Evolutionary genetics of flower color in lochroma (Solanaceae)

描述(由申请人提供)：识别适应性表型变化背后的遗传变化是进化生物学中的一个基本挑战。虽然作图方法对于检测基因组中影响性状变异的区域很有用，但在DNA序列水平上精确定位具体的变化仍然是困难的，除非该区域内的候选基因是已知的。这个项目使用候选基因的方法来鉴定番茄属茄科植物洛色玛在花色适应性转变过程中所涉及的遗传变化。花色是研究适应遗传基础的理想性状，因为它具有明确的适应意义，而且色素生物合成途径在遗传水平上具有很好的特征，并且在开花植物中高度保守。色泽植物间的颜色差异很大程度上是由于花青素的差异，花青素是类黄酮类的一种。这项拟议的研究将研究花青素途径中的遗传变化，该途径负责一枝黄花从紫色花到白色花的进化，以及花青素途径从紫花到红花的进化。结合对该途径的详细了解和研究物种中存在哪些色素的知识，可以对哪些花青素基因参与颜色转换做出强有力的预测。候选花青素基因与颜色差异的关联将通过(1)检查红色、白色和紫色物种间杂交中候选基因与花色表型的共分离，(2)克隆显示共分离的候选基因以在体外测试它们的功能，以及(3)使用表达研究来检查可能的调控差异，来评估候选花青素基因与颜色差异的关联。这些结果将有助于解决有关适应过程中涉及的基因变化的数量、位置和类型的基本问题。 此外，这项研究可以作为研究生化途径演变的模型，而生化途径反过来又对人类健康具有广泛的影响，从基因治疗到改进的药物靶向。此外，类黄酮(包括花青素)具有众所周知的抗氧化活性，这似乎有助于预防心脏病和癌症等慢性疾病。因此，更好地了解遗传变化如何改变类黄酮途径中的酶作用，增加了我们改进作物物种的潜力。

DESCRIPTION (provided by applicant): Identifying the genetic changes underlying adaptive phenotypic change is a fundamental challenge in evolutionary biology. While mapping approaches have been useful for detecting regions of the genome affecting trait variation, pinpointing the specific changes responsible at the DNA sequence level remains difficult, unless candidate genes within the region are known. This project uses a candidate gene approach to identify the genetic changes involved in adaptive transitions in flower color in lochroma, a genus in the tomato family, Solanaceae. Flower color is an ideal trait for studying the genetic basis of adaptation because it has clear adaptive significance and because the pigment biosynthetic pathways are well- characterized at the genetic level and highly conserved across flowering plants. Color differences among lochroma species are largely due to differences in anthocyanin pigments, a class of flavonoids. The proposed research will investigate the genetic changes in the anthocyanin pathway responsible for the evolutionary transition from purple to white flowers in I. loxense and from purple to red flowers in I. gesnerioides. Combining the detailed understanding of the pathway and knowledge of which pigments are present in the study species, strong predictions can be made about which anthocyanin genes were involved in the color transitions. The association of candidate anthocyanin genes and color differences will be assessed by (1) examining the cosegregation of candidate genes with flower color phenotypes in interspecific crosses between red, white, and purple species, (2) cloning candidate genes showing cosegregation to test their functionality in vitro, and (3) using expression studies to examine possible differences in regulation. The results will help to address basic questions regarding the number, location and types of genetic changes involved in the process of adaptation. Furthermore, this research may serve as a model for studying the evolution of biochemical pathways, which in turn, has broad implications for human health, from gene therapy to improved drug targeting. In addition, flavonoids (including anthocyanins) have well-known antioxidant activity, which appears to aid in preventing chronic diseases, such as heart disease and cancer. Thus, a better understanding of how genetic changes alter enzyme action in the flavonoid pathway adds to our potential for improving crop species.