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First published online July 9, 2004; 10.1104/pp.103.037473 Plant Physiology 135:1654-1665 (2004) © 2004 American Society of Plant Biologists Phylogenetic Analyses in Cornus Substantiate Ancestry of Xylem Supercooling Freezing Behavior and Reveal Lineage of Desiccation Related ProteinsDepartment of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana 479071165 (D.T.K., V.E.S., E.N.A.); Department of Botany, North Carolina State University, Raleigh, North Carolina 276957612 (Q.-Y.X.); and The Morton Arboretum, Lisle, Illinois 605321293 (A.M.S.)
The response of woody plant tissues to freezing temperature has evolved into two distinct behaviors: an avoidance strategy, in which intracellular water supercools, and a freeze-tolerance strategy, where cells tolerate the loss of water to extracellular ice. Although both strategies involve extracellular ice formation, supercooling cells are thought to resist freeze-induced dehydration. Dehydrin proteins, which accumulate during cold acclimation in numerous herbaceous and woody plants, have been speculated to provide, among other things, protection from desiccative extracellular ice formation. Here we use Cornus as a model system to provide the first phylogenetic characterization of xylem freezing behavior and dehydrin-like proteins. Our data suggest that both freezing behavior and the accumulation of dehydrin-like proteins in Cornus are lineage related; supercooling and nonaccumulation of dehydrin-like proteins are ancestral within the genus. The nonsupercooling strategy evolved within the blue- or white-fruited subgroup where representative species exhibit high levels of freeze tolerance. Within the blue- or white-fruited lineage, a single origin of dehydrin-like proteins was documented and displayed a trend for size increase in molecular mass. Phylogenetic analyses revealed that an early divergent group of red-fruited supercooling dogwoods lack a similar protein. Dehydrin-like proteins were limited to neither nonsupercooling species nor to those that possess extreme freeze tolerance.
1 Present address: Division of Plant and Soil Science, West Virginia University, Morgantown, WV 265066108. Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.103.037473. * Corresponding author; e-mail dale.karlson{at}mail.wvu.edu; fax 3042932960. Received December 9, 2003; returned for revision May 3, 2004; accepted May 4, 2004. This article has been cited by other articles:
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