Published online by Cambridge University Press: 20 January 2017
Leafy spurge seeds are responsive to alternating temperature rather thanconstant temperature for germination. Transcriptome changes of dry leafyspurge seeds and seeds imbibed for 1 and 3 d at 20 C constant (C) and 20 :30 C alternating (A) temperature were determined by microarray analysis toexamine temperature responsiveness. Principal component analysis revealeddifferences in the transcriptome of imbibed seeds based on the temperatureregime. Computational methods in bioinformatics parsed the data intooverrepresented AraCyc pathways and gene regulation subnetworks providingbiological context to temperature responses. After 1 d of imbibition, thedegradation of starch and sucrose leading to anaerobic respiration werecommon pathways at both temperature regimes. Several overrepresentedpathways unique to 1 d A were associated with generation of energy, reducingpower, and carbon substrates; several of these pathways remainedoverrepresented and up-regulated at 3 d A. At 1 d C, pathways for thephytohormones jasmonic acid and brassinosteroids were uniquelyoverrepresented. There was little similarity in overrepresented pathways at1 d C between leafy spurge and arabidopsis seeds,indicating species-specific effects upon imbibition of dry seeds.Overrepresented gene subnetworks at 1 d and 3 d at both temperature regimesrelated to signaling processes and stress responses. A major overrepresentedsubnetwork unique to 1 d C related to photomorphogenesis via the E3ubiquitin ligase COP1. At 1 d A, major overrepresented subnetworks involvedcircadian rhythm via LHY and TOC1 proteins and expression of stress-relatedgenes such as DREB1A, which is subject to circadianregulation. Collectively, substantial differences were observed in thetranscriptome of leafy spurge seeds imbibed under conditions that affect thecapacity to germinate.