Molecular Physiology of Endosperm-limited Seed Germination - Gene Function and Regulation in the Endosperm of Brassicaceae Species

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The mature seeds of most angiosperm species are endospermic and in many cases the micropylar endosperm that covers the radicle is a mechanical constraint to embryo expansion and seed germination. We have shown by cross-species work with Lepidium sativum (Lepidium, big seeds) and Arabidopsis that endosperm weakening is an important trait of these Brassicaceae species. We have used seed-tissue-specific transcriptome analysis, genetic transformation, qRT-PCR, germination physiology, cell-wall biochemistry, reverse-genetics, and biomechanics to establish Lepidium as a model system for interdisciplinary seed research. Our new work plan includes as goals to identify and analyse tissue-specific promoters for reverse-genetics and superior housekeeping genes for qRT-PCR for seed research by utilizing our seed-tissue-specific transcriptome. We want to further optimize our reverse-genetics techniques for Lepidium seeds. Two tissue specific reverse-genetics approaches have the GA receptor GID1 (upstream, signaling) and pectin modifying enzymes as downstream mechanism for Lepidium endosperm weakening as targets. Pectin-mediated mechanism(s) belong to the late weakening mechanisms. Endosperm-specific cDNA libraries and tissue-specific cross-species transcriptome analysis at early time points will be used to identify early endosperm weakening targets. This project aims to deliver transgenic seeds altered in upstream and downstream mechanisms of endosperm weakening for functional and biomechanical analysis and will provide novel insight into endosperm function during seed germination.