title: SCAR mediates light-induced root elongation in Arabidopsis through photoreceptors and proteasomes.
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.
authors.affiliation: Plant Biology Division, The Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401, USA.
authors.forename: Julia
authors.initials: J
authors.lastname: Dyachok
authors.forename: Ling
authors.initials: L
authors.lastname: Zhu
authors.forename: Fuqi
authors.initials: F
authors.lastname: Liao
authors.forename: Ji
authors.initials: J
authors.lastname: He
authors.forename: Enamul
authors.initials: E
authors.lastname: Huq
authors.forename: Elison B
authors.initials: EB
authors.lastname: Blancaflor
mesh_terms: D051376:Actin-Related Protein 2-3 Complex / Q000235:genetics / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003624:Darkness; D007976:Leupeptins / Q000494:pharmacology; D008027:Light; D055537:Light Signal Transduction / Q000502:physiology; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010641:Phenotype; D055519:Photoreceptors, Plant / Q000235:genetics / Q000378:metabolism*; D010834:Phytochrome / Q000235:genetics / Q000378:metabolism; D035261:Plant Components, Aerial / Q000235:genetics / Q000502:physiology / Q000528:radiation effects / Q000648:ultrastructure; D018517:Plant Roots / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects / Q000648:ultrastructure; D030821:Plants, Genetically Modified; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism*; D061988:Proteasome Inhibitors; D011485:Protein Binding; D036226:Seedlings / Q000235:genetics / Q000502:physiology / Q000528:radiation effects / Q000648:ultrastructure; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism
chemical_list: D051376:Actin-Related Protein 2-3 Complex; D000199:Actins; D029681:Arabidopsis Proteins; D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D008840:Microfilament Proteins; D055519:Photoreceptors, Plant; D061988:Proteasome Inhibitors; C510294:SCAR1 protein, Arabidopsis; D010834:Phytochrome; C471983:AT2G32950 protein, Arabidopsis; D044767:Ubiquitin-Protein Ligases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde