title: Auxin represses stomatal development in dark-grown seedlings via Aux/IAA proteins.
abstract: Stomatal development is tightly regulated through internal and external factors that are integrated by a complex signalling network. Light represents an external factor that strongly promotes stomata formation. Here, we show that auxin-resistant aux/iaa mutants, e.g. axr3-1, exhibit a de-repression of stomata differentiation in dark-grown seedlings. The higher stomatal index in dark-grown axr3-1 mutants when compared with the wild type is due to increased cell division in the stomatal lineage. Excessive stomata in dark-grown seedlings were also observed in mutants defective in auxin biosynthesis or auxin perception and in seedlings treated with the polar auxin transport inhibitor NPA. Consistent with these findings, exogenous auxin repressed stomata formation in light-grown seedlings. Taken together, these results indicate that auxin is a negative regulator of stomatal development in dark-grown seedlings. Epistasis analysis revealed that axr3-1 acts genetically upstream of the bHLH transcription factors SPCH, MUTE and FAMA, as well as the YDA MAP kinase cascade, but in parallel with the repressor of photomorphogenesis COP1 and the receptor-like protein TMM. The effect of exogenous auxin required the ER family of leucine-rich repeat receptor-like kinases, suggesting that auxin acts at least in part through the ER family. Expression of axr3-1 in the stomatal lineage was insufficient to alter the stomatal index, implying that cell-cell communication is necessary to mediate the effect of auxin. In summary, our results show that auxin signalling contributes to the suppression of stomatal differentiation observed in dark-grown seedlings.
authors: Botanical Institute and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, BioCenter, Zuelpicher Str. 47b, 50674 Cologne, Germany.
authors: Martin
authors: M
authors: Balcerowicz
authors: Botanical Institute and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, BioCenter, Zuelpicher Str. 47b, 50674 Cologne, Germany.
authors: Aashish
authors: A
authors: Ranjan
authors: Botanical Institute and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, BioCenter, Zuelpicher Str. 47b, 50674 Cologne, Germany.
authors: Laura
authors: L
authors: Rupprecht
authors: Botanical Institute and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, BioCenter, Zuelpicher Str. 47b, 50674 Cologne, Germany.
authors: Gabriele
authors: G
authors: Fiene
authors: Botanical Institute and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, BioCenter, Zuelpicher Str. 47b, 50674 Cologne, Germany hoeckeru@uni-koeln.de.
authors: Ute
authors: U
authors: Hoecker
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism; D002450:Cell Communication; D002454:Cell Differentiation; D004843:Epistasis, Genetic; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D008027:Light; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D010641:Phenotype; D010937:Plant Growth Regulators / Q000378:metabolism; D054046:Plant Stomata / Q000502:physiology*; D030821:Plants, Genetically Modified; D011485:Protein Binding; D015398:Signal Transduction; D014157:Transcription Factors
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D007210:Indoleacetic Acids; D009687:Nuclear Proteins; D010937:Plant Growth Regulators; D014157:Transcription Factors; C110728:AXR3 protein, Arabidopsis
keywords: Arabidopsis; Aux/IAA proteins; Auxin; Photomorphogenesis; Stomatal development