Biosynthetic origin and longevity in vivo of α- d -mannopyranosyl-(1 → 4)-α- d -glucuronopyranosyl-(1 → 2)- myo -inositol, an unusual extracellular oligosaccharide produced by cultured rose cells

Abstract

A non-reducing trisaccharide, alpha-D-mannopyranosyl-(1 --> 4)-alpha-D-glucuronopyranosyl-(1 --> 2)-myo-inositol (MGI) accumulated in the spent medium of cell-suspension cultures of 'Paul's Scarlet' rose (Rosa sp.) predominantly during the period of rapid cell growth. This trisaccharide was also produced by cultures of sycamore (Acer pseudoplatanus L.) but not by those of the graminaceous monocots maize (Zea mays L.) and tall fescue grass (Festuca arundinacea Schreb.). When added to cultured Rosa cells, [(14)C]MGI was neither taken up by the cells nor bound to the cell surface and was not metabolised extracellularly. When D-[6-(14)C]glucuronic acid was fed to cultured Rosa cells, extracellular [(14)C]MGI started to appear only after a 5-h lag period, compared with a 0.5-h lag period for labelling of extracelluar polysaccharides. Furthermore, [(14)C]MGI continued to accumulate in the medium for at least 20 h after the accumulation of (14)C-polymers had ceased. These observations indicate that extracellular MGI was produced from a slowly turning-over pool of a pre-formed intermediate. Structural considerations indicate that the intermediate could be a glucuronomannan or a phytoglycolipid (glycophosphosphingolipid). No Rosa polysaccharides could be found that generated MGI in the presence of living Rosa cells. We therefore favour phytoglycolipids as the probable biosynthetic origin of MGI.

Abnormal Glycosphingolipid Mannosylation Triggers Salicylic Acid–Mediated Responses inArabidopsis

“…Therefore, we propose that the Hex on the major GIPC species detected in this study is Man. A sphingolipid-derived oligosaccharide with this composition was previously isolated from bean (Phaseolus vulgaris), rose (Rosa sp), and maize (Zea mays) (Carter et al, 1958Carter and Koob, 1969;Smith and Fry, 1999), supporting our assignment. Our discovery that defective GDP-Man transport leads to defective GIPC synthesis has parallels with the phenotype of the yeast GDP-Man transporter mutant vrg4, which shows both a reduced growth rate (Poster and Dean, 1996) and a lack of mannosylated IPCs (Dean et al, 1997).…”

Identification of a sphingolipid‐specific phospholipase D activity associated with the generation of phytoceramide‐1‐phosphate in cabbage leaves

“…Alkaline phosphatase [8] in Spirodela oligorrhiza and arabinogalactan protein in Pyrus communis [9] are typical glycosylphosphatidylinositolanchored proteins containing a ceramide moiety as a hydrophobic residue. They hypothesized a signaling role for released mannopyranosyl glucuronopyranosyl inositol [10], and suggested GIPC as a source of the mannopyranosyl glucuronopyranosyl inositol. They concluded that PLD activity is involved in the release of arabinogalactan protein.…”

GIPC: Glycosyl Inositol Phospho Ceramides, the major sphingolipids on earth

“…Authors suggested that GIPCs could be the source of this growth activator compound. 29 Finally, a phospholipase D activity that specifically hydrolyzes GIPCs and produces phytoceramide-1-phosphate (PC1P) have been recently identified in Brassicaceae. 30 Authors suggested that GIPC-PLD may play an important signaling role in the biological response in plant cells by producing signaling molecules, but the mechanism of regulation of the enzyme activity is largely unknown.…”