title: ROP GTPases act with the receptor-like protein PAN1 to polarize asymmetric cell division in maize.
abstract: Plant Rho family GTPases (ROPs) have been investigated primarily for their functions in polarized cell growth. We previously showed that the maize (Zea mays) Leu-rich repeat receptor-like protein PANGLOSS1 (PAN1) promotes the polarization of asymmetric subsidiary mother cell (SMC) divisions during stomatal development. Here, we show that maize Type I ROPs 2 and 9 function together with PAN1 in this process. Partial loss of ROP2/9 function causes a weak SMC division polarity phenotype and strongly enhances this phenotype in pan1 mutants. Like PAN1, ROPs accumulate in an asymmetric manner in SMCs. Overexpression of yellow fluorescent protein-ROP2 is associated with its delocalization in SMCs and with aberrantly oriented SMC divisions. Polarized localization of ROPs depends on PAN1, but PAN1 localization is insensitive to depletion and depolarization of ROP. Membrane-associated Type I ROPs display increased nonionic detergent solubility in pan1 mutants, suggesting a role for PAN1 in membrane partitioning of ROPs. Finally, endogenous PAN1 and ROP proteins are physically associated with each other in maize tissue extracts, as demonstrated by reciprocal coimmunoprecipitation experiments. This study demonstrates that ROPs play a key role in polarization of plant cell division and cell growth and reveals a role for a receptor-like protein in spatial localization of ROPs.
authors.affiliation: University of California-San Diego, La Jolla, California 92093, USA. jhumphries@ucsd.edu
authors.forename: John A
authors.initials: JA
authors.lastname: Humphries
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Vejlupkova
authors.forename: Anding
authors.initials: A
authors.lastname: Luo
authors.forename: Robert B
authors.initials: RB
authors.lastname: Meeley
authors.forename: Anne W
authors.initials: AW
authors.lastname: Sylvester
authors.forename: John E
authors.initials: JE
authors.lastname: Fowler
authors.forename: Laurie G
authors.initials: LG
authors.lastname: Smith
mesh_terms: D000634:Aminoquinolines / Q000378:metabolism; D002455:Cell Division / Q000502:physiology*; D016764:Cell Polarity; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D018515:Plant Leaves / Q000166:cytology / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D054046:Plant Stomata / Q000166:cytology / Q000254:growth & development; D030821:Plants, Genetically Modified; D011743:Pyrimidines / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D003313:Zea mays / Q000166:cytology* / Q000201:enzymology* / Q000502:physiology*; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000634:Aminoquinolines; D007527:Isoenzymes; C487513:NSC 23766; D010940:Plant Proteins; D011743:Pyrimidines; D011993:Recombinant Fusion Proteins; D020741:rho GTP-Binding Proteins