Ole Herud

Max Planck Institute for Developmental Biology, Tübingen, Baden-Württemberg, Germany

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Publications (2)29.27 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Primary root formation in early embryogenesis of Arabidopsis thaliana is initiated with the specification of a single cell called hypophysis. This initial step requires the auxin-dependent release of the transcription factor MONOPTEROS (MP, also known as ARF5) from its inhibition by the Aux/IAA protein BODENLOS (BDL, also known as IAA12). Auxin-insensitive bdl mutant embryos and mp loss-of-function embryos fail to specify the hypophysis, giving rise to rootless seedlings. A suppressor screen of rootless bdl mutant seedlings yielded a mutation in the nuclear import receptor IMPORTIN ALPHA 6 (IMPα6) that promoted primary root formation through rescue of the embryonic hypophysis defects, without causing additional phenotypic changes. Aux/IAA proteins are continually synthesized and degraded, which is essential for rapid transcriptional responses to changing auxin concentrations. Nuclear translocation of bdl:3xGFP was slowed down in impα6 mutants as measured by FRAP analysis, which correlated with the reduced inhibition of MP by bdl in transient expression assays in impα6 knock-down protoplasts. The MP-BDL module acts like an auxin-triggered genetic switch because MP activates its own expression as well as the expression of its inhibitor BDL. Using an established simulation model, we determined that the reduced nuclear translocation rate of BDL in impα6 mutant embryos rendered the auxin-triggered switch unstable, impairing the fast response to changes in auxin concentration. Our results suggest that the instability of the inhibitor BDL necessitates a fast nuclear uptake in order to reach the critical threshold level required for auxin responsiveness of the MP-BDL module in primary root initiation. This article is protected by copyright. All rights reserved.
    No preview · Article · Dec 2015 · The Plant Journal
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    ABSTRACT: Early embryogenesis is the critical developmental phase during which the basic features of the plant body are established: the apical-basal axis of polarity, different tissue layers, and both the root pole and the shoot pole. Polarization of the zygote correlates with the generation of apical and basal (embryonic and extraembryonic) cell fates. Whereas mechanisms of zygote polarization are still largely unknown, distinct expression domains of WOX family transcription factors as well as directional auxin transport and local auxin response are known to be involved in early apical-basal patterning. Radial patterning of tissue layers appears to be mediated by cell-cell communication involving both peptide signaling and transcription factor movement. Although the initiation of the shoot pole is still unclear, the apical organization of the embryo depends on both the proper establishment of transcription factor expression domains and, for cotyledon initiation, upward auxin flow in the protoderm. Here we focus on the essential patterning processes, drawing mainly on data from Arabidopsis thaliana and also including relevant data from other species if available.
    No preview · Article · May 2011 · Annual Review of Plant Biology

Publication Stats

63 Citations
29.27 Total Impact Points

Institutions

  • 2011-2015
    • Max Planck Institute for Developmental Biology
      • Department of Cell Biology
      Tübingen, Baden-Württemberg, Germany