Coordinated Expression of FLOWERING LOCUS T and DORMANCY ASSOCIATED MADS-BOX-Like Genes in Leafy Spurge

Leafy spurge (Euphorbia esula L.) is a noxious perennial weed that produces underground adventitious buds, which are crucial for generating new vegetative shoots following periods of freezing temperatures or exposure to various control measures. It is also capable of flowering and producing seeds, but requires vernalization in some cases. DORMANCY ASSOCIATED MADS-BOX (DAM) genes have been proposed to play a direct role in the transition to winter-induced dormancy and maintenance through regulation of the FLOWERING LOCUS T (FT) gene, which also is likely involved in the vernalization process. To explore the regulation of FT and DAM during dormancy transitions in leafy spurge, the transcript accumulation of two previously cloned DAM splice variants and two different previously cloned FT genes was characterized. Under long-photoperiods (16 h light), both DAM and FT transcripts accumulate in a diurnal manner. Tissue specific expression patterns indicated the tissues with high DAM expression had low FT expression and vice versa. DAM expression is detected in leaves, stems, shoot tips, and crown buds. FT transcripts were detected mainly in leaves and flowers. Under dormancy inducing conditions, DAM and FT genes had an inverse expression pattern. Additionally, chromatin immunoprecipitation assays were performed using DAM-like protein specific antibodies to demonstrate that DAM or related proteins likely bind to cryptic and/or conserved CArG boxes in the promoter regions of FT genes isolated from endodormant crown buds. These results are consistent with the hypothesis that DAM proteins play a crucial role in leafy spurge dormancy transition and maintenance, potentially by negatively regulating the expression of FT.