一个给定物种中具有相同基因组的植物或动物却能发育成相差迥异的形式，它取决于环境条件，这个现象被称为“发育弹性”，该现象在自然界很普遍，但却很少从基因和分子角度对其进行描述。
图片来源： M. Herrmann
对线虫Pristionchus pacificus的一种新的捕食性特征（即嘴中额外的牙齿状结构的形成使得它们能够以真菌为食以及在种群密度过大时以其他线虫为食）所做的一项研究表明，它是由控制第四期幼虫（dauer larva）形成的同一内分泌体系调控的。（第四期幼虫状态相当于线虫的休眠期。）源自关键信号作用通道这种性状功能变化（称之为“co-options”或“exaptations”）的“弹性”可能有助于形态新颖性的形成。（生物谷Bioon.com）
生物谷推荐原文出处：
Nature doi:10.1038/nature09164
Co-option of the hormone-signalling module dafachronic acid–DAF-12 in nematode evolution
Gilberto Bento,Akira Ogawa& Ralf J. Sommer
Morphological novelties are lineage-specific traits that serve new functions1, 2. Developmental polyphenisms have been proposed to be facilitators of phenotypic evolution, but little is known about the interplay between the associated genetic and environmental factors3, 4, 5, 6, 7, 8, 9, 10, 11. Here, we study two alternative morphologies in the mouth of the nematode Pristionchus pacificus and the formation of teeth-like structures that are associated with bacteriovorous feeding and predatory behaviour on fungi and other worms12, 13, 14, 15, 16. These teeth-like denticles represent an evolutionary novelty, which is restricted to some members of the nematode family Diplogastridae but is absent from Caenorhabditis elegans and related nematodes14. We show that the mouth dimorphism is a polyphenism that is controlled by starvation and the co-option of an endocrine switch mechanism. Mutations in the nuclear hormone receptor DAF-12 and application of its ligand, the sterol hormone dafachronic acid, strongly influence this switch mechanism. The dafachronic acid–DAF-12 module has been shown to control the formation of arrested dauer larvae in both C. elegans and P. pacificus, as well as related life-history decisions in distantly related nematodes17, 18, 19, 20. The comparison of dauer formation and mouth morphology switch reveals that different thresholds of dafachronic acid signalling provide specificity. This study shows how hormonal signalling acts by coupling environmental change and genetic regulation and identifies dafachronic acid as a key hormone in nematode evolution.
