ARS | Publication request: Changes in the transcriptome of dry leafy spurge (Euphorbia esula) seeds imbibed at a constant and alternating temperature

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 27, 2011
Publication Date: January 23, 2012
Citation: Foley, M.E., Chao, W.S., Dogramaci, M., Horvath, D.P., Anderson, J.V. 2012. Changes in the transcriptome of dry leafy spurge (Euphorbia esula) seeds imbibed at a constant and alternating temperature. Weed Science. 60(1):48-56.

Interpretive Summary: Leafy spurge is a noxious perennial weed. We are investigating seed dormancy and germination to increase our knowledge aimed at biologically-based management for this species. Leafy spurge requires alternating- rather than constant-temperature for germination. Thus, we examined the effect of a constant and alternating temperature on global patterns of gene expression in seeds imbibed for 1 and 2 days using the transcriptome of dry seeds as the baseline. There were major differences in the global patterns of gene expression between seeds imbibed at constant versus alternating temperature. Patterns of gene expression under alternating temperature were associated with circadian rhythm, hormonal regulation, and stress-related signaling. The outcomes of this research will assist the scientific community in developing hypotheses to further investigate the effects of alternating temperature on germination of weed seeds.

Technical Abstract: Leafy spurge is an herbaceous perennial weed whose non-afterripened seeds are responsive to alternating temperature for germination. Transcriptome changes of mature, dry leafy spurge seeds that were imbibed for several days at 20°C constant (C) and 20:30°C (16:8 h) alternating (A) temperature were determined by microarray analysis to investigate temperature-responsiveness. Principal component analysis revealed clear differences in the transcriptome of dry and imbibed seed and temperature-based differences. Relative to dry seeds, after 1 d imbibition there were 496 and 532 differentially expressed genes in the transcriptome dataset for seeds imbibed for 1 d C and 1 d A, respectively; 91 genes were common between temperatures. After 2 d imbibition there were 1199 and 475 differentially expressed genes in the transcriptome dataset for seeds imbibed for 2 d C and 2 d A, respectively; 133 were common between temperatures. Gene set- and sub-network-enrichment analyses revealed over-represented AraCyc pathways and gene sub-networks, respectively provided biological context to transcriptome changes. There are noticeable processes and pathways in leafy spurge seeds related to stress and abscisic acid biosynthesis as demonstrated for arabidopsis. Otherwise, the sub-networks for alternating temperature centered on circadian rhythm, gibberellic acid and ethylene signaling, stress/temperature signaling, and flowering, whereas for constant temperature protein degradation and proteins involved with phenylpropanoid biosynthesis were prominent.