Comparative study of the expression profiles of the Cor/Lea gene family in two wheat cultivars with contrasting levels of freezing tolerance.

Expression profiles of a set of Cor/Lea genes were assessed during early stages of cold acclimation in seedlings of two wheat cultivars, which showed contrasting levels of freezing tolerance. These Cor/Lea family members consisted of three EST clones and 13 previously identified cDNA clones of wheat and rye. Northern blot analysis using RNA extracted from seedling leaves and roots showed that most of the genes exhibited a quite similar time-course of expression, although with different expression levels: They rapidly responded to low temperature and their transcript levels reached high plateaus within 3-5 days. The overall gene expression profiles were correlated with the time-dependent development and the level of freezing tolerance under low temperature in the two cultivars. Western blot analysis of protein accumulation further verified this observation. Abscissic acid response was proved for at least four genes. Light was stimulatory to most of the genes, and this positive light response associated with low temperature occurred not only in leaf-specific genes but also in leaf/root-expressed genes. Taken together, the present results suggest that the Cor/Lea gene family represents a major group of downstream genes involved in the ABA-dependent and -independent signal pathways and that most of them are co-regulated in determining freezing tolerance in wheat seedlings.