Long days induce adaptive secondary dormancy in the seeds of the Mediterranean plant Aethionema arabicum.

Secondary dormancy is an adaptive trait that increases reproductive success by aligning seed germination with permissive conditions for seedling establishment. Aethionema arabicum is an annual plant and member of the Brassicaceae that grows in environments characterized by hot and dry summers. Aethionema arabicum seeds may germinate in early spring when seedling establishment is permissible. We demonstrate that long-day light regimes induce secondary dormancy in the seeds of Aethionema arabicum (CYP accession), repressing germination in summer when seedling establishment is riskier. Characterization of mutants screened for defective secondary dormancy demonstrated that RGL2 mediates repression of genes involved in gibberellin (GA) signaling. Exposure to high temperature alleviates secondary dormancy, restoring germination potential. These data are consistent with the hypothesis that long-day-induced secondary dormancy and its alleviation by high temperatures may be part of an adaptive response limiting germination to conditions permissive for seedling establishment in spring and autumn. [Display omitted] • Light induces secondary dormancy in seeds of Aethionema arabicum (Brassicaceae) • Secondary dormancy is induced by long days and alleviated by dry and warm conditions • DELLA protein RGL2 mediates the establishment of secondary dormancy • Day-length-regulated dormancy cycling is an adaptation to Mediterranean environment Seed dormancy is a state when germination is prevented under otherwise favorable conditions. Light is known to alleviate dormancy and stimulate germination. Mérai et al. describe an opposite phenomenon, when light induces secondary dormancy in the seeds of Aethionema arabicum to avoid germination and seedling establishment during the warm and dry summer. [ABSTRACT FROM AUTHOR]