The 2012 ASHS Annual Conference

CBF proteins belong to the CBF/DRE binding sub-family of the Apetala2-ethylene responsive factor (AP2/ERF) super family of transcription factors that bind to a cis-element containing a conserved CCGA core sequence.  CBF genes have been shown to regulate a large number of cold-regulated genes that are associated with cold acclimation in both herbaceous and woody plants.  In Arabidopsis, cold temperatures initiate a global change in gene expression (at least 306 genes), 12% of which are members of the CBF regulon. In the present study, we utilized a 40,000 feature oligonucleotide-based microarray (Soria-Guerra, et al. 2011. Plant Mol Biol Rep.) to analyze the CBF-regulon in transgenic apple overexpressing a peach CBF gene. Levels of gene expression were compared in leaves of three sets of samples: a) Non-acclimated trees overexpressing a peach CBF gene (T166) vs. Non-Acclimated Untransformed ‘M.26’ (wt) trees; b) Non-Acclimated wt vs. Cold Acclimated wt trees; and c) Cold-Acclimated wt vs. T166 trees.  The acclimation regime consisted of placing trees at 4 °C and a short photoperiod (8/16) for two weeks.  Three biological replicates were included in the analysis where one of the replicates consisted of a dye-swap.  Wolfinger and JMP Genomics were utilized to determine the number of significantly up- and down-regulated genes at the 0.01 and 0.05 probability level. Wolfinger analysis indicated that there were 514 genes that were significantly up or down regulated in the T166 line compared to the non-acclimated ‘M.26’ trees while over 1,400 genes were significantly up or down regulated in the cold acclimated vs. the non-acclimated ‘M.26 trees.  There were 113 genes common to both cold acclimated and non-acclimated T166 trees.  This suggests that CBF regulon consists of about 8.5% of all cold-regulated genes.  Interestingly, there was a group of genes regulated by CBF that were not strictly regulated by low temperature. Additional statistical analyses are in progress as is the grouping of differentially regulated genes into specific functional categories.  This work represents the first attempt to define the CBF-regulon in fruit trees.