Many genes encoding CCT domain‐containing proteins regulate flowering time. In rice (Oryza sativa), 41 such genes have been identified, but only a few have been shown to regulate heading date. Here, to test whether and how additional CCT family genes regulate heading date in rice, we classified these genes into five groups based on their diurnal expression patterns. The expression patterns of genes in the same subfamily or in close phylogenetic clades tended to be similar. We generated knockout mutants of the entire gene family via CRISPR/Cas9. The heading dates of knockout mutants of only 4 of 14 genes previously shown to regulate heading date were altered, pointing to functional redundancy of CCT family genes in regulating this trait. Analysis of mutants of four other genes showed that OsCCT22, OsCCT38, and OsCCT41 suppress heading under long‐day conditions and promote heading under short‐day conditions. OsCCT03 promotes heading under both conditions and upregulates the expression of Hd1 and Ehd1, a phenomenon not previously reported for other such genes. To date, at least 18 CCT domain‐containing genes involved in regulating heading have been identified, providing diverse, flexible gene combinations for generating rice varieties with a given heading date.

中文翻译：

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CCT 家族敲除突变体的全球分析确定了参与调控水稻抽穗期的四个基因

许多编码含有 CCT 域的蛋白质的基因调节开花时间。在水稻 ( Oryza sativa ) 中，已经鉴定出 41 个这样的基因，但只有少数基因被证明可以调节抽穗期。在这里，为了测试额外的 CCT 家族基因是否以及如何调节水稻抽穗期，我们根据它们的昼夜表达模式将这些基因分为五组。同一亚科或相近系统进化枝中基因的表达模式趋于相似。我们通过 CRISPR/Cas9 生成了整个基因家族的敲除突变体。先前显示调节抽穗日期的 14 个基因中只有 4 个基因敲除突变体的抽穗日期发生了改变，表明 CCT 家族基因在调节该性状方面存在功能冗余。对其他四个基因突变体的分析表明，OsCCT22、OsCCT38和OsCCT41在长日照条件下抑制抽穗并在短日照条件下促进抽穗。OsCCT03在两种条件下都促进抽穗并上调Hd1和Ehd1的表达，这是其他此类基因以前未报道过的现象。迄今为止，已鉴定出至少 18 个参与调控抽穗的 CCT 结构域基因，为产生具有给定抽穗日期的水稻品种提供了多样化、灵活的基因组合。