TISSUE-SPECIFIC EXPRESSION OF GLUTATHIONE TRANSFERASE ISOZYMES IN FALL ARMYWORM LARVAE

Glutathione transferase (GST) isozymes were purified and isolated from larval midguts and fat bodies of the fall armyworm (Spodopera frugipe rda) using a three-step procedure involving ammonium sulfate fractiona tion, followed by affinity chromatography on a glutathione-agarose col umn and nondenaturing polyacrylamide gel electrophoresis. The midgut p ossessed five isozymes, namely, MG GST-1, MG GST-2, MG GST-3, MG GST-4 , and MG GST-5, all of which were heterodimers with subunit molecular weights of 26,700 to 30,000. The pI values ranged from 4.6 to 6.0 amon g these isozymes. No qualitative difference in isozyme composition was observed during larval development. The fat body contained three isoz ymes, namely, FB GST-1, FB GST-2, and FB GST-3, all of which were beli eved to be homodimers with subunit molecular weights of 20,100 to 29,0 00. The pI values ranged from 4.4 to 6.5 among these isozymes. Using i sozyme-specific antisera as probes, MG GST-2, MG GST-3, FB GST-2, and FB GST-3 were found to be immunologically related, possibly due to the ir sharing of some common subunits. MG GST-2 and MG GST-3 were also im munologically related to the GST from larval Malpighian tubules of fal l armyworm. Among the corn earworm, tobacco budworm, beer armyworm, an d cabbage looper, MG GST-3 (subunit) was immunologically related to GS Ts from all of these species except the cabbage looper, whereas MG GST -2 (subunit) was immunologically related only to the GST from the beet armyworm. (C) 1995 Academic Press, Inc.