The accumulation of a cold-regulated chloroplastic protein is light-dependent

The protein encoded by cDNA clone pt59 and induced in barley (Hordeum vulgare L.) by cold was over-expressed in coli to produce the matching antibody, which in vivo recognized a cold-induced protein of 14 kDa (COR14) that was found in the chloroplast stroma. The accumulation of COR14 occurred only at low temperatures after even a brief exposure of the plants to light. Plants grown and fully hardened in the dark accumulated a reduced amount of pt59-corresponding mRNA and only traces of COR14. Light exposure for as short as 5 min was enough to normalize the expression of pt59-corresponding mRNA and increase the accumulation of COR14. These findings indicate that one or more light-dependent factors are involved in transcription of the gene and accumulation of the protein. The COR14 protein was stored in amounts only slightly greater in the resistant barley cultivar. Onice than in the susceptible cultivar Gitane, although the former had a higher induction-temperature threshold for COR14 than the latter. This fact is an evolutionary advantage, enabling the resistant varieties in the field to prepare the cold well ahead of the susceptible ones.