EAGER: Self-incompatibility in elderberry

在地球上大约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，也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交花粉和近亲花粉的方法。这些所谓的“自交不亲和系统”是最常见和最有效的阻止自花授粉和有利于异花授粉的机制之一。到目前为止，控制自交不亲和性的基因，即S基因，只在少数几个植物科的三个系统中被识别出来。该项目将确定接骨木中的S基因，接骨木是一种新兴的特种作物，富含抗氧化剂，用于葡萄酒、补充剂和其他产品。使用一种新的方法识别候选基因，并对可能与花粉识别和表达数据相关的DNA序列差异进行优先排序。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接受或拒绝何种类型的花粉来评估这些候选基因。其他实验将发现更多的S基因变异。用来鉴定接骨木S基因的方法可能被应用于额外的自交不亲和系统，从而进一步有助于理解植物多样性的维持。自交不亲和系统是植物控制交配的最重要的遗传机制之一。通常情况下，控制SI的S基因具有大量的等位变异，基本上，SI允许植物拒绝具有相似等位基因的潜在配偶的花粉。SI种是专性异交种，因为自交花粉总是与雌蕊具有相同的S等位基因。尽管S基因对植物多样性、进化和适应性具有极其重要的作用，但它们只在少数SI系统中被鉴定出来。在这里，总体目标是阐明一种新的SI系统，鉴定控制S的基因，并促进它们在科学和农业领域的应用。我们对接骨木的SI进行了鉴定，并利用RNAseq技术鉴定了候选的S基因。遗传学实验将确定这些候选S基因是否真的控制接骨木的SI。将对分离出不同S等位基因候选者的四个群体进行基因分型和测试授粉，以确定他们是否拒绝含有相同等位基因的植物的花粉。接骨木是一种具有潜在健康价值的新兴特产作物，将在接骨木和相关植物中识别额外的S等位基因，以支持接骨木改良社区。具体地说，该项目将允许育种者和生产者预测商业品种的杂交行为。与接骨木生产和改良有关的项目活动将通过演示文稿、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优势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.