title: New insights into root gravitropic signalling.
abstract: An important feature of plants is the ability to adapt their growth towards or away from external stimuli such as light, water, temperature, and gravity. These responsive plant growth movements are called tropisms and they contribute to the plant's survival and reproduction. Roots modulate their growth towards gravity to exploit the soil for water and nutrient uptake, and to provide anchorage. The physiological process of root gravitropism comprises gravity perception, signal transmission, growth response, and the re-establishment of normal growth. Gravity perception is best explained by the starch-statolith hypothesis that states that dense starch-filled amyloplasts or statoliths within columella cells sediment in the direction of gravity, resulting in the generation of a signal that causes asymmetric growth. Though little is known about the gravity receptor(s), the role of auxin linking gravity sensing to the response is well established. Auxin influx and efflux carriers facilitate creation of a differential auxin gradient between the upper and lower side of gravistimulated roots. This asymmetric auxin gradient causes differential growth responses in the graviresponding tissue of the elongation zone, leading to root curvature. Cell biological and mathematical modelling approaches suggest that the root gravitropic response begins within minutes of a gravity stimulus, triggering genomic and non-genomic responses. This review discusses recent advances in our understanding of root gravitropism in Arabidopsis thaliana and identifies current challenges and future perspectives.
authors.affiliation: University of Antwerp, Biology Department, Plant Growth and Development, Groenenborgerlaan 171, 2020 Antwerpen, Belgium Centre for Plant Integrative Biology, University of Nottingham, Sutton Bonington LE12 5RD, UK.
authors.forename: Ethel Mendocilla
authors.initials: EM
authors.lastname: Sato
authors.affiliation: Centre for Plant Integrative Biology, University of Nottingham, Sutton Bonington LE12 5RD, UK.
authors.forename: Hussein
authors.initials: H
authors.lastname: Hijazi
authors.affiliation: Centre for Plant Integrative Biology, University of Nottingham, Sutton Bonington LE12 5RD, UK.
authors.forename: Malcolm J
authors.initials: MJ
authors.lastname: Bennett
authors.affiliation: University of Antwerp, Biology Department, Plant Growth and Development, Groenenborgerlaan 171, 2020 Antwerpen, Belgium ranjan.swarup@nottingham.ac.uk kris.vissenberg@uantwerp.be.
authors.forename: Kris
authors.initials: K
authors.lastname: Vissenberg
authors.affiliation: Centre for Plant Integrative Biology, University of Nottingham, Sutton Bonington LE12 5RD, UK ranjan.swarup@nottingham.ac.uk kris.vissenberg@uantwerp.be.
authors.forename: Ranjan
authors.initials: R
authors.lastname: Swarup
mesh_terms: D001692:Biological Transport; D018522:Gravitropism / Q000502:physiology*; D007210:Indoleacetic Acids / Q000378:metabolism; D008954:Models, Biological; D018517:Plant Roots / Q000502:physiology*; D015398:Signal Transduction
chemical_list: D007210:Indoleacetic Acids
keywords: Arabidopsis thaliana; auxin; calcium; differential growth; gravitropic response; root growth; tropism.