Lysine Malonylation of DgnsLIPID TRANSFER PROTEIN1 at the K81 Site Improves Cold Resistance in Chrysanthemum.

Lysine malonylation (Kmal) is a recently discovered posttranslational modification, and its role in the response to abiotic stress has not been reported in plants. In this study, we isolated a nonspecific lipid transfer protein, DgnsLTP1, from chrysanthemum (Dendranthema grandiflorum var. Jinba). Overexpression and CRISPR-Cas9-mediated gene editing of DgnsLTP1 demonstrated that the protein endows chrysanthemum with cold tolerance. Yeast 2-hybrid, bimolecular fluorescence complementation, luciferase complementation imaging, and coimmunoprecipitation experimental results showed that DgnsLTP1 interacts with a plasma membrane intrinsic protein (PIP) DgPIP. Overexpressing DgPIP boosted the expression of DgGPX (glutathione peroxidase), increased the activity of GPX, and decreased the accumulation of reactive oxygen species (ROS), thereby enhancing the low-temperature stress tolerance of chrysanthemum, while the CRISPR-Cas9-mediated mutant dgpip inhibited this process. Transgenic analyses in chrysanthemum showed that DgnsLTP1 improves the cold resistance of chrysanthemum in a DgPIP-dependent manner. Moreover, Kmal of DgnsLTP1 at the K81 site prevented the degradation of DgPIP in Nicotiana benthamiana and chrysanthemum, further promoted DgGPX expression, enhanced GPX activity, and scavenged excess ROS produced by cold stress, thereby further enhancing the cold resistance of chrysanthemum.