Sire Christelle. 2000. Recherche de marqueurs moléculaires de l'activité de méristèmes caulinaires de cocotiers (Cocos nucifera L.) cultivés in vitro. Toulouse : ENSAT, 57 p. Mémoire DAA : Biotechnologies, amélioration et protection des plantes : Ecole nationale supérieure agronomique de Toulouse
Résumé : For coconut palm, in vitro cloning with somatic embryogenesis was achieved 20 years ago and since then, a few vitroplants have been established in the field. However, many technical problems have to be overcome in order to permit mass propagation. Recent studies have shown that somatic embryo formation and regeneration can be obtained from plumules (zygotic embryo) explants, with reproducibility and higher yields than other types of explants (young leaves, calli, immature inflorescences). Nevertheless, coconut seems to be a recalcitrant plant with respect to in vitro regeneration. The major problem in coconut currently faced is the heterogeneous response and the loss of "meristematic potential" of explants. Preliminary studies show that most of explants whose regeneration is inhibited progress meristems with cells that do not follow a normal cell cycle pathway. Most of the cells are stopped in the early transitions, that is to say G0 or G1 stage. The purpose of the work was to study and to characterize two kinds of explants plumules which show a relatively good response in vitro and those in which growth is inhibited. To this end, we attempted to identify molecular markers involved in plumule physiology. Furthermore, the work is based on zygotic embryos because this type of culture provides a model system that could be applied to improve conditions used for the in vitro development of somatic embryos. Firstly we clearly demonstrated a difference of genes expression between the two explants studied, using differential display RT-PCR. Three markers of interest were identified, after testing each potential marker is tested by northern hybridization to check differential profiles. Secondly, we studied more precisely the cell cycle on the two types of plumules by screening cDNA libraries whith probes known to be important markers in the cell cycle, such as a retinoblastoma gene, cyclin genes and E2F gene. Using this we isolated and characterized a nearly full length cDNA sharing significant homology with a vegetal D-type cyclin. Forecasts, this work should help us to understand molecular mechanisms involved in the loss of "meristematic potential" but these markers are also a reliable tool to predict the behaviour of explant for in vitro regeneration. Otherwise, such markers should help us to improve in vitro culture conditions but also to modulate meristems activity through cell cycle gene expression.
Mots-clés Agrovoc : Cocos nucifera, culture in vitro, vitroplant, physiologie végétale, marqueur génétique, méristème, plumule, cycle cellulaire, technique analytique, PCR
Classification Agris : F02 - Multiplication végétative des plantes
F30 - Génétique et amélioration des plantes
F60 - Physiologie et biochimie végétale
Auteurs et affiliations
- Sire Christelle, CIRAD-CP-COCOTIER (FRA)
Autres liens de la publication
Source : Cirad - Agritrop (https://agritrop.cirad.fr/476997/)
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