Transgenerational somatic mutations and epigenetic imprints on selected DNA repair gene promoters in Arabidopsis thaliana due to pesticides.

Pesticides are known to induce genome instability. Reports on eukaryotes, including humans, mostly covers chromosomal aberrations and DNA strand breaks. Studies on scoring of the rates of loci-specific somatic mutations such as point mutations (PM), somatic homologous recombination (SHR), frameshift mutation (FSM), and transpositions due to pesticides are mostly confined to prokaryotes, using Ames test. Analogous eukaryotic model systems though are available for Drosophila, mouse and certain cell lines, reports using these are meagre, possibly due to the lethality of commercially-used pesticide doses and/or difficulty in assessing large population. DNA replication/repair being conserved among higher eukaryotes, the GUS reporter-based Arabidopsis thaliana system was used to score loci-specific mutations such as PM, SHR, FSM and transpositions. DNA repair gene expression and DNA methylation were studied using real-time PCR and methylation sensitive restriction enzyme digestion PCR, respectively. Four commercially used pesticides not only increased the rates of PM, SHR and FSM, and caused epimutations on selected DNA repair gene promoters, but also induced heritable transgenerational memory. While SHR rates were significantly high in the untreated progeny, FSM rates were high even in the grand progeny. Expression of 15 DNA repair genes increased under at least one of the pesticidal treatments. Eight of 21 DNA repair gene promoters showed altered methylation. MRE11A promoter showed demethylation in the untreated progeny due to all four pesticides. Malathion-induced demethylation was retained in the grand progeny also. Thus this work gauges the severity of various pesticides on inducing heritable loci-specific mutations/epimutations in a non-target system.