Publications

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

  Ramamoorthy V., Cahoon E.B., Thokala M., Kaur J., Li J., Shah D.M.

  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 ... >> More

  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 DeltaFgmt1 mutant produced C-9-methylated GlcCer like the wild-type strain, PH-1, whereas the DeltaFgmt2 mutant produced 65 to 75% nonmethylated and 25 to 35% methylated GlcCer. No DeltaFgmt1DeltaFgmt2 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 DeltaFgmt2 mutant exhibited severe growth defects and produced abnormal conidia, while the DeltaFgmt1 mutant grew like the wild-type strain, PH-1, under the conditions tested. The DeltaFgmt2 mutant also exhibited drastically reduced disease symptoms in wheat and much-delayed disease symptoms in Arabidopsis thaliana. Surprisingly, the DeltaFgmt2 mutant was less virulent on different host plants tested than the previously characterized DeltaFggcs1 mutant, which lacks GlcCer synthase activity and produces no GlcCer at all. Moreover, the DeltaFgmt1 and DeltaFgmt2 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. << Less

  Eukaryot. Cell 8:217-229(2009) [PubMed] [EuropePMC]

• Candida albicans sphingolipid C9-methyltransferase is involved in hyphal elongation.

  Oura T., Kajiwara S.

  C9-methylated glucosylceramide is a fungus-specific sphingolipid. This lipid is a major membrane component in the cell and is thought to play important roles in the growth and virulence of several fungal species. To investigate the importance of the methyl branch of the long-chain base in glucosyl ... >> More

  C9-methylated glucosylceramide is a fungus-specific sphingolipid. This lipid is a major membrane component in the cell and is thought to play important roles in the growth and virulence of several fungal species. To investigate the importance of the methyl branch of the long-chain base in glucosylceramides in pathogenic fungi, we identified and characterized a sphingolipid C9-methyltransferase gene (MTS1, C9-MethylTransferase for Sphingolipid 1) in the pathogenic yeast Candida albicans. The mts1 disruptant lacked (E,E)-9-methylsphinga-4,8-dienine in its glucosylceramides and contained (E)-sphing-4-enine and (E,E)-sphinga-4,8-dienine. Reintroducing the MTS1 gene into the mts1 disruptant restored the synthesis of (E,E)-9-methylsphinga-4,8-dienine in the glucosylceramides. We also created a disruptant of the HSX11 gene, encoding glucosylceramide synthase, which catalyses the final step of glucosylceramide synthesis, in C. albicans and compared this mutant with the mts1 disruptant. The C. albicans mts1 and hsx11 disruptants both had a decreased hyphal growth rate compared to the wild-type strain. The hsx11 disruptant showed increased susceptibility to SDS and fluconazole, similar to a previously reported sld1 disruptant that contained only (E)-sphing-4-enine in its glucosylceramides, suggesting that these strains have defects in their cell membrane structures. In contrast, the mts1 disruptant grew similarly to wild-type in medium containing SDS or fluconazole. These results suggest that the C9-methyl group of a long-chain base in glucosylceramides plays an important role in the hyphal elongation of C. albicans independent of lipid membrane disruption. << Less

  Microbiology 156:1234-1243(2010) [PubMed] [EuropePMC]

• Identification of fungal sphingolipid C9-methyltransferases by phylogenetic profiling.

  Ternes P., Sperling P., Albrecht S., Franke S., Cregg J.M., Warnecke D., Heinz E.

  Fungal glucosylceramides play an important role in plant-pathogen interactions enabling plants to recognize the fungal attack and initiate specific defense responses. A prime structural feature distinguishing fungal glucosylceramides from those of plants and animals is a methyl group at the C9-pos ... >> More

  Fungal glucosylceramides play an important role in plant-pathogen interactions enabling plants to recognize the fungal attack and initiate specific defense responses. A prime structural feature distinguishing fungal glucosylceramides from those of plants and animals is a methyl group at the C9-position of the sphingoid base, the biosynthesis of which has never been investigated. Using information on the presence or absence of C9-methylated glucosylceramides in different fungal species, we developed a bioinformatics strategy to identify the gene responsible for the biosynthesis of this C9-methyl group. This phylogenetic profiling allowed the selection of a single candidate out of 24-71 methyltransferase sequences present in each of the fungal species with C9-methylated glucosylceramides. A Pichia pastoris knock-out strain lacking the candidate sphingolipid C9-methyltransferase was generated, and indeed, this strain contained only non-methylated glucosylceramides. In a complementary approach, a Saccharomyces cerevisiae strain was engineered to produce glucosylceramides suitable as a substrate for C9-methylation. C9-methylated sphingolipids were detected in this strain expressing the candidate from P. pastoris, demonstrating its function as a sphingolipid C9-methyltransferase. The enzyme belongs to the superfamily of S-adenosylmethionine-(SAM)-dependent methyltransferases and shows highest sequence similarity to plant and bacterial cyclopropane fatty acid synthases. An in vitro assay showed that sphingolipid C9-methylation is membrane-bound and requires SAM and Delta4,8-desaturated ceramide as substrates. << Less

  J. Biol. Chem. 281:5582-5592(2006) [PubMed] [EuropePMC]

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