Low Temperature Signal Transduction, Gene Expression, And Cold Acclimation: Multiple Roles of Low Temperature

Abstract

Many plants develop resistance to freezing temperatures during exposure to a period of low but nonfreezing temperature (cold acclimation). During the past 5 years cold-induced genes have been cloned and characterized from several plants including alfalfa (Mohapatra et al., 1988, 1989; Monroy et al., 1993a; Wolfraim et al., 1993), Arabidopsis (Kurkela and Franck, 1990), barley (Cattivelli and Bartels, 1990; Dunn et al., 1991), Brassica (Orr et al., 1992), maize (Hahn and Walbot, 1990) and wheat (Houde et al., 1992). Some of the cold-induced genes isolated from alfalfa and wheat are specifically induced by cold, i.e. they are not induced by other environmental stresses or by the plant stress hormone ABA. It is clear from the sequence analysis of the cold-induced genes that, in agreement with the multigenic nature of freezing tolerance, cold acclimation is associated with a diversity of genes. Thus a rapid progress has been made towards understanding the molecular genetic basis of freezing tolerance. However, in order to cold acclimate a plant must be able to sense the low temperature signals and transduce them into specific biochemical processes leading to cold acclimation and development of freezing tolerance. We have been examining the role of calcium and protein phosphorylation in low temperature signal transduction during cold acclimation of alfalfa cells. Here we summarise evidence for the interlinking of calcium influx, protein phosphorylation, gene expression and the development of freezing tolerance during cold acclimation. For details of procedures and methods used in these studies see Mohapatra et al. (1989), Monroy and Dhindsa (1993), Monroy et al. (1993a,b) and Wolfraim et al., 1993).