title: The endoplasmic reticulum is a reservoir for WAVE/SCAR regulatory complex signaling in the Arabidopsis leaf.
abstract: During plant cell morphogenesis, signal transduction and cytoskeletal dynamics interact to locally organize the cytoplasm and define the geometry of cell expansion. The WAVE/SCAR (for WASP family verprolin homologous/suppressor of cyclic AMP receptor) regulatory complex (W/SRC) is an evolutionarily conserved heteromeric protein complex. Within the plant kingdom W/SRC is a broadly used effector that converts Rho-of-Plants (ROP)/Rac small GTPase signals into Actin-Related Protein2/3 and actin-dependent growth responses. Although the components and biochemistry of the W/SRC pathway are well understood, a basic understanding of how cells partition W/SRC into active and inactive pools is lacking. In this paper, we report that the endoplasmic reticulum (ER) is an important organelle for W/SRC regulation. We determined that a large intracellular pool of the core W/SRC subunit NAP1, like the known positive regulator of W/SRC, the DOCK family guanine nucleotide-exchange factor SPIKE1 (SPK1), localizes to the surface of the ER. The ER-associated NAP1 is inactive because it displays little colocalization with the actin network, and ER localization requires neither activating signals from SPK1 nor a physical association with its W/SRC-binding partner, SRA1. Our results indicate that in Arabidopsis (Arabidopsis thaliana) leaf pavement cells and trichomes, the ER is a reservoir for W/SRC signaling and may have a key role in the early steps of W/SRC assembly and/or activation.
authors.affiliation: Department of Agronomy and Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Chunhua
authors.initials: C
authors.lastname: Zhang
authors.forename: Eileen
authors.initials: E
authors.lastname: Mallery
authors.forename: Sara
authors.initials: S
authors.lastname: Reagan
authors.forename: Vitaly P
authors.initials: VP
authors.lastname: Boyko
authors.forename: Simeon O
authors.initials: SO
authors.lastname: Kotchoni
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Szymanski
mesh_terms: D000199:Actins / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism*; D007425:Intracellular Membranes / Q000378:metabolism; D046912:Multiprotein Complexes / Q000378:metabolism; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D015398:Signal Transduction; D064201:Trichomes / Q000378:metabolism
chemical_list: D000199:Actins; D029681:Arabidopsis Proteins; C505420:DIS3 protein, Arabidopsis; D046912:Multiprotein Complexes; C455512:SPIKE1 protein, Arabidopsis; D000251:Adenosine Triphosphatases; C498859:NAP1 protein, Arabidopsis