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，蔗糖是一种能量和碳水化合物来源。蔗糖是在光合节质组织中合成的，并运输到其他植物器官，在裂解至单糖或衍生物后使用。蔗糖合酶（SUS）是参与蔗糖分解的酶之一。为了了解甘薯糖分和代谢中的分子机制，我们分离了甘薯（IBSUS）的SUS的cDNA（1,191 bp）。 IBSU的推导氨基酸与马铃薯Sus.Loss.同源性（75％）最紧密相关（91％同源）（米饭和玉米）。已发表的拟南芥SUS序列出乎意料地显示出69％的同源性值。在结节根发展期间，SUS中SU的活性增加了。酶活性的增强伴随着淀粉含量的增加。块根根部的SUS活性高于其他组织中的活性，即叶片，叶柄，茎和纤维根。在叶片叶片中无法检测到酶促活性。通过Northem Bolt杂交评估了在不同组织中编码SUS的基因的表达。在叶柄，茎，纤维根和结节根中发现了大小约2.4 kbp的SURNA的信号。该基因在块茎根部表达最丰富。在叶柄和茎中发现了较低的表达水平，而在叶叶片中无法检测到表达水平。蔗糖在RNA水平上可以强烈诱导编码SU的基因。