Pérez-Henríquez Patricio, Nagawa Shingo, Liu Zhongchi, Pan Xue, Michniewicz Marta, Tang Wenxin, Rasmussen Carolyn, Cui Xinping, Van Norman Jaimie, Strader Lucia, Yang Zhenbiao
Institute of Integrated Genome Biology, and Department of Botany and Plant Sciences, University of California, Riverside, CA, 92521, USA.
Haixia Institute of Science and Technology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China.
Nat Commun. 2025 Feb 5;16(1):1380. doi: 10.1038/s41467-024-55480-8.
Directional auxin transport and formation of auxin maxima are critical for embryogenesis, organogenesis, pattern formation, and growth coordination in plants, but the mechanisms underpinning the initiation and establishment of these auxin dynamics are not fully understood. Here we show that a self-initiating and -terminating transient auxin flow along the marginal cells (MCs) contributes to the formation of an auxin maximum at the tip of Arabidopsis cotyledon that globally coordinates the interdigitation of puzzle-shaped pavement cells in the cotyledon epidermis. Prior to the interdigitation, indole butyric acid (IBA) is converted to indole acetic acid (IAA) to induce PIN2 accumulation and polarization in the marginal cells, leading to auxin flow toward and accumulation at the cotyledon tip. Once IAA levels at the cotyledon tip reaches a maximum, it activates pavement cell interdigitation as well as the accumulation of the IBA transporter TOB1 in MCs, which sequesters IBA to the vacuole and reduces IBA availability and IAA levels. The reduction of IAA levels results in PIN2 down-regulation and cessation of the auxin flow. Hence, our results elucidate a self-activating and self-terminating transient polar auxin transport system in cotyledons, contributing to the formation of localized auxin maxima that spatiotemporally coordinate pavement cell interdigitation.
生长素的定向运输和生长素最大值的形成对于植物的胚胎发生、器官发生、模式形成和生长协调至关重要，但这些生长素动态起始和建立的机制尚未完全了解。在这里，我们表明，沿着边缘细胞（MCs）的一种自我启动和终止的瞬时生长素流有助于在拟南芥子叶尖端形成生长素最大值，从而全局协调子叶表皮中拼图状铺板细胞的相互交错。在相互交错之前，吲哚丁酸（IBA）转化为吲哚乙酸（IAA），以诱导PIN2在边缘细胞中的积累和极化，导致生长素流向子叶尖端并在那里积累。一旦子叶尖端的IAA水平达到最大值，它就会激活铺板细胞的相互交错以及IBA转运蛋白TOB1在MCs中的积累，TOB1将IBA隔离到液泡中，降低IBA的可用性和IAA水平。IAA水平的降低导致PIN2下调和生长素流停止。因此，我们的结果阐明了子叶中一种自我激活和自我终止的瞬时极性生长素运输系统，有助于形成局部生长素最大值，从而在时空上协调铺板细胞的相互交错。
