Reduced mitochondrial and ascorbate-glutathione activity after artificial ageing in soybean seed

Mitochondrial structural and antioxidant system responses to aging in oat (Avena sativa L.) seeds with different moisture contents

We observed the relationship between lifespan and mitochondria, including antioxidant systems, ultrastructure, and the hydrogen peroxide and malondialdehyde contents in 4 h imbibed oat (Avena sativa L.) seeds that were aged with different moisture contents (4%, 10% and 16%) for 0 (the control), 8, 16, 24, 32 and 40 d at 45 °C. The results showed that the decline in the oat seed vigor and in the integrity of the mitochondrial ultrastructure occurred during the aging process, and that these changes were enhanced by higher moisture contents. Mitochondrial antioxidants in imbibed oat seeds aged with a 4% moisture content were maintained at higher levels than imbibed oat seeds aged with a 10% and 16% moisture content. These results indicated that the levels of mitochondrial antioxidants and malondialdehyde after imbibition were related to the integrity of the mitochondrial membrane in aged oat seeds. The scavenging role of mitochondrial superoxide dismutase was inhibited in imbibed oat seeds aged at the early stage. Monodehydroascorbate reductase and dehydroascorbate reductase played more important roles than glutathione reductase in ascorbate regeneration in aged oat seeds during imbibition.

The production, localization and spreading of reactive oxygen species contributes to the low vitality of long-term stored common beech (Fagus sylvatica L.) seeds

The common beech (Fagus sylvatica L.) is propagated by seeds, but the seed set is irregular with five to ten years in between crops. It is therefore necessary to store the seeds. However, beech seeds lose germinability during long-term storage. In this study, beech seeds were stored at -10°C under controlled conditions for 2, 5, 8, 11 and 13 years. Our results show that beech seeds lose germinability during storage in proportion to the duration of storage. The decrease in germinability correlated with increased electrolyte leakage and accumulation of superoxide anion radicals, hydrogen peroxide and hydroxyl radicals. Furthermore, a strong positive correlation was observed among the releases of superoxide anion radicals, hydrogen peroxide and hydroxyl radicals. In situ localization showed that superoxide anion radicals and hydrogen peroxide were first detectable in root cap cells. When the seed storage time was extended, the reactive oxygen species fluorescence expanded to more areas of the radicle, reaching the root apical meristem. A storage time-dependent decrease in catalase activity, observed in both embryonic axes and cotyledons, was also positively correlated with germinability. DNA fragmentation was observed in beech seeds during storage and occurred predominantly in embryonic axes stored for 5 years and more. Altogether, these results suggest that the loss of germinability in beech seeds during long-term storage depends on several factors, including strong of reactive oxygen species accumulation accompanied by reduced catalase activity as well as membrane injury and DNA alternations, which may be aging-related and ROS-derived. We suggest that the accumulating reactive oxygen species that spread to the root apical meristem are key factors that affect seed germinability after long-term storage.

Reactive oxygen species-provoked mitochondria-dependent cell death during ageing of elm (Ulmus pumila L.) seeds

Previous studies have shown that controlled deterioration treatment (CDT) induces programmed cell death in elm (Ulmus pumila L.) seeds, which undergo certain fundamental processes that are comparable to apoptosis in animals. In this study, the essential characteristics of mitochondrial physiology in elm seeds during CDT were identified by cellular ultrastructural analysis, whole-body optical imaging, Western blotting and semi-quantitative RT-PCR. The alteration in mitochondrial morphology was an early event during CDT, as indicated by progressive dynamic mitochondrial changes and rupture of the mitochondrial outer membrane; loss of mitochondrial transmembrane potential (Δψ(m)) ensued, and mitochondrial ATP levels decreased. The mitochondrial permeability transition pore inhibitor cyclosporine A effectively suppressed these changes during ageing. The in situ localization of production of reactive oxygen species (ROS), and evaluation of the expression of voltage-dependent anion-selective channel and cyclophilin D indicated that the levels of mitochondrial permeability transition pore components were positively correlated with ROS production, leading to an imbalance of the cellular redox potential and ultimately to programmed cell death. Pre-incubation with ascorbic acid slowed loss of mitochondrial Δψ(m), and decreased the effect of CDT on seed viability. However, there were no significant changes in multiple antioxidant elements or chaperones in the mitochondria during early stages of ageing. Our results indicate that CDT induces dynamic changes in mitochondrial physiology via increased ROS production, ultimately resulting in an irreversible loss of seed viability.