ARABIDOPSIS-THALIANA COR15B, AN APPARENT HOMOLOG OF COR15A, IS STRONGLY RESPONSIVE TO COLD AND ABA, BUT NOT DROUGHT

We previously described a cold-regulated (cor) gene from Arabidopsis thaliana, cor15a (formerly cor15), that encodes a 15 kDa polypeptide that is targeted to chloroplasts (C. Lin and M. Thomashow, Plant Physiol 99 (1992): 519-525). Here we describe an apparent homologue of cor15a, cor15b. col15b is located immediately downstream from cor15a (within 1 kb) and has the same relative 5' to 3' orientation as cor15a. The predicted coding regions for the two genes are 82% identical at the nucleic acid sequence level. Transcripts for cor15b, like those of cor15a, increase dramatically in response to low temperature and exogenous application of ABA. However, only cor15a transcripts accumulate to high levels in response to drought. The cor15a/cor15b gene pair is the third case in which A. thaliana cold-regulated genes have been found to exist as tandem gene pairs with the members of each pair being differentially regulated.