What Can Small Molecules Tell Us About Cold Stress Tolerance in Plants?

Abstract

Plants display a wide capacity range to survive cold and freezing conditions. Indeed, they are able to sense low, non-freezing temperatures and activate processes that lead to an increase in freezing tolerance, a phenomenon known as cold acclimation (CA). Metabolome analysis not only improves the recognition of the complex interactive nature of plant metabolic networks and their responses to environmental changes but also provides valuable information about plant abiotic stress resistance. Metabolomics is still an evolving field and has not reached adequate development, routine and coverage, such as other “omics” technologies. Volatilomics, a recently born “omics” science which allows to analyse the volatile component of the metabolome, has received considerable attention in abiotic stress studies. However, the integration of “omics” technologies is faced with some limitations, and, subsequently, of about 5000 primary and secondary metabolites that are present in a single plant metabolome, only a small portion has been identified. The main metabolome changes during cold stress include the production of osmoprotecting metabolites, which are involved in the regulation of cellular water relations and the reduction of cellular dehydration. Furthermore, they participate in the remodelling of membrane lipids and maintaining membrane integrity and energy sources. Cold-responsive metabolites have cryoprotective and scavenging activities and possibly also act as stabilisers of proteins and enzymes or as regulators of gene expression. Such cold-responsive metabolites particularly include soluble sugars, amino acids, betaines, organic acids, polyols, polyamines and lipids. Altogether, the accumulation of these functional metabolites is an important strategy for increasing plant survival under freezing temperatures. The analysis of metabolome dynamics in overwintering plants during the different stages of CA and plant development may provide valuable information for the improvement of cold tolerance in breeding processes. Interestingly, the majority of cold-responsive metabolites are also induced by other abiotic stresses, such as drought and salinity. In this chapter, we discuss the effects of cold stress on the metabolome and the roles of some functional metabolites during CA and overwintering.