Laboratory of Plant Molecular Genetics, Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan.
Nature. 2011 Jul 31;476(7360):332-5. doi: 10.1038/nature10272.
'Florigen' was proposed 75 years ago to be synthesized in the leaf and transported to the shoot apex, where it induces flowering. Only recently have genetic and biochemical studies established that florigen is encoded by FLOWERING LOCUS T (FT), a gene that is universally conserved in higher plants. Nonetheless, the exact function of florigen during floral induction remains poorly understood and receptors for florigen have not been identified. Here we show that the rice FT homologue Hd3a interacts with 14-3-3 proteins in the apical cells of shoots, yielding a complex that translocates to the nucleus and binds to the Oryza sativa (Os)FD1 transcription factor, a rice homologue of Arabidopsis thaliana FD. The resultant ternary 'florigen activation complex' (FAC) induces transcription of OsMADS15, a homologue of A. thaliana APETALA1 (AP1), which leads to flowering. We have determined the 2.4 Å crystal structure of rice FAC, which provides a mechanistic basis for florigen function in flowering. Our results indicate that 14-3-3 proteins act as intracellular receptors for florigen in shoot apical cells, and offer new approaches to manipulate flowering in various crops and trees.
“成花素”这一概念于 75 年前被提出，其被认为在叶片中合成后被运输到茎尖，在那里诱导开花。直到最近，遗传学和生物化学研究才确定成花素由 FLOWERING LOCUS T（FT）编码，FT 基因在高等植物中普遍存在。尽管如此，成花素在花诱导过程中的确切功能仍知之甚少，且其受体尚未被鉴定。在这里，我们表明水稻 FT 同源物 Hd3a 与茎尖细胞中的 14-3-3 蛋白相互作用，形成一个复合物，该复合物易位到细胞核并与拟南芥 FD 的水稻同源物 OsFD1 转录因子结合。由此产生的三元“成花素激活复合物”（FAC）诱导拟南芥 APETALA1（AP1）同源物 OsMADS15 的转录，从而导致开花。我们已经确定了水稻 FAC 的 2.4 Å 晶体结构，为成花素在开花中的功能提供了机制基础。我们的研究结果表明，14-3-3 蛋白在茎尖细胞中作为成花素的细胞内受体，为在各种作物和树木中操纵开花提供了新的方法。
