DISSERTATION RESEARCH: Evolutionary Genetics of Flowering Time Variation in Helianthus

这项研究将调查一年生向日葵一个重要的发育和生殖特征--开花时间的遗传基础，以及它对环境提示--日长的反应。向日葵表现出日长反应的异常多样性，值得注意的是，日长反应的变化与驯化、自然种群的克隆变异和物种形成相吻合。在测量日长的发育途径中，基因和蛋白质调节的保守和新颖方面将被评估。开花时间基因表达和日长反应的关联将在1)驯化向日葵，2)沿纬向倾斜的向日葵野生种群，以及3)杂交物种与其两个亲本分类群之间进行测量。开花时间基因的向日葵拷贝是否位于已知的影响开花的基因组区域也将得到确定。基于这些结果，最好的候选基因将在几个驯化品系、美洲原住民地方品种和几个向日葵物种的野生种群中进行测序，以询问这些基因是否以及在哪些谱系中经历了正向选择。该项目将识别与驯化、适应和物种形成有关的基因，并将支持显著不稳定特征的进化遗传学与经过充分研究的发育途径联系起来，可能会为促进进化的途径结构或基因调控的特征提供新的见解。将为一个重要的农业物种开发用于检测关键开花时间基因序列和表达变化的诊断工具。此外，这些资源将有助于保护联邦列入名单的受威胁物种，该项目可能会确定对该物种的生存至关重要的遗传变异。

The research will investigate the genetic basis of an important developmental and reproductive trait, flowering time, and its responsiveness to an environmental cue, daylength, in annual sunflowers. Sunflowers exhibit an extraordinary diversity of daylength responses, and notably, changes in daylength response coincide with domestication, clinal variation in natural populations, and speciation. Conserved and novel aspects of gene and protein regulation in the developmental pathway that measures daylength will be assessed. Association of flowering time gene expression and daylength response will be measured in 1) domesticated sunflower, 2) wild populations of Helianthus annuus along a latitudinal cline, and 3) between a hybrid species and its two parent taxa. Whether sunflower copies of flowering time genes are located in genomic regions known to influence flowering will also be determined. Based on these results, the best candidate genes will be sequenced across several domesticated lines, Native American landraces, and wild populations of several sunflower species to ask whether and in which lineages these genes experienced positive selection. The project will identify genes involved in domestication, adaptation, and speciation, and connecting the evolutionary genetics underpinning a remarkably labile trait to a well-studied developmental pathway may provide new insights into the features of pathway architecture or gene regulation that facilitate evolution. Diagnostic tools for detecting sequence and expression variation of key flowering time genes will be developed for an important agricultural species. In addition, these resources will aid in conservation of a federally listed threatened species, and the project may identify genetic variation important for persistence of this species.