Submitted to: Plant Molecular Biology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/24/2010
Publication Date: 4/9/2010
Citation: Dogramaci, M., Horvath, D.P., Chao, W.S., Foley, M.E., Christoffers, M.J., Anderson, J.V. 2010. Low Temperature Impacts Dormancy Status, Flowering Competence, and Transcript Profiles in Crown Buds of Leafy Spurge. Plant Molecular Biology. 73:207-226. DOI:10.1007/s11103-010-9621-8. Interpretive Summary: Leafy spurge is a noxious perennial weed. To increase our knowledge aimed at biologically-based management, we examined environmental effects on bud dormancy and flowering under controlled conditions. As a follow-up, we evaluated the global pattern of gene expression in crown buds which were paradormancy, endodormant, and in a flowering-competent and non-flowering-competent ecodormant state. We determined that endodormancy was induced by ramping down the temperature and photoperiod of intact paradormant plants. Flowering was induced by ramping down the temperature and photoperiod followed by vernalization; vernalization alone was ineffective at inducing flowering. Global patterns of gene expression indicate specific developmental switches associated transition through the well-defined states of dormancy to flowering based on the particular temperature treatment. Some of the regulatory switches are associated with the biological clock, environmental stress, and response to plant hormones.
Technical Abstract: Leafy spurge (Euphorbia esula) is an herbaceous perennial weed that reproduces vegetatively from an abundance of underground adventitious buds. In this study we report the effects of different growth conditions on vegetative reproduction and flowering competence, and determine molecular mechanisms associated with dormancy transitions under controlled environmental conditions. Reduction in temperature (27 to 10°C) and photoperiod (16 to 8 h) over a three-month period induced a para- to endo-dormant transition in crown buds. An additional eleven weeks of extended short-photoperiod and cold treatment (5-7°C) resulted in accelerated shoot growth from crown buds and 99% floral competence when plants were returned to growth promoting conditions. Paradormant crown buds exposed to a short-photoperiod and prolonged cold treatment alone, or endodormant crown buds without prolonged cold treatment, had delayed shoot growth and approximately 2% flowering when returned to growth promoting conditions. Transcriptome analyses revealed 834 genes (p<0.005) were differentially-expressed during dormancy transitions. Sub-network analysis identified expression targets and binding partners associated with circadian clock, dehydration/cold signaling, phosphorylation cascades, and response to abscisic acid, ethylene, gibberellic acid, and jasmonic acid. Comparison of trancriptomes from flower competent vs. non-flower competent crown buds following prolonged cold treatment identified 607 differentially-expression genes, and genes involved in cell cycle and DNA processing, glycolysis and anaerobic respiration, oxidative stress, flower regulation, and proteolysis were over-represented. Potential genetic pathways associated with these dormancy transitions and flowering were used to develop a proposed conceptual model.