Genetic and biochemical studies have greatly advanced our understanding of the biology of seeds in recent years. Another area of study, which could accelerate contemporary seed biology research, is phylogenomics that integrates the wealth of genome sequence data with evolutionary biology. The recent phylogenomic study of the DELAY OF GERMINATION1 family genes exemplifies how the molecular evolution of seed genes can be traced back through early diverging plants and what implications can be obtained from the analysis of seed gene diversification at ancient times. The identification of possible ancestors of seed genes in non-seed plants could illuminate the ancient roots of the molecular mechanisms driving seed maturation programmes. It is possible that the origins of molecular mechanisms associated with the induction of seed storage proteins and desiccation tolerance proteins date back to the time of, or even prior to, early diverging land plants. Abscisic acid-dependent growth arrest or dormancy mechanisms might date back to red algae, one of the oldest algal groups. Thus, understanding algal cell biology will also be an integral part of future seed biology research. Unravelling key events associated with the evolution of seed- and non-seed plants will not only advance basic research but could also contribute to applied aspects of seed science, potentially leading to technology development for agriculture.

Physiological dormancy has been described as a physiological inhibiting mechanism that prevents radicle emergence. It can be caused by the embryo (embryo dormancy) as well as by the structures that cover the embryo. One of its functions is to time plant growth and reproduction to the most optimal season and therefore, in nature, dormancy is an important adaptive trait that is under selective pressure. Dormancy is a complex trait that is affected by many loci, as well as by an intricate web of plant hormone interactions. Moreover, it is strongly affected by a multitude of environmental factors. Its induction, maintenance, cycling and loss come down to the central paradigm, which is the balance between two key hormonal regulators, i.e. the plant hormone abscisic acid (ABA), which is required for dormancy induction, and gibberellins (GA), which are required for germination. In this review we will summarize recent developments in dormancy research (mainly) in the model plant Arabidopsis thaliana, focusing on two key players for dormancy induction, i.e. the plant hormone ABA and the DELAY OF GERMINATION 1 (DOG1) gene. We will address the role of ABA and DOG1 in relation to various aspects of seed dormancy, i.e. induction during seed maturation, loss during dry seed afterripening, the rehydrated state (including dormancy cycling) and the switch to germination.