Fructan accumulation induced by nitrogen deficiency in barley leaves correlates with the level of sucrose:fructan 6-fructosyltransferase mRNA.
Hydroponically cultivated barley plants were exposed to nitrogen (N)-deficiency followed by N-resupply. Metabolic and genetic regulation of fructan accumulation in the leaves were investigated. Fructan accumulated in barley leaves under N-deficiency was mobilized during N-resupply. The enhanced total activity of fructan-synthesizing enzymes, sucrose:sucrose 1-fructosyltransferase (EC 2.4.1.99) and sucrose:fructan 6-fructosyltransferase (6-SFT; EC 2.4. 1.10) caused by N-deficiency decreased with the mobilization of fructan during N-resupply. The activity of the barley fructan-degrading enzyme, fructan exohydrolyase (EC 3.2.1.80) was less affected by the N status. The low level of foliar soluble acid invertase activity under N-deficiency conditions was maintained during the commencement of N-resupply but increased subsequently. Further analyses by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, western blot and northern blot demonstrated that the fructan accumulation and the total activity of fructan-synthesizing enzymes correlated with the 6-SFT mRNA level. We suggest that the changes in fructan levels under N stress are intimately connected with the regulation of fructan synthetic rate which is mostly controlled by 6-SFT.
Wang
C
C
Department of Botany, Stockholm University, Sweden.
Van den Ende
W
W
Tillberg
J E
JE
D005630:Fructans / Q000096:biosynthesis*; D005632:Fructose / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D005947:Glucose / Q000378:metabolism; D006602:Hexosyltransferases / Q000235:genetics* / Q000378:metabolism; D001467:Hordeum / Q000201:enzymology* / Q000235:genetics*; D018527:Hydroponics; D007700:Kinetics; D009584:Nitrogen / Q000378:metabolism*; D018515:Plant Leaves / Q000201:enzymology; D012333:RNA, Messenger / Q000235:genetics; D014158:Transcription, Genetic
D005630:Fructans; D012333:RNA, Messenger; D005632:Fructose; D006602:Hexosyltransferases; C097181:sucrose - fructan 6-fructosyltransferase; D005947:Glucose; D009584:Nitrogen