• The spatiotemporal control of meristem identity is critical for determining inflorescence architecture, and thus yield, of cereal plants. However, the precise mechanisms underlying inflorescence and spikelet meristem determinacy in cereals are still largely unclear.
• We have generated loss-of-function and overexpression mutants of the paralogous OsMADS5 and OsMADS34 genes in rice (Oryza sativa), and analysed their panicle phenotypes. Using chromatin immunoprecipitation, electrophoretic mobility-shift and dual-luciferase assays, we have also identified RICE CENTRORADIALIS 4 (RCN4), a TFL1-like gene, as a direct downstream target of both OsMADS proteins, and have analysed RCN4 mutants.
• The osmads5 osmads34 mutant lines had significantly enhanced panicle branching with increased secondary, and even tertiary and quaternary, branches, compared to wild-type (WT) and osmads34 plants. The osmads34 mutant phenotype could largely be rescued by also knocking out RCN4. Moreover, transgenic panicles overexpressing RCN4 had significantly increased branching, and initiated development of c. 7× more spikelets than WT.
• Our results reveal a role for OsMADS5 in panicle development, and show that OsMADS5 and OsMADS34 play similar functions in limiting branching and promoting the transition to spikelet meristem identity, in part by repressing RCN4 expression. These findings provide new insights to better understand the molecular regulation of rice inflorescence architecture.

中文翻译：

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水稻 SEPALLATA 基因 OsMADS5 和 OsMADS34 通过抑制 TERMINAL FLOWER1 样基因 RCN4 协同限制花序分枝

• 分生组织特性的时空控制对于确定谷类植物的花序结构和产量至关重要。然而，谷物中花序和小穗分生组织决定的确切机制仍不清楚。
• 我们已经在水稻（Oryza sativa ）中产生了旁系同源OsMADS5和OsMADS34基因的功能丧失和过表达突变体，并分析了它们的穗表型。使用染色质免疫沉淀、电泳迁移率变化和双荧光素酶测定，我们还鉴定了RICE CENTRORADIALIS 4 ( RCN4 )，一种TFL1样基因，作为两种 OsMADS 蛋白的直接下游靶标，并分析了 RCN4突变体。
• 与野生型 (WT) 和osmads34植物相比，osmads5 osmads34突变株系具有显着增强的圆锥花序分枝，具有增加的二级，甚至三级和四级分枝。osmads34突变表型在很大程度上可以通过敲除RCN4来挽救。此外，过表达RCN4的转基因穗显着增加了分枝，并开始了c的发育。小穗比 WT 多 7 倍。
• 我们的研究结果揭示了OsMADS5在穗发育中的作用，并表明OsMADS5和OsMADS34在限制分枝和促进向小穗分生组织转变方面发挥相似的功能，部分是通过抑制RCN4表达。这些发现为更好地理解水稻花序结构的分子调控提供了新的见解。