Nakamura Koki, Kikuchi Yuichi, Shiraga Mizuho, Kotake Toshihisa, Hyodo Kiwamu, Taketa Shin, Ikeda Yoko
Institute of Plant Science and Resources, Okayama University, 2-20-1 Chuo, Kurashiki, 710-0046 Japan.
Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama, 338-8570 Japan.
Plant Cell Physiol. 2025 May 30;66(5):705-721. doi: 10.1093/pcp/pcae150.
The awn is a bristle-like extension from the tip of the lemma in grasses. In barley, the predominant cultivars possess long awns that contribute to grain yield and quality through photosynthesis. In addition, various awn morphological mutants are available in barley, rendering it a useful cereal crop to investigate the mechanims of awn development. Here, we identified the gene causative of the short and crooked awn (sca) mutant, which exhibits a short and curved awn phenotype. Intercrossing experiments revealed that the sca mutant induced in the Japanese cultivar (cv.) "Akashinriki" is allelic to the independently isolated moderately short-awn mutant breviaristatum-a (ari-a). Map-based cloning and sequencing revealed that SCA encodes the Polycomb group-associated protein EMBRYONIC FLOWER 1. We found that SCA affects awn development through the promotion of cell proliferation, elongation, and cell wall synthesis. RNA sequencing of cv. Bowman backcross-derived near-isogenic lines of sca and ari-a6 alleles showed that SCA is directly or indirectly involved in promoting the expression of genes related to awn development. Additionally, SCA represses various transcription factors essential for floral organ development and plant architecture, such as MADS-box and Knotted1-like homeobox genes. Notably, the repression of the C-class MADS-box gene HvMADS58 by SCA in awns is associated with the accumulation of the repressive histone modification H3K27me3. These findings highlight the potential role of SCA-mediated gene regulation, including histone modification, as a novel pathway in barley awn development.
芒是禾本科植物外稃顶端的刺状延伸物。在大麦中，主要栽培品种具有长芒，这些长芒通过光合作用对籽粒产量和品质有贡献。此外，大麦中有各种芒形态突变体，这使其成为研究芒发育机制的有用谷类作物。在这里，我们鉴定了短而弯曲芒（sca）突变体的致病基因，该突变体表现出短而弯曲的芒表型。杂交实验表明，在日本品种“赤神力”中诱导产生的sca突变体与独立分离的中度短芒突变体breviaristatum-a（ari-a）等位。基于图谱的克隆和测序表明，SCA编码多梳蛋白家族相关蛋白EMBRYONIC FLOWER 1。我们发现SCA通过促进细胞增殖、伸长和细胞壁合成来影响芒的发育。对sca和ari-a6等位基因的cv. Bowman回交衍生近等基因系进行RNA测序表明，SCA直接或间接参与促进与芒发育相关基因的表达。此外，SCA抑制花器官发育和植物结构所必需的各种转录因子，如MADS-box和Knotted1样同源框基因。值得注意的是，SCA在芒中对C类MADS-box基因HvMADS58的抑制与抑制性组蛋白修饰H3K27me3的积累有关。这些发现突出了SCA介导的基因调控（包括组蛋白修饰）作为大麦芒发育新途径的潜在作用。
