LINKIES, A., MÜLLER, L., MORRIS, K., TUREČKOVÁ, Veronika, WENK, M., CADMAN, C. S. C., CORBINEAU, F., STRNAD, Miroslav, LYNN, J. R ., FINCH-SAVAGE, W. E., LEUBNER-METZGER, G. Ethylene Interacts with Abscisic Acid to Regulate Endosperm Rupture during Germination: A Comparative Approach Using Lepidium sativum and Arabidopsis thaliana. Plant Cell. 2009, 21(12), 3803-3822. ISSN 1040-4651. E-ISSN 1532-298X

The micropylar endosperm cap covering the radicle in the mature seeds of most angiosperms acts as a constraint that regulates seed germination. Here, we report on a comparative seed biology study with the close Brassicaceae relatives Lepidium sativum and Arabidopsis thaliana showing that ethylene biosynthesis and signaling regulate seed germination by a mechanism that requires the coordinated action of the radicle and the endosperm cap. The larger seed size of Lepidium allows direct tissue-specific biomechanical, biochemical, and transcriptome analyses. We show that ethylene promotes endosperm cap weakening of Lepidium and endosperm rupture of both species and that it counteracts the inhibitory action of abscisic acid (ABA) on these two processes. Cross-species microarrays of the Lepidium micropylar endosperm cap and the radicle show that the ethylene-ABA antagonism involves both tissues and has the micropylar endosperm cap as a major target.