The very long-chain fatty acid elongase FgElo2 governs tebuconazole sensitivity and virulence in Fusarium graminearum.

Abstract

Very long-chain fatty acids (VLCFAs), the precursors for the synthesis of sphingolipids (SLs), play pivotal roles in the development and stress response in eukaryotes. In Saccharomyces cerevisiae, VLCFAs are synthesized in the endoplasmic reticulum (ER) through a four-step elongation cycle. However, the functions of VLCFA elongases in phytopathogenic fungi remain largely unexplored. Here, we identified a single copy of the VLCFA elongase gene FgELO2 in Fusarium graminearum that causes Fusarium head blight worldwide. FgElo2 localized to ER membrane, and deletion mutant of FgELO2 exhibited serious defects in vegetative growth and conidiation. Importantly, ΔFgElo2 led to ergosterol content reduction and disrupted the ER-localization of 14-α-demethylase FgCyp51s, indicating that the scarce of SLs reduced ergosterol, which ultimately elevated the sensitivity of ΔFgElo2 to tebuconazole. Fluorescent microscopic examination suggested that FgElo2 was degraded upon cell membrane stress. ΔFgElo2 showed decreased phosphorylation of high osmolarity glycerol (HOG) pathway and subsequently exhibited remarkable sensitivity to osmotic stress. In addition, fungal virulence was dramatically reduced in ΔFgElo2 via inhibiting deoxynivalenol production and formation of infection structures. Together, this study demonstrates that the VLCFA elongase FgElo2 modulates fungal development, tebuconazole sensitivity, stress responses and virulence, which may advance our understanding of pathogen-host interactions mediated by VLCFAs.