Over-expression of CmSOS1 confers waterlogging tolerance in Chrysanthemum.

Manipulating the level of expression of Salt Overly Sensitive (SOS)1, a protein which regulates the movement and distribution of sodium ions, has been shown to enhance the salinity tolerance of a number of plant species, but its involvement in the response to hypoxia is less well established. Here, the contribution of the chrysanthemum homolog CmSOS1 on the expression of waterlogging tolerance has been explored. The overexpression of CmSOS1 improved the survival rate of plants exposed to waterlogging, while the performance of CmSOS1 knock-down plants was inferior to that of wild type ones. The leaf's relative electrical conductivity, malondialdehyde (MDA), peroxide (H2O2) and superoxide contents were all lowered in stressed overexpressors, whereas their soluble protein content and superoxide dismutase and catalase activity levels were all heightened. To further explore the mechanism, an oxidative stress regulator CmRCD1 was found to interact with CmSOS1, while CmRCD1 knock-down plants also appeared sensitive to waterlogging in chrysanthemum. The sensitivity to waterlogging of the Arabidopsis thaliana sos1 and rcd1 mutants was confirmed. The conclusion was that CmSOS1, via its interaction with CmRCD1, enhances the plants' waterlogging tolerance, presumably by maintaining the integrity of the plants' membranes and strengthening their capacity to neutralize reactive oxygen species.