Components of the Arabidopsis C-repeat/dehydration-responsive element binding factor cold-response pathway are conserved in Brassica napus and other plant species

Many plants increase in freezing tolerance in response to low, nonfreezing temperatures, a phenomenon known as cold acclimation. Cold acclimation in A rabidopsis involves rapid cold-induced expression of the C-repeat/dehydrati on-responsive element binding factor (CBF) transcriptional activators follo wed by expression of CBF-targeted genes that increase freezing tolerance. H ere, we present evidence for a CBF cold-response pathway in Brassica napus. We show that B. napus encodes CBF-like genes and that transcripts for thes e genes accumulate rapidly in response to low temperature followed closely by expression of the cold-regulated Bn115 gene, an ortholog of the Arabidop sis CBF-targeted COR15a gene. Moreover, we show that constitutive overexpre ssion of the Arabidopsis CBF genes in transgenic B. napus plants induces ex pression of orthologs of Arabidopsis CBF-targeted genes and increases the f reezing tolerance of both nonacclimated and cold-acclimated plants. Transcr ipts encoding CBF-like proteins were also found to accumulate rapidly in re sponse to low temperature in wheat (Triticum aestivum L. cv Norstar) and ry e (Secale cereale L. cv Puma), which cold acclimate, as well as in tomato ( Lycopersicon esculentum var. Bonny Best, Castle Mart, Micro-Tom, and D Huan g), a freezing-sensitive plant that does not cold acclimate. An alignment o f the CBF proteins from Arabidopsis, B. napus, wheat, rye, and tomato revea led the presence of conserved amino acid sequences, PKK/RPAGRxKFxETRHP and DSAWR, that bracket the AP2/EREBP DNA binding domains of the proteins and d istinguish them from other members of the AP2/EREBP protein family. We conc lude that components of the CBF cold-response pathway are highly conserved in flowering plants and not limited to those that cold acclimate.