Argonaute 1 negatively regulates cadmium tolerance via modulating jasmonic acid and gibberellin contents, antioxidant enzymes, and chlorophyll level in tobacco.

Cadmium (Cd) is one of the most toxic heavy metal pollutants that limits plant productivity and poses a threat to human health. In this study, we identified argonaute 1 (AGO1), a key factor in the RNA interference pathway, which is suppressed by Cd stress in Nicotiana tabacum L. Overexpression of NtAGO1 (AGO1-OE), knockout of NtAGO1 (ago1-KO), and wild-type (WT) plants were employed to investigate the mechanism of NtAGO1-mediated Cd tolerance in tobacco. The results showed that AGO1-OE plants exhibited higher levels of reactive oxygen species (ROS) and lower chlorophyll content, and their seedlings accumulated lower Cd levels than WT plants. Cd stress affected the content of endogenous plant hormones differently, with jasmonic acid (JA) increasing by 57.42 % and gibberellins (GA) decreasing by 24.51 %, both of which were negatively regulated by NtAGO1. Application of exogenous GA3 and methyl jasmonate confirmed that plant hormones up-regulate antioxidant enzyme activity. Furthermore, the foliar application of GA3 inhibited the expression of chlorophyll degradation-related genes, impeded Cd-induced chlorophyll degradation and promoted plant growth. Our results demonstrate that NtAGO1 negatively regulates the response of tobacco to Cd stress by decreasing JA and GA levels, providing a foundation for the use of genetic engineering methods to enhance the efficiency of phytoremediation.