• The molecular mechanisms controlling underwater elongation are based extensively on studies on internode elongation in the monocot rice (Oryza sativa) and petiole elongation in Rumex rosette species. Here, we characterize underwater growth in the dicot Nasturtium officinale (watercress), a wild species of the Brassicaceae family, in which submergence enhances stem elongation and suppresses petiole growth.
• We used a genome‐wide transcriptome analysis to identify the molecular mechanisms underlying the observed antithetical growth responses. Though submergence caused a substantial reconfiguration of the petiole and stem transcriptome, only little qualitative differences were observed between both tissues. A core submergence response included hormonal regulation and metabolic readjustment for energy conservation, whereas tissue‐specific responses were associated with defense, photosynthesis, and cell wall polysaccharides.
• Transcriptomic and physiological characterization suggested that the established ethylene, abscisic acid (ABA), and GA growth regulatory module for underwater elongation could not fully explain underwater growth in watercress.
• Petiole growth suppression is likely attributed to a cell cycle arrest. Underwater stem elongation is driven by an early decline in ABA and is not primarily mediated by ethylene or GA. An enhanced stem elongation observed in the night period was not linked to hypoxia and suggests an involvement of circadian regulation.

中文翻译：

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将枝条保持在水上-浸没会在豆瓣菜（Nasturtium officinale）的茎和叶柄中触发相反的生长反应。

• 控制水下伸长的分子机制上在单子叶植物水稻（节间伸长的研究广泛地基于稻）和叶柄伸长羊蹄莲座物种。在这里，我们表征了双子叶植物金莲花（豆瓣）的水下生长，该植物是十字花科的一种野生物种，其中浸没会增强茎的伸长并抑制叶柄的生长。
• 我们使用了全基因组的转录组分析来确定观察到的对立生长反应的分子机制。尽管浸没引起叶柄和茎转录组的实质性重构，但在两种组织之间仅观察到很少的定性差异。淹没的核心反应包括激素调节和代谢调整以节约能量，而组织特异性反应与防御，光合作用和细胞壁多糖相关。
• 转录组学和生理学特征表明，已建立的乙烯，脱落酸（ABA）和GA水下伸长的生长调节模块不能完全解释豆瓣的水下生长。
• 叶柄生长抑制可能归因于细胞周期停滞。水下茎伸长是由ABA的早期下降驱动的，而不主要由乙烯或GA介导。夜间观察到的茎伸长增加与缺氧没有关系，提示其参与了昼夜节律调节。