title: Temporal, but not spatial, changes in expression patterns of petal identity genes are associated with loss of papillate conical cells and the shift to bird pollination in Macaronesian Lotus (Leguminosae).
abstract: In the generally bee-pollinated genus Lotus a group of four species have evolved bird-pollinated flowers. The floral changes in these species include altered petal orientation, shape and texture. In Lotus these characters are associated with dorsiventral petal identity, suggesting that shifts in the expression of dorsal identity genes may be involved in the evolution of bird pollination. Of particular interest is Lotus japonicus CYCLOIDEA 2 (LjCYC2), known to determine the presence of papillate conical cells on the dorsal petal in L. japonicus. Bird-pollinated species are unusual in not having papillate conical cells on the dorsal petal. Using RT-PCR at various stages of flower development, we determined the timing of expression in all petal types for the three putative petal identity genes (CYC-like genes) in different species with contrasting floral morphology and pollination syndromes. In bird-pollinated species the dorsal identity gene, LjCYC2, is not expressed at the floral stage when papillate conical cells are normally differentiating in bee-pollinated species. In contrast, in bee-pollinated species, LjCYC2 is expressed during conical cell development. Changes in the timing of expression of the above two genes are associated with modifications in petal growth and lateralisation of the dorsal and ventral petals in the bird-pollinated species. This study indicates that changes in the timing, rather than spatial distribution, of expression likely contribute to the modifications of petal micromorphology and petal size during the transition from bee to bird pollination in Macaronesian Lotus species.
authors.affiliation: Department of Evolutionary Biology and Ecology, Université Libre de Bruxelles, Bruxelles, Belgium.
authors.forename: D I
authors.identifier: http://orcid.org/0000-0001-8181-4804
authors.initials: DI
authors.lastname: Ojeda
authors.affiliation: Jardin Botánico Canario Viera y Clavijo - Unidad Asociada CSIC, Las Palmas, Gran Canaria, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Jaén-Molina
authors.affiliation: Unidad de Botánica-ICIA, Puerto de la Cruz, Canary Islands, Tenerife, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Santos-Guerra
authors.affiliation: Jardin Botánico Canario Viera y Clavijo - Unidad Asociada CSIC, Las Palmas, Gran Canaria, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Caujape-Castells
authors.affiliation: The Biodiversity Research Centre, Department of Botany, University of British Columbia, Vancouver, Canada.
authors.forename: Q
authors.initials: Q
authors.lastname: Cronk
mesh_terms: D000818:Animals; D001516:Bees; D001717:Birds; D007887:Fabaceae / Q000166:cytology / Q000235:genetics* / Q000502:physiology; D035264:Flowers / Q000166:cytology / Q000235:genetics* / Q000254:growth & development; D018506:Gene Expression Regulation, Plant; D000070116:Lotus / Q000166:cytology / Q000235:genetics / Q000502:physiology; D059828:Plant Cells; D054817:Pollination; D062211:Spatio-Temporal Analysis
keywords: 
  
  CYCLOIDEA
  
  ; Canary Islands; ornithophily; papillate conical cells; petal identity; pollination shift