@article {2508, title = {Juvenile hormone is required to couple imaginal disc formation with nutrition in insects.}, journal = {Science }, volume = {312}, year = {2006}, month = {2006 Jun 2}, pages = {1385-8}, abstract = {

In starved larvae of the tobacco hornworm moth Manduca sexta, larval and imaginal tissues stop growing, the former because they lack nutrient-dependent signals but the latter because of suppression by juvenile hormone. Without juvenile hormone, imaginal discs form and grow despite severe starvation. This hormone inhibits the intrinsic signaling needed for disc morphogenesis and does so independently of ecdysteroid action. Starvation and juvenile hormone treatments allowed the separation of intrinsic and nutrient-dependent aspects of disc growth and showed that both aspects must occur during the early phases of disc morphogenesis to ensure normal growth leading to typical-sized adults.

}, keywords = {Animal Nutritional Physiological Phenomena, Animals, Ecdysteroids, Juvenile Hormones, Larva, Manduca, Morphogenesis, Pyridines}, issn = {1095-9203}, doi = {10.1126/science.1123652}, author = {Truman, J W and Hiruma, K and Allee, J P and Macwhinnie, S G B and Champlin, D T and Riddiford, L M} } @article {2453, title = {Ecdysteroid coordinates optic lobe neurogenesis via a nitric oxide signaling pathway.}, journal = {Development}, volume = {127}, year = {2000}, month = {2000 Aug 15}, pages = {3543-51}, abstract = {

Proliferation of neural precursors in the optic lobe of Manduca sexta is controlled by circulating steroids and by local production of nitric oxide (NO). Diaphorase staining, anti-NO synthase (NOS) immunocytochemistry and the NO-indicator, DAF-2, show that cells throughout the optic anlage contain NOS and produce NO. Signaling via NO inhibits proliferation in the anlage. When exposed to low levels of ecdysteroid, NO production is stimulated and proliferation ceases. When steroid levels are increased, NO production begins to decrease within 15 minutes independent of RNA or protein synthesis and cells rapidly resume proliferation. Resumption of proliferation is not due simply to the removal of NO repression though, but also requires an ecdysteroid stimulatory pathway. The consequence of these opposing pathways is a sharpening of the responsiveness to the steroid, thereby facilitating a tight coordination between development of the different elements of the adult visual system.

}, keywords = {Animals, Cell Division, Ecdysterone, Enzyme Inhibitors, Manduca, Neurons, NG-Nitroarginine Methyl Ester, Nitric Oxide, Nitric Oxide Synthase, Nitric Oxide Synthase Type I, Nonmammalian, Optic Lobe, Signal Transduction, Stem Cells}, issn = {0950-1991}, author = {Champlin, D T and Truman, J W} } @article {2457, title = {Ecdysteroids govern two phases of eye development during metamorphosis of the moth, Manduca sexta.}, journal = {Development}, volume = {125}, year = {1998}, month = {1998 Jun}, pages = {2009-18}, abstract = {

The eye primordium of the moth, Manduca sexta, shows two different developmental responses to ecdysteroids depending on the concentration to which it is exposed. Tonic exposure to moderate levels of 20-hydroxyecdysone (20E) or its precursor, ecdysone, are required for progression of the morphogenetic furrow across the primordium. Proliferation, cell-type specification and organization of immature ommatidial clusters occur in conjunction with furrow progression. These events can be reversibly started or stopped in cultured primordia simply by adjusting levels of ecdysteroid to be above or below a critical threshold concentration. In contrast, high levels of 20E cause maturation of the photoreceptors and the support cells that comprise the ommatidia. Ommatidial maturation normally occurs after the furrow has crossed the primordium, but premature exposure to high levels of 20E at any time causes precocious maturation. In such cases, the furrow arrests irreversibly and cells behind the furrow produce a well-formed, but miniature, eye. Precocious and catastrophic metamorphosis occurs throughout such animals, suggesting that ecdysteroids control development of other tissues in a manner similar to the eye. The threshold concentrations of 20E required for furrow progression versus ommatidial maturation differ by about 17-fold. This capacity to regulate distinct phases of development by different concentrations of a single hormone is probably achieved by differential sensitivity of target gene promoters to induction by the hormone-bound receptor(s).

}, keywords = {Amphibians, Animals, Biological, Ecdysone, Ecdysteroids, Ecdysterone, Eye, Gene Expression Regulation, Genes, Insect, Invertebrate, Larva, Manduca, Metamorphosis, Photoreceptor Cells, Pupa, Species Specificity, Steroids, Time Factors}, issn = {0950-1991}, author = {Champlin, D T and Truman, J W} }