Anthocyanins accumulate in various organs of rice, and the regulatory genes involved in pigmentation of specific organs, such as pericarp, hull, leaf, apiculus, and stigma have been elucidated. However, the corresponding gene for rice culm pigmentation has not been clarified. The well-known MYB-bHLH-WD40 (MBW) complex plays vital role in regulating the anthocyanin biosynthesis pathway in plants. However, the core members of MBW and the hierarchical regulation between these members are not fully elucidated in rice. Here, by map-based cloning, we identified the culm-specific pigmentation gene S1 whose alleles are also known for hull/pericarp pigmentation. We also clarified that one WD40 protein encoding gene, WA1, is indispensable for anthocyanin biosynthesis in rice. In the cascading regulation among MBW members, S1 (bHLH) acts as the master gene by activating the expression of C1 (MYB), and then C1 activates the expression of WA1 (WD40), which is unique in plant species. This enables MBW members to be coordinated in a common way to efficiently regulate anthocyanin biosynthesis genes. Based on these studies, we explored the minimal gene set required for anthocyanin biosynthesis in rice. These findings will help us design new rice varieties with anthocyanin accumulation in specific organs as needed.

中文翻译：

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揭示MYB-bHLH-WD40蛋白的分级调控及调控水稻花青素色素沉着

花青素在水稻的各个器官中积累，涉及特定器官如果皮、壳、叶、针叶和柱头色素沉着的调控基因已被阐明。然而，稻秆色素沉着的相应基因尚未阐明。众所周知的 MYB-bHLH-WD40 (MBW) 复合物在调节植物花青素生物合成途径中起着至关重要的作用。然而，MBW的核心成员以及这些成员之间的分级调控在水稻中并未完全阐明。在这里，通过基于图谱的克隆，我们鉴定了茎秆特异性色素沉着基因S1，其等位基因也因外壳/果皮色素沉着而闻名。我们还阐明了一种 WD40 蛋白编码基因WA1, 对水稻中花青素的生物合成是必不可少的。在MBW成员之间的级联调控中，S1（bHLH）作为主基因通过激活C1（MYB）的表达，然后C1激活WA1（WD40）的表达，这在植物物种中是独一无二的。这使得 MBW 成员能够以一种共同的方式进行协调，从而有效地调节花青素生物合成基因。基于这些研究，我们探索了水稻花青素生物合成所需的最小基因组。这些发现将帮助我们根据需要设计在特定器官中具有花青素积累的新水稻品种。