Senoo Kanata, Yoshioka Shunsuke, Yamamori Koichi, Nasuda Shuhei, Yoshikawa Takanori
Laboratory of Plant Breeding, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
Department of Genomics and Evolutionary Biology, National Institute of Genetics, Mishima 411-8540, Japan.
Plant Cell Physiol. 2025 Jul 24;66(6):900-911. doi: 10.1093/pcp/pcaf034.
Higher plants experience morphological and physiological changes during the vegetative stage called juvenile-to-adult (JA) phase transition. Despite the advanced studies in Arabidopsis, maize, and rice, the JA phase transition remains unexplored in wheat. This study aimed to elucidate when and how the transition occurs in wheat by investigating the temporal changes in leaf morphology, expression of its regulators, transcriptome, and photosynthetic activity in the common wheat cultivar Norin 61. As a result, leaf blade size, leaf tip shape, and trichome density on leaf blades exhibited major changes from the first to second leaf stages. The expression level of microRNA 156, a regulator of JA phase transition in plants, was the highest in the first leaf stage and decreased following the plant growth, whereas that of its targets, SQUAMOSA PROMOTER BINDING PROTEIN-like (SPL) genes, increased. Additionally, transcriptome profiles dramatically changed from the second to third leaf stages and from the fourth to fifth leaf stages, which could be characterized by the change in activity of photoreactions, material transport, and phytohormone signaling. Unlike rice, wheat showed high photosynthetic rates per unit area even in the first leaf, which may be a unique and noteworthy characteristic in wheat. Taken together, we conclude that wheat initiates the JA phase transition after the first leaf stage and reaches the adult phase before the fourth leaf stage; it subsequently enters the reproductive stage. The present study will provide a foundation for advanced studies on wheat JA phase transition.
高等植物在营养生长阶段会经历形态和生理变化，即幼年期到成年期（JA）的阶段转变。尽管在拟南芥、玉米和水稻方面已有深入研究，但小麦的JA阶段转变仍未得到探索。本研究旨在通过调查普通小麦品种Norin 61叶片形态的时间变化、其调控因子的表达、转录组和光合活性，来阐明小麦何时以及如何发生这种转变。结果表明，从第一片叶到第二片叶阶段，叶片大小、叶尖形状和叶片上的毛状体密度发生了主要变化。植物JA阶段转变的调控因子microRNA 156的表达水平在第一片叶阶段最高，并随着植株生长而降低，而其靶标SQUAMOSA启动子结合蛋白样（SPL）基因的表达水平则升高。此外，转录组图谱从第二片叶到第三片叶阶段以及从第四片叶到第五片叶阶段发生了显著变化，这可以通过光反应、物质运输和植物激素信号传导活性的变化来表征。与水稻不同，小麦即使在第一片叶时单位面积的光合速率也很高，这可能是小麦独特且值得注意的特征。综上所述，我们得出结论，小麦在第一片叶阶段后开始JA阶段转变，并在第四片叶阶段前进入成年期；随后进入生殖阶段。本研究将为小麦JA阶段转变的深入研究提供基础。
