Differential gene expression in cucumber plants in response to brief daily cold treatments

Abstract

The mechanisms of plant responses to short-term cold treatments applied daily in the period of active growth remain unknown. Cucumber ( Cucumis sativus L.) plants were subjected to brief drops of temper- ature (2 h, 12°C ) at the end of each night over a 6-day period (DROP treatment) and to prolonged (6 days) cool- ing at 12°C (permanent low-temperature treatment, PLT). The plants exposed to cold treatments and control plants grown at 20°C were compared in terms of cold resistance and changes in gene expression. Cold resis- tance of plants was determined on the basis of LT 50 temperature. The response of cucumber genetic machinery was assessed by means of a differential display method based on polymerase chain reaction (PCR). The changes in mRNA pool in cells of cucumber plants subjected to permanent and periodic chilling were assessed after comparing the populations of PCR fragments of cDNA. In both types of chilling protocols, the cold resistance started to increase from the 2nd day of low temperature treatment. At the end of the experiment (on the 6th day), the increment in cold resistance was three times larger for DROP compared to PLT treatment. Analysis of mRNA pool showed that the numbers of amplified fragments were nearly identical in both types of low-tem- perature treatment. The higher level of cold resistance under DROP conditions was assumed to depend on fea- tures of metabolism.