Genomics of Cold Hardiness in Woody Plants

Abstract

The term cold hardiness or freezing tolerance is used to represent, in a general sense, the ability of plants to adapt to and withstand freezing temperatures. It is a complex, multigenic trait that is too often viewed as a single entity when in fact it is composed of many aspects, all of which can be to some extent viewed as genetically distinct. Advances in molecular biology and genomics have provided significant advances in understanding how plants respond to low temperature and acquire freezing tolerance. Among the most important discoveries has been the identification of the CBF/DREB transcription factor. This transcription factor, along with its regulators such as ICE transcription factors, play a major role in sensing low temperature, initiating the process of cold acclimation, and inducing the expression of a large set of cold-regulated genes. These latter genes are presumed to ameliorate injury to plant cells as a result of freeze-induced desiccation and the presence of extracellular ice. The present review provides a comprehensive overview of CBF and ICE genes in a number of woody plants whose genomes have been sequenced and provides information on the attempts to identify genetic markers for use in marker-assisted selection (MAS) or to improve cold hardiness using genetic transformation technologies. Functional studies of CBF genes in woody plants have indicated that their regulation and impact on abiotic stress resistance are more complex than in herbaceous plants. In particular, the possible relationship of CBF to dormancy is highlighted. Cold hardiness is a complex trait and the challenge in the future will be to use the molecular and genetic tools that are being developed, as well as new developments in bioinformatics, to integrate complex sets of data into a systems view of plant biology. This approach holds the best promise for developing the ability to significantly improve cold hardiness in economically important crops while still maintaining high levels of plant productivity and yield.

Keywords:

• cold-induced signaling
• CBF
• COR genes
• Inducer-of-CBF-Expression (ICE)
• cold acclimation
• freezing tolerance

ACKNOWLEDGEMENTS

The research on the grape CBF pathway in the Nassuth lab is supported by grants from NSERC and ORF. The work on Eucalyptus CBF by the French team is carried out in the framework of the LabEx TULIP project (Towards a Unified theory of biotic Interactions: the roLe of environmental Perturbations). French embassies in Canada and the United States also contributed to this review by supporting the collaboration between the co-authors. This review covers research reported in the literature through January 2013.