Discovery of Dormancy-Associated Genes in Populus through Activation Tagging

Vegetative bud dormancy is an adaptive trait allowing woody perennial species from temperate latitudes to survive freezing and dehydration stress during winter months. We used activation tagging to identify genes that affect dormancy associated traits. Specifically we screened an activation tagging population for lines with precocious bud break under field conditions for two growing seasons. Three lines that showed early bud break were discovered and called EARLY BUD BREAK 1-3 (EBB1-3).  The mutant phenotype was validated under controlled growth chamber conditions. Here we report on the identification and characterization of one of these lines called EBB1. We showed through positioning of the tag, validation of activation and retransformation experiments that the tagged gene in EBB1 encodes a transcription factor from the AP2/ERF family. Transgenic up and downregulation of the gene caused accelerated and delayed bud break. Expression and microarray analyses indicate the EBB1 has a broad regulatory context linked to the reactivation of the meristem after winter dormancy.