Over-expression of a Poplar FLC-like MADS box gene impinges on low-temperature responses during vegetative bud dormancy

We characterized the poplar (Populus trichocarpa) MADS box gene family and identified six FLC-like genes (PtFLC1-6) in the poplar genome.  Expression analysis in revealed that 4 of the genes (PtFLC1-4) were detected in a range of tissues and growth conditions.  One gene, PtFLC2, was selected for further study since expression of this gene declined in apical buds during chilling induced dormancy release.  In addition to low-temperature associated declines in apical bud transcript abundance, low-temperature treatment also resulted in the generation of a number of splicing isoforms of PtFLC2.  Transgenic poplars that overexpressed a full-length cDNA of PtFLC2 displayed altered low-temperature responses during vegetative bud dormancy.  These altered responses include a significant increase in that duration of low-temperatures required for the release from bud dormancy and an increase in the duration of low-temperatures required for leaf senescence. Our results suggest that at least part of low-temperature dormancy release in poplar involves the repression of PtFLC2 and indicates a potential role of PtFLC2 in bud dormancy