Hd3a, a rice ortholog of the Arabidopsis FT gene, promotes transition to flowering downstream of Hd1 under short-day conditions

Shoko Kojima, Yuji Takahashi, Yasushi Kobayashi, Lisa Monna, Takuji Sasaki, Takashi Araki, Masahiro Yano
Plant and Cell Physiology, 2002, 43(10): 1096-1105  DOI: 10.1093/pcp/pcf156;      追溯原文......本站官方QQ群:62473826
Flowering time; Qtl; Rice; Short-day plant

Heading date 3a (Hd3a) has been detected as a heading-date-related quantitative trait locus in a cross between rice cultivars Nipponbare and Kasalath. A previous study revealed that the Kasalath allele of Hd3a promotes heading under short-day (SD) conditions. High-resolution linkage mapping located the Hd3a locus in a similar ~20-kb genomic region. In this region, we found a candidate gene that shows high similarity to the FLOWERING LOCUS T (FT) gene, which promotes flowering in Arabidopsis. Introduction of the gene caused an early-heading phenotype in rice. The transcript levels of Hd3a were increased under SD conditions. The rice Heading date 1 (Hd1) gene, a homolog of CONSTANS (CO), has been shown to promote heading under SD conditions. By expression analysis, we showed that the amount of Hd3a mRNA is up-regulated by Hd1 under SD conditions, suggesting that Hd3a promotes heading under the control of Hd1. These results indicate that Hd3a encodes a protein closely related to Arabidopsis FT and that the function and regulatory relationship with Hd1 and CO, respectively, of Hd3a and FT are conserved between rice (an SD plant) and Arabidopsis (a long-day plant).

拟南芥FT基因的水稻直系同源基因Hd3a促进水稻短日照条件下抽穗且位于Hd1下游

在日本晴和Kasalath杂交中Hd3a曾被检测出是与抽穗期相关的QTL。之前的研究表明Kasalath中的Hd3a等位基因促进短日照下水稻抽穗。通过高分辨率连锁图谱将Hd3a定位在约20kb的基因组区域内。在该区域内我们发现了一个与拟南芥促进开花的FT基因高度同源的候选基因。转化有该基因的植株出现早抽穗的表型。Hd3a的转录水平在短日照下会增加。拟南芥CO基因的水稻同源基因Hd1在短日照下促进水稻抽穗。通过表达分析我们发现在短日照下Hd3a受Hd1诱导上调,说明Hd3a促进水稻抽穗受Hd1的控制。这些结果表明Hd3a编码的蛋白与拟南芥的FT蛋白高度同源,同时Hd1与CO以及Hd3a和FT之间的功能和调节关系在短日照植物水稻和长日照植物拟南芥中是保守的。
结果:Hd3a候选基因的鉴定;将包含cds25的基因组片段转到日本晴中;在水稻中正义和反义过量表达Hd3a;在拟南芥中过量表达Hd3aHd3a在日本晴和近等基因系中的表达;Hd1Hd3a mRNA的量的昼夜变化。


基因列表
  成花素基因;抽穗期基因;生育期基因;光周期敏感基因;感光基因 Hd3a; FT
  成花素基因 RFT1; FT-L3