Professor and Head of Entomology
Plant Biology Affiliate
320 Morrill Hall MC-116
B.S., 1975, Yale University
Ph.D., 1980, Cornell University
IB109, Insects & People
IB444, Insect Ecology
IB445, Chemical Ecology
My current research addresses insect-plant co-evolution. One project addresses the effects of sunlight, particularly in the near ultraviolet range, on plant-insect interactions. Our investigations of insect resistance to plant toxins potentiated by ultraviolet light have recently demonstrated a high constitutive activity and lack of inducibility of anti-oxidant enzymes in Papilio polyxenes, an adapted specialist, in response to plant photo-toxins and the toxic oxyradicals they generate. Investigations of the genetic and physiological bases of resistance to UVB radiation in several plants, as well as the effects of UVB-induced alterations in allelochemical and nutritional content of foliage on specialist and generalist insects are being conducted with a view toward anticipating ecosystem impacts of enhanced UVB resulting from stratospheric ozone depletion.
Another project focuses on Depressaria pastinacella, the parsnip webworm, and Pastinaca sativa, the wild parsnip. We are using techniques of quantitative genetics to evaluate the likelihood of reciprocal genetic changes between interacting and ostensibly coevolving species. We have demonstrated that variation in furanocoumarin detoxification ability in parsnip webworms is partially under genetic control. We have also shown that wild parsnip plants that are not attacked in the field by parsnip webworms contain levels of furanocoumarins that are deleterious to webworm growth. We have also recently initiated an investigation into the ecological and evolutionary costs and benefits of web spinning by parsnip webworms. A third project revolves around the evolution of host specialization in swallowtail butterflies (Papilionidae). In collaboration with Mary Schuler, we are characterizing cytochrome P450 monooxygenases of these insects at biochemical and molecular levels. We have determined the quantitative genetic basis for variation among black swallowtail caterpillars in the ability to metabolize both linear and angular furanocoumarins. Variation in the relative ratios of angular to linear furanocoumarins suggest at least two furanocoumarin-metabolizing P450s exist, one of which may be specialized for angular furano-coumarins. We have succeeded in expressing two different alleles (CYP6B1.1 and CYP6B1.2). While minor differences exist between these alleles, both P450s are primarily restricted to metabolism of linear furanocoumarins. We have initiated studies in two other swallowtail species, paralleling those in the black swallowtail, to identify related P450s involved in furanocoumarin metabolism. We have also initiated studies aimed at characterizing furanocoumarin metabolites generated by one of the alleles.
Mao, W., Schuler, M.A., and Berenbaum, M.R. (2007). Cytochrome P450s in Papilio multicaudatus and the transition from oligophagy to polyphagy in the Papilionidae. Insect Mol Biol 16, 481-490.
Mao, W., Rupasinghe, S.G., Zangerl, A.R., Berenbaum, M.R., and Schuler, M.A. (2007). Allelic variation in the Depressaria pastinacella CYP6AB3 protein enhances metabolism of plant allelochemicals by altering a proximal surface residue and potential interactions with cytochrome P450 reductase. J Biol Chem 282, 10544-10552.
Zeng, R.S., Wen, Z., Niu, G., Schuler, M.A., and Berenbaum, M.R. (2007). Allelochemical induction of cytochrome P450 monooxygenases and amelioration of xenobiotic toxicity in Helicoverpa zea. J Chem Ecol 33, 449-461.