Molecular cloning of a novel heat induced/chilling tolerance related cDNA in tomato fruit by use of mRNA differential display

摘要

Chilling injury was circumvented by heat-treating mature green tomatoes (Lycopersicon esculentum cv. Mountain Springs) at 42deg C for two days prior to storing them at 2deg C for one or two weeks, whereas fruits stored at 2deg C without preheating developedtypical chilling injury symptoms and failed to ripen at 20deg C. Using mRNA differential display and screening of the cDNA libraries, a full-length HCT1 cDNA (heat induced/chilling tolerance related) was cloned from tomato fruit. The protein (17.6 kDa) predicted from the coding region of HCT1 cDNA showed high identity with class II cytosolic small HSPs (smHSPs). The gene corresponding to HCT1 cDNA was designated as LeHSP17.6. Southern-blot hybridization indicated that LeHSP17.6 belongs to a two-member genefamily. Northern blot analysis revealed that the heat-induced transcript of LeHSP17.6 remains up-regulated during subsequent exposure of the fruit to chilling temperatures for at least one week and upon transfer to ripening temperatures for one day. Fruits which were only chilled showed a low level of expression of the LeHSP17.6 transcript. It is hypothesized that LeHSP17.6 may be involved in protecting the cell from metabolic dysfunctions leading to ripening failure caused by chilling injury. This isthe first report of a class II cytosolic smHSPs encoding gene in tomato. Nucleotide sequence data for the LeHSP17.6 cDNA sequence have been submitted to the GenBank database under the accession number U72396.