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.

Environmental and genetic effects on tomato seed metabolic balance and its association with germination vigor

“…Controlled deterioration and post-harvest stress studies have shown an increase in protein degradation and increased levels of amino acids and their leakage accompanied by the loss of germination vigor [93–95]. Nevertheless protein degradation would be accompanied by a general increase in free amino acids, not in specific amino acids.…”

Metabolic Processes During Seed Germination

“…Depending on the stress intensity and genetic background, germination is delayed or suppressed. Plants have developed unique strategies including a tight regulation of germination ensuring species survival [95]. It was well known that stress exposure would produce early signals such as change in intracellular Ca…”

Seed-Specific Expression of a Feedback-Insensitive Form of CYSTATHIONINE-γ-SYNTHASE in Arabidopsis Stimulates Metabolic and Transcriptomic Responses Associated with Desiccation Stress

“…Lower GSH contents may lead to oxidative stress. To examine this possibility further, we measured the level of malondialdehyde (MDA), which results from lipid peroxidation of polyunsaturated fatty acids and is used as a metabolic marker for oxidative stress (Bai et al, 2012). The results showed a significant increase in MDA contents in both SSE seeds (Supplemental Fig.…”

“…Mature dry seeds (100 mg) from the wild-type and SSE genotypes were treated, and MDA contents were determined as reported previously (Bai et al, 2012).…”