Guevara David R, El-Kereamy Ashraf, Yaish Mahmoud W, Mei-Bi Yong, Rothstein Steven J
Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada.
Department of Biology, College of Science, Sultan Qaboos University, Muscat, Oman.
PLoS One. 2014 May 1;9(5):e96158. doi: 10.1371/journal.pone.0096158. eCollection 2014.
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.
在矿化氮（N）水平不足的条件下生长的植物会经历氮和碳（C）代谢重编程，这会导致可溶性和不溶性碳水化合物谱发生显著变化。然而，关于植物在适应氮限制条件期间控制碳水化合物分配的遗传因素，目前可用的信息相对较少。从水稻（Oryza sativa）中发现了一个编码尿苷二磷酸 - （UDP） - 葡萄糖4 - 表异构酶（OsUGE - 1）的基因对氮有响应。我们培育了组成型过表达OsUGE - 1基因的转基因水稻植株（OsUGE1 - OX1 - 2）。无论测试的氮水平如何，转基因水稻品系在营养生长阶段和成熟时的大小与野生型植株相似。然而，当处于次优氮水平时，与野生型相比，OsUGE1 - OX品系的地上部分蔗糖含量多18 - 24%，纤维素含量少12 - 22%。有趣的是，当在低氮条件下生长时，与野生型植株相比，OsUGE1 - OX品系在植物半纤维素多糖谱中保持了比例更高的半乳糖和葡萄糖。在OsUGE1 - OX品系中，氮限制期间细胞壁碳分配的改变似乎是由OsUGE1通过抑制与纤维素合成相关的基因OsSus1、OsCesA4、7和9介导的。这种关系可能暗示了UDP - 葡萄糖沉积到水稻细胞壁复杂多糖谱中的一个新控制点。然而，OsUGE1与氮限制期间细胞壁碳分配之间的直接关系需要进一步研究。
