Interchangeable functions of Arabidopsis PIROGI and the human WAVE complex subunit SRA1 during leaf epidermal development.
The WAVE complex is an essential regulator of actin-related protein (ARP) 2/3-dependent actin filament nucleation and cell shape change in migrating cells. Although the composition of the WAVE complex is well characterized, the cellular mechanisms that control its activity and localization are not well known. The 'distorted group' defines a set of Arabidopsis genes that are required to remodel the actin cytoskeleton and maintain the polarized elongation of branched, hair-like cells termed trichomes. Several loci within this group encode homologs of ARP2/3 subunits. In addition to trichome distortion, ARP2/3 subunit mutants have reduced shoot fresh weight and widespread defects in epidermal cell-cell adhesion. The precise cellular function of plant ARP2/3, and the means by which it is regulated, is not known. In this paper, we report that the 'distorted group' gene PIROGI encodes a homolog of the WAVE complex subunit SRA1. The similar cell shape and actin phenotypes of pir and ARP2/3 complex subunit mutants suggest that PIROGI positively regulates ARP2/3. PIROGI directly interacts with the small GTPase ATROP2 with isoform specificity and with selectivity for active forms of the protein. PIROGI shares only 30% amino acid identity with its human homolog. However, both WAVE subunit homologs are functionally interchangeable and display identical physical interactions with RHO family GTPases and the Arabidopsis homolog of the WAVE complex subunit NAP125. These results demonstrate the utility of the 'distorted group' mutants to study ARP2/3 complex functions from signaling input to cell shape output.
Basu
Dipanwita
D
Agronomy Department, Purdue University, Lilly Hall, 915 West State Street, West Lafayette, IN 47907-2054, USA.
El-Assal
Salah El-Din
Sel-D
Le
Jie
J
Mallery
Eileen L
EL
Szymanski
Daniel B
DB
D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism* / Q000502:physiology*; D002448:Cell Adhesion; D003598:Cytoskeletal Proteins / Q000378:metabolism; D005786:Gene Expression Regulation; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D008957:Models, Genetic; D009154:Mutation; D010641:Phenotype; D020161:Physical Chromosome Mapping; D018515:Plant Leaves / Q000196:embryology*; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D015398:Signal Transduction; D013997:Time Factors; D018797:Cell Cycle Proteins
D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D005982:Glutathione Transferase; C495926:ACTR2 protein, human; C495928:ACTR3 protein, human; C109916:CYFIP1 protein, human; C494965:PIR121 protein, Arabidopsis; D018797:Cell Cycle Proteins