Induction of Hydrolases by Allelochemicals and Host Plants in Fall Armyworm (Lepidoptera: Noctuidae) Larvae

Enzymes Involved in the Metabolism of Plant Allelochemicals

“…Sulfoxidation of phorate with fall armyworm larval midgut microsomes (Yu, 1985) showed that cytochrome P-450 catalyzes this reaction which produced phorate sulfoxide only, although phoratoxon, the P=O analog, was produced concurrently:…”

“…This reaction is catalyzed to a large extent by the FAD-monooxygenase in mouse liver microsomes (Tynes and Hodgson, 1985) but by cytochrome P-450 in microsomes from fall armyworm tissues (Yu, 1985), because metabolite formation was inhibited by piperonyl butoxide and carbon monoxide in the insect microsomes. This complete investigation of the metabolism of a given compound depends on the availability of pure, putative metabolite standards and/or on access to highresolution analytical instruments.…”

“…The insecticide phorate readily undergoes sulfoxidation catalyzed by FAD-monooxygenase from mammalian liver. There are no indications that this enzyme is involved in phorate sulfoxidation in midgut microsomes from the generalist feeder, the fall armyworm (Yu, 1985;section 2.3.3.). It may be of interest to search for this enzyme in insect herbivores that specialize to feed on plants with sulfur-containig allelochemicals.…”

“…Much less is known about the subcellular distribution and specificity of epoxide hydrolases in arthropod tissues, although both trans and cis epoxides are hydrolyzed in cytosolic and microsomal fractions Ottea and Hammock, unpubl.). A microsomal enzyme was purified from midguts of the southern armyworm (Mullin and Wilkinson, 1980) and occurs in many other insects including the blow fly, Calliphora erythrocephala Meigen (Diptera: Calliphoridae), the house fly (Brooks et al, 1970); the fruit fly (Baars, 1980), the mealworm (Brooks, 1973), the flour beetle, Tribolium .castaneum (Herbst) (Coleoptera: Tenebrionidae) (Cohen, 1981), the Madagascar cockroach (Slade et al, 1975), the American cockroach (Nelson and Matsumura, 1973), the fall armyworm Yu and Hsu, 1985), the orange tortrix and its ectoparasite, Oncophanes americanus (Weed) (Hymenoptera: Braconidae) , the honey bee, Apis mellifera L. (Hymenoptera: Apidae) (Yu et al, 1984), and in addition in 33 other insect species Mullin, Chapter 5 in this text). It also occurs in the twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), and the predatory mite Amblyseius fallacis (Garman) (Acari: Phytoseiidae) .…”

“…This is particularly important in studies of induction (see section 2.6.) because the different forms can respond differently to anyone inducer (Brattsten, 1979b, Yu, 1985Yu, Chapter 4 …”