A ROLE FOR SUCROSE SYNTHASE IN STARCH SYNTHESIS IN SWEET POTATO

蔗糖合成酶在甘薯淀粉合成中的作用

基本信息

批准号：
07456010
负责人：
SAITOU Kazuyuki
金额：
$ 5.12万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

In plants, sucrose is an energy and carbohydrate source. Sucrose is synthesized in photosynthetically sctive tissues and transported to other plant organs where it is used after cleavage to monosaccharides or derivatives. Sucrose synthase (SUS) is one of the enzymes involved in sucrose breakdown. To understand the molecular mechanisms in sugar distribution and metabolism of sweet potato, we have isolated a cDNA (1,191 bp) encoding SUS of sweet potato (IBSUS). The deduced amino acid of IBSUS was most closely related (91% homology) to potato SUS.Less homology (75%) was found to monocotyledonous sequences (rice and maize). The published Arabidopsis SUS sequence unexpectedly showed an even lower homology value of 69%. The activity of SUS in roots of sweet potato increased during development of tuberous roots. The enhancement of the enzymatic activity was accompanied by an increase in starch content. The activity of SUS in the tuberous roots was higher than that in the other tissues, namely, leaf blades, petioles, stems and fibrous roots. The enzymatic activity was not detectable in the leaf blade. Expression of the gene encoding SUS in different tissues of sweet potato was assessed by northem bolt hybridization. A signal of the SUS mRNA with a size of approximately 2.4 kbp was found in petioles, stems, fibrous roots and tuberous roots. The gene was most abundantly expressed in tuberous roots. Lower expression levels were found in petioles and stems, whereas no expression could be detected in leaf blades. The gene encoding SUS was strongly inducible by sucrose at the RNA level.

在植物中，蔗糖是能量和碳水化合物来源。蔗糖在光合活性组织中合成，并转运到其他植物器官，在其中裂解成单糖或衍生物后被使用。蔗糖合酶（SUS）是参与蔗糖分解的酶之一。为了了解甘薯糖分配和代谢的分子机制，我们分离了编码甘薯SUS（IBSUS）的cDNA（1,191 bp）。 IBSUS 的推导氨基酸与马铃薯 SUS 的相关性最密切（91% 同源性）。与单子叶植物序列（水稻和玉米）的同源性较低（75%）。已发表的拟南芥SUS序列出乎意料地显示出更低的同源性值，为69%。甘薯根部SUS活性在块根发育过程中增强。酶活性的增强伴随着淀粉含量的增加。块根中SUS的活性高于其他组织，即叶片、叶柄、茎和须根。在叶片中未检测到酶活性。通过Northem螺栓杂交评估了编码SUS的基因在甘薯不同组织中的表达。在叶柄、茎、须根和块根中发现了大小约为2.4 kbp的SUS mRNA信号。该基因在块根中表达最丰富。在叶柄和茎中发现较低的表达水平，而在叶片中未检测到表达。编码 SUS 的基因在 RNA 水平上可被蔗糖强烈诱导。