title: A light-regulated genetic module was recruited to carpel development in Arabidopsis following a structural change to SPATULA.
abstract: A key innovation of flowering plants is the female reproductive organ, the carpel. Here, we show that a mechanism that regulates carpel margin development in the model flowering plant Arabidopsis thaliana was recruited from light-regulated processes. This recruitment followed the loss from the basic helix-loop-helix transcription factor SPATULA (SPT) of a domain previously responsible for its negative regulation by phytochrome. We propose that the loss of this domain was a prerequisite for the light-independent expression in female reproductive tissues of a genetic module that also promotes shade avoidance responses in vegetative organs. Striking evidence for this proposition is provided by the restoration of wild-type carpel development to spt mutants by low red/far-red light ratios, simulating vegetation shade, which we show to occur via phytochrome B, PHYTOCHROME INTERACTING FACTOR4 (PIF4), and PIF5. Our data illustrate the potential of modular evolutionary events to generate rapid morphological change and thereby provide a molecular basis for neo-Darwinian theories that describe this nongradualist phenomenon. Furthermore, the effects shown here of light quality perception on carpel development lead us to speculate on the potential role of light-regulated mechanisms in plant organs that, like the carpel, form within the shade of surrounding tissues.
authors.affiliation: Laboratoire de Reproduction et Développement des Plantes (Unité Mixte de Recherche 5667, Centre National de la Recherche Scientifique-Institut National de la Recherche Agronomique-Université de Lyon), Ecole Normale Supérieure de Lyon, 69364 Lyon cedex 07, France.
authors.forename: Mathieu C
authors.initials: MC
authors.lastname: Reymond
authors.forename: Géraldine
authors.initials: G
authors.lastname: Brunoud
authors.forename: Aurélie
authors.initials: A
authors.lastname: Chauvet
authors.forename: Jaime F
authors.initials: JF
authors.lastname: Martínez-Garcia
authors.forename: Marie-Laure
authors.initials: ML
authors.lastname: Martin-Magniette
authors.forename: Françoise
authors.initials: F
authors.lastname: Monéger
authors.forename: Charles P
authors.initials: CP
authors.lastname: Scutt
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology / Q000235:genetics* / Q000254:growth & development / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics* / Q000378:metabolism; D019143:Evolution, Molecular; D035264:Flowers / Q000166:cytology / Q000235:genetics* / Q000254:growth & development / Q000528:radiation effects; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D008027:Light; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D059372:Nucleotide Motifs / Q000235:genetics; D010641:Phenotype; D010802:Phylogeny; D051939:Phytochrome B / Q000235:genetics; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary / Q000235:genetics; D017422:Sequence Analysis, DNA; D059467:Transcriptome
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D051939:Phytochrome B; C459466:PIF4 protein, Arabidopsis; C497729:PIF5 protein, Arabidopsis; C426006:SPT protein, Arabidopsis