成都生物所在苦荞淀粉合成的分子机制研究中获进展

苦荞是中国特色的植物资源，中国西南地区是苦荞起源中心和主要遗传资源基因库，其中四川凉山彝族自治州是目前世界上最大的苦荞栽培区域，占全球栽培面积的60%以上。

苦荞集营养、医药、保健于一体，近年来苦荞及其系列产品在国际、国内市场上供不应求, 特别是欧、美、日等发达地区和国家需求旺盛。

苦荞籽粒中直链淀粉的含量是决定其淀粉品质和食品特性的主要影响因素之一，籽粒胚乳中直链淀粉合成主要由Granule-bound starch synthase I (GBSSI)的编码基因控制，当GBSSI缺失或者功能丧失，将导致直链淀粉合成受阻，使籽粒表现糯性，此基因也被称为糯性waxy基因。目前，与荞麦淀粉合成的分子机制相关的研究还鲜见报道。

中国科学院成都生物研究所研究员王涛课题组博士后王迅克隆并分析了苦荞GBSSI(命名为FtGBSSI)基因序列，发现FtGBSSI基因含有3847个碱基，其中由14个外显子和13个内含子构成，其中第一个内含子位于5′端非翻译区域，而FtGBSSI编码起始于第二个外显子的中间序列。

FtGBSSI基因的cDNA序列与目前所报道的14个双子叶植物的cDNA序列的相似度为63.3%–75.1%，而与4种单子叶禾本科作物(水稻、小麦、玉米、大麦)的cDNA序列的相似度为56.6%–57.5%。从FtGBSSI的cDNA序列推导得到的氨基酸序列中，识别出8个保守区域，这8个保守区域普遍存在于植物淀粉合成酶的氨基酸序列中。

该研究有助于深入了解苦荞淀粉合成的分子机制，并为苦荞淀粉品质遗传改良研究提供了重要理论基础。

原文摘要：

Identification and characterization of granule bound starch synthase I (GBSSI) gene of tartary buckwheat (Fagopyrum tataricum Gaertn.)

Xun Wang, Bo Feng, Zhibin Xu, Francesco Sestili, Guojun Zhao, Chao Xiang, Domenico Lafiandra, Tao Wang

Tartary buckwheat (Fagopyrum tataricum Gaertn.) is increasingly considered as an important functional food material because of its rich nutraceutical compounds. Reserve starch is the major component of tartary buckwheat seed. However, the gene sequences and the molecular mechanism of tartary buckwheat starch synthesis are unknown so far. In this study, the complete genomic sequence and full-size cDNA coding tartary buckwheat granule-bound starch synthase I (FtGBSSI), which is responsible for amylose synthesis, were isolated and analyzed. The genomic sequence of the FtGBSSI contained 3947 nucleotides and was composed of 14 exons and 13 introns. The cDNA coding sequence of FtGBSSI shared 63.3%–75.1% identities with those of dicots and 56.6%–57.5% identities with monocots (Poaceae). In deduced amino acid sequence of FtGBSSI, eight motifs conserved among plant starch synthases were identified. A cleavage at the site IVC↓G of FtGBSSI protein produces the chloroplast transit sequence of 78 amino acids and the mature protein of 527 amino acids. The FtGBSSI mature protein showed an identity of 73.4%–77.8% with dicot plants, and 67.6%–70.4% with monocot plants (Poaceae). The mature protein was composed of 20 α-helixes and 16 β-strands, and folds into two main domains, N- and C-terminal domains. The critical residues which are involved in ADP and sugar binding were predicted. These results will be useful to modulate starch composition of buckwheat kernels with the aim to produce novel improved varieties in future breeding programs.

标签: 苦荞淀粉合成 FtGBSSI基因

作者：中科院 点击：次