Persistence of cadmium-induced adaptive response to genotixicity of maleic hydrazide and methyl mercuric chloride in root meristem cells of Allium cepa L.: Differential inhibition by cycloheximide and buthionine sulfoximine

Abstract

With an objective to determine the period of persistence of the metal-induced adaptive response to chemical mutagens and heavy metals, growing root meristems of Allium cepa were conditioned by cadmium sulfate (CdSO 4), 4×10 −7 and 4×10 −6 M for 1 h and subsequently challenged by maleic hydrazide (MH), 5×10 −3 M or methyl mercuric chloride (MMCl), 1.26×10 −6 M for 3 h at different time intervals ranging from a few minutes to several hours following the conditioning dose. Root meristems, fixed at regular intervals during recovery from 6 to 48 h, were cytologically analysed for cells with micronuclei (MNC). The adaptive responses to MH and MMCl were observed as early as 5 min after the Cd-conditioning that persisted for at least 48 h. Metabolic inhibitors, cycloheximide (CH), 10 −7 M and buthionine sulfoximine (BSO), 10 −4 M administered either prior to or simultaneous with Cd-conditioning effectively prevented the adaptive response to MH. Whereas BSO, an inhibitor of phytochelatin synthesis, prevented the adaptive responses from 15 min to 8 h after the conditioning dose, CH an inhibitor of cytoplasmic protein synthesis prevented the same from 6 to 48 h. The findings underscored the differential roles of phytochelatins and proteins underlying the foregone metallo-adaptive response.