Recent insights into cell responses to cold stress in plants: Signaling, defence, and potential functions of phosphatidic acid

Upon exposure to cold stress (CS), crop plants face an array of detrimental effects on growth, development, and final yield. Seed germination, seedling emergence, leaf number, root morphology, photosynthetic activity and metabolism are all disrupted by CS. Plants have evolved various mechanisms to avoid or induce cold tolerance from the cellular level to the whole plant level. Phosphatidic acid (PA) is considered a prime signaling phospholipid in plant membranes that plays an important role in signal transduction in stress avoidance responses. Recent research studies have advanced our understanding of the functions of PA in plant response to abiotic stress. As a second messenger, PA can bind to target proteins to enhance plant cold response and adaption. However, there is a paucity of information on PA-mediated alterations in lipid metabolism as a plant cold tolerance mechanism. Firstly, this review presents plant response to CS at morphological, physiological, biochemical, and molecular levels. The authors also discuss the roles of protective proteins, osmo-protectants, antioxidant systems and lipid metabolisms in plant cold tolerance mechanisms. Furthermore, the current review documents state of the art literature on the effects of CS on plant PA biosynthesis pathways (PLD and PLC-DGK pathways) in plants and its promising role in improving cold tolerance. Finally, we summarized the PA signaling in plant cold tolerance and suggested research directions in CS studies in the future.