Submitted to: Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 30, 1998
Publication Date: N/A
Interpretive Summary: Levels of three major proteins (molecular weights of 65, 60, and 14 kD) increase in flower buds of dormant blueberry plants during the winter and decrease during the spring with the resumption of growth. Levels of these proteins are closely associated with cold acclimation and, thus, winter survival. Characterization of these proteins found them to be membes of a family of plant proteins induced by drought and freezing stress called dehydrins. Here we report the isolation and sequencing of a gene (copied from messenger RNA) encoding the 60 kD dehydrin. A lysine-rich region, indicative of dehydrins, was repeated five times throughout the encoded protein. These lysine-rich segments were contained within larger repeats which comprised 85% of the protein. 60 kD dehydrin-messenger RNA level was examined in two blueberry cultivars, Bluecrop and Tifblue, with different cold hardiness levels (Bluecrop being more cold hardy than Tifblue). The messenger RNA increased to a higher level more quickly in Bluecrop than in Tifblue, reaching a maximum about mid November in Bluecrop as compared to mid December in Tifblue.
Levels of three dehydrins of 65, 60, and 14 kD increase in floral buds of dormant blueberry (Vaccinium corymbosum and Vaccinium ashei) during cold acclimation and decrease during deacclimation and resumption of growth. Peptide sequence information from the 65 and 60 kD dehydrins was used to synthesize degenerate DNA primers for amplification of a part of the gene(s) encoding these proteins. One pair of primers amplified a 174 bp fragment. The 174 bp fragment was used to screen a cDNA library (prepared from RNA from cold acclimated bluebery floral buds) and resulted in the isolation of a cDNA clone with a 2.0 kb insert. The cDNA was sequenced and found to be a full-length clone encoding a K5 type dehydrin (5 K boxes). Peptide sequences within the clone suggested that it encodes the 60kD dehydrin. The dehydrin cDNA hybridized on RNA blots to two chilling-responsive messages of 2.0 and 0.5 kb. Both the 2.0 and 0.5 kb messages increased to relatively higher levels more quickly in the cold hardy cultivar Bluecrop than in the less hardy cultivar Tifblue. In addition, the 0.5 kb message remained at a higher level longer in Bluecrop than in Tifblue. The dehydrin cDNA hybridized on DNA blots to an RFLP marker suitable for mapping in a diploid blueberry population, segregating for chilling requirement and cold hardiness.