Singh Sunil Kumar, Eland Cathlene, Harholt Jesper, Scheller Henrik Vibe, Marchant Alan
Department of Forest Genetics and Plant Physiology, SLU, 901 83 Umeå, Sweden.
Plant J. 2005 Aug;43(3):384-97. doi: 10.1111/j.1365-313X.2005.02455.x.
Despite the fact that several hundred glycosyltransferases have been identified from sequencing of plant genomes, the biological functions of only a handful have been established to date. A Poplar glycosyltransferase 64 (GT64) family member that is differentially expressed during the cell division and elongation phases of cambial growth was identified from previously generated transcript profiling of cambium tissues. The predicted Poplar GT64 protein has a closely related Arabidopsis homolog ECTOPICALLY PARTING CELLS (EPC1). Mutation of the EPC1 gene, one of three Arabidopsis GT64 family members, results in plants with a dramatically reduced growth habit, defects in vascular formation and reduced cell-cell adhesion properties in hypocotyl and cotyledon tissues. Secondary growth is enhanced in epc1 hypocotyl tissues and it is proposed that this results from the abnormal cell-cell adhesion within the cortical parenchyma cell layers. Loss of cell-cell contacts within cotyledon and leaf tissues is also proposed to account for vascular patterning defects and the fragile nature of epc1 tissues. The EPC1 protein thus plays a critical role during plant development in maintaining the integrity of organs via cell-cell adhesion, thereby providing mechanical strength and facilitating the movement of metabolites throughout the plant.
尽管通过植物基因组测序已鉴定出数百种糖基转移酶，但迄今为止仅确定了少数几种的生物学功能。从先前生成的形成层组织转录谱中鉴定出一种杨树糖基转移酶64（GT64）家族成员，该成员在形成层生长的细胞分裂和伸长阶段差异表达。预测的杨树GT64蛋白与拟南芥中一个密切相关的同源物异位分裂细胞（EPC1）。EPC1基因是拟南芥GT64家族的三个成员之一，其突变导致植株生长习性显著降低、维管形成缺陷以及下胚轴和子叶组织中细胞间粘附特性降低。epc1下胚轴组织中的次生生长增强，据推测这是由于皮层薄壁细胞层内细胞间粘附异常所致。子叶和叶片组织中细胞间接触的丧失也被认为是epc1组织维管模式缺陷和脆弱性质的原因。因此，EPC1蛋白在植物发育过程中通过细胞间粘附维持器官完整性方面起着关键作用，从而提供机械强度并促进代谢物在整个植物中的运输。
