FLOWERING LOCUS T (FT), a florigen in Arabidopsis, plays critical roles in floral transition. Among 13 FT-like members in rice, OsFTL2 (Hd3a) and OsFTL3 (RFT1), two rice homologues of FT, have been well characterized to act as florigens to induce flowering under short-day (SD) and long-day (LD) conditions, respectively, but the functions of other rice FT-like members remain largely unclear. Here, we show that OsFTL12 plays an antagonistic function against Hd3a and RFT1 to modulate the heading date and plant architecture in rice. Unlike Hd3a and RFT1, OsFTL12 is not regulated by daylength and highly expressed in both SD and LD conditions, and delays the heading date under either SD or LD conditions. We further demonstrate that OsFTL12 interacts with GF14b and OsFD1, two key components of the florigen activation complex (FAC), to form the florigen repression complex (FRC) by competing with Hd3a for binding GF14b. Notably, OsFTL12-FRC can bind to the promoters of the floral identity genes OsMADS14 and OsMADS15 and suppress their expression. The osmads14 osmads15 double mutants could not develop panicles and showed erect leaves. Taken together, our results reveal that different FT-like members can fine-tune heading date and plant architecture by regulating the balance of FAC and FRC in rice.

中文翻译：

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OsFTL12 是 FT 样家族的成员，通过水稻成花素抑制复合物调节抽穗日期和植物结构

FLOWERING LOCUS T (FT) 是拟南芥中的一种成花素，在花转变中发挥着关键作用。在水稻的 13 个类似 FT 的成员中，OsFTL2 (Hd3a) 和 OsFTL3 (RFT1) 是 FT 的两个水稻同源物，已被充分表征为可在短日照 (SD) 和长日照 (LD) 下诱导开花。条件分别，但其他水稻类 FT 成员的功能仍不清楚。在这里，我们发现 OsFTL12 对 Hd3a 和 RFT1 发挥拮抗作用，以调节水稻的抽穗日期和植株结构。与Hd3a和RFT1不同，OsFTL12不受日长调节并且在SD和LD条件下高度表达，并且在SD或LD条件下延迟抽穗日期。我们进一步证明，OsFTL12 与成花素激活复合物（FAC）的两个关键成分 GF14b 和 OsFD1 相互作用，通过与 Hd3a 竞争结合 GF14b 形成成花素抑制复合物（FRC）。值得注意的是，OsFTL12-FRC 可以与花识别基因OsMADS14和OsMADS15的启动子结合并抑制其表达。osmads14 osmads15双突变体不能发育圆锥花序并显示直立的叶子。综上所述，我们的结果表明，不同的 FT 类成员可以通过调节水稻中 FAC 和 FRC 的平衡来微调抽穗日期和植株结构。