Genetic Change Associated with Flower-Color Adaptation in Morning

这个项目是先前发现的延伸，这些发现强烈表明牵牛花属植物Ipomoea Quamoclit的花色适应性进化伴随着部分花色苷色素途径的退化。这个项目的主要目标是(1)明确地确定这种途径退化是否发生在I.Quamoclit中，以及(2)确定这种退化的进化现象有多普遍。将通过使用体外酶分析和体内互补分析来评估途径退化，以确定途径中的单个基因是否保留其祖先功能。系统发育分析和祖先状态重建将被用来确定在色素沉着的适应性转变转变之后是否发生了一些功能丧失的替换，如果这些替换反映了路径退化，那么预计会发生这些替换。除了更详细地研究I.quamoclit和密切相关的红花物种外，我们还将评估月桂组的白花牵牛花和模式物种拟南芥中是否发生了花青素色素途径的退化，在拟南芥中，只产生蓝色而不是红色的花青素。进化生物学的一个一般原则是，特征的进化损失通常是永久性的。虽然许多研究都记录了这种模式，但对于为什么性格丧失是不可逆转的，我们知之甚少。这项研究的总体科学意义在于，它试图评估并提供机制上的理由，支持或反对不可逆转的假设，即不可逆性是由当前未使用的复杂字符的进化崩溃造成的。

This project is an extension of previous findings that strongly suggest that adaptive evolution of flower color in a species of morning glory, Ipomoea quamoclit, is accompanied by degeneration of part of the anthocyanin pigment pathway. The primary objectives of this project are (1) to determine definitively whether such pathway degeneration has occurred in I. quamoclit, and (2) to determine how general an evolutionary phenomenon such degeneration is. Pathway degeneration will be assessed by using in vitro enzyme assays and in vivo complementation assays to determine whether individual genes in the pathway retain their ancestral function. Phylogenetic analyses and ancestral state reconstruction will be used to determine whether some loss-of-function substitutions occurred after the adaptive transition shift in pigmentation, as would be expected if those substitutions reflect pathway degeneration. In addition to examining I. quamoclit and closely related red-flowered species in more detail, we will also assess whether anthocyanin pigment pathway degeneration has occurred in white-flowered morning glories in the Calonyction group, and in the model species Arabidopsis thaliana, in which only blue and not red anthocyanins are produced.A general principle in evolutionary biology is that evolutionary loss of characters is often permanent. While many investigations have documented this pattern, little is known about why character loss is irreversible. The general scientific importance of this research is that it seeks to evaluate, and provide mechanistic justification for or against, the hypothesis that irreversibility results from the evolutionary breakdown of complex characters that are not currently used.