Integrated evaluation of methidathion-induced toxicity in Allium cepa with a multifactorial biological approach

In this study, the physiological parameters (germination percentage, root length, weight gain), cytogenetics [mitotic index (MI), micronucleus (MN) frequency, chromosomal abnormalities (CAs)], biochemical [malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), chlorophyll a and b], and anatomical (root meristem cell damage) toxicity induced by the insecticide methidathion (MTD) were investigated in Allium cepa L. Additionally, the Comet assay was employed to detect DNA damage, while molecular docking analyses were performed to investigate the interactions of MTD with essential macromolecules. A. cepa bulbs were allocated into four groups: one serving as the control and the remaining three exposed to MTD at concentrations of 15, 30, and 45 mg/L, respectively. Tap water was applied to the control group. Following germination, root and leaf samples were collected for analysis. The control group exhibited the highest values for physiological parameters, MI, DNA integrity, and chlorophyll content, along with the lowest levels of MDA, antioxidant enzyme activity, MN frequency, and CAs. MTD exposure caused a dose-dependent decrease in physiological and cytogenetic parameters and chlorophyll content, while significantly increasing MDA levels, enzyme activities, MN frequency, and CAs. It also induced various types of CAs and anatomical damage in root meristem cells. The Comet assay revealed a dose-dependent reduction in head DNA percentage and an increase in tail DNA percentage. Molecular docking indicated that MTD interacts with DNA, tubulin, topoisomerase, and 5-aminolevulinic acid dehydratase, contributing to its multifaceted toxicity. In conclusion, it was demonstrated that MTD caused significant toxicity in A. cepa and this model organism served as an effective model for the evaluation of toxicological effects of environmental pollutants.