Transcription factors (TFs) are important regulators of plant growth and development and responses to stresses. TFs themselves are also prone to multiple posttranslational modifications (PTMs). However, redox-mediated PTM of TFs in plants remains poorly understood. Here, we established that NON-RIPENING (NOR), a master TF regulating tomato (Solanum lycopersicum) fruit ripening, is a target of the Met sulfoxide reductases A and B, namely E4 and SlMsrB2, respectively, in tomato. Met oxidation in NOR, i.e. sulfoxidation, or mimicking sulfoxidation by mutating Met-138 to Gln, reduces its DNA-binding capacity and transcriptional regulatory activity in vitro. E4 and SlMsrB2 partially repair oxidized NOR and restore its DNA-binding capacity. Transgenic complementation of the nor mutant with NOR partially rescues the ripening defects. However, transformation of nor with NOR-M138Q, containing mimicked Met sulfoxidation, inhibits restoration of the fruit ripening phenotype, and this is associated with the decreased DNA-binding and transcriptional activation of a number of ripening-related genes. Taken together, these observations reveal a PTM mechanism by which Msr-mediated redox modification of NOR regulates the expression of ripening-related genes, thereby influencing tomato fruit ripening. Our report describes how sulfoxidation of TFs regulates developmental processes in plants.

转录因子（TFs）是植物生长发育和对胁迫的反应的重要调节剂。TF本身也易于进行多种翻译后修饰（PTM）。但是，人们对植物中TF的氧化还原介导的PTM知之甚少。在这里，我们确定了非成熟（NOR），一个主要的TF调控番茄（Solanum lycopersicum）果实成熟，是番茄中Met亚砜还原酶A和B（分别为E4和SlMsrB2）的目标。NOR中的Met氧化，即亚硫酸氧化，或通过将Met-138突变为Gln来模仿亚硫酸氧化，会降低其DNA结合能力和体外转录调控活性。E4和SlMsrB2部分修复氧化的NOR并恢复其DNA结合能力。nor的转基因互补NOR突变体可以部分挽救成熟的缺陷。但是，用模仿的Met亚砜氧化的NOR-M138Q进行转化也抑制了果实成熟表型的恢复，这与许多成熟相关基因的DNA结合减少和转录激活有关。综上所述，这些发现揭示了PTM机制，通过该机制，Msr介导的NOR的氧化还原修饰调节成熟相关基因的表达，从而影响番茄果实的成熟。我们的报告描述了TFs的硫氧化作用如何调节植物的发育过程。