EAGER: Self-incompatibility in elderberry

地球上大约 352,000 种开花植物中，大约有一半拥有有利于异花授粉的机制。 这种繁殖策略对于产生和维持植物生存和适应所需的遗传多样性至关重要。 人类直接依赖植物多样性来改良作物，并间接依赖植物多样性来支持生态系统。 许多植物已经进化出识别和拒绝自体花粉和近亲花粉的方法。 这些所谓的“自交不亲和系统”是防止自花授粉和有利于异花授粉的最常见和最有效的机制之一。 迄今为止，控制自交不亲和性的基因（称为 S 基因）仅在少数植物科中运行的三个系统中被发现。 该项目将鉴定接骨木果中的 S 基因，接骨木果是一种富含抗氧化剂的新兴特种作物，用于葡萄酒、补充剂和其他产品。 使用一种优先考虑可能与花粉识别和表达数据相关的 DNA 序列差异的新方法来鉴定候选基因。 实验将通过测试特定 S 基因的存在或不存在是否可靠地预测哪些类型的花粉被接受或拒绝来评估这些候选基因。 其他实验将鉴定其他 S 基因变异。 用于识别接骨木浆果 S 基因的方法可应用于其他自交不亲和系统，从而进一步有助于了解植物多样性的维持。自交不亲和（SI）系统是植物用来控制交配的最重要的遗传机制之一。 通常，控制 SI 的基因（S 基因）具有许多等位基因变体，并且基本上，SI 允许植物拒绝来自具有相似等位基因的潜在配偶的花粉。 SI 物种是专性异交者，因为自花花粉始终具有与雌蕊相同的 S 等位基因。 尽管 S 基因对于植物多样性、进化和适应性非常重要，但仅在少数 SI 系统中被发现。 在这里，总体目标是阐明新的 SI 系统，识别控制 S 基因，并促进其在科学和农业界的使用。 我们对接骨木浆果 (Sambucus canadensis) 中的 SI 进行了表征，并使用 RNASeq 来鉴定候选 S 基因。 基因实验将确定这些候选 S 基因是否真正控制接骨木浆果的 SI。 将针对不同的 S 等位基因候选物分离的四个群体进行基因分型并进行授粉测试，以确定它们是否拒绝来自带有相同等位基因的植物的花粉。 接骨木浆果是一种新兴的特种作物，具有潜在的健康益处，我们将在接骨木浆果和相关植物中鉴定出更多的 S 等位基因，以支持接骨木浆果改良界。 具体来说，该项目将允许育种者和生产者预测商业品种的杂交行为。 与接骨木浆果生产和改良相关的项目活动将通过演示、视频和推广出版物广泛传播。 该项目还将通过提供实验室和实地植物科学方面的本科生研究培训来促进人力资源开发。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Roughly half of the approximately 352,000 species of flowering plants on earth possess mechanisms that favor cross-pollination. This reproductive strategy is crucial for generating and sustaining the genetic diversity that plants need to survive and adapt. Humans rely on plant diversity both directly, for crop improvement, and indirectly, for ecosystem support. Many plants have evolved ways to recognize and reject self-pollen and pollen from close relatives. These so-called “self-incompatibility systems” are among the most common and effective mechanisms that prevent self-pollination and favor cross-pollination. To date, the genes controlling self-incompatibility, called S-genes, have been identified in only three systems that operate in a handful of plant families. This project will identify S-genes in elderberry, an emerging specialty crop rich in antioxidants that is used in wine, supplements, and other products. Candidate genes were identified using a novel approach prioritizing DNA sequence differences that could relate to pollen recognition as well as expression data. Experiments will evaluate these candidate genes by testing whether the presence or absence of particular S-genes reliably predicts what types of pollen are accepted or rejected. Other experiments will identify additional S-gene variants. The approach used to identify elderberry S-genes may be applied to additional self-incompatibility systems and, thus, further contribute to understanding maintenance of plant diversity. Self-incompatibility (SI) systems are among the most important genetic mechanisms plants use to control mating. Typically, the genes controlling SI, S-genes, have numerous allelic variants, and, basically, SI allows plants to reject pollen from potential mates with similar alleles. SI species are obligate outcrossers because self-pollen always has the same S-alleles as the pistil. Notwithstanding their outsized importance for plant diversity, evolution and adaptability, S-genes have only been identified in a handful of SI systems. Here, the overall goals are to elucidate a new SI system, identify the controlling S-genes, and facilitate their use in the scientific and agriculture communities. We characterized SI in elderberry (Sambucus canadensis) and used RNASeq to identify candidate S-genes. Genetic experiments will ascertain whether these candidate S-genes truly control SI in elderberry. Four populations segregating for distinct S-allele candidates will be genotyped and test pollinated to determine whether they reject pollen from plants bearing the same alleles. Elderberry is an emerging specialty crop valued for potential health benefits, and additional S-alleles will be identified in elderberry and related plants to support the elderberry improvement community. Specifically, the project will allow breeders and producers to predict the crossing behavior of commercial varieties. Project activities related to elderberry production and improvement will be broadly disseminated via presentations, video, and Extension publications. The project also will contribute to human resource development by providing undergraduate research training in both laboratory- and field-based plant science.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.