Nitrogen is essential for plant growth and development. SNF1-related protein kinase 1 (SnRK1) is an evolutionarily conserved protein kinase pivotal for regulating plant responses to nutrient deficiency. Here, we discovered that the expression and activity of the SnRK1 α-catalytic subunit (SnRK1α1) increased in response to low-nitrogen stress. SnRK1α1 overexpression enhanced seedling tolerance, nitrate uptake capacity, apoplastic reactive oxygen species (ROS) accumulation, and NADPH oxidase activity in tomato (Solanum lycopersicum L.) under low-nitrogen stress compared to wild type plants, while snrk1α1 mutants exhibited the opposite phenotypes. Mutation of the NADPH oxidase gene Respiratory burst oxidase homolog 1 (RBOH1) suppressed numerous nitrate uptake and metabolism genes during low-nitrogen stress. rboh1 mutants displayed lower NADPH oxidase activity, apoplastic ROS production, and seedling tolerance to low nitrogen. Silencing RBOH1 expression also compromised SnRK1α1-mediated seedling tolerance to low-nitrogen stress. SnRK1α1 interacts with and activates RBOH1 through phosphorylation of three N-terminal serine residues, leading to increased apoplastic ROS production and enhanced tolerance to low nitrogen conditions. Furthermore, RBOH1-dependent ROS oxidatively modified the transcription factor TGA4 at residue Cys-334, which increased NRT1.1 and NRT2.1 expression under low-nitrogen stress. These findings reveal a SnRK1α1-mediated signaling pathway and highlight the essential role of RBOH1-dependent ROS production in enhancing plant tolerance to low nitrogen.

中文翻译：

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SnRK1α1 介导的 RBOH1 磷酸化调节活性氧以增强番茄对低氮的耐受性


氮对植物的生长和发育至关重要。SNF1 相关蛋白激酶 1 （SnRK1） 是一种进化上保守的蛋白激酶，是调节植物对营养缺乏反应的关键。在这里，我们发现 SnRK1 α催化亚基 （SnRK1α1） 的表达和活性在低氮胁迫下增加。与野生型植株相比，SnRK1α1 过表达增强了低氮胁迫下番茄 （Solanum lycopersicum L.） 幼苗耐受性、硝酸盐吸收能力、质外体活性氧 （ROS） 积累和 NADPH 氧化酶活性，而 snrk1α1 突变体表现出相反的表型。NADPH 氧化酶基因突变呼吸爆发氧化酶同源物 1 （RBOH1） 在低氮胁迫期间抑制了许多硝酸盐摄取和代谢基因。rboh1 突变体表现出较低的 NADPH 氧化酶活性、质外体 ROS 产生和幼苗对低氮的耐受性。沉默 RBOH1 表达也损害了 SnRK1α1 介导的幼苗对低氮胁迫的耐受性。SnRK1α1 通过磷酸化三个 N 端丝氨酸残基与 RBOH1 相互作用并激活 RBOH1，导致质外体 ROS 产生增加并增强对低氮条件的耐受性。此外，RBOH1 依赖性 ROS 氧化修饰了残基 Cys-334 的转录因子 TGA4，从而在低氮胁迫下增加了 NRT1.1 和 NRT2.1 的表达。这些发现揭示了 SnRK1α1 介导的信号通路，并强调了 RBOH1 依赖性 ROS 产生在增强植物对低氮的耐受性中的重要作用。