Molecular Markers in Plant-Based Bioassays for the Detection of Molecular Endpoints to Probe of Aquatic Genotoxicity-An Overview

Many contaminants entering the aquatic environment have been lipophilic by nature and can be readily taken up by aquatic organisms or absorbed by particulate matter. Examples of such compounds include polycyclic aromatic hydrocarbons, polychlorinated biphenyls and phthalates. Therefore, the impact of these aquatic contaminants on ecosystems largely depends upon factors including uptake and biotransformation by different species, and effects can be easily seen at the cellular level through the individual, population and ultimately the ecosystem as a whole. Research in this particular area has gained much attention and momentum in the recent past, with particular interests thrust upon the presence of different genotoxic agents surrounding in the environment. Results from the U.S. Environmental Protection Agency's (EPAs) Toxic Release Inventory (TRI) found out that several known and many dubious mutagenic and genotoxic chemicals could be readily accounted in contaminated surface waters, of which one third of these toxicants from effluent discharges are practically rodent carcinogens. Moreover, 800 metric tonnes of chemicals released into surface waters every year have been detected to be class 1, 2A or 2B carcinogens as classified by the International Agency for Research on Cancer (IARC). It is therefore clear that the assessment of complex mixtures for their genotoxic potential fits in the list of an extremely important consideration for environmental pollution monitoring and management, especially while considering the implications of these compounds in initiation, propagation and development of carcinogenesis, inherited disease and teratogenesis. Concomitantly, it is important to develop reliable and effective methods for detecting endpoints indicative of exposure to genotoxicants in particular using test methods that would be simple, rapid and cost effective.

Antioxidant enzymes, i.e., ROS scavengers, chromosomal abnormalities resultant of altered mitotic index and micronuclei formation, the alkaline COMET Assay, RAPD, AFLP coupled with RT-PCR can be employed as effective biochemical, cytogenetic and molecular markers in plants (as model systems for aquatic toxicology) which serve as best tools to detect the mode of action and levels of genotoxic endpoints upon exposure to different genotoxins in aquatic environments.