Stress-Inducible Circadian Rhythms in Gymnosperms
2The David-Schwartz Lab, Institute of Plant Sciences at the Agricultural Research Organisation (ARO), Volcani Center, Israel
Circadian systems that regulate ~24 hour innate free-running rhythms are almost ubiquitous amongst eukaryotic organisms from bacteria and fungi, to plants and animals. In plants, the circadian system controls the expression of about one-third of the genome and regulates key metabolic, developmental, hormonal, abiotic and biotic stress signaling pathways. A robust circadian system that is correctly synched to the plant’s environment contributes to reproductive success, growth and vitality. The circadian system has been extensively explored in Arabidopsis and several other angiosperm models. By contrast, almost nothing is known about the circadian system in gymnosperms. Gymnosperms originate about 390 million years ago, preceding the other major group of plants, angiosperms, by 90 million years.
Surprisingly, given the ubiquity of circadian rhythms, a recent study reported that the model gymnosperm, Norway spruce, lacked innate free-running rhythms. However, in preliminary experiments carried out in our lab, we observed circadian rhythms under heat stress conditions in Aleppo pines, another gymnosperm, leading us to hypothesize that gymnosperms have the capacity for circadian rhythmicity but that rhythmicity might be conditional.
We hypothesize that having a robust high amplitude rhythm may be adaptive for gymnosperms growing under stressful conditions but less necessary when conditions are optimal. In this project we are examining the circadian responses to different stress conditions in Aleppo pines and a range of other gymnosperms. We are also using available databases to identify genes that may be involved in the circadian oscillator mechanism and examine their regulation.