Keeping the cold out

As published in the April 1st issue of Genes & Development, Dr. Jian-Kang Zhu and colleagues from the University of Arizona have cloned and characterized one of the key factors regulating a plant’s response to cold temperatures. This factor, HOS-1, is the first protein of its type to be identified in cold signal transduction in any organism.

Plants have evolved a set of specialized cold-response genes. Cold-response genes encode proteins that induce tolerance to freezing, alter water absorption and initiate a host of other processes to help the plant survive. Although this network of cold-responsive genes has been characterized in some depth, the specific factors that regulate their activity have, until now, remained elusive.

Dr. Zhu and colleagues report that the protein HOS1 negatively regulates cold-response genes. In response to low temperatures, the HOS1 protein relocalizes from the cytoplasm to the cell nucleus, where it can regulate the set of cold-response genes. HOS-1 mutants display an excessive induction of the cold-response genes in low temperatures. This finding provides an example of a simple, yet effective, mechanism that plants use to adapt to changing environmental conditions.