Functional characterization of the rice UDP-glucose 4-epimerase 1, OsUGE1: a potential role in cell wall carbohydrate partitioning during limiting nitrogen conditions.
Plants grown under inadequate mineralized nitrogen (N) levels undergo N and carbon (C) metabolic re-programming which leads to significant changes in both soluble and insoluble carbohydrate profiles. However, relatively little information is available on the genetic factors controlling carbohydrate partitioning during adaptation to N-limitation conditions in plants. A gene encoding a uridine-diphospho-(UDP)-glucose 4-epimerase (OsUGE-1) from rice (Oryza sativa) was found to be N-responsive. We developed transgenic rice plants to constitutively over-express the OsUGE-1 gene (OsUGE1-OX1-2). The transgenic rice lines were similar in size to wild-type plants at the vegetative stage and at maturity regardless of the N-level tested. However, OsUGE1-OX lines maintained 18-24% more sucrose and 12-22% less cellulose in shoots compared to wild-type when subjected to sub-optimal N-levels. Interestingly, OsUGE1-OX lines maintained proportionally more galactose and glucose in the hemicellulosic polysaccharide profile of plants compared to wild-type plants when grown under low N. The altered cell wall C-partitioning during N-limitation in the OsUGE1-OX lines appears to be mediated by OsUGE1 via the repression of the cellulose synthesis associated genes, OsSus1, OsCesA4, 7, and 9. This relationship may implicate a novel control point for the deposition of UDP-glucose to the complex polysaccharide profiles of rice cell walls. However, a direct relationship between OsUGE1 and cell wall C-partitioning during N-limitation requires further investigation.
Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada.
David R
DR
Guevara
Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada.
Ashraf
A
El-Kereamy
Department of Biology, College of Science, Sultan Qaboos University, Muscat, Oman.
Mahmoud W
MW
Yaish
Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada.
Yong
Y
Mei-Bi
Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada.
Steven J
SJ
Rothstein
D050260:Carbohydrate Metabolism; D002473:Cell Wall / Q000201:enzymology / Q000378:metabolism*; D002482:Cellulose / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D009584:Nitrogen / Q000378:metabolism*; D012275:Oryza / Q000166:cytology / Q000201:enzymology* / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018520:Plant Shoots / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics; D013395:Sucrose / Q000378:metabolism; D014534:UDPglucose 4-Epimerase / Q000235:genetics / Q000378:metabolism*; D014532:Uridine Diphosphate Glucose / Q000378:metabolism
D010940:Plant Proteins; D013395:Sucrose; D002482:Cellulose; D014534:UDPglucose 4-Epimerase; D009584:Nitrogen; D014532:Uridine Diphosphate Glucose