Seed dormancy; Seed coat; Arabidopsis; Abscisic acid (ABA); Gibberellic acid (GA); RGL2; DELLA factors; ABI3 ABI5; gibberellins; Abscisic acid; seed germination; ABI5
Lee Keun Pyo, Lopez-Molina Luis (2013), A seed coat bedding assay to genetically explore in vitro how the endosperm controls seed germination in Arabidopsis thaliana., in Journal of Visualized Experiments (JoVE)
, 81, 5.
Lee Keun Pyo, Piskurewicz Urszula, Turecková Veronika, Strnad Miroslav, Lopez-Molina Luis (2012), A seed coat bedding assay shows that RGL2-dependent release of abscisic acid by the endosperm controls embryo growth in Arabidopsis dormant seeds., in Proceedings of the National Academy of Sciences of the United States of America
, 107(44), 19108-13.
Lee KP Lopez-Molina L (2012), Control of seed germination in the shade, in Cell Cycle
, 11(24), 4489-4490.
Lee KP Piskurewicz U Turečková V Carat S Chappuis R Strnad M Fankhauser C Lopez-Molina L. (2012), Spatially and genetically distinct control of seed germination by phytochromes A and B, in Genes & Development
, 26(17), 1984-1996.
In Arabidopsis it is well established that repression of seed germination in dormant seeds upon seed imbibition is an active process requiring de novo and constitutive synthesis of the phytohormone abscisic-acid (ABA). In this project proposal, we present preliminary results showing that dormant seeds constitutively express the gibberellic acid (GA)-response factor RGL2, a DELLA factor of the GRAS family recently shown to stimulate endogenous ABA synthesis. Unlike non-dormant seeds, dormant seeds are unable to down-regulate RGL2 expression (mRNA and protein) in response to GA. We propose to explore the hypothesis that de novo ABA synthesis is due to the constitutive accumulation of RGL2. Furthermore, our proposed experiments address the questions of how RGL2 constitutive expression is achieved and how dormancy-breaking treatments (e.g. stratification) down-regulate RGL2 expression.We also present a novel “seed coat bedding assay” that physically separates the seed coat and the embryo while still keeping active the repression of germination by the seed coat. This assay shows that the seed coat is a tissue producing diffusible signals necessary to prevent embryonic growth. Furthermore, the assay allows using seed coats of different genotypic backgrounds to genetically dissect the germination-repressing activities produced by the seed coat. We propose experiments aimed at identifying such diffusible signals as well as to test the hypothesis that the seed coat is an essential organ for ABA production to sustain ABA-dependent repression in dormant embryos.