title: The Arabidopsis trichome is an active mechanosensory switch.
abstract: Trichomes ('hair cells') on Arabidopsis thaliana stem and leaf surfaces provide a range of benefits arising from their shape and disposition. These include tempting herbivores to sample constitutive toxins before they reach the bulk of the tissue. We asked whether, in addition, small mechanical disturbances such as an insect can make elicit signals that might help the plant respond to herbivory. We imaged, pressed and brushed trichomes in several ways, most notably with confocal microscopy of trichomes transgenically provided with apoplastic pH reporter apo-pHusion and cytosolic Ca2+reporter cameleon. In parallel, we modelled trichome wall mechanics with finite element analysis. The stimulated trichome focuses force on a pliant zone and the adjoining podium of the stalk. A buckling instability can further focus force on a skirt of cells surrounding the podium, eliciting oscillations of cytosolic Ca2+and shifts in apoplastic pH. These observations represent active physiological response. Modelling establishes that the effectiveness of force focusing and buckling is due to the peculiar tapering wall structure of the trichome. Hypothetically, these active mechanosensing functions enhance toxin synthesis above constitutive levels, probably via a priming process, thus minimizing the costly accumulation of toxins in the absence of herbivore attack but assuring rapid build-up when needed.
authors.affiliation: Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, St. Louis, MO, 63130, USA.|Bioinspired Engineering & Biomechanics Center, Xi'an Jiaotong University, Xi'an, 710049, China.|Gladys Levis Allen Laboratory of Plant Sensory Physiology, Biology Department, Washington University in St. Louis, St. Louis, MO, 63130, USA.
authors.forename: Li Hong
authors.initials: LH
authors.lastname: Zhou
authors.affiliation: Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, St. Louis, MO, 63130, USA.|Bioinspired Engineering & Biomechanics Center, Xi'an Jiaotong University, Xi'an, 710049, China.|Gladys Levis Allen Laboratory of Plant Sensory Physiology, Biology Department, Washington University in St. Louis, St. Louis, MO, 63130, USA.
authors.forename: Shao Bao
authors.initials: SB
authors.lastname: Liu
authors.affiliation: Bioinspired Engineering & Biomechanics Center, Xi'an Jiaotong University, Xi'an, 710049, China.|Qian Xuesen Laboratory of Space Technology, China Academy of Space Technology, Beijing, 100094, China.
authors.forename: Peng Fei
authors.initials: PF
authors.lastname: Wang
authors.affiliation: Bioinspired Engineering & Biomechanics Center, Xi'an Jiaotong University, Xi'an, 710049, China.
authors.forename: Tian Jian
authors.initials: TJ
authors.lastname: Lu
authors.affiliation: Bioinspired Engineering & Biomechanics Center, Xi'an Jiaotong University, Xi'an, 710049, China.|Ministry of Education Key Laboratory of Biomedical Information Engineering, School of Life Science & Technology, Xi'an Jiaotong University, Xi'an, 710049, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Xu
authors.affiliation: Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, St. Louis, MO, 63130, USA.|Bioinspired Engineering & Biomechanics Center, Xi'an Jiaotong University, Xi'an, 710049, China.
authors.forename: Guy M
authors.initials: GM
authors.lastname: Genin
authors.affiliation: Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, St. Louis, MO, 63130, USA.|Gladys Levis Allen Laboratory of Plant Sensory Physiology, Biology Department, Washington University in St. Louis, St. Louis, MO, 63130, USA.
authors.forename: Barbara G
authors.initials: BG
authors.lastname: Pickard
mesh_terms: D017360:Arabidopsis / Q000378:metabolism* / Q000502:physiology; D020013:Calcium Signaling; D002451:Cell Compartmentation; D002473:Cell Wall / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D040542:Mechanotransduction, Cellular; D064201:Trichomes / Q000378:metabolism* / Q000502:physiology
keywords: apoplast pH shift; calcium oscillation; force focusing; mechanical buckling; mechanosensing; wall taper