title: Arabidopsis cell expansion is controlled by a photothermal switch.
abstract: In Arabidopsis, the seedling hypocotyl has emerged as an exemplar model system to study light and temperature control of cell expansion. Light sensitivity of this organ is epitomized in the fluence rate response where suppression of hypocotyl elongation increases incrementally with light intensity. This finely calibrated response is controlled by the photoreceptor, phytochrome B, through the deactivation and proteolytic destruction of phytochrome-interacting factors (PIFs). Here we show that this classical light response is strictly temperature dependent: a shift in temperature induces a dramatic reversal of response from inhibition to promotion of hypocotyl elongation by light. Applying an integrated experimental and mathematical modelling approach, we show how light and temperature coaction in the circuitry drives a molecular switch in PIF activity and control of cell expansion. This work provides a paradigm to understand the importance of signal convergence in evoking different or non-intuitive alterations in molecular signalling.
authors.affiliation: Synthetic and Systems Biology (SynthSys), University of Edinburgh, CH Waddington Building, Mayfield Road, Edinburgh EH9 3JD, UK.
authors.forename: Henrik
authors.initials: H
authors.lastname: Johansson
authors.affiliation: Synthetic and Systems Biology (SynthSys), University of Edinburgh, CH Waddington Building, Mayfield Road, Edinburgh EH9 3JD, UK.
authors.forename: Harriet J
authors.initials: HJ
authors.lastname: Jones
authors.affiliation: Synthetic and Systems Biology (SynthSys), University of Edinburgh, CH Waddington Building, Mayfield Road, Edinburgh EH9 3JD, UK.
authors.forename: Julia
authors.initials: J
authors.lastname: Foreman
authors.affiliation: Synthetic and Systems Biology (SynthSys), University of Edinburgh, CH Waddington Building, Mayfield Road, Edinburgh EH9 3JD, UK.
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Hemsted
authors.affiliation: Synthetic and Systems Biology (SynthSys), University of Edinburgh, CH Waddington Building, Mayfield Road, Edinburgh EH9 3JD, UK.
authors.forename: Kelly
authors.initials: K
authors.lastname: Stewart
authors.affiliation: Synthetic and Systems Biology (SynthSys), University of Edinburgh, CH Waddington Building, Mayfield Road, Edinburgh EH9 3JD, UK.
authors.forename: Ramon
authors.initials: R
authors.lastname: Grima
authors.affiliation: Synthetic and Systems Biology (SynthSys), University of Edinburgh, CH Waddington Building, Mayfield Road, Edinburgh EH9 3JD, UK.
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Halliday
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism / Q000528:radiation effects*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D018546:Hypocotyl / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D008027:Light; D051939:Phytochrome B / Q000235:genetics / Q000378:metabolism; D013696:Temperature
chemical_list: D029681:Arabidopsis Proteins; D051939:Phytochrome B