Plants have evolved a number of cold-response genes encoding proteins that induce tolerance to freezing, alter water absorption and initiate many other low temperature induced processes. In the 1 April Genes and Development, Jian-Kang Zhu and colleagues of the Department of Plant Sciences, University of Arizona, shed light on how these genes are regulated.
Lee et al. report that the protein HOS1 negatively regulates cold-response genes in Arabidopsis. At low temperatures, HOS1 relocalizes from the cytoplasm to the nucleus where it regulates gene expression; hos1 mutants show an excessive induction of cold-response genes. The HOS1 gene was mapped to chromosome II of Arabidopsis and cloned. It encodes a protein of 915 amino acids with a nuclear localization signal and a RING finger. Proteins with this motif have been implicated in the breakdown of other proteins by a process that involves ubiquitination.
Lee et al. speculate that HOS1 might regulate the function of cold-response genes by targeting the gene products for degradation.
Lee H, Xiong L, Gong Z, Ishitani M, Stevenson B, Zhu JK: The Arabidopsis HOS1 gene negatively regulates cold signal transduction and encodes a RING finger protein that displays cold-regulated nucleo-cytoplasmic partitioning. Genes Dev 2001, 15.
Department of Plant Sciences, University of Arizona