National Key Laboratory of Crop Genetic Improvement and National Center of Plant Gene Research (Wuhan), Huazhong Agricultural University, Wuhan 430070, China.
Mol Plant. 2011 Mar;4(2):319-30. doi: 10.1093/mp/ssq070. Epub 2010 Dec 10.
Rice yield and heading date are two distinct traits controlled by quantitative trait loci (QTLs). The dissection of molecular mechanisms underlying rice yield traits is important for developing high-yielding rice varieties. Here, we report the cloning and characterization of Ghd8, a major QTL with pleiotropic effects on grain yield, heading date, and plant height. Two sets of near isogenic line populations were developed for the cloning of Ghd8. Ghd8 was narrowed down to a 20-kb region containing two putative genes, of which one encodes the OsHAP3 subunit of a CCAAT-box binding protein (HAP complex); this gene was regarded as the Ghd8 candidate. A complementary test confirmed the identity and pleiotropic effects of the gene; interestingly, the genetic effect of Ghd8 was dependent on its genetic background. By regulating Ehd1, RFT1, and Hd3a, Ghd8 delayed flowering under long-day conditions, but promoted flowering under short-day conditions. Ghd8 up-regulated MOC1, a key gene controlling tillering and branching; this increased the number of tillers, primary and secondary branches, thus producing 50% more grains per plant. The ectopic expression of Ghd8 in Arabidopsis caused early flowering by 10 d-a situation similar to the one observed by its homolog AtHAP3b, when compared to wild-type under long-day conditions; these findings indicate the conserved function of Ghd8 and AtHAP3b in flowering in Arabidopsis. Our results demonstrated the important roles of Ghd8 in rice yield formation and flowering, as well as its opposite functions in flowering between rice and Arabidopsis under long-day conditions.
水稻产量和抽穗期是由数量性状位点（QTL）控制的两个截然不同的特征。解析水稻产量性状的分子机制对于开发高产水稻品种非常重要。在这里，我们报告了 Ghd8 的克隆和特征，Ghd8 是一个对粒产量、抽穗期和株高具有多效性的主要 QTL。为了克隆 Ghd8，我们开发了两套近等基因系群体。Ghd8 被缩小到一个包含两个假定基因的 20-kb 区域，其中一个基因编码 CCAAT 盒结合蛋白（HAP 复合物）的 OsHAP3 亚基；这个基因被认为是 Ghd8 的候选基因。一个互补测试证实了该基因的身份和多效性；有趣的是，Ghd8 的遗传效应取决于其遗传背景。通过调节 Ehd1、RFT1 和 Hd3a，Ghd8 在长日照条件下延迟开花，但在短日照条件下促进开花。Ghd8 上调了控制分蘖和分枝的关键基因 MOC1；这增加了分蘖、一级和二级分枝的数量，从而使每株植物的产量增加了 50%。Ghd8 在拟南芥中的异位表达导致其在长日照条件下比野生型早开花 10 天——这与它的同源物 AtHAP3b 的情况类似；这些发现表明 Ghd8 和 AtHAP3b 在拟南芥开花中的保守功能。我们的研究结果表明，Ghd8 在水稻产量形成和开花中起着重要作用，并且在长日照条件下，Ghd8 在水稻和拟南芥的开花中具有相反的功能。
