Effects of gene expressions in companion cells on the growth of higher plants

韧皮部是高等植物体内物质和信号远距离运输的通道。筛管元件是筛管的单个细胞成分，高度专门用于同化物转运，并在分化过程中失去大部分细胞内细胞器，例如细胞核、液泡、高尔基体和大多数核糖体。然而，蛋白质被认为是维持筛管生理功能所必需的，并且被推测是通过胞间连丝从邻近的伴胞提供的。在筛选元件-伴随细胞复合物中检测到的蛋白质已按功能分类，如结构蛋白、参与氧化还原调节的维持蛋白、与信号转导相关的蛋白质等（Hayashi et al.2000 for review）。然而，在韧皮部汁液中检测到的大多数可溶性蛋白尚未被鉴定或characteristic.In本实验中，我们确定了水稻筛管蛋白，分子量为31 kDa，RPP 31，作为谷胱甘肽S-转移酶（GST）。并对水稻韧皮部汁液的化学成分和维管组织中的thoredoxtn h、GST、GS、GOGAT等基因表达进行了详细的分析。

Phloem is a route for long distance transport of metabolites and signals in higher plants. Sieve elements, the individual cell components of sieve tubes, are highly specialized for assimilate translocation, and lose most of their intracellular organelles, such as nuclei, vacuoles, Golgi bodies, and most ribosomes during the course of differentiation. However, proteins are thought to be required for the maintenance of the physiological functions of sieve tubes, and are presumed to be supplied from neighboring companion cells through plasmodesmata. Proteins detected in sieve element-companion cell complexes have been categorized by function, such as structural proteins, maintenance proteins involved in redox regulation, proteins related to signal transduction, and others (Hayashi et al. 2000 for review). However, most of the soluble proteins detected in phloem sap have not yet been identified or characterized.In this experiments, we identified a rice sieve-tube protein with a molecular mass of 31 kDa, RPP31, as a glutathione S-transferase (GST). And we analyzed the detailed chemical composition of rice phloem sap together with the gene expressions in the vascular tissues such as, thoredoxtn h, GST, GS, GOGAT etc..