Water deficit impairs growth and survival of plants. Many water stress responses are under control of abscisic acid (ABA) but little is known about growth control under osmotic stress. Based on the previously described growth-promoting activity of the peptide hormone phytosulfokine (PSK), we hypothesized that it may contribute to growth regulation under water stress conditions. To test this hypothesis, we analyzed the Arabidopsis thaliana PSK receptor (PSKR) null mutant pskr1-3 pskr2-1 under mannitol and drought stress. In particular under mild water stress, fresht weight and photosynthetic efficiency were more reduced in pskr1-3 pskr2-1 than in wild type. Hydroponic and grafting experiments showed that PSKR signaling was not required for long-distance signaling from mannitol-stressed roots to shoot but rather for cell growth promotion in the shoot. Unlike wild type, pskr1-3 pskr2-1 shoots did not accumulate ABA in response to mannitol, showed misregulation of ABA synthesis genes and elevated expression of ABI1 and ABI2, repressors of ABA signaling whereas application of ABA partially reversed shoot growth inhibition by mannitol in pskr1-3 pskr2-1. In turn, mannitol and ABA induced expression of PSK3 and PSKR1, and ABA promoted expression of PSK2 and PSK4 revealing feedback regulatory loops between PSKR and osmotic stress signaling.

中文翻译：

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PSK信号控制ABA稳态和信号基因，并在渗透胁迫下维持枝条生长

缺水会损害植物的生长和存活。许多水分胁迫反应都在脱落酸（ABA）的控制下，但对渗透胁迫下的生长控制知之甚少。基于先前描述的肽激素植物硫素（PSK）的促生长活性，我们假设它可能有助于水分胁迫条件下的生长调节。为了验证该假设，我们分析了甘露醇和干旱胁迫下拟南芥PSK受体（PSKR）无效突变体pskr1-3 pskr2-1。特别是在温和的水分胁迫下，pskr1-3 pskr2-1的鲜重和光合效率比野生型降低更多。水培和嫁接实验表明，从甘露醇胁迫的根到芽的长距离信号传递不需要PSKR信号传递，而在芽中促进细胞生长则不需要PSKR信号传递。与野生型不同，pskr1-3 pskr2-1芽未响应甘露醇而积累ABA，显示ABA合成基因的调节异常以及ABI1和ABI2的表达升高，ABA信号的阻遏物，而ABA的应用部分逆转了甘露醇对甘露醇的生长抑制作用。 pskr1-3 pskr2-1。反过来，甘露醇和ABA诱导PSK3和PSKR1的表达，而ABA促进PSK2和PSK4的表达，揭示了PSKR和渗透压信号之间的反馈调节环。结果显示，ABA合成基因的调控异常，ABA信号的阻遏物ABI1和ABI2的表达升高，而ABA的应用部分逆转了pskr1-3 pskr2-1中甘露醇对芽生长的抑制作用。反过来，甘露醇和ABA诱导PSK3和PSKR1的表达，而ABA促进PSK2和PSK4的表达，揭示了PSKR和渗透压信号之间的反馈调节环。结果显示，ABA合成基因的调控异常，ABA信号的阻遏物ABI1和ABI2的表达升高，而ABA的应用部分逆转了pskr1-3 pskr2-1中甘露醇对芽生长的抑制作用。反过来，甘露醇和ABA诱导PSK3和PSKR1的表达，而ABA促进PSK2和PSK4的表达，揭示了PSKR和渗透压信号之间的反馈调节环。