Wild and cultivated barleys show differences in the expression pattern of a cold-regulated gene family under different light and temperature conditions

Cold acclimation in plants involves the expression of many genes and gene families. The present study reports the expression analysis of three members of the blt14 gene family in barley. Gene-specific antisense oligonucleotides were used as probes in northern experiments so as to follow independently the expression of individual members of the gene family. Each clone revealed different accumulation kinetics when a spring and a winter cultivar were compared, suggesting that the different regulatory mechanisms leading to mRNA accumulation of an individual member of the blt14 gene family are genotype-dependent. In a collection of Hordeum spontaneum genotypes both qualitative and quantitative polymorphisms were found for the accumulation of blt14-related mRNAs, although no clear relationships were found between blt14 expression and frost resistance.The accumulation of the blt14-related mRNAs was also modulated by light and by the albino mutation an. The effects of light on the accumulation of the transcripts corresponding to the blt14 gene family were evaluated by comparing etiolated and green plants. Etiolated plants accumulate the blt14-related mRNAs at a detectable level already at 22 °C. When the same plants are exposed to cold in absence of light an increased mRNA accumulation above the level present in green cold-treated plants can be detected. On the contrary, etiolated plants showed a reduced blt14 accumulation when exposed to cold in the presence of light. Cold-induced expression of the blt14 gene family was strongly reduced in plants carrying the albino mutation an. This mutant showed a defective molecular response to cold even when probed with a cDNA coding for LEA type protein (paf93). The albino mutant an was not able to harden when exposed to low temperature providing a direct evidence of the relationship between expression of cold-regulated (COR) genes and the development of cold hardening. Failure of cold acclimation in the mutant cannot be merely ascribed to the absence of photosynthetic activity, since etiolated wild-type plants accumulated COR mRNAs and improved frost resistance when exposed to cold.