Cadmium tolerance and phytochelatin content of Arabidopsis seedlings over-expressing the phytochelatin synthase gene AtPCS1

Previous studies demonstrated that expression of the Arabidopsis phytochelatin (PC) biosynthetic gene AtPCS1 in Nicotiana tabacum plants increases the Cd tolerance in the presence of exogenous glutathione (GSH). In this paper, the Cd tolerance of Arabidopsis plants over-expressing AtPCS1 (AtPCSox lines) has been analysed and the differences between Arabidopsis and tobacco are shown. Based on the analysis of seedling fresh weight, primary root length, and alterations in root anatomy, evidence is provided that, at relatively low Cd concentrations, the Cd tolerance of AtPCSox lines is lower than the wild type, while AtPCS1 over-expressing tobacco is more tolerant to Cd than the wild type. At higher Cd concentrations, Arabidopsis AtPCSox seedlings are more tolerant to Cd than the wild type, while tobacco AtPCS1 seedlings are as sensitive as the wild type. Exogenous GSH, in contrast to what was observed in tobacco, did not increase the Cd tolerance of AtPCSox lines. The PC content in wild-type Arabidopsis at low Cd concentrations is more than three times higher than in tobacco and substantial differences were also found in the PC chain lengths. These data indicate that the differences in Cd tolerance and in its dependence on exogenous GSH between Arabidopsis and tobacco are due to species-specific differences in the endogenous content of PCs and GSH and may be in the relative abundance of PCs of different length

Does air pollution influence the success of species translocation? Trace elements, ultrastructure and photosynthetic performances in transplants of a threatened forest macrolichen

Species translocation can be considered as a primary conservation strategy with reference to in situ conservation. In the case of lichens, translocations often risk to fail due stress factors associated with unsuitable receptor sites. Considering the bioecological characteristics of lichens, air pollution is among the most limiting stress factors. In this study, the forest macrolichen Lobaria pulmonaria was used as a model to test the hypothesis that the translocation of sensitive lichens is effective only in unpolluted environments. At purpose, 500 fragments or whole thalli were translocated in selected beech forests of Central Europe (the Western Carpathians, Slovakia) where the species disappeared in the past and in oak forests of Southern Europe (Tuscany, Central Italy) where native populations are present. Prior to the translocation (May 2016) and after one year, morphological and ultrastructural features, trace elements as well as chlorophyll a fluorescence emission were analysed. Four years later, the effectiveness of lichen translocation was further evaluated as presence of the transplants and of newly formed individuals. After one year, the translocation ensured an effective survival of the thalli in remote oak and beech forests characterized by a negligible or low contamination by heavy metals. The transplants were considered successful and developed new lobules and rhizines, attaching by themselves to the bark of the host trees, looking overall healthy, without evident signs of alteration also at ultrastructural level. Moreover, in a few cases newly formed individuals were observed after four years. On the other hand, the results highlighted the link between the unsuccess of the translocation and air pollution in other areas of the Western Carpathians and suggested that current air quality still limits the possibility of recolonization in areas where the model species disappeared

Cadmium accumulation and effects in two important crop plants for human consumption (tobacco and carrot)

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An evolutionary survey on the intracellular response to heavy metals in plants

The enzyme phytochelatin synthase (PCS) is a γ-glutamylcysteine dipeptidyl transpeptidase constitutively expressed in the majority of plants, but also in other eukaryota and some cyanobacteria. In the presence of metal(loid)s such as cadmium, lead, mercury, arsenic and excesses of copper and zinc, PCS is promptly activated, leading to the production of phytochelatins (PCn), thiol-peptide compounds, able to chelate these metals and compartmentalise them inside the vacuole, with a consequent detoxification of the cell environment. Nonetheless, since PCS is ubiquitously and constitutively expressed in plants, even in the complete absence of toxic metal(loid)s, it is postulated that this enzyme could have primordial function(s) other than mere metal detoxification. This hypothesis is supported by the evidence that plants, able to hyper-accumulate toxic metal(loid)s, in no way show an adaptative increase of PCn synthesis. Thus, a relevant primary function performed by PCS might be the regulation of the physiological requirements of Fe(II) and Fe(III), since this element is and has always been widely present in all environments, even though it has serious solubility and bioavailability problems for the vast majority of organisms. To validate this idea, I intend to study the involvement of PCS enzyme in the homeostatic balance of Fe using as model organism the liverwort Marchantia polymorpha, an ancient bryophyte interesting for its pivotal position in land plant phylogeny and known for the capability to accumulate metals. This investigation may possibly be carried out using other early bryophytes and tracheophytes. Furthermore, other elements could be studied, such as zinc, in possible cross-homeostasis with iron, as well as copper, but also toxic metals such as cadmium, the main inducer of PCn, and arsenic, present in inorganic forms such as arsenate and arsenite. Due the multi-tasking nature of PCS enzyme (for example its hypothesized function in callose deposition and in auxin metabolism of the model-plant Arabidopsis thaliana), it seems therefore promising to investigate the involvement of PCS in function(s) other than detoxification of toxic metals

Spatial and temporal management of the response to heavy metals in plants, lichens and algae

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Welcome to Stresses: The Only Gold Open Access International Journal Treating Responses to All Stresses in All Biological Systems, with an Interdisciplinary Vision

A warm welcome from the Founder and Editor-in-Chief of Stresses, Luigi Sanità di Toppi, Full Professor of Botany at the University of Pisa, Italy [...

Novel Coronavirus: How atmospheric particulate affects our environment and health

It is well-known that atmospheric pollution, first and foremost the particulate matter (PM), causes serious diseases in humans. China’s metropolises and Italy’s Po Valley have in fact achieved a concerning degree of notoriety thanks to runaway air pollution problems. The spread of viral respiratory diseases is facilitated in polluted environments, an example of which is the respiratory syncytial virus bronchiolitis. In this opinion paper, we consider the possible relationship between air pollution, primarily airborne PM10–2.5, and the spread of the novel coronavirus in Northern Italy. If it is true that the novel coronavirus remains active from some hours to several days on various surfaces, it is logical to postulate that the same can occur when it is adsorbed or absorbed by the atmospheric particulate matter, which may also help carry the virus into the human respiratory system. As the Earth presents us with a very high bill to pay, governments and other authorities need to take prompt action to counter excessive pollution levels, both in Italy and in other countries

Responses to Cadmium in Early-Diverging Streptophytes (Charophytes and Bryophytes): Current Views and Potential Applications

Several transition metals are essential for plant growth and development, as they are involved in various fundamental metabolic functions. By contrast, cadmium (Cd) is a metal that can prove extremely toxic for plants and other organisms in a dose-dependent manner. Charophytes and bryophytes are early-diverging streptophytes widely employed for biomonitoring purposes, as they are able to cope with high concentrations of toxic metal(loid)s without showing any apparent heavy damage. In this review, we will deal with different mechanisms that charophytes and bryophytes have evolved to respond to Cd at a cellular level. Particular attention will be addressed to strategies involving Cd vacuolar sequestration and cell wall immobilization, focusing on specific mechanisms that help achieve detoxification. Understanding the effects of metal(loid) pollution and accumulation on the morpho-physiological traits of charophytes and bryophytes can be in fact fundamental for optimizing their use as phytomonitors and/or phytoremediators