Cold-induced freezing tolerance in Arabidopsis

Changes in the physiology of plant leaves are correlated with enhanced free zing tolerance and include accumulation of compatible solutes, changes in m embrane composition and behavior, and altered gene expression. Some of thes e changes are required for enhanced freezing tolerance, whereas others are merely consequences of low temperature. In this study we demonstrated that a combination of cold and light is required for enhanced freezing tolerance in Arabidopsis leaves, and this combination is associated with the accumul ation of soluble sugars and proline. Sugar accumulation was evident within 2 h after a shift to low temperature, which preceded measured changes in fr eezing tolerance. In contrast, significant freezing tolerance was attained before the accumulation of proline or major changes in the percentage of dr y weight were detected. Many mRNAs also rapidly accumulated in response to low temperature. All of the cold-induced mRNAs that we examined accumulated at low temperature even in the absence of light, when there was no enhance ment of freezing tolerance. Thus, the accumulation of these mRNAs is insuff icient for cold-induced freezing tolerance.