There is No Somatic Meiosis in Embryogenic Leaves of Cichorium |
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Authors: | RAMBAUD CAROLINE; BLERVACQ ANNE-SOPHIE; DEVAUX PIERRE; DUBOIS THERESE; DUBOIS JEAN; LAMMIN FRANCOIS; VASSEUR JACQUES |
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Institution: | Laboratoire de Physiologie cellulaire et Morphogenèse végétales, Université des Sciences et Technologies de Lille, SN2, 59655 Villeneuve d'Ascq, Cedex Florimond-Desprez, Laboratoire de Biotechnologie, BP 41, Cappelle en Pévèle, 59242, France |
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Abstract: | Several papers dealing with carrot cell cultures describe meiosis-likedivisions and haploid cells prior to somatic embryogenesis.We have studied the first division in embryogenic mesophyllcells of a diploidCichorium intybus L. and of a tetraploid hybridC.intybus L.xC. endivia L. which undergo direct somatic embryogenesisfrom single cells when leaf fragments are placed in a liquidagitated inductive medium (modified MS with 1x10-7M NAA and2.5x10-6M 2-iP), in darkness, at 35°C. MicrosporogenesisinC. intybus provided aspects of meiosis for comparison. Inleaves incubated in inductive conditions, DAPI staining of nucleishowed normal mitosis on days 36; about 0.6% cells inprophase had undergone spontaneous endoreduplication leadingto a tetraploid somatic embryo. Immunocytochemistry of tubulinrevealed the constant presence of a preprophase band, as ina normal mitosis. The first pluricellular somatic embryos becamevisible on day 5 of culture. Flow cytometric determination ofnuclear DNA on days 4, 5 and 6 did not show any peak correspondingto the 1C DNA level for the diploid plant or to the 2C DNA levelfor the tetraploid. Instead there was a weak but constant peakat the 4C and 8C levels. We conclude that inCichorium leaves,the first division of somatic embryogenesis is a normal mitosis,with a small shift to endoreduplication. In our opinion, somaticmeiosis is not a prerequisite during direct somatic embryogenesis. Cichorium ; chicory; somatic embryogenesis; cell division; flow cytometry; tubulin |
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