基因復(fù)制為演化上的新功能提供一個重要模板，盡管這些新功能是在基因復(fù)制之前還是之后出現(xiàn)的仍是一個激烈爭論的話題,。很多基因是在它們積累有害突變時從基因組中消失的,，但其中一些通過分割它們的先祖功能或增添新功能逃過這一命運,。基因復(fù)制產(chǎn)物的一個有趣,、但尚未證實的命運是,，分開的基因版本中先祖功能有所改進，推動這種改進的是正選擇,。David Des Marais 和Mark Rausher發(fā)現(xiàn),，這一過程發(fā)生在一個為植物花青素通道中一個關(guān)鍵酶編碼的基因中，而且他們提出,，這一過程比以前所認為的更普遍,。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature 454, 762-765 (7 August 2008) | doi:10.1038/nature07092
Escape from adaptive conflict after duplication in an anthocyanin pathway gene
David L. Des Marais & Mark D. Rausher
Department of Biology and University Program in Genetics and Genomics, Box 90338, Duke University, Durham, North Carolina 27708-0338, USA
Gene duplications have been recognized as an important source of evolutionary innovation and adaptation since at least Haldane1, and their varying fates may partly explain the vast disparity in observed genome sizes2. The expected fates of most gene duplications involve primarily non-adaptive substitutions leading to either non-functionalization of one duplicate copy or subfunctionalization3, neither of which yields novel function. A significant evolutionary problem is thus elucidating the mechanisms of adaptive evolutionary change leading to evolutionary novelty. Currently, the most widely recognized adaptive process involving gene duplication is neo-functionalization (NEO-F), in which one copy undergoes directional selection to perform a novel function after duplication4. An alternative, but understudied, adaptive fate that has been proposed is escape from adaptive conflict (EAC), in which a single-copy gene is selected to perform a novel function while maintaining its ancestral function5, 6. This gene is constrained from improving either novel or ancestral function because of detrimental pleiotropic effects on the other function. After duplication, one copy is free to improve novel function, whereas the other is selected to improve ancestral function. Here we first present two criteria that can be used to distinguish NEO-F from EAC. Using both tests for positive selection and assays of enzyme function, we then demonstrate that adaptive evolutionary change in a duplicated gene of the anthocyanin biosynthetic pathway in morning glories (Ipomoea) is best interpreted as EAC. Finally, we argue that this phenomenon likely occurs more often than has been previously believed and may thus represent an important mechanism in generating evolutionary novelty.
