Plant Science Group, School of Environmental and Life Sciences, The University of Newcastle, Newcastle NSW 2308, Australia.
Plant J. 2010 Aug;63(4):651-61. doi: 10.1111/j.1365-313X.2010.04269.x.
Transfer cells are specialised transport cells containing invaginated wall ingrowths that generate an amplified plasma membrane surface area with high densities of transporter proteins. They trans-differentiate from differentiated cells at sites at which enhanced rates of nutrient transport occur across apo/symplasmic boundaries. Despite their physiological importance, little is known of the molecular mechanisms regulating construction of their intricate wall ingrowths. We investigated the genetic control of wall ingrowth formation in phloem parenchyma transfer cells of leaf minor veins in Arabidopsis thaliana. Wall ingrowth development in these cells is substantially enhanced upon exposing plants to high-light or cold treatments. A hierarchical bioinformatic analysis of public microarray datasets derived from the leaves of plants subjected to these treatments identified GIGANTEA (GI) as one of 46 genes that are commonly up-regulated twofold or more under both high-light and cold conditions. Histological analysis of the GI mutants gi-2 and gi-3 showed that the amount of phloem parenchyma containing wall ingrowths was reduced 15-fold compared with wild-type. Discrete papillate wall ingrowths were formed in gi-2 plants but failed to develop into branched networks. Wall ingrowth development in gi-2 was not rescued by exposing these plants to high-light or cold conditions. In contrast, over-expression of GI in the gi-2 background restored wall ingrowth deposition to wild-type levels. These results indicate that GI regulates the ongoing development of wall ingrowth networks at a point downstream of inputs from environmental signals.
转移细胞是一种特殊的运输细胞，含有内陷的细胞壁内突，可产生扩增的质膜表面积，并且具有高密度的转运蛋白。它们在发生增强的养分跨质膜/共质体边界运输的部位从分化细胞中转分化而来。尽管它们具有重要的生理功能，但对于调节其复杂细胞壁内突形成的分子机制却知之甚少。我们研究了拟南芥叶片小叶脉韧皮部转移细胞中细胞壁内突形成的遗传控制。这些细胞中的细胞壁内突发育在暴露于高光或冷处理时会显著增强。对来源于经历这些处理的植物叶片的公共微阵列数据集进行分层生物信息学分析，确定 GI（GIGANTEA）是在高光和冷条件下都普遍上调两倍或更多的 46 个基因之一。GI 突变体 gi-2 和 gi-3 的组织学分析表明，含有细胞壁内突的韧皮部薄壁细胞的数量比野生型减少了 15 倍。gi-2 植物中形成了离散的乳突状细胞壁内突，但未能发育成分支网络。将这些植物暴露于高光或冷条件下并不能挽救 gi-2 中的细胞壁内突发育。相比之下，在 gi-2 背景下过表达 GI 可将细胞壁内突沉积恢复到野生型水平。这些结果表明，GI 在环境信号输入的下游点调节细胞壁内突网络的持续发育。
