DISSERTATION RESEARCH: Genetic basis of population level divergence in flower morph production induced by variable threshold environmental conditions

论文研究：可变阈值环境条件诱导的花形态生产群体水平差异的遗传基础

• 批准号: 1407148
• 负责人: John Willis
• 金额: $ 2.04万
• 依托单位: Duke University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-06-01 至 2018-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1407148&HistoricalAwards=false
• 关键词: DISSERTATION; RESEARCH; Genetic; basis; population

Unlike many animals, plants are sessile and unable to escape from unfavorable environments, so they must rely on developmental flexibility to cope with unpredictable changes in their environment. It is well known that plants accomplish this goal by responding to seasonal cues such as temperature and day length, and use these cues to initiate major life history transitions such as, from vegetative growth to flowering at the appropriate time of year. One of the most striking morphological switches is the shift between different flower forms on the same plant. Such species can shift from a flower that is relatively large and attracts pollinators that promotes mating between individual plants to a flower that is relatively much smaller, in part because it does not need to attract an animal to visit it to reproduce, because it is capable of mating with itself. This developmental shift is thought to be triggered when an environmental cue reaches a threshold. However, reproduction by each flower type comes with different consequences; small self-pollinating flowers produce inbred offspring that often suffer from a reduction in vigor compared to progeny produced from matings between individuals. The researchers will uncover genetic components of the pathways that result in populations exhibiting different thresholds for variable environmental responses using Mimulus douglasii, an emerging model plant that is capable of floral morph switching. They will examine the selective advantage of the loci responsible for floral morph shifts under natural field conditions. One prediction is that populations living in harsh environments with limited water and nutrients will be selected to lower their threshold and produce more self-pollinating flowers to save resources despite the potential reduction in vigor following inbreeding. The results of the proposed study could be used to enhance understanding of how agricultural species sense and respond to the environment, and could be used to modify crops to allow them to grow under novel environments. The ways in which plants can adjust to novel habitats will be shared with elementary, middle school, and high school students in the Durham area. Additionally the researchers will mentor Duke undergraduate students in the lab and the field. This study will (1) determine how a polyphenic environmental response threshold shift can occur, by examining the molecular genetic basis of the difference in threshold responsiveness and (2) assess the fitness consequences of these genetic loci under natural field conditions to understand why the shift in threshold occurred. To accomplish these goals two populations of M. douglasii that occur at the extremes of environmental responsiveness will be hybridized to form F2 individuals. First, a genetic mapping experiment will be done to find the genomic loci that correlate with a change in threshold for the production of particular floral morphs under long-day photoperiods. Mapped loci from this objective will form the basis for the second line of investigation: F3 hybrid individuals will be grown in two field common gardens. Correlates to fitness that will be measured include germination, flower number, flower type, and total seed production per plant. These fitness measurements will be correlated with the genomic loci mapped for floral morph production thresholds. To gain greater insights the researchers have the whole genome sequence data for M. douglasii, its sister species M. kelloggii, and an assembled and roughly annotated genome of a close relative, M. guttatus, where the latter two species exhibit only one flower morph. Collectively these data will aid in the understanding of the genetic basis of the role of threshold responses influencing the evolution of life history strategies.

与许多动物不同，植物是无懈可击的，无法逃脱不利的环境，因此它们必须依靠发育灵活性来应对环境中的不可预测的变化。 众所周知，植物通过响应季节性提示（例如温度和日长度）来实现这一目标，并使用这些提示来启动主要的生活历史过渡，例如从营养生长到一年中的适当时间开花。最引人注目的形态开关之一是同一植物上不同花形式之间的转移。这样的物种可以从相对较大的花朵转移，并吸引授粉媒介，从而促进单个植物之间的交配转向相对较小的花，部分原因是它不需要吸引动物来参观它来繁殖，因为它能够与自己交配。当环境提示达到阈值时，人们认为这种发展转变会触发。但是，每种花类型的繁殖都会带来不同的后果。与个体之间的套件相比，小型的自聚粉花产生的近交子源通常会减少活力。研究人员将使用Mimulus douglasii（一种能够具有花卉变形的新兴模型植物）来发现途径的遗传成分，这些途径的遗传成分会导致种群表现出不同的阈值。他们将检查负责在自然田间条件下导致花卉变形转移的基因座的选择性优势。一个预测是，将选择生活在有限的水和养分的恶劣环境中的人群，以降低其阈值并产生更多的自我授粉花，以节省资源，尽管近亲繁殖后有可能减少活力。拟议的研究的结果可用于增强对农业物种如何感知和对环境反应的理解，并可用于修饰农作物以使其在新的环境下生长。植物可以适应新型栖息地的方式将与达勒姆地区的小学，中学和高中生共享。此外，研究人员将指导实验室和领域的杜克大学本科生。 这项研究将（1）通过检查阈值反应性差异的分子遗传基础，确定如何发生多形环境响应阈值转移，以及（2）评估这些遗传基因座在自然场条件下的适应性后果，以了解为什么阈值发生转移。为了实现这些目标，在环境响应的极端情况下发生的两种douglasii种群将被杂交以形成F2个体。首先，将进行遗传学映射实验，以找到与在长期光周期下生产特定花卉形态的阈值变化相关的基因组基因座。该目标的映射基因座将构成第二道调查的基础：F3混合动力个体将在两个田间共同花园中种植。与适应性相关的相关性，包括发芽，花数，花型和每植物的总种子产量。这些适应性测量结果将与映射的花卉形态产生阈值的基因组基因座相关。为了获得更多的见解，研究人员拥有多格拉西菌（M. douglasii）的整个基因组序列数据，其姊妹物种M. kelloggii，以及一个近亲Guttatus M. guttatus的组装和大致注释的基因组，后两个物种仅表现出一种花变形。这些数据总的来说，这些数据将有助于理解影响生命历史策略演变的阈值反应作用的遗传基础。