FUNCTION AND REGULATION OF ARABIDOPSIS-THALIANA COR (COLD-REGULATED) GENES

Like many plants, Arabidopsis thaliana increases in freezing tolerance in response to low non-freezing temperatures, a phe nomenon known as cold acclimation. Associated with cold acclimation are a number of bio chemical changes including the expression of COR (cold-regulated) gene s. Here we summarize recent progress we have made in understanding the function and regulation of these genes. One significant finding regar ding COR gene function is that constitutive expression of COR15a in tr ansgenic Arabidopsis plants enhances the freezing tolerance of both ch loroplasts and protoplasts. These results provide the first direct evi dence for a COR gene having a role in freezing tolerance. The precise mechanism of COR15a action is not yet know, but current results indica te the gene has a role in stabilizing membranes against freeze-induced damage. In regards to COR gene regulation, we have isolated a cDNA fo r CBF1, the first identified transcriptional activator that binds to t he CRT (C-repeat)/DRE (drought responsive element), a cold-and drought -responsive DNA regulatory element present in the promoters of COR gen es. Our working hypothesis is that CBF1 binds to the CRT/DRE sequence and participates in the regulation of COR genes in response to low tem perature and drought.