Identification of a Sphingolipid α-Glucuronosyltransferase That Is Essential for Pollen Function in Arabidopsis

• Published in: The Plant cell Vol. 26; no. 8; pp. 3314 - 3325
• Main Authors: Rennie, Emilie A., Ebert, Berit, Miles, Godfrey P., Cahoon, Rebecca E., Christiansen, Katy M., Stonebloom, Solomon, Khatab, Hoda, Twell, David, Petzold, Christopher J., Adams, Paul D., Dupree, Paul, Heazlewood, Joshua L., Cahoon, Edgar B., Scheller, Henrik Vibe
• Format: Journal Article
• Language: English
• Published: England American Society of Plant Biologists 01-08-2014
• Subjects: Arabidopsis - enzymology; Arabidopsis - genetics; Arabidopsis - physiology; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Arabidopsis Proteins - physiology; Ceramides; Gene Silencing; Glucosylceramides; Glucuronic Acid - metabolism; Glucuronosyltransferase - genetics; Glucuronosyltransferase - metabolism; Glucuronosyltransferase - physiology; Humans; Inositols; Lipids; Mass spectroscopy; Nicotiana - genetics; Nicotiana - metabolism; Plant cells; Plants; Pollen; Pollen - enzymology; Pollen - metabolism; Pollen - physiology; Saccharomyces cerevisiae - genetics; Sphingolipids; Sphingolipids - metabolism; Yeasts
• ISSN: 1040-4651; 1532-298X
• DOI: 10.1105/tpc.114.129171

Glycosyl inositol phosphorylceramide (GIPC) sphingolipids are a major class of lipids in fungi, protozoans, and plants. GIPCs are abundant in the plasma membrane in plants, comprising around a quarter of the total lipids in these membranes. Plant GIPCs contain unique glycan decorations that include a conserved glucuronic acid (GIcA) residue and various additional sugars; however, no proteins responsible for glycosylating GIPCs have been identified to date. Here, we show that the Arabidopsis thaliana protein INOSITOL PHOSPHORYLCERAMIDE GLUCURONOSYLTRANSFERASE1 (IPUT1) transfers GIcA from UDP-GIcA to GIPCs. To demonstrate IPUT1 activity, we introduced the IPUT1 gene together with genes for a UDP-glucose dehydrogenase from Arabidopsis and a human UDP-GIcA transporter into a yeast mutant deficient in the endogenous inositol phosphorylceramide (IPC) mannosyttransferase. In this engineered yeast strain, IPUT1 transferred GIcA to IPC. Overexpression or silencing of IPUT1 in Nicotiana benthamiana resulted in an increase or a decrease, respectively, in IPC glucuronosyltransferase activity in vitro. Plants in which IPUT1 was silenced accumulated IPC, the immediate precursor, as well as ceramides and glucosylceramides. Plants overexpressing IPUT1 showed an increased content of GIPCs. Mutations in IPUT1 are not transmitted through pollen, indicating that these sphingolipids are essential in plants.