Supervisors

Seed germination is an adaptive trait of higher plants that is controlled by both internal growth regulators and environmental cues. Among internal factors, plant hormones such as abscisic acid (ABA) play important regulatory role in seed germination. Whereas ABA is involved in maintaining seed dormancy and inhibiting germination, GAs are known to break seed dormancy and promote germination. Upon seed imbibition (water uptake), ABA levels decreases, whereas level of GAs increases. Once the seeds imbibe, other physiological processes and chemical reactions involve activation of metabolic pathways, increase of fresh weight and beginning of embryo growth. Cell elongation is necessary and is generally accepted to be sufficient for the completion of radicle protrusion (visible germination).

Light has been considered to stimulate germination and to terminate seed dormancy. There has been much less attention paid to the response of seeds to the shorter wavelengths of the visible spectrum, although there is some evidence that they can perceive blue light (BL). Dependent on plant species, seed germination can be stimulated or inhibited  by BL. Work has been done to identify the photoreceptor(s) mediating the responses to these wavelengths. The model proposes that BL and ABA stimulate the G-protein-coupled receptor (GCR1) through two separate receptors. Cross-talk of ABA and BL in seed germination was recently supported by the observation that CRY2 negatively regulates Arabidopsis germination in ABA-dependent manner. The long-term objective of our work is to contribute to understanding of the role of light signaling pathways in plant growth and development. Plant material: Experiments will be conducted with Arabidopsis thaliana (L.) Heynh. Arm-1 (mutant) and its corresponding WT (i.e. isogenic line). Plant growth conditions: Arabidopsis seeds will be incubated and germinating on the basal MS culture medium (Murashige and Skoog 1962) (in vitro) in the dark or in blue light at the temperature 23°C. Depending on the experiment, the MS medium will be supplemented with mannitol (0-300 mM), NaCl 0-250 mM), an inhibitor of phototropin activity DPI. The germination rate of Arm-1 and Col will be  monitored in conditions in vitro under light conditions for 7 days, and the percentage of inhibition of
seed germination will be calculated etc.