynthesis were reported to present in Phytophthora and Pythium species (Wang et al, 2021a). These two enzymes were proposed to modify the exogenous sterols, especially DCHR7 was effective in converting ergosterol into brassicasterol in Phytophthora capsici (Wang et al, 2021b). Conversely, Saprolegnia parasitica and Aphanomyces euteiches are sterol autotrophs (i.e., synthesis cholesterol derivatives and fucosterol, respectively) and the sterol biosynthesis sub-branch has been identified in these two oomycete pathogens (Madoui et al, 2009;Warrilow et al, 2014).…”