How to survive mild winters: Cold acclimation, deacclimation, and reacclimation in winter wheat and barley

Cold acclimation and vernalization represent the major evolutionary adaptive responses to ensure winter survival of temperate plants. Due to climate change, mild winters can paradoxically worsen plant winter survival due to cold deacclimation induced by warm periods during winter. It seems that the ability of cold reacclimation in overwintering Triticeae cereals is limited, especially in vernalized plants. In the present review, the major factors determining cold acclimation (CA), deacclimation (DA) and reacclimation (RA) processes in winter-type Triticeae, namely wheat and barley, are discussed. Recent knowledge on cold sensing and signaling is briefly summarized. The impacts of chilling temperatures, photoperiod and light spectrum quality as the major environmental factors, and the roles of soluble proteins and sugars (carbohydrates) as well as cold stress memory molecular mechanisms as the major plant-based factors determining CA, DA, and RA processes are discussed. The roles of plant stress memory mechanisms and development processes, namely vernalization, in winter Triticeae reacclimation are elucidated. Recent findings about the role of O-glucose N-acetylation of target proteins during vernalization and their impacts on the expression of VRN1 gene and other target proteins resulting in coldresponsive modules reprogramming are presented.