Staying Alive: Molecular Aspects of Seed Longevity

Abstract

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.

SUMO-Dependent Synergism Involving Heat Shock Transcription Factors with Functions Linked to Seed Longevity and Desiccation Tolerance

“…We cannot exclude that A9/A4a SUMOylation may also induce conformational changes that, as shown for HSF1 and CHIP1 (Kim et al, 2005), could contribute to the proposed recruitment. We showed that HSF SUMOylation is required for a transcriptional synergism that is involved in the enhancement of two crucial functions in seeds (Tejedor-Cano et al, 2014, and references therein): longevity and desiccation tolerance, both acquired in maturing zygotic embryos (reviewed by Dekkers et al, 2015; Sano et al, 2016; Leprince et al, 2017). Precedent studies in plants have only indicated functional connections of SUMOylation with non-embryonic development, for example with the control of flowering (Xu and Yang, 2013; Elrouby et al, 2013; Elrouby, 2014).…”

Orthodox Seeds and Resurrection Plants: Two of a Kind?

“…Seeds of Arabidopsis mutants that do not degrade Chl properly failed to germinate after 23 months of storage, whereas wildtype seeds maintained high germination rates after 42 months of storage (Nakajima et al, 2012). Phytyl tails released as a result of Chl breakdown are thought to serve as a substrate for the biosynthesis of tocopherols (well-known antioxidants involved in seed longevity; for review, see Sano et al, 2016). Craterostigma wilmsii plants in the dry state under simulated field conditions did not survive for more than 3 months, whereas 10 months of dry storage did not affect plant survival in X. humilis (Bajic, 2006).…”

“…Although ROS may act as signaling molecules to regulate biological processes, they also damage cellular components and reduce longevity in the dry state Sano et al, 2016). Therefore, ROS levels must be tightly controlled in the cell via enzymatic and nonenzymatic ROS-scavenging systems Sano et al, 2016).…”

“…Therefore, ROS levels must be tightly controlled in the cell via enzymatic and nonenzymatic ROS-scavenging systems Sano et al, 2016). Seeds and resurrection plants use a complex array of inherent antioxidant molecules to protect themselves from abiotic stress, such as superoxide dismutases, catalases, glutathione and ascorbate peroxidases, flavonoids, and tocopherols (Illing et al, 2005;Djilianov et al, 2011;Dinakar and Bartels, 2012;Gechev et al, 2013;Sano et al, 2016;Farrant et al, 2017).…”

Mining seed proteome: from protein dynamics to modification profiles

“…In this context, the mechanisms underlying seed viability and ensuring high quality of food protein need to be well understood. It is important to note that seed quality can be affected by prolonged storage (Sano et al, 2016), especially under high humidity and/or temperature conditions (Murthy, Kumar, and Sun, 2003;Walters, Ballesteros, and Vertucci, 2010;Sum, Sreenivasan, Singh, and Radhamani, 2013). Not less important are environmental conditions of seed development.…”