Abstract
Pharmaceuticals remain in treated wastewater used to irrigate agricultural crops. Their effect on terrestrial plants is practically unknown. Here we tested whether these compounds can be considered as plant stress inducers. Several features characterize the general stress response in plants: production of reactive oxygen species acting as stress-response signals, MAPKs signaling cascade inducing expression of defense genes, heat shock proteins preventing protein denaturation and degradation, and amino acids playing signaling roles and involved in osmoregulation. Tomato seedlings bathing in a cocktail of pharmaceuticals (Carbamazepine, Valporic acid, Phenytoin, Diazepam, Lamotrigine) or in Carbamazepine alone, at different concentrations and during different time-periods, were used to study the patterns of stress-related markers. The accumulation of the stress-related biomarkers in leaf and root tissues pointed to a cumulative stress response, mobilizing the cell protection machinery to avoid metabolic modifications and to restore homeostasis. The described approach is suitable for the investigation of stress response of different crop plants to various contaminants present in treated wastewater.
Highlights
Valproic acid (VAL) is used to treat epilepsy and bipolar disorder and to prevent migraine headaches
The general stress response includes the overproduction of reactive oxygen species (ROS), which activate the mitogen-activated protein kinase (MAPK) signaling cascade, the upregulation of chaperone/heat shock proteins (HSPs) genes, the activation of elements of the γ-aminobutyric acid (GABA) shunt, and the accumulation of amino acids and sugars involved in maintaining the cells osmotic balance[26,27,28]
To improve our understanding of how pharmaceuticals interact with biochemical pathways of plants, we studied the patterns of stress protein biomarkers, such as HSPs and MAPKs, GABA-shunt components including key enzyme of GABA biosynthesis, glutamate decarboxylase (GAD1 and 2), as well as several of other stress-induced amino acids
Summary
VAL is used to treat epilepsy and bipolar disorder and to prevent migraine headaches. The present study aimed at filling some of these gaps It appears that many compounds remaining in treated wastewater induce detoxification processes in plants, which include enhanced activities of detoxification enzymes such as superoxide dismutase, peroxidase and glutathione-S-transferase[23,24]. To improve our understanding of how pharmaceuticals interact with biochemical pathways of plants, we studied the patterns of stress protein biomarkers, such as HSPs and MAPKs, GABA-shunt components including key enzyme of GABA biosynthesis, glutamate decarboxylase (GAD1 and 2), as well as several of other stress-induced amino acids Changes in these molecular stress markers were conspicuous in leaf and root of tomato seedlings treated with a mix of pharmaceutical compounds (CBZ, LTG, VAL, PHY, DZP) and with CBZ alone. We conclude that pharmaceuticals present in treated wastewater induce a typical stress response in tomato plants
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