Fructans, but not the sucrosyl-galactosides, raffinose and loliose, are affected by drought stress in perennial ryegrass.
The aim of this study was to evaluate the putative role of the sucrosyl-galactosides, loliose [alpha-D-Gal (1,3) alpha-D-Glc (1,2) beta-D-Fru] and raffinose [alpha-D-Gal (1,6) alpha-D-Glc (1,2) beta-D-Fru], in drought tolerance of perennial ryegrass and to compare it with that of fructans. To that end, the loliose biosynthetic pathway was first established and shown to operate by a UDP-Gal: sucrose (Suc) 3-galactosyltransferase, tentatively termed loliose synthase. Drought stress increased neither the concentrations of loliose and raffinose nor the activities of loliose synthase and raffinose synthase (EC 2.4.1.82). Moreover, the concentrations of the raffinose precursors, myoinositol and galactinol, as well as the gene expressions of myoinositol 1-phosphate synthase (EC 5.5.1.4) and galactinol synthase (EC 2.4.1.123) were either decreased or unaffected by drought stress. Taken together, these data are not in favor of an obvious role of sucrosyl-galactosides in drought tolerance of perennial ryegrass at the vegetative stage. By contrast, drought stress caused fructans to accumulate in leaf tissues, mainly in leaf sheaths and elongating leaf bases. This increase was mainly due to the accumulation of long-chain fructans (degree of polymerization > 8) and was not accompanied by a Suc increase. Interestingly, Suc but not fructan concentrations greatly increased in drought-stressed roots. Putative roles of fructans and sucrosyl-galactosides are discussed in relation to the acquisition of stress tolerance.
Amiard
Véronique
V
Unité Mixte de Recherche Institut National de la Recherche Agronomique-Université de Caen-Basse Normandie, Laboratoire de Physiologie et Biochimie végétales, Institut de Recherche en Biologie Appliquée, Université, 14032 Caen cedex, France.
Morvan-Bertrand
Annette
A
Billard
Jean-Pierre
JP
Huault
Claude
C
Keller
Felix
F
Prud'homme
Marie-Pascale
MP
D004190:Disasters; D005630:Fructans / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D008129:Lolium / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D009005:Monosaccharides / Q000378:metabolism; D009928:Organ Specificity; D018515:Plant Leaves / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism; D011887:Raffinose / Q000096:biosynthesis / Q000378:metabolism*; D013395:Sucrose / Q000378:metabolism; D014312:Trisaccharides / Q000378:metabolism*; D014867:Water / Q000378:metabolism*
D005630:Fructans; D009005:Monosaccharides; D014312:Trisaccharides; C478028:galactopyranosyl-1-3-glucopyranosyl-1-2-fructofuranose; D014867:Water; D013395:Sucrose; D011887:Raffinose