title: Genetic dissection of hormonal responses in the roots of Arabidopsis grown under continuous mechanical impedance.
abstract: We investigated the role of ethylene and auxin in regulating the growth and morphology of roots during mechanical impedance by developing a new growing system and using the model plant Arabidopsis (Arabidopsis thaliana). The Arabidopsis seedlings grown horizontally on a dialysis membrane-covered agar plate encountered adequate mechanical impedance as the roots showed characteristic ethylene phenotypes: 2-fold reduction in root growth, increase in root diameter, decrease in cell elongation, and ectopic root hair formation. The root phenotype characterization of various mutants having altered response to ethylene biosynthesis or signaling, the effect of ethylene inhibitors on mechanically impeded roots, and transcription profiling of the ethylene-responsive genes led us to conclude that enhanced ethylene response plays a primary role in changing root morphology and development during mechanical impedance. Further, the differential sensitivity of horizontally and vertically grown roots toward exogenous ethylene suggested that ethylene signaling plays a critical role in enhancing the ethylene response. We subsequently demonstrated that the enhanced ethylene response also affects the auxin response in roots. Taken together, our results provide a new insight into the role of ethylene in changing root morphology during mechanical impedance.
authors.affiliation: Center for Supports to Research and Education Activities Isotope Division , Kobe University, Nada, Kobe 657-8501, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Okamoto
authors.forename: Seiji
authors.initials: S
authors.lastname: Tsurumi
authors.forename: Kyohei
authors.initials: K
authors.lastname: Shibasaki
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Obana
authors.forename: Hironori
authors.initials: H
authors.lastname: Takaji
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Oono
authors.forename: Abidur
authors.initials: A
authors.lastname: Rahman
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development*; D001483:Base Sequence; D008969:Molecular Sequence Data; D010937:Plant Growth Regulators / Q000502:physiology*; D018517:Plant Roots / Q000254:growth & development*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction
chemical_list: D010937:Plant Growth Regulators