title: Polyploidization mechanisms: temperature environment can induce diploid gamete formation in Rosa sp.
abstract: Polyploidy is an important evolutionary phenomenon but the mechanisms by which polyploidy arises still remain underexplored. There may be an environmental component to polyploidization. This study aimed to clarify how temperature may promote diploid gamete formation considered an essential element for sexual polyploidization. First of all, a detailed cytological analysis of microsporogenesis and microgametogenesis was performed to target precisely the key developmental stages which are the most sensitive to temperature. Then, heat-induced modifications in sporad and pollen characteristics were analysed through an exposition of high temperature gradient. Rosa plants are sensitive to high temperatures with a developmental sensitivity window limited to meiosis. Moreover, the range of efficient temperatures is actually narrow. 36 °C at early meiosis led to a decrease in pollen viability, pollen ectexine defects but especially the appearance of numerous diploid pollen grains. They resulted from dyads or triads mainly formed following heat-induced spindle misorientations in telophase II. A high temperature environment has the potential to increase gamete ploidy level. The high frequencies of diplogametes obtained at some extreme temperatures support the hypothesis that polyploidization events could have occurred in adverse conditions and suggest polyploidization facilitating in a global change context.
authors.affiliation: Institut Méditerranéen d'Ecologie et de Paléoécologie UMR CNRS 6116, Université Paul Cézanne Aix-Marseille III, Av. Escadrille Normandie-Niemen, F-13397 Marseille, France.
authors.forename: Yann
authors.initials: Y
authors.lastname: Pécrix
authors.forename: Géraldine
authors.initials: G
authors.lastname: Rallo
authors.forename: Hélène
authors.initials: H
authors.lastname: Folzer
authors.forename: Mireille
authors.initials: M
authors.lastname: Cigna
authors.forename: Serge
authors.initials: S
authors.lastname: Gudin
authors.forename: Manuel
authors.initials: M
authors.lastname: Le Bris
mesh_terms: D004171:Diploidy; D035264:Flowers / Q000235:genetics / Q000502:physiology / Q000648:ultrastructure; D055993:Germ Cells, Plant / Q000378:metabolism*; D008540:Meiosis / Q000235:genetics / Q000502:physiology; D018625:Microscopy, Atomic Force; D011058:Pollen / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D011123:Polyploidy; D027826:Rosa / Q000235:genetics* / Q000502:physiology* / Q000648:ultrastructure; D013696:Temperature