In-field and in-vitro study of the moss Leptodictyum riparium as bioindicator of toxic metal pollution in the aquatic environment: Ultrastructural damage, oxidative stress and HSP70 induction

Abstract

This study evaluates the effects of toxic metal pollution in the highly contaminated Sarno River (South Italy), by using the aquatic moss Leptodictyum riparium in bags at 3 representative sites of the river. Biological effects were assessed by metal bioaccumulation, ultrastructural changes, oxidative stress, as Reactive Oxygen Species (ROS) production and Glutathione S-transferase (GST) activity, as well as Heat Shock Proteins 70 (HSP70s) induction. The results showed that L. riparium is a valuable bioindicator for toxic metal pollution of water ecosystem, accumulating different amounts of toxic metals from the aquatic environment. Toxic metal pollution caused severe ultrastructural damage, as well as increased ROS production and induction of GST and HSP70s, in the samples exposed at the polluted sites. To assess the role and the effect of toxic metals on L. riparium, were also cultured in vitro with Cd, Cr, Cu, Fe, Ni, Pb, Zn at the same concentrations as measured at the 3 sites. Ultrastructure, ROS, GST, and HSP70s resulted severely affected by toxic metals. Based on our findings, we confirm L. riparium as a model organism in freshwater biomonitoring surveys, and GST and HSP70s as promising biomarkers of metal toxicity.

The Moss Leptodictyum riparium Counteracts Severe Cadmium Stress by Activation of Glutathione Transferase and Phytochelatin Synthase, but Slightly by Phytochelatins

“…The slight cytohistological and ultrastructural damage caused by Cd suggests very efficient metal detoxification processes functioning in this moss, despite that-as a general sign of suffering-photochemical efficiency was negatively affected by both Cd concentrations. Interestingly, the mechanisms based on Cd immobilization at the cell wall level have previously been demonstrated not to play a relevant role [31,34]. By contrast, intracellularly-synthesized stress proteins (such as the heat shock protein 70) might be important in repairing the damage caused by Cd, especially at high concentrations, possibly by allowing the correct refolding of Cd-impaired proteins [31,34].…”

“…Previous studies have demonstrated that the cosmopolitan moss Leptodictyum riparium (Bryophyta) can accumulate, and seemingly tolerate, very high concentrations of toxic metals, including Cd [30][31][32], with a bioconcentration factor higher than that of other plants, even of some angiosperms [33]. Thanks to its apparent tolerance to metal stress and to its high efficiency for metal removal, L. riparium has therefore been proposed as a useful tool for biomonitoring metal contamination, as well as for carrying out phytoremediation projects in polluted areas [31][32][33]. Interestingly, L. riparium performs little Cd immobilization at the cell wall level, and therefore the metal enters the cytosol rather easily [31,34].…”

“…Thanks to its apparent tolerance to metal stress and to its high efficiency for metal removal, L. riparium has therefore been proposed as a useful tool for biomonitoring metal contamination, as well as for carrying out phytoremediation projects in polluted areas [31][32][33]. Interestingly, L. riparium performs little Cd immobilization at the cell wall level, and therefore the metal enters the cytosol rather easily [31,34]. Thus, the apparent Cd tolerance showed by this moss in the open environment might be due to efficient intracellular (symplastic), rather than to cell wall (apoplastic), detoxification processes.…”

“…Although the L. riparium gametophytes collected in the open appear to possess an elevated tolerance to Cd [31,32], until now no ad hoc studies have been carried out in the laboratory-confined environment. The latter experiments could therefore address the issue in mechanistic terms, when the moss is subjected to strong and prolonged Cd stress in controlled conditions.…”

Aquatic Mosses as Adaptable Bio-Filters for Heavy Metal Removal from Contaminated Water

“…Probably because of this characteristic, aquatic mosses have been shown to accumulate more heavy metals (HM) than vascular plants at contaminated sites. Several studies evidenced the ability of Leptodictyum riparium isolated from polluted freshwater to serve as bioindicator, accumulating several heavy metals such as chromium, lead, and zinc [ 3 , 4 ]. Drepanocladus spp.…”