The mechanism and regulation of seed dormancy and germination

Seeds are the link between two successive generations of plants. Seeds allow the plant to survive periods during which conditions are not optimal to complete its life cycle, but also allow it to be transported to a new location. Thus, the timing of germination is of extreme importance: when a seed germinates at moments or under conditions that the plant cannot complete its life cycle it will die. This timing of germination is controlled by seed dormancy.

Seed dormancy is an important adaptive trait that, together with flowering time, is a primary component of the different life history strategies of plants. Dormancy can be considered as a mechanism by which growth and development are arrested, despite the presence of favorable environmental conditions. Specific environmental and developmental triggers can overcome this arrest. These environmental cues can act during seed development on the mother plant, during seed storage (after-ripening) and in imbibed mature seeds (which may lead to germination of non-dormant seeds). We are interested to identify genes and pathways that control seed dormancy in natural conditions.

Our approach:

We study seed dormancy and germination using variation that occurs in nature by means of different accessions of Arabidopsis thaliana. Genetics and physiology have shown the important role of the plant hormones abscisic acid and gibberellin in the regulation of dormancy and germination. The use of quantitative genetics and mutant approaches allows the further genetic dissection of these traits and the identification of thus far unknown components. Molecular biology and especially expression studies, transcriptome and proteome analysis, are powerful tools for the analysis of seed dormancy and germination. In addition, we employ a ‘physiological genetical genomics’ and (signaling) networks approach to further integrate information from different levels of complexity of the seeds. We preferentially use Arabidopsis thaliana because of the molecular genetic resources available for this species.

Selected references:

Alonso-Blanco, C., Aarts, M.G.M., Bentsink, L., Keurentjes, J.J.B., Reymond, M., Vreugdenhil, D and Koornneef, M. (2009) What has natural variation taught us about plant development, physiology, and adaptation? The Plant Cell 21, 1877-1896
Finch-Savage, W.E., Cadman, C.S.C., Toorop, P.E., Lynn, J.R.and Hilhorst, H.W.M. 2007. Seed dormancy release in Arabidopsis Cvi by dry after-ripening, low temperature, nitrate and light shows common quantitative patterns of gene expression directed by environment specific sensing. The Plant Journal 51: 60-78;
Hilhorst, H.W.M. 2007. Definition and hypotheses of seed dormancy. In: K.J. Bradford and H. Nonogaki (Eds.) Chapter 4: Seed development, dormancy and germination. Annual Plant Reviews Vol. 27. Blackwell Publishing, Sheffield, UK, pp 50-71.