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Accueil du site → Doctorat → Allemagne → 2018 → Evaluation of the plastidic antioxidant system in Jatropha curcas and Swietenia macrophylla seedlings submitted to drought stress

Freie Universität Berlin (2018)

Evaluation of the plastidic antioxidant system in Jatropha curcas and Swietenia macrophylla seedlings submitted to drought stress

Sarmiento, Aneth

Titre : Evaluation of the plastidic antioxidant system in Jatropha curcas and Swietenia macrophylla seedlings submitted to drought stress

Auteur : Sarmiento, Aneth

Université de soutenance : Freie Universität Berlin

Grade : Doctor rerum naturalium (Dr. rer. nat.) 2018

Résumé
Tropical plants species face a very particular environment with highly variable light intensity, heat, low mineral availability and other abiotic stresses which might have led to the evolution of specific protective mechanisms. The understanding of mechanisms for tolerance over abiotic stress in these plants could help to protect tropical forests, allow a more intelligent grow of economically interesting species and improve crops. The study of non-model plants, the category for most tropical species, is hindered by the amount of available information and the quality of this data. Swietenia macrophylla has not been sequenced, since the end of this work. To perform an evaluation of gene expression it was necessary to clone previously partial sequences for all required genes and to design specific primers for PCR amplification, including the reference genes. This work was supported by phylogenetic analysis, nourished by available sequences of related species. On the contrary, Jatropha curcas is on its way to becoming a novel model-species for genetic and eco-physiological studies. The species was sequenced in 2010 and had already some studies of gene expression under abiotic stress. Even when it is a helpful aspect to be able to compare results with other studies, it was demonstrated here that the provided information still needs to be carefully evaluated before it is used. The validity of the information for 2CP, APX, GPX and CAT obtained in two different databases, was corroborated by cloning full cDNA sequences. The characterization of genes belonging to the enzymatic antioxidant system in chloroplasts was performed by studies of exon and for 2CP and APX, the chloroplast targeting was confirmed by transient transformation of N. benthamiana with a construct carrying the signal peptide and a reporter gene. Stress experiments were performed in outdoor conditions in Panama for Swietenia, and also in greenhouse conditions in Berlin, for Jatropha ; they included mainly variations in temperature and irradiance. Physiological parameters such as stem elongation, leaf area, and biomass production seemed different between the two species, praising Jatropha for its capacity of growth regulation during mild and severe drought stress. Nevertheless, PSII quantum yield and CO2 assimilation rates in Swietenia unveiled an unexpected photosynthetic capacity during drought.

Mots clés  : Molecular plant physiology antioxidant drought tropical Jatropha Swietenia

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