Brassinosteroids are plant hormones that play an important role in the regulation of the growth, development, and stress responses in plants, particularly, in the induction of tolerance to oxidative stress. It is known that the oxidative stress in plants, which consists in a sharp accumulation of reactive oxygen species (ROS), is induced by a methyl viologen herbicide. Since calcium plays an important role in the transduction of brassinosteroid signals in plant cells and closely interacts with a ROS network in the cells, the role of calcium in the modulation of ROS balance by brassinosteroids was studied using 35S::AtCAX1 transgenic tobacco plants. It was established that 35S::AtCAX1 tobacco plants with an artificial calcium deficiency in the cytosol are more sensitive to the oxidative damage induced by the effect of methyl viologen. The level of lipid peroxidation and oxidized glutathione was higher; however, the activation of superoxide dismutase and glutathione reductase was lower in mutated plants. In 35S::AtCAX1 plants, the effect of brassinosteroids on the induction of the oxidative state changes. A partial restoration of the chlorophyll level, weakening of lipid peroxidation, and a decrease in the level of oxidized glutathione, as well as the activation of superoxide dismutase and glutathione reductase, induced by brassinosteroids were less pronounced in the transgenic plants. The results of the analysis of gene coexpression, protein–protein interactions, and posttranslational modifications in silico confirm that brassinosteroids regulate the mechanisms of tobacco plant response to the effect of methyl viologen using calcium-dependent signaling processes, contributing to the formation of a balance of reactive oxygen species.

油菜素类固醇是植物激素，在调节植物的生长、发育和应激反应中发挥重要作用，特别是在诱导对氧化应激的耐受性中。众所周知，植物中的氧化应激是由甲基紫罗碱除草剂引起的，其中活性氧（ROS）的急剧积累。由于钙在植物细胞中油菜素类固醇信号的转导中起着重要作用，并且与细胞中的ROS网络密切相互作用，因此利用35S::AtCAX1转基因烟草植物研究了钙在油菜素类固醇调节ROS平衡中的作用。已确定35S::AtCAX1细胞质中人工缺钙的烟草植物对甲基紫精作用引起的氧化损伤更敏感。脂质过氧化和氧化型谷胱甘肽水平较高；然而，突变植物中超氧化物歧化酶和谷胱甘肽还原酶的激活较低。35S ::AtCAX1植物中，油菜素类固醇对诱导氧化状态变化的作用。油菜素类固醇诱导的叶绿素水平的部分恢复、脂质过氧化的减弱、氧化型谷胱甘肽水平的降低以及超氧化物歧化酶和谷胱甘肽还原酶的激活在转基因植物中不太明显。基因共表达、蛋白质-蛋白质相互作用和翻译后修饰的计算机分析结果证实，油菜素类固醇利用钙依赖性信号传导过程调节烟草植物对甲基紫精作用的反应机制，有助于形成平衡活性氧。