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Heavy metal (HM) pollution of marine coastal areas is a big concern worldwide. The marine phanerogam Posidonia oceanica (L.) Delile is widely considered to be a sensitive bioindicator of water pollution due to its ability to sequester trace elements from the environment. The analysis of specific biomarkers, like reactive oxygen species scavengers, could allow us to correlate the physiological response of P. oceanica meadows to water pollution. In this study, we analysed the activity of some antioxidant enzymes and the expression level of the corresponding genes in the leaves of P. oceanica plants harvested from four meadows distributed along the Tyrrhenian coast; lipid peroxidation and the expression level of two genes related to HM response, metallothionein-2b and chromethylase, were also measured. The results of biochemical and molecular analyses were correlated with the concentration of some HMs, such as Cr, Cd, Cu, Ni and Pb, measured in P. oceanica leaves. We found a very strong antioxidant response in plants from the Murelle meadow whose HM concentration was the lowest for most of the analysed HMs, particularly Cu.

In plant defense, priming is a physiological process by which a plant prepares to more quickly or aggressively respond to a future biotic or abiotic stress. This unique physiological state can be induced by beneficial microbes or by treatment with natural or synthetic compounds. Priming has been described copiously, mainly in dicots, but the study on the molecular mechanisms regulating the phenomenon is still at its infancy. A fascinating possibility is that epigenetic changes may be the main actors on priming establishment. A more accessible chromatin structure, due to DNA methylation and/or histone modifications, could facilitate a quicker and more potent gene response to a subsequent attack. Here, we investigated the impact of methyl jasmonate (MeJA)-induced priming on the response efficacy to mechanical wounding of a monocot (Oryza sativa). In particular, we showed that MeJA primes plants for increased expression of defense-related genes, such as OsBBPI and OsPOX, upon wounding. Finally, we provided evidence that MeJA modulates histone modifications in the promoter region of OsBBPI, as well as changes at genome-wide DNA methylation level. Together these studies corroborate the importance of priming in strengthening plant defense and support the growing evidence that epigenetic regulation plays a pivotal role in priming onset., (Copyright © 2018 The Authors. Published by Elsevier GmbH.. All rights reserved.)