Expression and Function of Dormancy Associated Mads-BOX Genes during Dormancy Transitions in Leafy Spurge

Leafy spurge, is a perennial noxious weed, that produces underground adventitious buds to survive freezing winter temperatures and to escape various control measures. DORMANCY ASSOCIATED MADS-BOX (DAM) genes may play a direct role in winter dormancy induction and maintenance through regulation of FLOWERING LOCUS T (FT) gene. To identify the roles and regulation pattern of DAM and FT genes in the control of dormancy transitions in leafy spurge (Euphorbia esula L.), two DAM splice variants and two different FT genes were cloned and studied. DAM genes expressed following circadian rhythm and had relatively high expression in leaves, stems, shoot tips, and crown buds, but little expression was detected in flowers and roots. Correspondingly, the transcript levels of FT genes increased following daybreak and dropped dramatically as soon as lights were turned off. The RNA abundance of FT genes in different organs was variable, but no expression was detected in roots. Furthermore, the expression patterns of FT and DAM genes under dormancy induction showed that, generally, DAM genes expression levels increased significantly after one week dormancy induction, meanwhile FT genes expression was suppressed. Using DAM protein specific antibodies, Chromatin immunoprecipitation assays were performed and indicated that DAM proteins bound to FT promoter regions concurrent with their down-regulation during endodormancy induction.  Collectively, above study suggests that DAM genes play a crucial role in leafy spurge dormancy induction and maintenance through negative regulation of FT genes.  Subsequently, two different splice variants of the leafy spurge DAM cDNA were expressed in poplar under their own promoter. An analysis of these transgenic poplar lines will be presented.