Nutrient enrichment affects the mechanical resistance of aquatic plants
Résumé
In mammals, cadmium is widely considered as a non-genotoxic carcinogen acting through a methylation-dependent For many plant species, nutrient availability induces important anatomical responses, particularly the production of epigenetic mechanism. Here, the effects of Cd treatment on the DNA methylation patten are examined together with low-density tissues to the detriment of supporting tissues. Due to the contrasting biomechanical properties of plant its effect on chromatin reconfiguration in Posidonia oceanica. DNA methylation level and pattern were analysed in tissues, these anatomical responses may induce important modifications in the biomechanical properties of plant actively growing organs, under short- (6 h) and long- (2 d or 4 d) term and low (10 mM) and high (50 mM) doses of Cd, organs. The aim of this study was to determine the effects of nutrient enrichment on the anatomical traits of two through a Methylation-Sensitive Amplification Polymorphism technique and an immunocytological approach, freshwater plant species and its consequences on plant biomechanical performance. Two plant species were grown respectively. The expression of one member of the CHROMOMETHYLASE (CMT) family, a DNA methyltransferase, under controlled conditions in low versus high nutrient levels. The anatomical and biomechanical traits of the plant was also assessed by qRT-PCR. Nuclear chromatin ultrastructure was investigated by transmission electron stems were measured. Both species produced tissues with lower densities under nutrient-rich conditions, accompa- microscopy. Cd treatment induced a DNA hypermethylation, as well as an up-regulation of CMT, indicating that de nied by modifications in the structure of the aerenchyma for one species. As expected, nutrient enrichment also led to novo methylation did indeed occur. Moreover, a high dose of Cd led to a progressive heterochromatinization of important modifications in the biomechanical properties of the stem for both species. In particular, mechanical resist- interphase nuclei and apoptotic figures were also observed after long-term treatment. The data demonstrate that Cd ance (breaking force and strength) and stiffness of stems were significantly reduced under nutrient rich conditions. perturbs the DNA methylation status through the involvement of a specific methyltransferase. Such changes are The production of weaker stem tissues as a result of nutrient enrichment may increase the risk of plants to mechani- linked to nuclear chromatin reconfiguration likely to establish a new balance of expressed/repressed chromatin. cal failure, thus challenging plant maintenance in mechanically stressful or disturbed habitats.