Leveraging Atriplex hortensis choline monooxygenase to improve chilling tolerance in cotton

Low temperature is a major factor limiting seedling growth and the production of cotton (Gossypium hirsutum L.). However, enhancing chilling tolerance is typically negatively correlated with yield in agricultural production. Here, we demonstrate that transgenic cotton expressing Atriplex hortensis choline monooxygenase (AhCMO) greatly enhanced resistance to chilling stress. The promotion of chilling tolerance is mainly due to an increase in the content of osmoprotectants, especially glycine betaine and proline. The increased chilling tolerance was further verified at the molecular level using genome-wide expression profiling by RNA-sequencing. Further detailed analysis showed that the number of genes involved in scavenging of reactive oxygen species (ROS) was down-regulated and the activity of superoxide dismutase (SOD) and catalase (CAT) were decreased in AhCMO transgenic cotton compared with wild type after low temperture treatment. More importantly, overexpression of AhCMO in cotton moderately improved cotton fiber yield in normal growth condition. These data show that AhCMO transgenic cotton enhances low temperature tolerance via directly accumulating cellular osmoprotectants. Manipulating the expression of AhCMO by biotechnological tools could be a powerful method to enhance chilling tolerance in cotton.