The cyclic hydroxamic acid, 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA), is the main secondary metabolite in maize and wheat [1]. DIMBOA presents in younger tissues of cereal plants mainly as glucoside, which is released by enzymatic hydrolysis after tissue injury [2]. DIMBOA is associated with resistance to herbivorous insects such as the European corn borer Ostrinia nubilalis [3], Asian corn borer Ostrinia furnacalis [4], Stalk corn borer Sesamia nonagrioides [5], and aphid Rhopalosiphum padi [6]. However, effects of DIMBOA on enzymatic systems, growth, and development of such insects are not well investigated.
DIMBOA influences on activity levels of nervous system enzymes in insects. Effect of DIMBOA on the activity of acetylcholinesterase (AChE), an important enzyme in normal functioning of the central nervous system in insects, was reported [4]. For example, AChE activity of Asian corn borer O. furnacalis larvae was decreased after DIMBOA consumed. The sensitivity of sensory organs may be altered by dietary DIMBOA, and O. furnacalis may refuse to continue to feed. This fact may be one possible physiological explanation for the antifeedant property of DIMBOA [4]. Besides that, AChE from aphid Rhopalosiphum padi and cholinesterases from other insects were inhibited by DIMBOA [6].
DIMBOA affects on activities of some detoxification enzymes such as esterase, glutathione transferase, and cytochrome P450 monooxygenase [4]. Esterase and glutathione transferase activities of S. nonagrioides [5], R. padi [7] were decreased by DIMBOA, whereas cytochrome P450 monooxygenase and glutathione S-transferase in larvae of O. furnacalis were induced to higher levels [4]. Moreover, the levels of activities of some enzymes (e.g. cytochrome b5, NADPH-cytochrome c reductase, NADH-cytochrome c reductase, NADH oxidase, and O-demethylase) implicated in a detoxification processes in the larval midgut of the European corn borer O. nubinalis were higher as increase of DIMBOA concentration [3].
DIMBOA influences on activities of some hydrolysis enzymes, such as proteases, lipase, and amylase which play important roles to growth and development of the insects [4,6,8]. DIMBOA inhibits the activity of elastase-like proteases in larvae of S. nonagrioides in short-term assays. In long-term assays, the relative growth rate and the efficiency conversion index were significantly reduced, and growth time required to complete two instars for the highest dose were consumed in the case with presence of DIMBOA [6]. DIMBOA had little effect on amylase and lipase activity [4].
In conclusion, DIMBOA affects on enzymatic systems, growth, and development of insects. Therefore, further biochemical and molecular biological research are needed to fully understand the relationships between DIMBOA and physiological adaptations of insects.
REFERENCES
[1]. Niemeyer, H. M., (1988). Hydroxamic acids (4-hydroxy-1,4-benzoxazin-3-ones), defence chemicals in Gramineae. Phytochem. 27: 3349-3358.
[2]. Niemeyer, H. M., (2009). Hydroxamic acids derived from 2-hydroxy-2H-1,4-benzoxazin-3(4H)-one: key defence chemicals of cereals. J. Agric. Food Chem. 57 (5): 1677-1696.
[3]. Feng, R., Houseman, J. G., Downe, A. E. R., Atkinson, J., Arnason, J. T., (1992). Effects of 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) and 6-methoxybenzoxazolinone (MBOA) on the detoxification processes in the larval midgut of the European corn borer. Pest. Biochem. Physiol. 44: 147-154.
[4]. Yan F., Xu C., Li S., Lin C. and Li J., (1995). Effects of DIMBOA on several enzymatic systems in Asian corn borer Ostrinia furnacalis (Guene´e). Journal of Chemical Ecology 21 (12): 2047-2056.
[5]. Ortego F., Ruı´z M., Castanera P., (1998). Effect of DIMBOA on Growth and Digestive Physiology of Sesamia nonagrioides (Lepidoptera: Noctuidae) Larvae. J. Insect Physiol. 44 (2): 95-101.
[6]. Cuevas, L.; Niemeyer, H. M., (1993). Effect of hydroxamic acids from cereals on aphid cholinesterases. Phytochemistry 34 (4): 983-985.
[7]. Mukanganyama S., Figueroa C.C., Hasler J.A., Niemeyer H.M., (2003). Effects of DIMBOA on detoxification enzymes of the aphid Rhopalosiphum padi (Homoptera: aphididae). Journal of Insect Physiology 49: 223-229.
[8]. Yan, F.; Liang, X.; Zhu, X., (1999). The role of DIMBOA on the feeding of Asian corn borer, Ostrinia furnacalis (Guene´e) (Lep., Pyralidae). J. Appl. Entomol. 123: 49-53.