Gene expression and microscopic analysis of arabidopsis exposed to chloroacetanilide herbicides and explosive compounds.: A phytoremediation approach

Understanding the function of detoxifying enzymes in plants toward xenobiotics is of major importance for phytoremediation applications. In this work, Arabidopsis ( Arabidopsis thaliana; ecotype Columbia) seedlings were exposed to 0.6 mM acetochlor ( AOC), 2 mM metolachlor ( MOC), 0.6 mM 2,4,6- trinitrotoluene ( TNT), and 0.3 mM hexahydro- 1,3,5- trinitro- 1,3,5- triazine ( RDX). In vivo glutathione ( GSH) conjugation reactions of AOC, MOC, RDX, and TNT were studied in root cells using a multiphoton microscope. In situ labeling with monochlorobimane, used as a competitive compound for conjugation reactions with GSH, confirmed that AOC and MOC are conjugated in Arabidopsis cells. Reverse transcription- PCR established the expression profile of glutathione S- transferases ( GSTs) and nitroreductases enzymes. Genes selected for this study were AtGSTF2, AtGSTU1, AtGSTU24, and two isoforms of 12- oxophytodienoate reductase ( OPR1 and OPR2). The five transcripts tested were induced by all treatments, but RDX resulted in low induction. The mRNA level of AtGSTU24 showed substantial increase for all chemicals ( 23- fold induction for AOC, 18- fold for MOC, 5- fold for RDX, and 40- fold for TNT). It appears that GSTs are also involved in the conjugation reactions with metabolites of TNT, and to a lesser extent with RDX. Results indicate that OPR2 is involved in plant metabolism of TNT ( 11- fold induction), and in oxidative stress when exposed to AOC ( 7- fold), MOC ( 9- fold), and RDX ( 2- fold). This study comprises gene expression analysis of Arabidopsis exposed to RDX and AOC, which are considered significant environmental contaminants, and demonstrates the importance of microscopy methods for phytoremediation investigations.