Max Planck Institute for Plant Breeding Research, Carl von Linne Weg 10, D-50829 Cologne, Germany.
Plant J. 2009 Nov;60(4):614-25. doi: 10.1111/j.1365-313X.2009.03986.x. Epub 2009 Jul 25.
Flowering is controlled by a network of pathways that converge to regulate a small number of floral integrator genes. We studied the interactions in Arabidopsis between three of these integrators, flowering locus T (FT), twin sister of FT (TSF) and suppressor of overexpression of constans 1 (SOC1), as well as their repression by the MADS box transcription factor short vegetative phase (SVP). FT is a mobile signal transmitted from the leaf to the meristem to initiate flowering. Using mRNA null alleles, we show that FT and the closely related TSF are not essential for flowering, but that the double mutant is photoperiod-insensitive. Inactivation of both genes also fully suppresses the early-flowering phenotype caused by over-expression of constans (CO), a transcriptional regulator in the photoperiod pathway. In addition, we demonstrate that TSF and FT have similar biochemical functions by showing that they interact in yeast with the same bZIP transcription factors. Expression of FT or TSF from promoters specific for phloem companion cells drives early flowering of the double mutant, so no expression of either gene is required in the meristem. Furthermore, TSF, like FT, is repressed by SVP, but the triple mutant svp-41 ft-10 tsf-1 expresses SOC1 in the meristem sooner and flowers earlier than ft-10 tsf-1. Thus we distinguish the functions of SVP in repressing FT and TSF in the leaf and SOC1 in the meristem. In addition, a time course of in situ hybridizations suggested that repression of SVP and activation of SOC1 proceed simultaneously in the meristem. These observations clarify the relationships between these early regulators of the floral transition, and further emphasize the relatedness of mechanisms acting in the leaf and meristem to control flowering time.
开花受途径网络的控制，该网络汇聚以调节少数几个花的整合基因。我们研究了拟南芥中三个整合基因——开花 locus T（FT）、FT 的孪生姊妹（TSF）和CONSTANS1 过表达抑制子（SOC1）——以及它们被 MADS 盒转录因子短营养生长期（SVP）抑制之间的相互作用。FT 是从叶片传递到分生组织以启动开花的可移动信号。使用 mRNA 缺失突变体，我们表明 FT 和密切相关的 TSF 对于开花并非必需，但双突变体对光周期不敏感。两个基因的失活也完全抑制了 CONSTANS（CO）过表达引起的早花表型，CO 是光周期途径中的转录调节剂。此外，我们通过表明它们在酵母中与相同的 bZIP 转录因子相互作用，证明 TSF 和 FT 具有相似的生化功能。从韧皮部伴胞特异启动子表达 FT 或 TSF 驱动双突变体的早花，因此在分生组织中不需要任一基因的表达。此外，与 FT 一样，TSF 被 SVP 抑制，但 svp-41 ft-10 tsf-1 三重突变体在分生组织中更早表达 SOC1 并更早开花。因此，我们区分了 SVP 在叶片中抑制 FT 和 TSF 以及在分生组织中抑制 SOC1 的功能。此外，原位杂交的时间进程表明 SVP 的抑制和 SOC1 的激活在分生组织中同时进行。这些观察结果阐明了这些花转变早期调控因子之间的关系，并进一步强调了在叶片和分生组织中起作用以控制开花时间的机制的相关性。
