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Doctoral thesis2019Open access

Signalling mechanisms and epigenetic regulation of seed development in Arabidopsis thaliana

Batista, Rita


In flowering plants, seed development starts with a double fertilisation event, leading to the formation of the embryo and the endosperm. Though only the embryo contributes to the next generation, control of endosperm proliferation, as well as the timing of its cellularisation are crucial for embryo viability. Both the embryo and the endosperm are enclosed by the seed coat, a maternal tissue that serves as a protective layer and is important for various aspects of seed development. Despite not arising directly from a fertilization event, the seed coat responds to fertilization by expanding and differentiating, accompanying the growth of the embryo and the endosperm. Therefore, successful seed development requires a set of signalling networks that coordinate growth between the embryo, the endosperm, and the seed coat. In this thesis, I show that auxin is a key player in these signalling networks. Its biosynthesis occurs in the endosperm, depends on the activity of imprinted paternally expressed genes, and serves two purposes: i) it triggers and sustains endosperm proliferation, and ii) it is exported to the integuments, which kick-starts seed coat development. In later stages of seed development, a reduction of auxin activity in the endosperm is required to initiate endosperm cellularisation, and the seed abortion phenotypes observed in interploidy crosses are connected with atypical levels of this hormone. The present work also identified two endosperm-expressed MADS-box transcription factors (TFs) as the upstream transcriptional regulators of auxin biosynthesis and transport genes. Interestingly, one of these TFs – the imprinted paternally expressed PHERES1 – controls the expression of several other imprinted genes, and accesses its targets through specific DNA-binding sites, which are significantly associated with transposable elements (TEs). TEs were previously implicated in providing epigenetic landscapes conducive to imprinted gene expression. I further propose that these elements have been co-opted as cis-regulatory sequences that facilitate PHERES1 binding to promoters of imprinted genes. Overall, this thesis makes important contributions to further increase our understanding of seed development: not only it uncovers the hormone auxin as a key factor that coordinates the development of different seed components, but also clarifies the previously elusive role of MADS-box genes in the transcriptional networks controlling endosperm development.


seed, endosperm, seed coat, auxin, imprinting, MADS-box, PHERES1

Published in

Acta Universitatis Agriculturae Sueciae
2019, number: 2019:39ISBN: 978-91-7760-396-2, eISBN: 978-91-7760-397-9
Publisher: Department of Plant Biology, Swedish University of Agricultural Sciences

    UKÄ Subject classification

    Biochemistry and Molecular Biology
    Cell Biology

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