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Overexpression of a blueberry-derived CBF gene enhances cold tolerance in a southern highbush blueberry cultivar

Walworth, Aaron E., Rowland, Lisa J., Polashock, James J., Hancock, James F., Song, Guo-qing
Molecular breeding 2012 v.30 no.3 pp. 1313
Cauliflower mosaic virus, Vaccinium corymbosum, acclimation, buds, cold, cold tolerance, cultivars, developmental stages, explants, flowers, freezing, gene overexpression, genetically modified organisms, leaves, regulon, spring, temperature, transcription factors, winter
Blueberry cultivars are subject to freezing damage in the winter and early spring. C-repeat binding factor (CBF) genes are transcription factors known to induce the expression of genes associated with cold acclimation and freezing tolerance. A CBF-encoding gene (BB-CBF) was isolated from the northern highbush blueberry Bluecrop (a cold-tolerant cultivar) and introduced into the southern highbush blueberry Legacy (a more cold-sensitive cultivar) to determine the effects on cold tolerance. The BB-CBF coding sequence was linked to the cauliflower mosaic virus 35S promoter and the 35S polyA terminator and was subsequently introduced into Legacy using Agrobacterium-mediated transformation of leaf explants. Fifty-seven transgenic events were obtained. Non-acclimated mature leaves, dormant flower buds, and flowers at various developmental stages from transformants and nontransgenic plants were subjected to electrolyte leakage assays over the course of 3 years, 2009–2011. Transgenic lines showed an increase in freezing tolerance in leaves and dormant buds. Expression of putative downstream components of the blueberry CBF regulon was increased in non-acclimated transgenic lines, and, in some cases, to a level similar to that of acclimated control plants. Following low temperature exposure, BB-CBF-overexpressing transgenics and controls expressed these genes at similar levels.