来自中国和美国的科学家在新一期《自然—遗传学》杂志电子版上报告说，他们发现水稻的一个特定基因负责控制米粒的大小和分量。
参与研究的宾夕法尼亚大学华人科学家马宏说，他们的研究工作表明，通过加强某个特定基因的表达，可以实现稻米增产的目标。这个新基因的发现将有助于培育高产转基因水稻新品种。
领导此项研究的中国科学院生物学家何祖华在新闻公报中介绍说，他们首先在水稻中筛选出一些米粒分量明显不足的变异植株，并从中鉴别出一种特殊的变异植株，这一植株根本无法长出正常大小的米粒。于是，他们对该植株进行进一步的研究，发现它的GIF1基因出现变异。
GIF1基因负责控制水稻中转化酶的活动。转化酶位于水稻的细胞壁上，负责将蔗糖转化为用于合成淀粉的物质，这些物质继续发育后长成米粒。如果转化酶不活跃，水稻就很难长出饱满的颗粒。
试验发现，如果GIF1基因正常无变异，转化酶活性正常；如果GIF1因发生变异而表达不够，转化酶的活性仅为正常水稻的17%。研究小组培育出一种转基因水稻，使GIF1基因过度表达，结果发现，这种水稻的颗粒比正常水稻的大，分量也要重。
科学家希望他们的这一成果能够帮助水稻育种科研人员培育出颗粒更大、更饱满的新杂交品种。(生物谷Bioon.com)
生物谷推荐原始出处:
Nature Genetics Published online: 28 September 2008 | doi:10.1038/ng.220
Control of rice grain-filling and yield by a gene with a potential signature of domestication
Ertao Wang1,2, Jianjun Wang3, Xudong Zhu2, Wei Hao1, Linyou Wang3, Qun Li1, Lixia Zhang3, Wei He1, Baorong Lu4, Hongxuan Lin1, Hong Ma5, Guiquan Zhang6 & Zuhua He1
1 Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai 200032, China.
2 China National Rice Research Institute, 359 TiyuChang Road, Hangzhou 31006, China.
3 Zhejiang Academy of Agricultural Sciences, 198 Shiqiao Road, Hangzhou 310021, China.
School of Life Sciences, Fudan University, 220 Handan Road, Shanghai 200433, China.
4 Department of Biology and the Huck Institutes of Life Sciences, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
5 College of Agriculture, South China Agricultural University, Guangzhou 510642, China.
Grain-filling, an important trait that contributes greatly to grain weight, is regulated by quantitative trait loci and is associated with crop domestication syndrome1, 2, 3, 4. However, the genes and underlying molecular mechanisms controlling crop grain-filling remain elusive. Here we report the isolation and functional analysis of the rice GIF1 (GRAIN INCOMPLETE FILLING 1) gene that encodes a cell-wall invertase required for carbon partitioning during early grain-filling. The cultivated GIF1 gene shows a restricted expression pattern during grain-filling compared to the wild rice allele, probably a result of accumulated mutations in the gene's regulatory sequence through domestication. Fine mapping with introgression lines revealed that the wild rice GIF1 is responsible for grain weight reduction. Ectopic expression of the cultivated GIF1 gene with the 35S or rice Waxy promoter resulted in smaller grains, whereas overexpression of GIF1 driven by its native promoter increased grain production. These findings, together with the domestication signature that we identified by comparing nucleotide diversity of the GIF1 loci between cultivated and wild rice, strongly suggest that GIF1 is a potential domestication gene and that such a domestication-selected gene can be used for further crop improvement.
