EFFECT OF COLD STRESS ON BLUEBERRY DEHYDRIN ACCUMULATION

Authors: PANTA, GANESH - GEORGE WASHINGTON UNIV; Rowland, Lisa

Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/13/2001
Publication Date: 10/20/2001
Citation: Panta, G.R., Rowland, L.J. 2001. Effect of cold stress on blueberry dehydrin accumulation. Journal of American Society for Horticultural Science.

Interpretive Summary: Perennial plants, like blueberry, must undergo physiological changes in order to prepare for and ultimately survive the winter. In a recent survey of blueberry research and extension scientists in the United States, lack of cold hardiness and susceptibility to spring frosts were identified as the most important genetic limitations of current cultivars. How these factors are controlled genetically is not well understood. For these reasons, molecular approaches are being used to investigate genetic controls of cold hardiness and related factors in blueberry. Previously, three dehydrins (proteins found in plants that are induced by cold and drought stress) were identified as the predominant proteins present in cold-acclimated blueberry flower buds. In addition, dehydrin levels were shown to be associated with cold hardiness levels in blueberry. Here, we have examined dehydrin levels in response to cold treatment in other organs, in addition to flower buds, including leaves, stems, and roots. Dehydrin accumulation was observed in all organs examined, but accumulated to higher levels in stems and roots than in leaves. This is probably because winter survival of stems and roots is critical for whole plant survival whereas leaves are not. Identification and characterization of proteins/genes associated with cold hardiness and winter survival will help scientists to develop more effective strategies for increasing cold hardiness of existing varieties or developing new, more cold-hardy varieties of blueberry.

Technical Abstract: Previously, three dehydrins of 65, 60, and 14 kDa were identified as the predominant proteins present in cold acclimated blueberry (Vaccinium corymbosum Linnaeus) floral buds. Levels were shown to increase with cold acclimation and decrease with deacclimation and resumption of growth. In the present study, to determine if dehydrins are induced in other organs in response to low temperature treatment (4 C), accumulation of dehydrins was examined in leaves, stems, and roots of two cultivars and one wild selection ('Bluecrop', V. corymbosum; 'Climax', V. ashei Reade; Florida4B, V. darrowi Camp) of blueberry by SDS-polyacrylamide gel electrophoresis followed by immunoblotting. Dehydrin accumulation was observed in all organs examined. Dehydrins accumulated to higher levels in stems and roots than in leaves in the case of 'Climax' and Fla4B and to higher levels in stems than roots or leaves in the case of 'Bluecrop'. The level of dehydrin accumulation was correlated with expected level of plant cold hardiness in the three genotypes. Furthermore, cold treatment combined with dark treatment induced higher levels of dehydrins than cold treatment combined with a 10 hour light/14 hour dark photoperiod. Using a full-length cDNA clone of bbdhn1, which encodes the 60 kDa dehydrin of blueberry, as a probe on RNA blots, dehydrin transcript levels were also examined in response to cold treatment. A comparison of dehydrin transcript and protein levels during cold treatment indicated that higher dehydrin transcript levels are partly responsible for the abundance of dehydrins but that other levels of control are operating as well, such as protein stability and possibly translational control.