Isolation and characterization of a heat-induced gene, hcit2, encoding a novel 16.5 kDa protein: Expression coincides with heat-induced tolerance to chilling stress

Heat treatment of tomato fruits induces tolerance to chilling injury. We have previously shown that specific heatshock proteins (HSPs) are expressed in heated tomato fruits after cold storage. To search for heat-induced genes that are expressed at low temperatures, a cDNA library prepared from pre-heated chilled tomato fruits was differentially screened. A novel cDNA clone, hcit2, encoding a protein of ca. 16.5 kDa, was isolated. The predicted protein contains three putative trans-membrane hydrophobic sequences, suggesting that the protein is membrane-localized. The expression of hcit2 in fruits was induced by high temperature, but not by other stresses such as low temperature, drought or anaerobic conditions, and not during fruit ripening. A high level of hcit2 transcript was found in heated fruits after 2 weeks at 2 °C. High temperatures also induced hcit2 expression in tomato leaves, flowers and stems. The HCIT2 protein may be involved in the acquisition of tolerance to chilling injury.