Stieper Bradley C, Kupershtok Mania, Driscoll Michael V, Shingleton Alexander W
Department of Zoology, Michigan State University, East Lansing, Michigan 48824, USA.
Dev Biol. 2008 Sep 1;321(1):18-26. doi: 10.1016/j.ydbio.2008.05.556. Epub 2008 Jun 9.
The regulation of body size in animals involves mechanisms that terminate growth. In holometabolous insects growth ends at the onset of metamorphosis and is contingent on their reaching a critical size in the final larval instar. Despite the importance of critical size in regulating final body size, the developmental mechanisms regulating critical size are poorly understood. Here we demonstrate that the developing adult organs, called imaginal discs, are a regulator of critical size in larval Drosophila. We show that damage to, or slow growth of, the imaginal discs is sufficient to retard metamorphosis both by increasing critical size and extending the period between attainment of critical size and metamorphosis. Nevertheless, larvae with damaged and slow growing discs metamorphose at the same size as wild-type larvae. In contrast, complete removal of all imaginal tissue has no effect on critical size. These data indicate that both attainment of critical size and the timely onset of metamorphosis are regulated by the imaginal discs in Drosophila, and suggest that the termination of growth is coordinated among growing tissues to ensure that all organs attain a characteristic final size.
动物体型的调节涉及终止生长的机制。在全变态昆虫中，生长在变态开始时结束，并且取决于它们在最后一龄幼虫期达到临界大小。尽管临界大小在调节最终体型方面很重要，但调节临界大小的发育机制却知之甚少。在这里，我们证明发育中的成虫器官，即成虫盘，是幼虫果蝇临界大小的调节因子。我们表明，成虫盘的损伤或生长缓慢足以通过增加临界大小和延长达到临界大小与变态之间的时间来延迟变态。然而，成虫盘受损且生长缓慢的幼虫与野生型幼虫在相同大小下发生变态。相比之下，完全去除所有成虫组织对临界大小没有影响。这些数据表明，在果蝇中，临界大小的达到和变态的适时开始均由成虫盘调节，这表明生长组织之间生长的终止是协调的，以确保所有器官达到特征性的最终大小。
