ANALYSIS OF THE LONG-DISTANCE SIGNAL TRANSPORT IN RICE SIEVE TUBES

筛管在光同化物的运输中起作用，也被认为是将某些信号从源传递到汇。据报道，植物激素和成花诱导信号是通过筛管传递的，虽然这些信号传递系统已被分配给筛管，但筛管中也可能存在其他类型的信号传递系统。筛管不通过胞间连丝与伴生细胞以外的其他细胞相连，这一特性表明外源信号可能通过筛子元件-伴生细胞复合体的细胞膜进行传递。这些信号将被转运到细胞，改变作为第二信使的游离钙离子的水平，并通过随后筛管中蛋白质的磷酸化来触发细胞中的某些事件。我们已经通过使用水稻植物纯韧皮部汁液的生理实验证明，水稻计划的韧皮部汁液中存在钙依赖蛋白激酶(CDPK)。在本项目中，我们试图克隆水稻叶片中CDPK的编码基因。通过聚合酶链式反应克隆和文库筛选，我们克隆了水稻叶片中表达的CDPK和CRK(CDPK-Related Kinase)基因，并利用本课题组已克隆的这些蛋白和韧皮部特异启动子获得转基因水稻植株。

Sieve tubes function in the transport of photoassimilates and are also thought to convey certain signals from source to sink. It has been reported that plant hormones and the signal for floral induction are transported via sieve tubes.While these signal-transport systems have been assigned to the sieve tube, it is also possible that other types of signal-transport system might exist in the sieve tube. The nature of the sieve tubes, which is not connected via plasmodesmata to other cells apart from the companion cells, suggests that exogenous signals might be transduced via the cell membrane of the sieve element-companion cell complex. Such signals would be transpoted to the cell, change the level of free Ca^<2+>ions, which can act as a second messenger, and trigger certain events in the cell via the subsequent phosphorylation of proteins in the sieve tube.We already suggested that the Ca-dependent-protein kinases (CDPK) were present in the phloem sap of rice plans by the physiological experiments using a pure phloem sap from rice plants. In this project, we try to clone the gene which encode the CDPK in the leaf of rice plants. By PCR cloning and cDNA libraly screening, we cloned the gene which encode CDPK and CRK (CDPK-related kinase) which is express in rice leaf blade.Now we are making the transgenic rice plant using these kinases and phloem specific promoter which already cloned by our group.