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Title: Transcriptome analysis identifies novel responses and potential regulatory genes involved in seasonal dormancy transitions of leafy spurge (Euphorbia esula L.)

item Horvath, David
item Chao, Wun
item Suttle, Jeffrey
item Anderson, James

Submitted to: BMC Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/30/2008
Publication Date: 11/12/2008
Citation: Horvath, D.P., Chao, W.S., Suttle, J.C., Anderson, J.V., Thimmapuram, J. 2008. Transcriptome analysis identifies novel responses and potential regulatory genes involved in seasonal dormancy transitions of leafy spurge (Euphorbia esula L.). Biomed Central (BMC) Genomics. 9:536. DOI:10.1186/1471-2164-9-536.

Interpretive Summary: Leafy spurge (Euphorbia esula) is an invasive perennial rangeland weed that is difficult to control because it produces large numbers of underground shoot buds that remain dormant through the growing season. In the summer, hormones and sugar produced in the above-ground tissue keep these buds from growing. In the fall, a physiological change occurs and the buds will not grow even if they are separated from the above ground portion of the plant. In the winter, these buds become capable of growth again and also become capable of flowering. However they still do not grow until it is warm enough to do so. In the spring the buds grow and the resulting shoots flower. This paper used new 23,000 element microarrays we developed for leafy spurge and cassava to identify nearly 1000 genes that were turned on or off as underground shoot buds of leafy spurge transitioned from summer to fall and then into winter. Genes involved in cold tolerance, response to hormones such as auxin, abscisic acid, and jasmonic acid were turned on and off suggesting these hormones play a role in seasonal transitions. Genes involved in sugar use and transport were also turned on and off through the transitions suggesting these processes need to be regulated seasonally. We also identified a number of related transcription factors named DORMANCY ASSOCIATED MADS-BOX (DAM) that were turned on during the transition into fall. We hypothesized that these act to induce dormancy by turning off another gene called FLOWERING LOCUS T (FT). Turning on of FT was shown to prevent dormancy induction in poplar, and genes similar to DAM are known to regulate FT expression in the model plant Arabidopsis thaliana.

Technical Abstract: Dormancy transitions in crown buds of leafy spurge were investigated using 23K element cDNA microarrays. These data represent the first large-scale transcriptome analysis of dormancy in underground buds of an herbaceous perennial species. Crown buds collected monthly from August through December, over a five year period, were used to monitor the changes in the transcriptome during dormancy transitions. Of the nearly 1,000 differentially-expressed genes identified in this study, expected patterns of gene expression observed for previously characterized genes and physiological processes indicated that resolution in our analysis was sufficient for identifying shifts in global gene expression. Gene ontology of differentially-expressed genes suggests dormancy transitions require specific alterations in transport functions (including induction of a series of mitochondrial substrate carriers, and sugar transporters), ethylene, jasmonic acid, auxin, gibberellic acid, and abscisic acid responses, and responses to stress (primarily oxidative and cold/drought). Comparison to other dormancy microarray studies indicated that nearly half of the genes identified in our study were also differentially expressed in at least two other plant species during dormancy transitions. This comparison allowed us to identify a particular MADS-box transcription factor related to the DORMANCY ASSOCIATED MADS-BOX genes from peach and hypothesize that it may play a direct role in dormancy induction and maintenance through regulation of FLOWERING LOCUS T.