Thota Kanishka Rao, Amity University Kolkata
Excessive amounts of heavy metals, discharged from industrial and natural sources, are hazardous to human health. They are major aquatic toxicants.
The maximum allowable metal concentrations in natural and drinking water are carefully monitored in many nations. For a guideline of aquatic heavy metal, many observable techniques have been developed, including instrumental analyses, for example, flame atomic absorption spectrometry, electrothermal atomic absorption spectrometry, inductively coupled plasma optical emission spectrometry, and inductively coupled plasma mass spectrometry.
Nevertheless, these strategies are costly and time-consuming and hence, simple, fast, and effective techniques are wanted for constant heavy metal monitoring (REF).
Biomonitoring is probably one of the simplest approaches to distinguish toxins, i.e., evaluating toxicity based on biological responses. Various organisms, for example, algae, zooplankton, insects, and fish have been utilised as biomonitors for aquatic pollutants in the past.
To facilitate heavy metal monitoring in water, researchers developed transgenic Daphnia that is profoundly sensitive to heavy metals and react to them rapidly. Daphnia magna is a small freshwater crustacean, used as an aquatic pollution bioindicator and model organism in ecotoxicology. Daphnia is commonly more sensitive to ecological changes than fish, and subsequently, it is normal that transgenic Daphnia could be utilised as an indicator of heavy metals. It has been reported that the metallo-thionein quality of D. pulex is activated by exposures to Cd11 and other heavy metals. Metallothionein A, which was a metal reaction gene, and its promoter region was obtained from Daphnia magna.
A chimeric gene intertwining the promoter region with a green fluorescent protein (GFP) gene was coordinated into D. magna utilising the TALEN technique and transgenic Daphnia named D. magna MetalloG were produced. At the point when D. magna MetalloG was presented to heavy metal answers for 1 h, GFP articulation was induced distinctly in their midgut and hepatopancreas. The most minimal concentrations of heavy metals that initiated GFP articulation were 1.2 µM Zn2+, 130 nM Cu2+, and 70 nM Cd2+. Heavy metal exposure for 24 h could bring down the thresholds considerably further. D. magna MetalloG encourages aqueous heavy metal detection and might upgrade water quality monitoring.
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Source:
Arao, T., Kato, Y., Nong, Q.D. et al. Production of genome-edited Daphnia for heavy metal detection by fluorescence. Sci Rep 10, 21490 (2020). https://doi.org/10.1038/s41598-020-78572-z
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