Keywords: methylcytosine / shoot apex / vegetative development / water deficit / productivity Abstract • Several reports on annual plants have already shown the involvement of epigenetic modifiers such as DNA methylation in their adaptation to abiotic stresses.• Nevertheless, the genotypic variations of epigenetic modifiers, their possible correlations with morphological traits and the impact of water deficit have not been described for perennial plants.• Six genotypes of Populus deltoides × P. nigra were subjected or not to a moderate water deficit treatment. Various morphological traits such as the height of the plants, their biomass and the total leaf area were measured to characterize the productivity in both conditions. Levels of DNA methylation, histone acetylation and the activities and isoform accumulation of the corresponding enzymes were measured at the shoot apex, the site of morphogenesis. Genotypic variation was observed for the morphological traits and the epigenetic variables and correlations were established among them. Genotypic variation for DNA methylation was detected in hybrid poplars. A positive correlation was demonstrated between DNA methylation percentage and productivity under well watered conditions.• While there was a general decrease of growth for all genotypes in response to a moderate water deficit, genotypic dependant variations of DNA methylation were found suggesting different strategies among hybrids. Mots-clés : Résumé -Méthylation de l'ADN et acétylation des histones : variations génotypiques chez des peupliers hybrides, impact d'un déficit hydrique et relations avec la productivité.• Plusieurs études sur des plantes annuelles ont déjà montré l'implication des modifications épi-génétiques telles que la méthylation de l'ADN dans la plasticité de leurs réponses aux contraintes abiotiques.• Néanmoins, les variations génotypiques de ces modifications épigénétiques, leur possible corréla-tion avec des variables de croissance et l'impact d'un déficit hydrique n'ont pas été décrits sur une plante pérenne.• Six génotypes de Populus deltoïdes × P. nigra ont été soumis ou non à un déficit hydrique modéré et plusieurs variables de croissance ont été mesurées afin de caractériser leur productivité. Les niveaux de méthylation de l'ADN, d'acétylation des histones, les activités enzymatiques et l'accumulation des isoformes correspondantes ont été mesurés sur des apex caulinaires, site de la morphogenèse. Des variations génotypiques ont été observées pour les variables de croissance et épigénétiques. Une corrélation positive a été mise en évidence entre la méthylation de l'ADN et la productivité en condition hydrique favorable.• Bien qu'il y ait une diminution générale de la croissance de tous les génotypes en réponse à un défi-cit hydrique modéré, des variations génotype-dépendant de la méthylation de l'ADN ont été trouvées suggérant différentes stratégies entre hybrides.

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In order to evaluate the permanent chromatin remodeling in plant allowing their high developmental plasticity, three sugarbeet cell lines (Beta vulgaris L. altissima) originating from the same mother plant and exhibiting graduate states of differentiation were analyzed. Cell differentiation has been estimated by the cell redox state characterized by 36 biochemical parameters as reactive oxygen species steady-state levels, peroxidation product contents and enzymatic or non-enzymatic protective systems. Chromatin remodeling has been estimated by the measurement of levels of DNA methylation, histone acetylation and corresponding enzyme activities that were shown to differ between cell lines. Furthermore, distinct loci related to proteins involved in cell cycle, gene expression regulation and cell redox state were shown by restriction landmark genome scanning or bisulfite sequencing to display differential methylation states in relation to the morphogenic capacity of the lines. DNA methylating, demethylating and/or histone acetylating treatments allowed to generate a collection of sugarbeet cell lines differing by their phenotypes (from organogenic to dedifferentiated), methylcytosine percentages (from 15.0 to 43.5%) and acetylated histone ratios (from 0.37 to 0.52). Correlations between methylcytosine or acetylated histone contents and levels of various parameters (23 or 7, respectively, out of 36) of the cell redox state could be established. These data lead to the identification of biomarkers of sugarbeet morphogenesis in vitro under epigenetic regulation and provide evidence for a connection between plant morphogenesis in vitro, cell redox state and epigenetic mechanisms.

The existing body of information defines some regulatory functions to secondary metabolites like coumarin (COU). Experience and some experimental results in our laboratory tempted us to test a GA-like activity of COU. Experiments were conducted with endospermic (de-embryonated) and embryonic wheat half grains treated with different concentrations of COU, for different time courses, alone or in combination with the GAbiosynthesis inhibitor paclobutrazol (P). Results showed that treatment with COU caused stimulation of amylase synthesis and secretion from aleurone layer cells. P did not affect synthesis but slightly reduced excretion of amylase. However, germination percentage of intact wheat grains and seedling growth were inhibited by COU in a concentration-dependent manner. This indicates that COU has some GA-like effect, and also affects other aspects of germination and seedling establishment. This GA-like effect was also confirmed by the observed increase in elongation of wheat seedlings second leaf sheath and pea stem when treated with COU. These potential regulatory roles of COU may indicate that secondary metabolites have more important roles during different plant developmental processes.

Thaumatin-like proteins (TLPs) constitutes a homogeneous family, members of which are produced by plants in response to different kinds of stress. NP24 protein is one of such salt-induced protein from tomato (Solanum lycopersicum) and it belongs to TLPs family. NP24 is a 24 kDa (207 amino acid) antimicrobial TLP found in tomato fruits. One isoform (NP24I) of NP24 was discovered in the outer pericarp of tomato fruit and is reported to play a possible role in ripening of the fruit in addition to its antimicrobial activity. In this study, the total RNA was isolated successfully from the outer pericarp of ripe (red) tomato fruit. cDNA was prepared and the gene coding for NP24I protein was amplified using conventional polymerase chain reaction (PCR). The gene was then cloned into Mach1™-T1® Escherichia coli cells, then subcloned into the over-expression vector pET-28a (+) using BL21 expression bacteria. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that the gene was over-expressed in E. coli as inclusion bodies. Optimization of the recombinant NP24I protein solubility was achieved by cold induction through decreasing both expression temperature and Isopropyl-beta-thio galactopyranoside (IPTG) concentration. The recombinant NP24I protein was purified using Ni-NTA resin, and then the antimicrobial activity of the purified recombinant NP24I protein was tested. The aims of this work were to study the cloning and expression of NP24 protein from local tomato cultivar in a prokaryotic system and to test the activity of the recombinant NP24, as well as to prove the activity of native protein on the bacterial as well as fungal growth.