title: A family of ROP proteins that suppresses actin dynamics, and is essential for polarized growth and cell adhesion.
abstract: In plants, the ROP family of small GTPases has been implicated in the polarized growth of tip-growing cells, such as root hairs and pollen tubes; however, most of the data derive from overexpressing ROP genes or constitutively active and dominant-negative isoforms, whereas confirmation by using loss-of-function studies has generally been lacking. Here, in the model moss Physcomitrella patens, we study ROP signaling during tip growth by using a loss-of-function approach based on RNA interference (RNAi) to silence the entire moss ROP family. We find that plants with reduced expression of ROP genes, in addition to failing to initiate tip growth, have perturbed cell wall staining, reduced cell adhesion and have increased actin-filament dynamics. Although plants subjected to RNAi against the ROP family also have reduced microtubule dynamics, this reduction is not specific to loss of ROP genes, as it occurs when actin function is compromised chemically or genetically. Our data suggest that ROP proteins polarize the actin cytoskeleton by suppressing actin-filament dynamics, leading to an increase in actin filaments at the site of polarized secretion.
authors.affiliation: Department of Biology, University of Massachusetts-Amherst, 611 N. Pleasant Street, Amherst, MA 01003, USA Plant Biology Graduate Program, University of Massachusetts-Amherst, 611 N. Pleasant Street, Amherst, MA 01003, USA.
authors.forename: Graham M
authors.initials: GM
authors.lastname: Burkart
authors.affiliation: Department of Biology, University of Massachusetts-Amherst, 611 N. Pleasant Street, Amherst, MA 01003, USA.
authors.forename: Tobias I
authors.initials: TI
authors.lastname: Baskin
authors.affiliation: Department of Biology, University of Massachusetts-Amherst, 611 N. Pleasant Street, Amherst, MA 01003, USA bezanilla@bio.umass.edu.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Bezanilla
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism*; D019068:Bryopsida / Q000201:enzymology* / Q000235:genetics; D002448:Cell Adhesion / Q000502:physiology; D003599:Cytoskeleton / Q000235:genetics / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D000199:Actins; D010940:Plant Proteins; D020558:GTP Phosphohydrolases
keywords: Actin; GTPase; Polarity