Persistence and prevention of aluminium- and paraquat-induced adaptive response to methyl mercuric chloride in plant cells in vivo

Abstract

Induction and persistence of adaptive response by aluminium (Al), 1 or 10 μM, and paraquat (PQ), 5 or 10 μM, against genotoxicity of methyl mercuric chloride (MMCl), 1.26 μM, a standard environmental genotoxin, was investigated in root meristem cells of Allium cepa. Subsequently, three metabolic inhibitors, namely, 3-aminobezamide (3-AB, 10 or 100 μM), an inhibitor of poly(ADP-ribose) polymerase (PARP) implicated in DNA repair and/or apoptosis, cycloheximide (CH, 0.1 or 1 μM), an inhibitor of protein synthesis, and buthionine sulfoximine (BSO, 100 μM or 1 mM), an inhibitor of glutathione synthesis were tested for their ability to prevent the adaptive response induced by conditioning doses of Al, 10 or 100 μM; and PQ, 5 or 100 μM, against MMCl-challenge, 1.26 or 100 μM, in root meristems of A. cepa or embryonic shoots of Hordeum vulgare, respectively. The findings demonstrated that once triggered, the Al- or PQ-adaptive response to MMCl could persist for at least 48 h in root meristems of A. cepa. Furthermore, the adaptive response could effectively be prevented by 3-AB, to a lesser degree by CH, and the least by BSO, suggesting primarily the involvement of PARP and implicating DNA repair in the underlying mechanisms of adaptive response in plant cells in vivo.