Comparison of the ability to catabolize DIMBOA, a maize antibiotic, between Ostrinia furnacalis and Ostrinia scapulalis (Lepidoptera: Crambidae), with reference to their hybrids

Maize contains 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA), which functions as a feeding deterrent, growth inhibitor, and toxin against many herbivorous insects. The Asian corn borer Ostrinia furnacalis (Guen,e) (Lepidoptera: Crambidae) feeds on maize, whereas the sympatric congener O. scapulalis (Walker) does not. In laboratory assays, the addition of 0.3 mg/g of DIMBOA to an artificial diet markedly affected the survival of O. scapulalis larvae but not that of O. furnacalis larvae. Hybrids of O. furnacalis and O. scapulalis, crossed in both directions, tolerated DIMBOA to the same extent as O. furnacalis, indicating that this tolerance was conferred by a single or a few autosomal genes that are dominant to those of O. scapulalis. In vitro, DIMBOA was rapidly catabolized when incubated with the homogenate of the digestive tract of O. furnacalis in the presence of uridine diphosphate (UDP)-glucose. The UDP-glucose-dependent DIMBOA-catabolizing activities of the homogenate of the digestive tracts of O. scapulalis and hybrids correlated with their tolerance; low in O. scapulalis and high in the hybrids. These results reconfirmed that UDP-glucosyltransferase (UGT) or other UDP-dependent enzymes are involved in the catabolism of DIMBOA in O. furnacalis; however, consistent with our previous findings, DIMBOA-glucoside, the expected product of UGT, was not detected in the products of in vitro assays.