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Etude de l'impact de la différenciation cellulaire sur la biosynthèse de la galanthamine chez Leucojum aestivum L. (Amaryllidaceae)

Abstract : Leucojum aestivum L. is a medicinal plant which contains isoquinoline alkaloids, in particular galanthamine, which is used in the treatment of Alzheimer disease in the whole world because of its inhibiting activities of acetylcholinesterase. This alkaloid possesses cholinesterase inhibitory activity. Facing the growing demand from the pharmaceutical market, related to the ageing of the population, the natural sources is insufficient. The aim of this thesis is to produce galanthamine by plant tissue cultures from genetically modified tissues or not as an alternative way to obtain this valuable metabolite. It is known that the undifferentiated state of the cells in in vitro cultures strongly limits the alkaloid synthesis. A strategy consists in leading the cells to a sufficient level of differentiation to allow an activation of the secondary metabolism. This level could be reached by the addition of exogenic phytoregulators in the culture medium or, by the transfer of the rol genes of Agrobacterium rhizogenes which, by modulating the metabolis.m of the endogenous phytoregulators, induce a cellular differentiation. Primary explants of 1. aestivum. were placed in various culture media to study their capacity to develop callogenesis. Under certain conditions of culture, an indirect embryogenesis was observed as well as a direct organogenesis which appeared by the development of bulblets and roots. A genetic protocol of transformation of 1. aestivum. with A. rhizogenes (LBA 9402) and A. tumefaciens modified (C58ClRifR) was devèloped. Gnly of genetic transformation by SAAT of bulbs in vivo explants with LBA 9402 led to hairy roots formation, which integrated the genes rol A, Band C. We also developed an analysis technical by H.P.Le. which enabled us to determine the content of galanthamine various in vitro materials. The highest content of galanthamine was observed in the embryogenic callus cultivated on medium MS 30 + 10[micro]M 2.4-D + 10[micro]lM BAP. The aim of the last part of this work is to increase the biosynthesis of galanthamine in the in vitro cultures by introducing into the culture medium a biogenetic precursor, the 4'-O-methylnorbelladine. The biosynthesis of the galanthamine was increased in the embryogenic callus, it passed from 0% to 62.6% 10 -3% M.S.
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Submitted on : Thursday, March 29, 2018 - 10:49:35 AM
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Mamadou Falilou Diop. Etude de l'impact de la différenciation cellulaire sur la biosynthèse de la galanthamine chez Leucojum aestivum L. (Amaryllidaceae). Biologie cellulaire. Université Henri Poincaré - Nancy 1, 2007. Français. ⟨NNT : 2007NAN10154⟩. ⟨tel-01747018⟩



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