Hd3a promotes lateral branching in rice

Hiroyuki Tsuji, Chika Tachibana, Shojiro Tamaki, Ken-ichiro Taoka, Junko Kyozuka, Ko Shimamoto
The Plant Journal, 2015, 82(2): 256-266  DOI: 10.1111/tpj.12811;      追溯原文......本站官方QQ群:62473826
meristem action; organ development; rice (Oryza sativa L.); florigen; florigen activation complex; branching

Accumulating evidence indicates that the FLOWERING LOCUS T (FT) protein is the mobile floral signal known as florigen. A rice FT homolog, Heading date 3a (Hd3a), is transported from the phloem to shoot apical cells, where it interacts with 14–3–3 proteins and transcription factor OsFD1 to form a florigen activation complex (FAC) that activates a rice homolog of the floral identity gene APETALA1. Recent studies showed that florigen has roles in plant development beyond flowering; however, the exact nature of these roles is not well understood. It is not clear whether FT is transported to organs outside the shoot apex, and whether FAC formation is required for processes other than flowering. We show here that the Hd3a protein accumulates in axillary meristems to promote branching, and that FAC formation is required. Analysis of transgenic plants revealed that Hd3a promotes branching through lateral bud outgrowth. Hd3a protein produced in the phloem reached the axillary meristem in the lateral bud, and its transport was required for promotion of branching. Moreover, mutant Hd3a proteins defective in FAC formation but competent with respect to transport did not promote branching. Finally, we show that Hd3a promotes branching independently from strigolactone and FC1, a transcription factor that inhibits branching in rice. Together, these results suggest that Hd3a functions as a mobile signal for branching in rice.

Hd3a促进水稻分枝形成

越来越多证据表明FT蛋白是可移动的开花信号,即“成花素”。水稻中FT同源蛋白Hd3a,从韧皮部运输到茎尖细胞,并在这儿与14-3-3蛋白和转录因子OsFD1一起形成“成花素活化复合体(FAC)”,进而激活水稻中花身份决定基因APETALA1的同源基因。最新研究表明,除了开花外,成花素在植物其它发育过程中也发挥作用,但是这些作用的确切机理仍知之甚少。FT是否运输到茎尖外的其它器官,以及除了开花外FAC是否也参与其它生物进程,这些都不清楚。本文中,我们发现Hd3a蛋白在叶腋分生组织积累,促进分枝形成,并且此过程需要FAC形成。转基因植株分析表明,Hd3a通过激活侧芽生长促进分枝形成。Hd3a蛋白在韧皮部产生,运输到侧芽的叶腋分生组织,它的运输对促进分枝形成至关重要。此外,FAC形成有缺陷但不影响自身运输的Hd3a突变蛋白,不能够促进分枝形成。最后,我们还发现Hd3a促进分枝是独立于独脚金内酯和FC1的,FC1是一个抑制水稻分枝的转录因子。综合以上结果表明,Hd3a作为一个移动信号,参与水稻的分枝。


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
  14-3-3蛋白 GF14c; 14-3-3