Influence of chemical treatments on glutathione S-transferases of maize with activity towards metolachlor and cinnamic acid.

The subcellular distribution of glutathione S-transferase (GST) activity extracted from shoots of 3-day-old etiolated seedlings of maize (Zea mays L., Northrup-King 9283 hybrid) and the induction of soluble and membrane-bound GST activity by the safener benoxacor, the herbicide metolachlor and their combination (CGA-180937) were investigated. GST activity extracted from maize shoots was detected in both cytosolic and microsomal fractions and utilized 1-chloro-2,4-dinitrobenzene (CDNB), metolachlor, and trans-cinnamic acid (CA) as substrates. Soluble GST activity extracted from maize shoots was greater than microsomal with CDNB or metolachlor as substrate. Membrane-bound GST activity was greater than soluble with cinnamic acid as substrate. Washing the microsomal preparations from maize shoots with Triton X-100 increased GST(CA) activity. Pretreatment with the safener benoxacor or a formulated combination of the herbicide metolachlor with benoxacor induced soluble GST(CDNB), GST(metolachlor) and GST(CA) activities in maize shoots. Benoxacor and CGA-180937 induced also membrane-bound GST(CDNB) and GST(CA) activities in maize shoots, but did not affect membrane-bound GST(metolachlor) activity. These results confirm that maize contains multiple GST isozymes that differ in their substrate specificity and inducibility by safeners or other chemicals.