Abstract
Ethylene is an essential regulatory factor in the signaling pathway of plant responses to abiotic stress, included cold stress, and also plays a regulatory role in cold response. Recent studies have shown that exogenous application of ACC (1-aminocyclopropane-1-carboxylate), an ethylene promoter, affects plant cold hardiness. It is well known that the cold-responsive specific gene DREB (dehydration-responsive element (DRE)-binding protein) plays a crucial role in enhancing cold hardiness in plants by activating some cold-responsive (CORs) genes. However, the molecular mechanism of how the ethylene biosynthesis pathway regulated this gene in the cold response of thermophilic plants had yet to be well explained. In this study, using the thermophilic plant P. indica ( Plumbago indica L.) as an example, physiological and transcriptomic analyses revealed that cold stress treatment induced the synthesis of endogenous ACC and regulated the ethylene signaling activator PiERF1, while cold signaling also activated PiDERB1A. Spraying experiments were also showed that ACC-induced up-regulation of the PiERF1 gene reduced cold tolerance of P. indica, and decreased the expression level of the PiDREB1A gene; reverse experiments have shown that spraying AVG (aminoethoxyvinylglycine) resulted in the down-regulation of the PiERF1 gene, while the expression level of PiDREB1A was increased, and chilled symptoms were alleviated. These results indicated that ethylene signaling directly regulates the downstream gene PiERF1 and initiates the DREB-COR cold-responsive signaling pathway to regulate cold hardiness, exhibiting negative regulation of cold hardiness in thermophilic plants.