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Exploring Angiosperms353: an open, community toolkit for collaborative phylogenomic research on flowering plantsThe unveiling of the angiosperm (flowering plant) tree of life over the past three decades has been one of the great success stories of modern plant biology. Flowering plants underpin most terrestrial biomes: they fix vast amounts of terrestrial carbon, in turn producing a substantial fraction of planetary oxygen, and drive major biogeochemical cycles. The bulk of human calories are derived either directly (crops) or indirectly (fodder) from angiosperms, as are many medicines, fuel, dyes, beverages, timber, fibers, and other materials. Countless indispensable and mundane items that impact human existence find their origins in flowering plants, and without them, life would be decidedly drearier—imagine a world without herbs, spices, or garden flowers, for example. In this context, the importance of a comprehensive understanding of the angiosperm tree of life cannot be overstated. The tree of life is the fundamental, biological roadmap to the evolution and properties of plants (e.g., Wong et al., 2020). For evolutionary biologists, phylogenies allow us to better understand the spectacular rise of the flowering plants to dominance over the past 140 million or so years (e.g., Lutzoni et al., 2018; Ramírez-Barahona et al., 2020). Information about angiosperm phylogenetic relationships also underpins modern angiosperm classification (e.g., APG IV, 2016), and helps us to better understand species origins and boundaries (e.g., Fazekas et al., 2009). Today, tree of life research is undergoing a renaissance due to the development of powerful, new phylogenomic methods (Dodsworth et al., 2019). In this special issue of the American Journal of Botany, together with a companion issue of Applications in Plant Sciences, we gather a set of papers that focus on a new, common phylogenomic toolkit, the Angiosperms353 probe set (Johnson et al., 2019), and illustrate its potential for evolutionary synthesis by promoting open collaboration across our community.
Exploring Angiosperms353: developing and applying a universal toolkit for flowering plant phylogenomicsSpecial Issue Introduction. Target enrichment represents a useful, cost-effective method for researchers working on the phylogenomics of non-model organisms (e.g., Cronn et al., 2012; Hale et al., 2020). The ability to sequence a customizable predefined genomic subset for several dozens or even hundreds of taxa allows in-depth analyses and the testing of phylogenetic hypotheses in ways that were not previously possible (reviewed in McKain et al., 2018). The most popular methods for targeted sequencing of genomic loci in phylogenomics include (long-)amplicon sequencing (Rothfels et al., 2017) and hybridization capture (Mandel et al., 2014; Weitemier et al., 2014). Targeted amplicon sequencing is based on single-fragment PCR amplification or by using multiplexing methods such as a microfluidic PCR-based amplification of multiple pre-selected genomic regions (e.g., Zhang and Ozdemir, 2009; Ho et al., 2014), which can then be pooled and sequenced. Massively parallel amplicon sequencing was first used in medical diagnostics (Turner et al., 2009) and was later applied to metazoan phylogenetics (Bybee et al., 2011; O’Neill et al., 2013). Microfluidic PCR and long-amplicon sequencing were subsequently applied in plant systematics (Uribe-Convers et al., 2014, 2016; Gostel et al., 2015). Amplicon-based methods can be time consuming as they require careful optimization and validation of primers. These methods are also susceptible to many of the common problems in PCR (such as nonspecific products, inability to amplify large loci in their entirety, or simply no products). Recently, amplicon approaches have been largely supplanted by hybridization-based targeted enrichment, which allows for relatively rapid probe design with reference to a few related transcriptomes or genomes, and allows simultaneous and efficient recovery of many hundreds of genes.