title: Complex regulation of Arabidopsis AGR1/PIN2-mediated root gravitropic response and basipetal auxin transport by cantharidin-sensitive protein phosphatases.
abstract: Polar auxin transport, mediated by two distinct plasma membrane-localized auxin influx and efflux carrier proteins/complexes, plays an important role in many plant growth and developmental processes including tropic responses to gravity and light, development of lateral roots and patterning in embryogenesis. We have previously shown that the Arabidopsis AGRAVITROPIC 1/PIN2 gene encodes an auxin efflux component regulating root gravitropism and basipetal auxin transport. However, the regulatory mechanism underlying the function of AGR1/PIN2 is largely unknown. Recently, protein phosphorylation and dephosphorylation mediated by protein kinases and phosphatases, respectively, have been implicated in regulating polar auxin transport and root gravitropism. Here, we examined the effects of chemical inhibitors of protein phosphatases on root gravitropism and basipetal auxin transport, as well as the expression pattern of AGR1/PIN2 gene and the localization of AGR1/PIN2 protein. We also examined the effects of inhibitors of vesicle trafficking and protein kinases. Our data suggest that protein phosphatases, sensitive to cantharidin and okadaic acid, are likely involved in regulating AGR1/PIN2-mediated root basipetal auxin transport and gravitropism, as well as auxin response in the root central elongation zone (CEZ). BFA-sensitive vesicle trafficking may be required for the cycling of AGR1/PIN2 between plasma membrane and the BFA compartment, but not for the AGR1/PIN2-mediated root basipetal auxin transport and auxin response in CEZ cells.
authors.affiliation: Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA.
authors.forename: Heungsop
authors.initials: H
authors.lastname: Shin
authors.forename: Hwa-Soo
authors.initials: HS
authors.lastname: Shin
authors.forename: Zibiao
authors.initials: Z
authors.lastname: Guo
authors.forename: Elison B
authors.initials: EB
authors.lastname: Blancaflor
authors.forename: Patrick H
authors.initials: PH
authors.lastname: Masson
authors.forename: Rujin
authors.initials: R
authors.lastname: Chen
mesh_terms: D017360:Arabidopsis / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000378:metabolism / Q000502:physiology*; D001692:Biological Transport / Q000502:physiology; D002193:Cantharidin / Q000378:metabolism / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D018522:Gravitropism / Q000502:physiology*; D007210:Indoleacetic Acids / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism / Q000502:physiology*; D009154:Mutation; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D013997:Time Factors
chemical_list: D029681:Arabidopsis Proteins; D002193:Cantharidin; D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins; D010749:Phosphoprotein Phosphatases; C117013:AT5G57090 protein, Arabidopsis