Freezing Tolerance of Lactuca sativa and Induction of CBF and GolS Genes during Cold Treatment

Plants respond to several environmental changes such as low- and high-temperatures, drought, flood, and so on, leading to development of stress tolerance. Acquisition abilities of freezing tolerance of three lettuce cultivars were investigated. All the investigated cultivars showed improvement of freezing tolerance at -3°C after exposure to non-freezing low-temperature at 2°C for 7 days. Out of them, papa lettuce cultivar was used to investigate expression levels of cold-responsive genes. The cultivar showed induction of CBF and GolS genes, which are well known as cold-responsive genes in other plants, during cold treatment. These results showed that lettuce has at least one cold-responsive signal pathway, suggesting a possibility that genetical modification might enhance the freezing tolerance.