RESEARCH

Ultraspiracle protein in the epidermis of Manduca during the pupal molt. The rosette of cells make a pit ("pockmark") in the pupal cuticle.

Insect molting and metamorphosis are regulated by two hormones, ecdysone which causes molting and juvenile hormone (JH) which allows larval molting but prevents metamorphosis. We use the epidermis of the tobacco hornworm, Manduca sexta, to study: 1) the molecular basis of this unique action of JH which allows the modulation of ongoing gene expression by ecdysteroid but prevents its activation of new genes, 2) the role of ecdysteroids in coordination of gene expression during a molt. Our attention is currently focused on the molting and metamorphic changes in both ecdysteroid receptors and the ecdysteroid-induced transcription factors and how these changes lead to alterations of expression of specific structural genes. In addition, we are studying the cellular and molecular action of JH on metamorphosis of both the abdominal integument and the nervous system in Drosophila. An emerging theme of the laboratory in conjunction with the laboratory of Professor James Truman is the evolution of metamorphosis. We are particularly interested in how the hormonal control of embryonic development in the ancestral insects may have driven the evolution of complete metamorphosis. Therefore, we are using diverse species such as firebrats, locusts, crickets, and snake flies in addition to Manduca and Drosophila to study the effects of JH on embryonic development and on the development of imaginal primordia.

Selected Publications:

Zhou, X. and Riddiford, L. M. (2002). Broad-Complex specifies pupal development and mediates the prevention of the pupal-adult transformation by juvenile hormone in Drosophila and Manduca. Development 129, 2259-2269.

Zhou, B. and Riddiford, L. M. (2001). Hormonal regulation and patterning of the Broad Complex in the epidermis and wing discs of the tobacco hornworm, Manduca sexta. Dev. Biol. 231, 125-137.

Hiruma, K. and Riddiford, L. M. (2001). Regulation of the transcription factors, MHR4 and b-FTZ-F1, by 20-hydroxyecdysone during a larval molt in the tobacco hornworm, Manduca sexta. Dev. Biol. 232, 265-274.

Langelan, R. E., Fisher, J. E., Hiruma, K., Palli, S. R., and Riddiford, L. M. (2000). Patterns of MHR3 expression in the epidermis during a larval molt of the tobacco hornworm, Manduca sexta. Dev. Biol. 227, 481-494.

Truman, James W. & Lynn M. Riddiford (1999). The Origins of Insect Metamorphosis. Nature 401:447-452.

Riddiford, L. M., Hiruma, K., Lan, Q. and Zhou, B. (1999). Regulation and role of nuclear hormone receptors during larval molting and metamorphosis of Lepidoptera. Amer. Zool. 39: 736-746.

Hiruma, K., Shinoda, T., Malone, F., and Riddiford, L. M. (1999). Juvenile hormone modulates 20-hydroxyecdysone-inducible ecdysone receptor and ultraspiracle gene expression in the tobacco hornworm, Manduca sexta. Dev., Genes, Evol. 209: 18-30.

Zhou, B., Hiruma, K., Shinoda, T., and Riddiford, L. M. (1998). Juvenile hormone prevents ecdysteroid-induced expression of Broad Complex RNAs in the epidermis of the tobacco hornworm, Manduca sexta. Dev. Biol. 203: 233-244.

Hegstrom, C. D., Riddiford, L. M., and Truman, J. W. (1998). Steroid and neuronal regulation of ecdysone receptor expression during metamorphosis of muscle in the moth, Manduca sexta. J. Neurosci. 18: 1786-1794.

Charles, J-P., Chihara, C., Nejad, S., and Riddiford, L. M. (1997). A cluster of cuticle protein genes of Drosophila melanogaster at 65A: Structure, sequence and evolution. Genetics 147: 1213-1224.