Cloning and characterization of maize herbicide safener-induced cDNAs encoding subunits of glutathione S-transferase isoforms I, II and IV

Abstract

Several GSTs have been characterised in maize. GST I is a homodimer of 29 kDa subunits, GST II a hetrodimer of 27 kDa and 29 kDa subunits and GST IV a homodimer of 27 kDa subunits. We report the isolation and characterization of a herbicide-safener inducible cDNA clone, GST-27. Based on partial amino acid sequence, GST-27 encodes the 27 kDa subunit present in both glutathione S-transferase isoforms GST II and IV. Northern blotting was used to compare the expression patterns of GST-27 with that of GST-29. Transcripts corresponding to GST-27 were found to be constitutively expressed in RNA isolated from the root, but no expression was detected in RNA isolated from aerial parts of the plant. The application of herbicide safener caused a dramatic increase in the expression of GST-27 in all aerial plant parts tested. GST-29 was found to be constitutively expressed in RNA isolated from a number of maize tissues. The basal level of GST-29 expression showed a minimal increase upon herbicide safener treatment. Although a range of hormonal, environmental and physiological stimuli failed to elevate GST-27 levels, some increase in GST-27 mRNA was observed in the late stages of leaf senescence and after treatments resulting in phytotoxic effects.

Isolation and Characterization of GlutathioneS-Transferase Isozymes from Sorghum1

“…Acceptable and less acceptable amino acid substitutions are defined by the GCG software. Sequences from sorghum were compared with GSTs from sugarcane (Singhal et al, 1991), maize GST I, (Shah et al, 1986), maize GST III (Grove et al, 1988), maize GST IV (GST II, new nomenclature; Jepson et al, 1994;Dixon et al, 1997), wheat GST A1 (Dudler et al, 1991), Hyoscyamus muticus (Bilang et al, 1993), Arabidopsis pm239 (Bartling et al, 1993), tobacco parB (Takahashi and Nagata, 1992), Arabidopsis pm24 (Zhou and Goldsbrough, 1993), Silene cucubalus (Kutchan and Hochberger, 1992), and Arabidopsis ERD11 (Kiyosue et al, 1993).…”

Safeners recruit multiple signalling pathways for the orchestrated induction of the cellular xenobiotic detoxification machinery in Arabidopsis

“…ZmGSTL1) and a putative aldo-keto reductase (In2.2), respectively (Hershey & Stoner 1991;Jepson et al 1994). Both transcripts are strongly induced in maize roots and shoots after treatment with benzene sulfonamide safeners (Hershey & Stoner 1991).…”

Old Enzymes for a New Job (Herbicide Detoxification in Plants)

“…The first GSH conjugation shown to occur in plants was that of the herbicide atrazine in maize (Lamoureux et al, 1970). A number of plant GST isoenzymes, mainly from maize but also from other plants, have since been characterized and cloned (Irzyk and Fuerst, 1993;Jepson et al, 1994). The various GSTs differ in their regulation and display distinct but sometimes overlapping substrate specificities.…”

“…Evidente has been accumulating that safeners enhance herbicide metabolism through increased activities of Cyt P450, GSTs, and glucosyltransferases, and by raising glutathione levels (Farago et al, 1994). More recent investigations indicate that the families of GSTs and Cyt P450s comprise both constitutive as well as safener-inducible isoenzymes (Irzyk and Fuerst, 1993;Jepson et al, 1994;Potter et al, 1995). Regulation of GST has been shown to be exerted, at least in part, at the leve1 of mRNA abundance, and this is probably also the case in safener regulation of the other enzymes mentioned above.…”