水稻DZ1及其抑制子基因SOD1调控籽粒大小的分子遗传网络解析

Rice grain size is an important agronomic trait, and control of grain size is also a fundamental question in developmental biology. However, the genetic and molecular mechanisms that set final grain size are largely unknown despite their central importance. To understand the genetic and molecular mechanisms of grain size control, we have isolated a set of mutants with altered grain size in rice and identified numerous genes of grain size control. The dz1-1 mutant shows large grains compared with the wild type. DZ1 encodes a putative transcription factor with unknown functions. To understand the genetic and molecular mechanisms of DZ1 in grain size control, we have isolated the suppressors of dz1-1 (sod). Genetic analyses show that sod1-1 is epistatic to dz1-1 with respect to grain size, indicating that DZ1 and SOD1 act in a common pathway to control grain size. SOD1 encodes a predicted regulator of transcriptional regulation. Further results show that DZ1 interacts with SOD1 in the nuclei. These findings provide an opportunity to reveal novel mechanisms of grain size control in rice. The three major objectives of this project are: 1, To investigate developmental and cellular basis and biochemical activities of DZ1 and SOD1. 2, To identify the binding sites (cis-elements) of DZ1 in genome and build up a transcriptional network for DZ1 and SOD1-mediated grain size control. 3, To identify other components of the DZ1/SOD1 complex and elucidate the molecular mechanisms of DZ1 and SOD1 in grain size control. This study will make a breakthrough in rice grain size control and discover important genes for engineering high crop yield.

水稻籽粒大小是重要的产量性状，但籽粒大小调控的分子遗传网络目前仍不清楚。申请人实验室已系统分离了水稻籽粒大小改变的突变体。其中，dz1-1突变体产生较大的种子。DZ1基因编码了一个未知功能的转录因子。我们进一步分离了dz1-1的抑制子突变体sod1，SOD1编码了一个预测的转录调控因子。遗传分析表明DZ1和SOD1作用在同一遗传途径。DZ1能够与SOD1在细胞核内互作作用。本项目拟从以下三个方面，解析DZ1和SOD1调控籽粒大小的分子遗传网络。1、解析DZ1和SOD1调控籽粒大小的细胞学和发育生物学基础及其生化活性。2、鉴定DZ1结合的顺式元件，DZ1和SOD1调控的靶基因，建立DZ1和SOD1调控籽粒大小的转录网络。3、鉴定DZ1和SOD1复合体的其他成员，解析DZ1和SOD1互作调控籽粒大小的新机制。该研究有望在水稻籽粒大小调控领域取得重要突破，也将为高产育种提供理论基础和基因资源。

提高粮食产量是现代农业的一个主要目标。水稻籽粒大小是一个重要的产量性状，研究其分子机制有助于培育高产品种。通过本项目的研究，我们发现转录因子DZ1/OsGRF4是一个重要的籽粒大小调控基因。OsGRF4的表达受到OsmiR396的调控。当OsGRF4基因上OsmiR396的结合位点发生突变时，由于OsmiR396不能结合而导致OsGRF4的表达量升高，最终导致籽粒的增大和产量的增加。进一步的研究显示OsGRF4能够同转录共激活因子OsGIF1/2/3相互作用，而且过表达OsGIF1也形成大的籽粒。提示OsGRF4和OsGIF1通过相互作用来调控籽粒的大小。因此，本研究一定程度上揭示了OsGRF4、OsGIF1以及OsmiR396调控籽粒大小的分子机制，为培育高产水稻品种提供了理论基础和种质资源。相关成果已在Nature Plants、Molecular Plant、The Plant Journal以及Rice等杂志发表。并应邀在Current Opinion in Plant Biology和Journal of Experimental Botany杂志发表籽粒大小相关综述2篇。