MacWhinnie Steven G B, Allee J Paul, Nelson Charles A, Riddiford Lynn M, Truman James W, Champlin David T
Department of Biology, University of Southern Maine, 96 Falmouth Street, Portland, ME 04103-9300, USA.
Dev Biol. 2005 Sep 15;285(2):285-97. doi: 10.1016/j.ydbio.2005.06.021.
With the exception of the wing imaginal discs, the imaginal discs of Manduca sexta are not formed until early in the final larval instar. An early step in the development of these late-forming imaginal discs from the imaginal primordia appears to be an irreversible commitment to form pupal cuticle at the next molt. Similar to pupal commitment in other tissues at later stages, activation of broad expression is correlated with pupal commitment in the adult eye primordia. Feeding is required during the final larval instar for activation of broad expression in the eye primordia, and dietary sugar is the specific nutritional cue required. Dietary protein is also necessary during this time to initiate the proliferative program and growth of the eye imaginal disc. Although the hemolymph titer of juvenile hormone normally decreases to low levels early in the final larval instar, eye disc development begins even if the juvenile hormone titer is artificially maintained at high levels. Instead, creation of the late-forming imaginal discs in Manduca appears to be controlled by unidentified endocrine factors whose activation is regulated by the nutritional state of the animal.
除翅成虫盘外，烟草天蛾的成虫盘直到末龄幼虫早期才形成。这些由成虫原基发育而来的晚期形成的成虫盘，其发育的早期步骤似乎是对在下一次蜕皮时形成蛹表皮的不可逆承诺。与其他组织在后期的蛹期承诺类似，broad基因表达的激活与成虫眼原基中的蛹期承诺相关。在末龄幼虫期需要进食以激活眼原基中broad基因的表达，而膳食糖是所需的特定营养信号。在此期间，膳食蛋白质对于启动眼成虫盘的增殖程序和生长也是必需的。尽管保幼激素的血淋巴滴度通常在末龄幼虫早期降至低水平，但即使保幼激素滴度被人为维持在高水平，眼盘发育仍会开始。相反，烟草天蛾中晚期形成的成虫盘的形成似乎受未明确的内分泌因子控制，这些因子的激活受动物营养状态的调节。
