• Cytokinins control critical aspects of plant development and environmental responses. Perception of cytokinin ultimately leads to the activation of proteins belonging to the type‐B Response Regulator family of cytokinin response activators. In Arabidopsis thaliana , ARR1 is one of the most abundantly expressed type‐B Response Regulators.
• We investigated the link between cytokinin signaling, protein synthesis, plant growth and osmotic stress tolerance.
• We show that the increased cytokinin signaling in ARR1 gain‐of‐function transgenic lines is associated with increased rates of protein synthesis, which lead to growth inhibition and hypersensitivity to osmotic stress. Cytokinin‐induced growth inhibition and osmotic stress hypersensitivity were rescued by treatments with ABA, a hormone known to inhibit protein synthesis. We also demonstrate that cytokinin‐induced protein synthesis requires isoforms of the ribosomal protein L4 encoded by the cytokinin‐inducible genes RPL4A and RPL4D , and that RPL4 loss‐of‐function increases osmotic stress tolerance and decreases sensitivity to cytokinin‐induced growth inhibition.
• These findings reveal that an increase in protein synthesis negatively impacts growth and osmotic stress tolerance and explain some of the adverse effects of elevated cytokinin action on plant development and stress physiology.

中文翻译：

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细胞分裂素诱导的蛋白质合成抑制生长和渗透胁迫耐受性。

• 细胞分裂素控制植物发育和环境响应的关键方面。细胞分裂素的感知最终会导致细胞分裂素反应激活剂的B型反应调节剂家族的蛋白质被激活。在拟南芥中，ARR1是表达最丰富的B型应答调节因子之一。
• 我们研究了细胞分裂素信号传导，蛋白质合成，植物生长和渗透胁迫耐受性之间的联系。
• 我们表明，ARR1功能获得性转基因品系中细胞分裂素信号传导的增加与蛋白质合成速率的增加有关，这导致生长抑制和对渗透胁迫的超敏反应。细胞分裂素诱导的生长抑制和渗透压超敏反应通过使用ABA（一种抑制蛋白质合成的激素）治疗得以缓解。我们还证明了细胞分裂素诱导的蛋白合成需要细胞分裂素诱导基因RPL4A和RPL4D编码的核糖体蛋白L4的同工型，并且RPL4功能丧失会增加渗透压耐受性并降低对细胞分裂素诱导的生长抑制的敏感性。
• 这些发现表明，蛋白质合成的增加会对生长和渗透胁迫的耐受性产生负面影响，并解释了细胞分裂素作用升高对植物发育和胁迫生理的某些不利影响。