Influence of culture conditions on 7S globulins accumulation in somatic embryos of oil palm (Elaeis Guineens Jacq.)
1998
Morcillo, Fabienne | Aberlenc-Bertossi, Frédérique | Duval, Yves | Hartmann, Caroline
Embryogenic suspension cultures allow the in vitro mass propagation of oil palm (Elaeis guineensis Jacq.). In this way, single somatic embryos displaying structural similarities with zygotic embryos are produced. In mature zygotic embryos of oil palm, 7S globulins predominate. These storage proteins are heterogeneous oligomers (Mr of 150 and 200 kD) comprising, as detected by means of SDS-PAGE, a polypeptide triplet of Mr ranging between 45 and 65 kD. N-terminal sequences determined for two of the latter polypeptides displayed similarities with those of vicilin-like proteins of maize embryos. A zygotic embryo cDNA library has been constructed and cDNAs corresponding to these proteins have been isolated. In oil palm somatic embryos, 7S globulins have been identified using Western blotting. The 7S globulin content, as measured using an ELISA-based method, was found to be 80 times lower in somatic embryos than in zygotic embryos. The addition to the culture media of several substances known to improve the accumulation of proteins during somatic embryogenesis in other plant species (i.e. ABA, sucrose, PEG, glutamine and arginine) was investigated. Each of these compounds was found to enhance the total soluble protein content, but levels were still low as compared to those in zygotic embryos. Preliminary results using the cloned cDNA suggest that the lack of 7S globulins in somatic embryos is associated with a lower level of 7S globulin mRNA. (Résumé d'auteur)
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