• Rice (Oryza sativa) is a short‐day (SD) plant originally having strong photoperiod sensitivity (PS), with SDs promoting and long days (LDs) suppressing flowering. Although the evolution of PS in rice has been extensively studied, there are few studies that combine the genetic effects and underlying mechanism of different PS gene combinations with variations in PS.
• We created a set of isogenic lines among the core PS‐flowering genes Hd1, Ghd7 and DTH8 using CRISPR mutagenesis, to systematically dissect their genetic relationships under different day‐lengths. We investigated their monogenic, digenic, and trigenic effects on target gene regulation and PS variation.
• We found that Hd1 and Ghd7 have the primary functions for promoting and repressing flowering, respectively, regardless of day‐length. However, under LD conditions, Hd1 promotes Ghd7 expression and is recruited by Ghd7 and/or DTH8 to form repressive complexes that collaboratively suppress the Ehd1‐Hd3a/RFT1 pathway to block heading, but under SD conditions Hd1 competes with the complexes to promote Hd3a/RFT1 expression, playing a tradeoff relationship with PS flowering. Natural allelic variations of Hd1, Ghd7 and DTH8 in rice populations have resulted in various PS performances.
• Our findings reveal that rice PS flowering is controlled by crosstalk of two modules – Hd1–Hd3a/RFT1 in SD conditions and (Hd1/Ghd7/DTH8)–Ehd1–Hd3a/RFT1 in LD conditions – and the divergences of these genes provide the basis for rice adaptation to broad regions.

中文翻译：

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水稻抽穗中强光周期敏感性是由Hd1、Ghd7和DTH8之间的合作和竞争控制的

• 水稻 ( Oryza sativa ) 是一种短日照 (SD) 植物，最初具有很强的光周期敏感性 (PS)，SD 促进开花，长日照 (LD) 抑制开花。尽管水稻PS的进化已被广泛研究，但将不同PS基因组合的遗传效应和潜在机制与PS变异结合起来的研究很少。
• 我们利用 CRISPR 诱变在核心 PS 开花基因Hd1、Ghd7和DTH8之间创建了一组等基因系，以系统地剖析它们在不同日长下的遗传关系。我们研究了它们对靶基因调控和 PS 变异的单基因、双基因和三基因效应。
• 我们发现，无论日长如何，Hd1和Ghd7分别具有促进和抑制开花的主要功能。然而，在 LD 条件下，Hd1 促进Ghd7表达，并被 Ghd7 和/或 DTH8 募集形成抑制复合物，协同抑制Ehd1 - Hd3a / RFT1途径以阻止标题，但在 SD 条件下，Hd1 与复合物竞争以促进Hd3a/ RFT1的表达量，与PS开花起到权衡关系。水稻群体中Hd1、Ghd7和DTH8的天然等位基因变异导致了不同的PS性能。
• 我们的研究结果表明，水稻PS开花是由两个模块的串扰控制的——SD条件下的Hd1 – Hd3a / RFT1和LD条件下的(Hd1 / Ghd7 / DTH8 ) – Ehd1–Hd3a / RFT1 – 这些基因的差异提供了基础使水稻适应更广泛的地区。