Functional characterization of the rice UDP-glucose 4-epimerase 1, OsUGE1: a potential role in cell wall carbohydrate partitioning during limiting nitrogen conditions

PLoS One. 2014 May 1;9(5):e96158. doi: 10.1371/journal.pone.0096158. eCollection 2014.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carbohydrate Metabolism
  • Cell Wall / enzymology
  • Cell Wall / metabolism*
  • Cellulose / metabolism
  • Gene Expression Regulation, Plant
  • Nitrogen / metabolism*
  • Oryza / cytology
  • Oryza / enzymology*
  • Oryza / genetics
  • Plant Proteins / genetics
  • Plant Proteins / metabolism*
  • Plant Shoots / metabolism
  • Plants, Genetically Modified / enzymology
  • Plants, Genetically Modified / genetics
  • Sucrose / metabolism
  • UDPglucose 4-Epimerase / genetics
  • UDPglucose 4-Epimerase / metabolism*
  • Uridine Diphosphate Glucose / metabolism

Substances

  • Plant Proteins
  • Sucrose
  • Cellulose
  • UDPglucose 4-Epimerase
  • Nitrogen
  • Uridine Diphosphate Glucose

Grants and funding

This work was partially supported by the Natural Sciences and Engineering Research Council of Canada and Syngenta Biotechnology Inc. to SJR, and by the Ministry of Research and Innovation Post-Doctoral Fellowship to D.R.G. There are no products in development or marketed products to declare. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.