ShCTR1 Interacts with ShRBOH1 to Positively Regulate Aerenchyma Formation in Saussurea inversa through ROS Mediation

Saussurea inversa is one of the Tibetan medicine with developed aerenchyma. In this study, we investigated the function of the ShCTR1 gene related to the formation of aerenchyma. The study of the occurrence and formation of aerenchyma in S. inversa has certain theoretical significance in revealing the special mechanism of alpine plants adapting to the environment. The results of yeast two-hybrid experiments showed that S. inversa ShCTR1 interacted with the ShRBOH1, which is a key producer of reactive oxygen species (ROS), and it was hypothesized that ShCTR1 regulation of aerenchyma formation in S. inversa mainly mediated by ROS. Aerenchyma induction and inhibition experiments were carried out on S. inversa seedlings, it was shown that ROS inducer (AT) and Ethene (ETH) induced the formation of aerenchyma in S. inversa well in roots, stems, and leaves, and Ethylene inhibitor (1-MCP) and ROS inhibitor DPI (diphenylene iodonium) inhibited the formation of aerenchyma of S. inversa in different degrees, which proved that ROS and ethylene (ET) were positively correlated with the formation of aerenchyma. Meanwhile, AT and ETH well induced the expression of the ShCTR1 gene, and 1-MCP and DPI inhibited the expression of the ShCTR1 gene to different degrees, which proved that ROS and ET were also positively correlated with the expression of the ShCTR1 gene. ShCTR1 was transferred into tobacco (Nicotiana tabacum L.), then repeat the above experiment. It was shown that positive rate and porosity were lowest and highest after DPI and AT treatments, respectively, it showed a positive correlation, which proved that the ShCTR1 gene was positively regulating the formation of aerenchyma. Overexpression of the ShCTR1 gene increased the content of ROS, consequently, the regulation of aerenchyma formation by the ShCTR1 gene is mainly mediated by ROS. It suggested that the formation of aerenchyma in S. inversa was related to hypoxia in the alpine environment, and ShCTR1 interacts with ShRBOH1 to positively regulate the formation of aerenchyma mainly mediated by ROS.