Sphingolipid C-9 methyltransferases are important for growth and virulence but not for sensitivity to antifungal plant defensins in Fusarium graminearum

Vellaisamy Ramamoorthy, Edgar B. Cahoon, Mercy Thokala, Jagdeep Kaur, Jia Li, Dilip M. Shah

Research output: Contribution to journalArticle

40 Scopus citations

Abstract

The C-9-methylated glucosylceramides (GlcCers) are sphingolipids unique to fungi. They play important roles in fungal growth and pathogenesis, and they act as receptors for some antifungal plant defensins. We have identified two genes, FgMT1 and FgMT2, that each encode a putative sphingolipid C-9 methyltransferase (C-9-MT) in the fungal pathogen Fusarium graminearum and complement a Pichia pastoris C-9-MT-null mutant. The ΔFgmt1 mutant produced C-9-methylated GlcCer like the wild-type strain, PH-1, whereas the ΔFgmt2 mutant produced 65 to 75% nonmethylated and 25 to 35% methylated GlcCer. No ΔFgmt1ΔFgmt2 double-knockout mutant producing only nonmethylated GlcCer could be recovered, suggesting that perhaps C-9-MTs are essential in this pathogen. This is in contrast to the nonessential nature of this enzyme in the unicellular fungus P. pastoris. The ΔFgmt2 mutant exhibited severe growth defects and produced abnormal conidia, while the ΔFgmt1 mutant grew like the wild-type strain, PH-1, under the conditions tested. The ΔFgmt2 mutant also exhibited drastically reduced disease symptoms in wheat and much-delayed disease symptoms in Arabidopsis thaliana. Surprisingly, the ΔFgmt2 mutant was less virulent on different host plants tested than the previously characterized ΔFggcs1 mutant, which lacks GlcCer synthase activity and produces no GlcCer at all. Moreover, the ΔFgmt1 and ΔFgmt2 mutants, as well as the P. pastoris strain in which the C-9-MT gene was deleted, retained sensitivity to the antifungal plant defensins MsDef1 and RsAFP2, indicating that the C-9 methyl group is not a critical structural feature of the GlcCer receptor required for the antifungal action of plant defensins.

Original languageEnglish (US)
Pages (from-to)217-229
Number of pages13
JournalEukaryotic Cell
Volume8
Issue number2
DOIs
StatePublished - Feb 2009

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology

Fingerprint Dive into the research topics of 'Sphingolipid C-9 methyltransferases are important for growth and virulence but not for sensitivity to antifungal plant defensins in Fusarium graminearum'. Together they form a unique fingerprint.

  • Cite this