Expression of a Solanum sogarandinum SK3-type dehydrin enhances cold tolerance in transgenic cucumber seedlings

The expression pattern of a Solanum sogarandinum pGT∷Dhn24 gene fusion encoding a SK3-type DHN24 dehydrin and the potential role of that protein in cold tolerance in cucumber were analyzed in five T1 transgenic lines. Accumulation of both the Dhn24 transcript and DHN24 protein was detected in leaves, cotyledons, stems and roots of the transgenic seedlings by RT-PCR and Western blot analysis, with the highest DHN24 protein level observed in roots. No DHN24 transcript and no recombinant DHN24 protein were detected in non-transgenic control plants. Three transgenic lines, designated TCH3, TCH11 and TCH15, showed a significantly reduced chilling injury value (severity of chilling injury, SCI) compared to the non-transgenic line. Expression levels of the DHN24 protein varied among transgenic lines and overall, no correlation between the DHN24 protein level and the degree of chilling tolerance was found. However, transgenic line TCH10 exhibited a significantly enhanced freezing tolerance compared to the non-transgenic controls, as evaluated by an electrolyte leakage test, and had the highest expression level of the DHN24 protein in its roots. We conclude that the DHN24 dehydrin originated from a cold-acclimated species S. sogarandinum is essentially linked to low temperature tolerance in cold-sensitive species such as cucumber and can be used to improve chilling/freezing tolerance through a transgenic approach.