DEHYDRIN GENE FAMILY MEMBERS ARE INDICATORS FOR DORMANCY AND COLD HARDINESS STATUS IN BUD TISSUE OF Pinus sylvestris

¹ Agrotechnology & Food Innovations, P.O. Box 17, 6700 AA Wageningen, The Netherlands

² Plant Research International, Postbus 16, 6700 AA Wageningen, The Netherlands

³ Danish Institute for Agricultural Sciences, Kirstinebjergvej 10, DK-5792 Aarslev, Denmark

⁴ Forestry Commission Research Agency, Northern Research Station, EH25 9SY Roslin, Midlothian, United Kingdom

Dehydrins are highly conserved genes that are involved in protection against dehydration, cold or salt stress in plants throughout the plant kingdom. Among 2000 sequenced clones, derived from three dormant bud cDNA libraries; one general, one enriched for low temperature induced genes and one enriched for dormancy related genes, at least 85 dehydrin homologues were present. Contig analysis reduced this to 9 different sequences, representing 3 dehydrin types. The 3 types of dehydrins were differentially regulated over time in bud tissue from Pinus sylvestris, grown in Denmark or Scotland. The K4S type showed no clear relation with development of dormancy and cold hardiness. K2S dehydrin was downregulated when the buds became dormant, whereas a group of K2 genes was strongly induced in the same period. High levels of K2 coincide with cold hardiness. Using realtime PCR we showed that in all pine samples tested, the physiological switch from ecodormancy to endodormancy is marked by a transition of K2/ K2S from <1 to >1. By including samples from different provenances and from trees from the same provenance grown in different climates we were able to zoom in on the actual physiological change and distinguish that from random climate or provenance effects. This work is part of the COLDTREE project, an EU funded programme aimed at unraveling the molecular processes underlying cold hardiness and dormancy in forest tree species.