State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 311400, China.
College of Agriculture and Biotechnology, Zhejiang University, State Key Laboratory of Rice Biology, Zhejiang Provincial Key Laboratory of Crop Genetic Resources, Institute of Crop Science, Hangzhou 310058, China.
Plant Cell. 2022 Sep 27;34(10):3632-3646. doi: 10.1093/plcell/koac190.
Rice (Oryza sativa) is one of the most important crops worldwide. Heading date is a vital agronomic trait that influences rice yield and adaption to local conditions. Hd3a, a proposed florigen that primarily functions under short-day (SD) conditions, is a mobile flowering signal that promotes the floral transition in rice. Nonetheless, how Hd3a is transported from leaves to the shoot apical meristem (SAM) under SDs remains elusive. Here, we report that FT-INTERACTING PROTEIN9 (OsFTIP9) specifically regulates rice flowering time under SDs by facilitating Hd3a transport from companion cells (CCs) to sieve elements (SEs). Furthermore, we show that the tetratricopeptide repeat (TPR) protein OsTPR075 interacts with both OsFTIP9 and OsFTIP1 and strengthens their respective interactions with Hd3a and the florigen RICE FLOWERING LOCUS T1 (RFT1). This in turn affects the trafficking of Hd3a and RFT1 to the SAM, thus regulating flowering time under SDs and long-day conditions, respectively. Our findings suggest that florigen transport in rice is mediated by different OsFTIPs under different photoperiods and those interactions between OsTPR075 and OsFTIPs are essential for mediating florigen movement from leaves to the SAM.
水稻（Oryza sativa）是全球最重要的作物之一。抽穗期是一个重要的农艺性状，影响水稻的产量和对当地条件的适应。Hd3a 是一种拟南芥成花素，主要在短日照（SD）条件下发挥作用，是一种促进水稻花发育的移动开花信号。然而，Hd3a 在 SD 条件下如何从叶片运输到茎尖分生组织（SAM）仍然难以捉摸。在这里，我们报告说，FT-INTERACTING PROTEIN9（OsFTIP9）通过促进 Hd3a 从伴细胞（CC）到筛管（SE）的运输，特异性调节水稻在 SD 下的开花时间。此外，我们表明四肽重复（TPR）蛋白 OsTPR075 与 OsFTIP9 和 OsFTIP1 相互作用，并增强它们与 Hd3a 和成花素 RICE FLOWERING LOCUS T1（RFT1）的各自相互作用。这反过来又影响 Hd3a 和 RFT1 向 SAM 的运输，从而分别调节 SD 和长日照条件下的开花时间。我们的研究结果表明，在不同的光周期下，不同的 OsFTIPs 介导了水稻成花素的运输，而 OsTPR075 和 OsFTIPs 之间的相互作用对于介导成花素从叶片向 SAM 的运动是必不可少的。
