title: Light intensity modulates the regulatory network of the shade avoidance response in Arabidopsis.
abstract: Plants such as Arabidopsis thaliana respond to foliar shade and neighbors who may become competitors for light resources by elongation growth to secure access to unfiltered sunlight. Challenges faced during this shade avoidance response (SAR) are different under a light-absorbing canopy and during neighbor detection where light remains abundant. In both situations, elongation growth depends on auxin and transcription factors of the phytochrome interacting factor (PIF) class. Using a computational modeling approach to study the SAR regulatory network, we identify and experimentally validate a previously unidentified role for long hypocotyl in far red 1, a negative regulator of the PIFs. Moreover, we find that during neighbor detection, growth is promoted primarily by the production of auxin. In contrast, in true shade, the system operates with less auxin but with an increased sensitivity to the hormonal signal. Our data suggest that this latter signal is less robust, which may reflect a cost-to-robustness tradeoff, a system trait long recognized by engineers and forming the basis of information theory.
authors.affiliation: Swiss Institute of Bioinformatics, CH-1015 Lausanne, Switzerland.
authors.forename: Micha
authors.initials: M
authors.lastname: Hersch
authors.forename: Séverine
authors.initials: S
authors.lastname: Lorrain
authors.forename: Mieke
authors.initials: M
authors.lastname: de Wit
authors.forename: Martine
authors.initials: M
authors.lastname: Trevisan
authors.forename: Karin
authors.initials: K
authors.lastname: Ljung
authors.forename: Sven
authors.initials: S
authors.lastname: Bergmann
authors.forename: Christian
authors.initials: C
authors.lastname: Fankhauser
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000502:physiology* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D053263:Gene Regulatory Networks / Q000187:drug effects / Q000528:radiation effects*; D007210:Indoleacetic Acids / Q000494:pharmacology; D008027:Light; D008954:Models, Biological; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development / Q000528:radiation effects
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids
keywords: auxin biosynthesis; auxin signaling; phytochrome B; regulatory network model
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