Photoperiodic Regulation of a 24-kD Dehydrin-Like Protein in Red-Osier Dogwood (Cornus sericea L.) in Relation to Freeze-Tolerance

Abstract

;A predominant 24-kD dehydrin-like protein was previously found to fluctuate seasonally within red-osier dogwood (Cornus sericea L.) stems. The current study attempted to determine what environmental cues triggered the accumulation of the 24-kD protein and to assess its potential role in winter survival. Controlled photoperiod and field studies confirmed that photoperiod regulates a reduction of stem water content (SWC), freeze-tolerance enhancement and accumulation of the 24-kD protein.Diverse climatic ecotypes, which are known to respond to different critical photoperiods, displayed differential reduction of SWC and accumulation of the 24-kD protein. A time-course study confirmed that prolonged exposure to short days is essential for SWC reduction, 24-kD protein accumulation, and freeze-tolerance enhancement. Water deficit induced 24-kD protein accumulation and enhanced freeze-tolerance under long-day conditions. In all instances, freeze-tolerance enhancement and 24-kD protein accumulation was preceded by a reduction of SWC. These results are consistent with the hypothesis that C. sericea responds to decreasing photoperiod, which triggers a reduction in SWC. Reduced SWC in turn may trigger the accumulation of the 24-kD protein and a parallel increase in freezetolerance.

Phylogenetic Analyses inCornusSubstantiate Ancestry of Xylem Supercooling Freezing Behavior and Reveal Lineage of Desiccation Related Proteins

“…In a previous study, we determined that a photoperiod controlled SWC reduction is highly correlated to freeze tolerance and dehydrin-like protein accumulation in C. sericea and likely serves as a cue for the acquisition of freezing tolerance prior to the onset of winter (Karlson et al, 2003). When two representative redfruited species were examined under controlled conditions, they failed to respond to photoperiod, and neither reduced stem water content nor accumulated 24-kD-like proteins.…”

“…We were interested to determine if representative red-fruited dogwood species have the capacity to accumulate similar 24-kD-like proteins under known inductive conditions. Therefore, we reproduced similar controlled experiments as previously described (Karlson et al, 2003). Two supercooling species (Cornus florida and Cornus kousa) from the red-fruited group that did not accumulate 24-kD-like proteins in winter conditions were exposed to prolonged controlled short day and long day photoperiod treatments as previously described (Karlson, 2001).…”

“…Replicates of C. sericea were propagated as stem cuttings as previously described (Karlson et al, 2003). All plants were transferred into large pots (0.07 m 3 ) containing Scott's MetroMix 560 substrate (Marysville, OH) and grown in a computer controlled glass house where temperature was maintained at 24°C/18°C day/night during the summer of 2000.…”

“…All replicates were watered daily and supplemented with 20-20-20 NPK fertilizer regimes. Six replicates of each species were harvested prior to initiation of controlled photoperiod conditions for a time zero determination of SWC (as described by Karlson et al, 2003) and total protein extraction and blotting analyses as previously described (Sarnighausen et al, 2002). Six replicates from each photoperiod treatment were sampled after 8 weeks exposure and processed for SWC determination and total protein extraction.…”

“…One of the examined nonsupercooling species, C. sericea, is among the most freeze tolerant plants known and is capable of withstanding gradual cooling to the temperature of liquid helium (2269°C; Guy et al, 1986). In addition, our recent study in C. sericea xylem documented the marked winter accumulation (Sarnighausen et al, 2002) of a 24-kD dehydrin-like protein that directly correlates to increased freeze tolerance (Karlson et al, 2003). The Cornus genus provides us with a model system to investigate the evolutionary significance of xylem freezing behavior and the role of dehydrin-like proteins.…”