Staying Alive: Molecular Aspects of Seed Longevity

Mature seeds are an ultimate physiological status that enables plants to endure extreme conditions such as high and low temperature, freezing and desiccation. Seed longevity, the period over which seed remains viable, is an important trait not only for plant adaptation to changing environments, but also, for example, for agriculture and conservation of biodiversity. Reduction of seed longevity is often associated with oxidation of cellular macromolecules such as nucleic acids, proteins and lipids. Seeds possess two main strategies to combat these stressful conditions: protection and repair. The protective mechanism includes the formation of glassy cytoplasm to reduce cellular metabolic activities and the production of antioxidants that prevent accumulation of oxidized macromolecules during seed storage. The repair system removes damage accumulated in DNA, RNA and proteins upon seed imbibition through enzymes such as DNA glycosylase and methionine sulfoxide reductase. In addition to longevity, dormancy is also an important adaptive trait that contributes to seed lifespan. Studies in Arabidopsis have shown that the seed-specific transcription factor ABSCISIC ACID-INSENSITIVE3 (ABI3) plays a central role in ABA-mediated seed dormancy and longevity. Seed longevity largely relies on the viability of embryos. Nevertheless, characterization of mutants with altered seed coat structure and constituents has demonstrated that although the maternally derived cell layers surrounding the embryos are dead, they have a significant impact on longevity.