Callery E M, Elinson R P
Department of Anatomy and Cell Biology and Department of Zoology, University of Toronto, Toronto, Ontario, Canada M5S 3G5.
Proc Natl Acad Sci U S A. 2000 Mar 14;97(6):2615-20. doi: 10.1073/pnas.050501097.
The direct developing anuran, Eleutherodactylus coqui, lacks a tadpole, hatching as a tiny frog. We investigated the role of the metamorphic trigger, thyroid hormone (TH), in this unusual ontogeny. Expression patterns of the thyroid hormone receptors, TRalpha and TRbeta, were similar to those of indirect developers. TRbeta mRNA levels increased dramatically around the time of thyroid maturation, when remodeling events reminiscent of metamorphosis occur. Treatment with the goitrogen methimazole inhibited this remodeling, which was reinitiated on cotreatment with TH. Despite their radically altered ontogeny, direct developers still undergo a TH-dependent metamorphosis, which occurs before hatching. We propose a new model for the evolution of anuran direct development.
直接发育的无尾目动物,斑腿泛树蛙,没有蝌蚪阶段,孵化时即为小青蛙。我们研究了变态触发因子甲状腺激素(TH)在这种不寻常个体发育中的作用。甲状腺激素受体TRα和TRβ的表达模式与间接发育者相似。在甲状腺成熟前后,TRβ mRNA水平急剧增加,此时发生了类似于变态的重塑事件。用甲状腺肿剂甲巯咪唑处理可抑制这种重塑,在与TH联合处理时可重新启动。尽管它们的个体发育发生了根本性改变,但直接发育者仍会经历依赖于TH的变态,这种变态发生在孵化之前。我们提出了一个关于无尾目动物直接发育进化的新模型。