RESEARCH-PGR: Investigating how internal and external cues coordinate floral organ development and the consequences for plant reproduction

被子植物的非凡多样性得益于它们的花，花促进了异交。异交保持遗传变异，是杂种种子生产的必要条件。然而，自花授粉和异花授粉的结合往往促进了作物生产。因此，植物育种者培育优先自花或异花授粉的植物的能力是非常有用的，但目前仅限于少数作物。两种相关的作物，生菜和向日葵，有非常相似的花解剖结构。尽管有这些相似之处，莴苣完全是自花授粉，而向日葵则依靠昆虫异花授粉。以生菜和向日葵为模型，一个多元化的研究团队（加州大学戴维斯分校：PI Harmer；加州大学伯克利分校：co-PI Blackman；爱荷华州立大学：co-PI Barb）研究了内部和外部因素如何相互作用，以产生生菜和向日葵的这些不同的繁殖策略。具体来说，研究人员使用基因组学、生理学和定量遗传学方法来更好地了解花发育后期的精确时间如何促进自花授粉或异花授粉。更好地了解这些过程的调控可能会导致新的方法来修改作物物种的自花授粉和异花授粉的频率，为育种者提供重要的新工具。考虑到未来气候的预期挑战以及野生和人工传粉媒介种群数量的下降，更好地了解植物交配策略及其受环境因素调节的特征是未来农艺改进和全球粮食安全的关键。拟议的研究还为下一代科学家提供跨学科培训，以便在高度综合研究的时代茁壮成长。原雄性，即一朵花先雄后雌的情况，是一种促进许多植物物种异交的繁殖策略，包括栽培向日葵。初步数据表明，雌雄同体是由生物钟和环境共同调节的。莴苣几乎完全自花授粉，小花形态与栽培向日葵相似，但雄花和雌花同时发生。这两种作物，向日葵和莴苣将被用作模型来定义环境和内部线索如何指导花器官生长以促进异交或自花授粉。比较转录组学研究用于确定控制后期花发育时间的途径。该团队使用定量基因组研究来揭示影响小花成熟的遗传变异的潜在结构，并辨别其对自花授粉和异花授粉的影响。利用野外和传粉者笼研究来评估异交与自交生殖策略中花发育（开花）时间相对于其他花性状的重要性。这些研究突出了在非最佳传粉者活动下提高产量的目标，并可能促进对传粉者更具吸引力的自交系的发展，从而可能为杂交种子生产者节省大量成本。高中生、本科生和社区志愿者在教室、实验室、野外和加州大学植物园为基于发现的研究做出贡献。本科实习生是从连接STEM领域中代表性不足的群体与研究人员的项目中招募的。这些努力也为项目支持的博士后学者和研究生提供了良好的教学机会。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The extraordinary diversity of angiosperms is facilitated by their flowers, which promote outcrossing. Outcrossing maintains genetic variation and is essential for hybrid seed production. Crop production however is often facilitated by a combination of self- and cross-pollination. Thus, the ability of plant breeders to generate plants that preferentially self- or cross-pollinate is extremely useful, but currently limited to a small number of crops. Two related crops, lettuce and sunflower, have very similar floral anatomy. Despite these similarities, lettuce is exclusively self-pollinating, while sunflower depends upon cross-pollination by insects. Using lettuce and sunflowers as models, a diverse team of researcher (UC Davis: PI Harmer; UC Berkeley: co-PI Blackman; Iowa State: co-PI Barb) investigate how internal and external factors interact to generate these distinct reproductive strategies in lettuce and sunflower. Specifically, the investigators use genomic, physiological, and quantitative genetic approaches to better understand how the precise timing of late stage floral development promotes self- or cross-pollination. A better understanding of the regulation of these processes is likely to lead to new approaches to modify the frequency of self- and cross-pollination in crop species, providing important new tools for breeders. Given the anticipated challenges of future climates and observed declines in both wild and managed pollinator populations, a better understanding of the traits underlying plant mating strategies and their modulation by environmental factors is key to future agronomic improvements and global food security. The proposed research also provides interdisciplinary training for the next generation of scientists to thrive in an era of highly integrative research. Protandry, the condition in which a single flower is first male and then female, is a reproductive strategy that promotes out-crossing in many plant species including cultivated sunflower. Preliminary data has shown that protandry is regulated both by the circadian clock and the environment. In lettuce, which is almost entirely self-pollinating, floret morphology is similar to cultivated sunflower, but the male and female phases occur simultaneously. These two crops, sunflower and lettuce will be used as models to define how environmental and internal cues direct floral organ growth to promote out-crossing or self-pollination. Comparative transcriptomic studies are used to identify pathways controlling the timing of late-stage floral development. The team uses quantitative genomic studies to uncover the underlying architecture of the genetic variation that affects floret maturation and discern its impact on self- and cross-pollination. Open field and pollinator cage studies are used to assess the importance of the timing of late floral development (anthesis) relative to other floral traits in the reproductive strategies of out-crossing versus selfing. These studies highlight targets for improving yield under suboptimal pollinator activity and may facilitate development of inbred lines that are more attractive to pollinators, potentially leading to substantial cost savings by hybrid seed producers. High school students, undergraduates, and community volunteers contribute to discovery-based research in the classroom, lab, field, and at the UC Botanical Garden. Undergraduate interns are recruited from programs that connect underrepresented groups in STEM fields with researchers. These efforts also provide excellent teaching opportunities for postdoctoral scholars and graduate students supported by the project.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.