AUTHOR=Wang Weizhen , Cui Tongshan , Zhang Fan , Xue Zhaolin , Zhang Borui , Liu Xili 

TITLE=Functional Analysis of the C-5 Sterol Desaturase PcErg3 in the Sterol Auxotrophic Oomycete Pathogen Phytophthora capsici

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.811132

DOI=10.3389/fmicb.2022.811132

ISSN=1664-302X

ABSTRACT=<p>Although sterols play an important role in most eukaryotes, some oomycetes, including <italic>Phytophthora</italic> spp., have lost the sterol synthesis pathway. Nevertheless, the <italic>ERG3</italic> gene encoding C-5 sterol desaturase in the sterol synthesis pathway is still present in the genomes of <italic>Phytophthora</italic> spp. <italic>Phytophthora capsici</italic>, a destructive pathogen with a broad range of plant hosts, poses a significant threat to the production of agriculture. This study focused on the <italic>ERG3</italic> gene in <italic>P. capsici</italic> (<italic>PcERG3</italic>) and explored its function in this pathogen. It showed that the <italic>PcERG3</italic> gene could be expressed in all tested developmental stages of <italic>P. capsici</italic>, with sporangium and mycelium displaying higher expression levels. A potential substrate of Erg3 (stellasterol) was used to treat the <italic>P. capsici</italic> wild-type strain and a <italic>PcERG3</italic>Δ transformant, and their sterol profiles were determined by GC-MS. The wild-type strain could convert stellasterol into the down-stream product while the transformant could not, indicating that PcErg3 retains the C-5 sterol desaturase activity. By comparing the biological characteristics of different strains, it was found that <italic>PcERG3</italic> is not important for the development of <italic>P. capsici</italic>. The pathogenicity of the <italic>PcERG3</italic>Δ transformants and the wild-type strain was comparable, suggesting that <italic>PcERG3</italic> is not necessary for the interaction between <italic>P. capsici</italic> and its hosts. Further investigations revealed that the <italic>PcERG3</italic>Δ transformants and the wild-type strain displayed a similar level of tolerance to external adversities such as unsuitable temperatures, high osmotic pressures, and intemperate pH, signifying that <italic>PcERG3</italic> is not essential for <italic>P. capsici</italic> to cope with these environmental stresses.</p>