title: Ecotypic variability in the metabolic response of seeds to diurnal hydration-dehydration cycles and its relationship to seed vigor.
abstract: Seeds in the seed bank experience diurnal cycles of imbibition followed by complete dehydration. These conditions pose a challenge to the regulation of germination. The effect of recurring hydration-dehydration (Hy-Dh) cycles were tested on seeds from four Arabidopsis thaliana accessions [Col-0, Cvi, C24 and Ler]. Diurnal Hy-Dh cycles had a detrimental effect on the germination rate and on the final percentage of germination in Col-0, Cvi and C24 ecotypes, but not in the Ler ecotype, which showed improved vigor following the treatments. Membrane permeability measured by ion conductivity was generally increased following each Hy-Dh cycle and was correlated with changes in the redox status represented by the GSSG/GSH (oxidized/reduced glutathione) ratio. Among the ecotypes, Col-0 seeds displayed the highest membrane permeability, whilst Ler was characterized by the greatest increase in electrical conductivity following Hy-Dh cycles. Following Dh 2 and Dh 3, the respiratory activity of Ler seeds significantly increased, in contrast to the other ecotypes, indicative of a dramatic shift in metabolism. These differences were associated with accession-specific content and patterns of change of (i) cell wall-related laminaribiose and mannose; (ii) fatty acid composition, specifically of the unsaturated oleic acid and α-linoleic acid; and (iii) asparagine, ornithine and the related polyamine putrescine. Furthermore, in the Ler ecotype the content of the tricarboxylic acid (TCA) cycle intermediates fumarate, succinate and malate increased in response to dehydration, in contrast to a decrease in the other three ecotypes. These findings provide a link between seed respiration, energy metabolism, fatty acid β-oxidation, nitrogen mobilization and membrane permeability and the improved germination of Ler seeds following Hy-Dh cycles.
authors.affiliation: French Associates Institute for Agriculture & Biotechnology of Drylands, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Israel.
authors.forename: Bing
authors.initials: B
authors.lastname: Bai
authors.forename: Noga
authors.initials: N
authors.lastname: Sikron
authors.forename: Tanya
authors.initials: T
authors.lastname: Gendler
authors.forename: Yana
authors.initials: Y
authors.lastname: Kazachkova
authors.forename: Simon
authors.initials: S
authors.lastname: Barak
authors.forename: Gideon
authors.initials: G
authors.lastname: Grafi
authors.forename: Inna
authors.initials: I
authors.lastname: Khozin-Goldberg
authors.forename: Aaron
authors.initials: A
authors.lastname: Fait
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D000975:Antioxidants / Q000378:metabolism; D017360:Arabidopsis / Q000166:cytology / Q000196:embryology* / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism; D002940:Circadian Rhythm / Q000502:physiology*; D002952:Citric Acid Cycle; D003681:Dehydration; D060146:Ecotype; D004553:Electric Conductivity; D005227:Fatty Acids / Q000378:metabolism; D008401:Gas Chromatography-Mass Spectrometry; D018525:Germination / Q000502:physiology; D019803:Glutathione Disulfide / Q000378:metabolism; D006019:Glycolysis; D050356:Lipid Metabolism; D008954:Models, Biological; D010084:Oxidation-Reduction; D025341:Principal Component Analysis; D012639:Seeds / Q000166:cytology / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D000975:Antioxidants; D029681:Arabidopsis Proteins; D005227:Fatty Acids; D019803:Glutathione Disulfide