Arabidopsis NAP1 is essential for Arp2/3-dependent trichome morphogenesis.
The dynamic nature of the eukaryotic actin cytoskeleton is essential for the locomotion of animal cells and the morphogenesis of plant and fungal cells. The F-actin nucleating/branching activity of the Arp2/3 complex is a key function for all of these processes. The SCAR/WAVE family represents a group of Arp2/3 activators that are associated with lamellipodia formation. A protein complex of PIR121, NAP1, ABI, and HSPC300 is required for SCAR regulation by cell signaling pathways, but the exact nature of this interaction is controversial and represents a continually evolving model. The mechanism originally proposed was of a SCAR trans repressing complex supported by evidence from in vitro experiments. This model was reinforced by genetic studies in the Drosophila central nervous system and Dictyostelium, where the knockout of certain SCAR-complex components leads to excessive SCAR-mediated actin polymerization. Conflicting data have steadily accumulated from animal tissue culture experiments suggesting that the complex activates rather than represses in vivo SCAR activity. Recent biochemical evidence supports the SCAR-complex activator model. Here, we show that genetic observations in Arabidopsis are compatible with an activation model and provide one potential mechanism for the regulation of the newly identified Arabidopsis Arp2/3 complex.
The Integrative Cell Biology Laboratory, School of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, United Kingdom.
Michael J
MJ
Deeks
Despina
D
Kaloriti
Brendan
B
Davies
Rui
R
Malhó
Patrick J
PJ
Hussey
D051377:Actin-Related Protein 2; D051376:Actin-Related Protein 2-3 Complex; D051378:Actin-Related Protein 3; D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000235:genetics; D003599:Cytoskeleton / Q000378:metabolism; D008840:Microfilament Proteins / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D008954:Models, Biological; D008969:Molecular Sequence Data; D009024:Morphogenesis; D018515:Plant Leaves / Q000648:ultrastructure*; D016415:Sequence Alignment; D015398:Signal Transduction / Q000502:physiology; D051300:Wiskott-Aldrich Syndrome Protein Family
C512742:ARP2 protein, Arabidopsis; D051377:Actin-Related Protein 2; D051376:Actin-Related Protein 2-3 Complex; D051378:Actin-Related Protein 3; D000199:Actins; D029681:Arabidopsis Proteins; D003598:Cytoskeletal Proteins; C478027:DIS1 protein, Arabidopsis; D008840:Microfilament Proteins; D051300:Wiskott-Aldrich Syndrome Protein Family