Cold-regulated gene expression and freezing tolerance in an Arabidopsis thaliana mutant

Low temperature is an important environmental factor influencing plant grow th and development. In this study, we report the characterization of a gene tic locus, HOS2, which is defined by three Arabidopsis thaliana mutants. Th e hos2-1, hos2-2 and hos2-3 mutations result in enhanced expression of RD29 A and other stress genes under low temperature treatment. Gene expression i n response to osmotic stress or ABA is not affected in the hos2 mutants. Ge netic analysis indicates that the hos2 mutations are recessive and in a nuc lear gene. Compared with the wild-type plants, the hos2-1 mutant plants are less capable of developing freezing tolerance when treated with low non-fr eezing temperatures. However, the hos2-1 mutation does not impair the verna lization response. These results indicate that HOS2 is a negative regulator of low temperature signal transduction important for plant cold acclimatio n.