title: The evolutionary dynamics of ancient and recent polyploidy in the African semiaquatic species of the legume genus Aeschynomene.
abstract: The legume genus Aeschynomene is notable in the ability of certain semiaquatic species to develop nitrogen-fixing stem nodules. These species are distributed in two clades. In the first clade, all the species are characterized by the use of a unique Nod-independent symbiotic process. In the second clade, the species use a Nod-dependent symbiotic process and some of them display a profuse stem nodulation as exemplified in the African Aeschynomene afraspera. To facilitate the molecular analysis of the symbiotic characteristics of such legumes, we took an integrated molecular and cytogenetic approach to track occurrences of polyploidy events and to analyze their impact on the evolution of the African species of Aeschynomene. Our results revealed two rounds of polyploidy: a paleopolyploid event predating the African group and two neopolyploid speciations, along with significant chromosomal variations. Hence, we found that A. afraspera (8x) has inherited the contrasted genomic properties and the stem-nodulation habit of its parental lineages (4x). This study reveals a comprehensive picture of African Aeschynomene diversification. It notably evidences a history that is distinct from the diploid Nod-independent clade, providing clues for the identification of the specific determinants of the Nod-dependent and Nod-independent symbiotic processes, and for comparative analysis of stem nodulation.
authors.affiliation: Laboratoire des Symbioses Tropicales et Méditerranéennes, IRD, UMR LSTM, Campus International de Baillarguet, 34398, Montpellier, France.
authors.forename: Clémence
authors.initials: C
authors.lastname: Chaintreuil
authors.affiliation: Laboratoire des Symbioses Tropicales et Méditerranéennes, IRD, UMR LSTM, Campus International de Baillarguet, 34398, Montpellier, France.
authors.forename: Djamel
authors.initials: D
authors.lastname: Gully
authors.affiliation: CIRAD, UMR AGAP, Plateau de Cytogénétique Moléculaire, 34398, Montpellier, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Hervouet
authors.affiliation: School of Biotechnology, Institute of Agricultural Technology, Suranaree University of Technology, Nakhon Ratchasima, Thailand.
authors.forename: Panlada
authors.initials: P
authors.lastname: Tittabutr
authors.affiliation: Laboratoire de Microbiologie de l'Environnement/Centre National de Recherche sur l'Environnement, Antananarivo, 101, Madagascar.
authors.forename: Herizo
authors.initials: H
authors.lastname: Randriambanona
authors.affiliation: Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91 198, Gif-sur-Yvette, France.
authors.forename: Spencer C
authors.initials: SC
authors.lastname: Brown
authors.affiliation: Comparative Plant and Fungal Biology Department, Royal Botanic Gardens Kew, Richmond, Surrey, TW9 3AB, UK.
authors.forename: Gwilym P
authors.initials: GP
authors.lastname: Lewis
authors.affiliation: Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91 198, Gif-sur-Yvette, France.
authors.forename: Mickaël
authors.initials: M
authors.lastname: Bourge
authors.affiliation: Laboratoire des Symbioses Tropicales et Méditerranéennes, IRD, UMR LSTM, Campus International de Baillarguet, 34398, Montpellier, France.
authors.forename: Fabienne
authors.initials: F
authors.lastname: Cartieaux
authors.affiliation: Laboratoire des Symbioses Tropicales et Méditerranéennes, IRD, UMR LSTM, Campus International de Baillarguet, 34398, Montpellier, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Boursot
authors.affiliation: Laboratoire de Microbiologie de l'Environnement/Centre National de Recherche sur l'Environnement, Antananarivo, 101, Madagascar.
authors.forename: Heriniaina
authors.initials: H
authors.lastname: Ramanankierana
authors.affiliation: CIRAD, UMR AGAP, Plateau de Cytogénétique Moléculaire, 34398, Montpellier, France.
authors.forename: Angélique
authors.initials: A
authors.lastname: D'Hont
authors.affiliation: School of Biotechnology, Institute of Agricultural Technology, Suranaree University of Technology, Nakhon Ratchasima, Thailand.
authors.forename: Neung
authors.initials: N
authors.lastname: Teaumroong
authors.affiliation: Laboratoire des Symbioses Tropicales et Méditerranéennes, IRD, UMR LSTM, Campus International de Baillarguet, 34398, Montpellier, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Giraud
authors.affiliation: Laboratoire des Symbioses Tropicales et Méditerranéennes, IRD, UMR LSTM, Campus International de Baillarguet, 34398, Montpellier, France.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Arrighi
mesh_terms: D059001:Aquatic Organisms / Q000235:genetics*; D005075:Biological Evolution; D001947:Breeding; D007887:Fabaceae / Q000235:genetics*; D035264:Flowers / Q000033:anatomy & histology; D020440:Gene Duplication; D018745:Genome, Plant; D006824:Hybridization, Genetic; D059785:Karyotype; D010802:Phylogeny; D018547:Plant Stems / Q000502:physiology; D011123:Polyploidy; D013045:Species Specificity; D013997:Time Factors; D059467:Transcriptome / Q000235:genetics
keywords: Aeschynomene; dysploidy; genome downsizing; polyploidy; stem nodulation; symbiosis