PiERF1 regulates cold tolerance in Plumbago indica L. through ethylene signalling

Ethylene is a signalling factor that plays a key role in the response of plants to abiotic stresses, such as cold stress. Recent studies have shown that the exogenous application of 1-aminocyclopropane-1-carboxylate (ACC), an ethylene promoter, affects plant cold tolerance. The cold-responsive specific gene DREB plays a crucial role in enhancing cold tolerance in plants by activating several cold-responsive (COR) genes. However, how the ethylene biosynthesis pathway regulates this gene in the cold response of thermophilic plants has yet to be fully elucidated. In this study, the thermophilic plant Plumbago indica L. was used as an example. Physiological experiments and transcriptomic analyses revealed that cold stress treatment induced the synthesis of endogenous ACC and regulated the ethylene signalling activator PiERF1, and cold signalling also activated PiDREB1A. Spray experiments also revealed that ACC-induced upregulation of the PiERF1 gene reduced the cold tolerance of P. indica and decreased the expression level of the PiDREB1A gene. These results indicate that ethylene signalling directly regulates the downstream gene PiERF1 and initiates the DREB‒COR cold-responsive signalling pathway to regulate cold tolerance, resulting in the negative regulation of cold tolerance in thermophilic plants.