Abstract
The ARP2/3 complex, a highly conserved nucleator of F-actin, and its activator, the SCAR complex, are essential for growth in plants and animals. In this article, we present a pathway through which roots of Arabidopsis thaliana directly perceive light to promote their elongation. The ARP2/3-SCAR complex and the maintenance of longitudinally aligned F-actin arrays are crucial components of this pathway. The involvement of the ARP2/3-SCAR complex in light-regulated root growth is supported by our finding that mutants of the SCAR complex subunit BRK1/HSPC300, or other individual subunits of the ARP2/3-SCAR complex, showed a dramatic inhibition of root elongation in the light, which mirrored reduced growth of wild-type roots in the dark. SCAR1 degradation in dark-grown wild-type roots by constitutive photomorphogenic 1 (COP1) E3 ligase and 26S proteasome accompanied the loss of longitudinal F-actin and reduced root growth. Light perceived by the root photoreceptors, cryptochrome and phytochrome, suppressed COP1-mediated SCAR1 degradation. Taken together, our data provide a biochemical explanation for light-induced promotion of root elongation by the ARP2/3-SCAR complex.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Actin-Related Protein 2-3 Complex / genetics
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Actin-Related Protein 2-3 Complex / metabolism*
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Actins / metabolism
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Arabidopsis / genetics
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Arabidopsis / physiology*
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Arabidopsis / radiation effects
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Arabidopsis / ultrastructure
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Arabidopsis Proteins / genetics
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Arabidopsis Proteins / metabolism*
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Cysteine Proteinase Inhibitors / pharmacology
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Darkness
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Leupeptins / pharmacology
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Light
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Light Signal Transduction / physiology
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Microfilament Proteins / genetics
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Microfilament Proteins / metabolism*
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Mutation
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Phenotype
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Photoreceptors, Plant / genetics
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Photoreceptors, Plant / metabolism*
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Phytochrome / genetics
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Phytochrome / metabolism
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Plant Components, Aerial / genetics
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Plant Components, Aerial / physiology
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Plant Components, Aerial / radiation effects
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Plant Components, Aerial / ultrastructure
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Plant Roots / genetics
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Plant Roots / physiology*
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Plant Roots / radiation effects
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Plant Roots / ultrastructure
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Plants, Genetically Modified
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Proteasome Endopeptidase Complex / genetics
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Proteasome Endopeptidase Complex / metabolism*
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Proteasome Inhibitors
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Protein Binding
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Seedlings / genetics
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Seedlings / physiology
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Seedlings / radiation effects
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Seedlings / ultrastructure
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Ubiquitin-Protein Ligases / genetics
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Ubiquitin-Protein Ligases / metabolism
Substances
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Actin-Related Protein 2-3 Complex
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Actins
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Arabidopsis Proteins
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Cysteine Proteinase Inhibitors
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Leupeptins
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Microfilament Proteins
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Photoreceptors, Plant
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Proteasome Inhibitors
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SCAR1 protein, Arabidopsis
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Phytochrome
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AT2G32950 protein, Arabidopsis
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Ubiquitin-Protein Ligases
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Proteasome Endopeptidase Complex
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ATP dependent 26S protease
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benzyloxycarbonylleucyl-leucyl-leucine aldehyde