NAPP and PIRP encode subunits of a putative wave regulatory protein complex involved in plant cell morphogenesis.
The ARP2/3 complex is an important regulator of actin nucleation and branching in eukaryotic organisms. All seven subunits of the ARP2/3 complex have been identified in Arabidopsis thaliana, and mutation of at least three of the subunits results in defects in epidermal cell expansion, including distorted trichomes. However, the mechanisms regulating the activity of the ARP2/3 complex in plants are largely unknown. In mammalian cells, WAVE and WASP proteins are involved in activation of the ARP2/3 complex. WAVE1 activity is regulated by a protein complex containing NAP1/HEM/KETTE/GEX-3 and PIR121/Sra-1/CYFIP/GEX-2. Here, we show that the WAVE1 regulatory protein complex is partly conserved in plants. We have identified Arabidopsis genes encoding homologs of NAP1 (NAPP), PIR121 (PIRP), and HSPC300 (BRK1). T-DNA inactivation of NAPP and PIRP results in distorted trichomes, similar to ARP2/3 complex mutants. The napp-1 mutant is allelic to the distorted mutant gnarled. The actin cytoskeleton in napp-1 and pirp-1 mutants shows orientation defects and increased bundling compared with wild-type plants. The results presented show that activity of the ARP2/3 complex in plants is regulated through an evolutionarily conserved mechanism.
Brembu
Tore
T
Department of Biology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway.
Winge
Per
P
Seem
Martin
M
Bones
Atle M
AM
D008841:Actin Cytoskeleton / Q000235:genetics / Q000378:metabolism; D051377:Actin-Related Protein 2; D051376:Actin-Related Protein 2-3 Complex; D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence / Q000235:genetics; D017360:Arabidopsis / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D016282:Aspartic Acid Endopeptidases / Q000235:genetics; D029742:Caenorhabditis elegans Proteins / Q000235:genetics; D003599:Cytoskeleton / Q000235:genetics; D018076:DNA, Complementary / Q000032:analysis / Q000235:genetics; D019143:Evolution, Molecular; D008840:Microfilament Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010802:Phylogeny; D021122:Protein Subunits / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D051300:Wiskott-Aldrich Syndrome Protein Family; D018797:Cell Cycle Proteins
D051377:Actin-Related Protein 2; D051376:Actin-Related Protein 2-3 Complex; D000199:Actins; D029681:Arabidopsis Proteins; D016282:Aspartic Acid Endopeptidases; D029742:Caenorhabditis elegans Proteins; D018076:DNA, Complementary; D008840:Microfilament Proteins; D021122:Protein Subunits; D051300:Wiskott-Aldrich Syndrome Protein Family; C512742:ARP2 protein, Arabidopsis; C493650:BRK1 protein, Arabidopsis; C450821:GEX-2 protein, C elegans; C493648:NAPP protein, Arabidopsis; C494965:PIR121 protein, Arabidopsis; D018797:Cell Cycle Proteins