Global inspection of plant genomes identifies genes maintained in low copies across taxa and under strong purifying selection, which are likely to have essential functions. Based on this rationale, we investigated the function of the low-duplicated CYP715 cytochrome P450 gene family that appeared early in seed plants and evolved under strong negative selection. Arabidopsis CYP715A1 showed a restricted tissue-specific expression in the tapetum of flower buds and in the anther filaments upon anthesis. cyp715a1 insertion lines showed a strong defect in petal development, and transient alteration of pollen intine deposition. Comparative expression analysis revealed the downregulated expression of genes involved in pollen development, cell wall biogenesis, hormone homeostasis, and floral sesquiterpene biosynthesis, especially TPS21 and several key genes regulating floral development such as MYB21, MYB24, and MYC2. Accordingly, floral sesquiterpene emission was suppressed in the cyp715a1 mutants. Flower hormone profiling, in addition, indicated a modification of gibberellin homeostasis and a strong disturbance of the turnover of jasmonic acid derivatives. Petal growth was partially restored by the active gibberellin GA3 or the functional analog of jasmonoyl-isoleucine, coronatine. CYP715 appears to function as a key regulator of flower maturation, synchronizing petal expansion and volatile emission. It is thus expected to be an important determinant of flower-insect interaction.

Bioinformatics for Predictive Genomics URGV INRA Université d'Evry Val d'Essonne CNRS 91057 Evry France

Graduate School of Agriculture Shizuoka University Shizuoka 422 8529 Japan

Institute of Plant Molecular Biology Centre National de la Recherche Scientifique University of Freiburg 79104 Freiburg Germany

Institute of Plant Molecular Biology Centre National de la Recherche Scientifique University of Strasbourg 67084 Strasbourg France

Laboratoire de Biométrie et Biologie Évolutive Université Lyon 1 CNRS 69622 Villeurbanne France

Laboratory of Growth Regulators and Department of Chemical Biology and Genetics Centre of the Region Haná for Biotechnological and Agricultural Research Faculty of Science Palacký University and Institute of Experimental Botany AS CR 771 47 Olomouc Czech Republic

Plateforme d'Imagerie In Vitro IFR 37 de Neurosciences 67084 Strasbourg France

Rothamsted Research Harpenden Hertfordshire AL5 2JQ UK

Transcriptomic Platform Unité de Recherche en Génomique Végétale INRA Université d'Evry Val d'Essonne CNRS 91057 Evry France

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