The last several years have seen revolutionary advances in DNA sequencing technologies with the advent of next-generation sequencing (NGS) techniques. NGS methods now allow millions of bases to be ...sequenced in one round, at a fraction of the cost relative to traditional Sanger sequencing. As costs and capabilities of these technologies continue to improve, we are only beginning to see the possibilities of NGS platforms, which are developing in parallel with online availability of a wide range of biological data sets and scientific publications and allowing us to address a variety of questions not possible before. As techniques and data sets continue to improve and grow, we are rapidly moving to the point where every organism, not just select “model organisms”, is open to the power of NGS. This volume presents a brief synopsis of NGS technologies and the development of exemplary applications of such methods in the fields of molecular marker development, hybridization and introgression, transcriptome investigations, phylogenetic and ecological studies, polyploid genetics, and applications for large genebank collections.
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•Five lineages are determined in the polyphyletic Pueraria based on three gene regions.•Ancestral state reconstruction of four diagnostic characters support segregate ...lineages.•Results support taxonomic revisions including reinstatement of Neustanthus.•Movement of Pueraria stricta to Teyleria is supported.•Two new genera are suggested: Haymondia and Toxicopueraria.
Several taxonomic and phylogenetic studies have hypothesized polyphyly within Pueraria DC., a genus comprising 19 species (24 with varieties) including the highly invasive Pueraria montana var. lobata (Kudzu) introduced to the U.S.A. about 150years ago. Previous efforts to investigate monophyly of the genus have been hampered by limited taxon sampling or a lack of comprehensive evolutionary context that would enable definitive taxonomic associations. This work presents a comprehensive phylogenetic investigation of Pueraria within the context of tribe Phaseoleae (Leguminosae). Polyphyly was found to be more extensive than previously thought, with five distinct lineages spread across the tribe and spanning over 25mya of divergence strongly supported by two chloroplast and one nuclear marker, AS2, presented here as a phylogenetic marker for the first time. Our phylogenies support taxonomic revisions to rectify polyphyly within Pueraria, including the resurrection of Neustanthus, moving one species to Teyleria, and the creation of two new genera, Haymondia and Toxicopueraria (taxonomic revisions published elsewhere).
Capsaicinoids are compounds synthesized exclusively in the genus Capsicum and are responsible for the burning sensation experienced when consuming hot pepper fruits. To date, only one gene, AT3, a ...member of the BAHD family of acyltransferases, is currently known to have a measurable quantitative effect on capsaicinoid biosynthesis. Multiple AT3 paralogs exist in the Capsicum genome, but their evolutionary relationships have not been characterized well. Recessive alleles at this locus result in absence of capsaicinoids in pepper fruit. To explore the evolution of AT3 in Capsicum and the Solanaceae, we sequenced this gene from diverse Capsicum genotypes and species, along with a number of representative solanaceous taxa. Our results revealed that the coding region of AT3 is highly conserved throughout the family. Further, we uncovered a tandem duplication that predates the diversification of the Solanaceae taxa sampled in this study. This pair of tandem duplications were designated AT3-1 and AT3-2. Sequence alignments showed that the AT3-2 locus, a pseudogene, retains regions of amino acid conservation relative to AT3-1. Gene tree estimation demonstrated that AT3-1 and AT3-2 form well supported, distinct clades. In C. rhomboideum, a non-pungent basal Capsicum species, we describe a recombination event between AT3-1 and AT3-2 that modified the putative active site of AT3-1, also resulting in a frame-shift mutation in the second exon. Our data suggest that duplication of the original AT3 representative, in combination with divergence and pseudogene degeneration, may account for the patterns of sequence divergence and punctuated amino acid conservation observed in this study. Further, an early rearrangement in C. rhomboidium could account for the absence of pungency in this Capsicum species.
Fabaceae are the third largest angiosperm family, with 765 genera and ∼19 500 species. They are important both economically and ecologically, and global Fabaceae crops are intensively studied in part ...for their nitrogen-fixing ability. However, resolution of the intrasubfamilial Fabaceae phylogeny and divergence times has remained elusive, precluding a reconstruction of the evolutionary history of symbiotic nitrogen fixation in Fabaceae. Here, we report a highly resolved phylogeny using >1500 nuclear genes from newly sequenced transcriptomes and genomes of 391 species, along with other datasets, for a total of 463 legumes spanning all 6 subfamilies and 333 of 765 genera. The subfamilies are maximally supported as monophyletic. The clade comprising subfamilies Cercidoideae and Detarioideae is sister to the remaining legumes, and Duparquetioideae and Dialioideae are successive sisters to the clade of Papilionoideae and Caesalpinioideae. Molecular clock estimation revealed an early radiation of subfamilies near the K/Pg boundary, marked by mass extinction, and subsequent divergence of most tribe-level clades within ∼15 million years. Phylogenomic analyses of thousands of gene families support 28 proposed putative whole-genome duplication/whole-genome triplication events across Fabaceae, including those at the ancestors of Fabaceae and five of the subfamilies, and further analyses supported the Fabaceae ancestral polyploidy. The evolution of rhizobial nitrogen-fixing nodulation in Fabaceae was probed by ancestral character reconstruction and phylogenetic analyses of related gene families and the results support the hypotheses of one or two switch(es) to rhizobial nodulation followed by multiple losses. Collectively, these results provide a foundation for further morphological and functional evolutionary analyses across Fabaceae.
Legumes are one of the most species-rich and important plant families. Analyses of thousands of nuclear genes revolved relationships among Fabaceae lineages, provide estimated divergence times, and support numerous polyploidization events. Sequence comparison and molecular evolution of gene families that contain known genes for root nodulation for symbiont nitrogen fixation support hypotheses for switch(es) to rhizobial nodulation in the early history of Fabaceae. The polyploidizations and functional innovation in nitrogen-fixing rhizobial nodulation may have promoted the species richness of legumes.
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•Mulberries (Morus) are one of the most economically and ecologically important plant groups.•The systematics of Morus is challenging due to its widespread distribution and ...hybridization.•The phylogeny of Morus especially for the Asian species is fully resolved using single copy nuclear genes.•There are strong phylogenetic relationships discordance of Morus.•The discordances could be explained by both hybridization/introgression and ILS.
Mulberries (genus Morus), belonging to the order Rosales, family Moraceae, are important woody plants due to their economic values in sericulture, as well as for nutritional benefits and medicinal values. However, the taxonomy and phylogeny of Morus, especially for the Asian species, remains challenging due to its wide geographical distribution, morphological plasticity, and interspecific hybridization. To better understand the evolutionary history of Morus, we combined plastomes and a large-scale nuclear gene analyses to investigate their phylogenetic relationships. We assembled the plastomes and screened 211 single-copy nuclear genes from 13 Morus species and related taxa. The plastomes of Morus species were relatively conserved in terms of genome size, gene content, synteny, IR boundary and codon usage. Using nuclear data, our results elucidated identical topologies based on coalescent and concatenation methods. The genus Morus was supported as monophyletic, with M. notabilis as the first diverging lineage and the two North American Morus species, M. microphylla and M. rubra, as sister to the other Asian species. In the Asian Morus species, interspecific relationships were completely resolved. However, cyto-nuclear discordances and gene tree-species tree conflicts were detected in the phylogenies of Morus, with multiple evidences supporting hybridization/introgression as the main cause of discordances between nuclear and plastid phylogenies, while gene tree-species tree conflicts were mainly caused by ILS.
Polyploidy is a widespread speciation mechanism, particularly in plants. Estimating the time of origin of polyploid species is important for understanding issues such as gene loss and changes in ...regulation and expression among homoeologous copies that coexist in a single genome owing to polyploidy. Polyploid species can originate in various ways; the effects of mode of origin, genetic system, and sampling on estimates of the age of polyploid origin using distances between alleles of polyploids and their diploid progenitors, or between homoeologous loci in a polyploid genome, are explored. Even in the simplest cases, simulations confirm that different loci are expected to give very different estimates of the date of origin. The time of polyploid origin is at least as old as the time estimated from comparison of an allele sampled from the polyploid with the most closely related allele in the diploid progenitor. The polyploidy literature often does not make clear the longstanding observation that the divergence of homoeologous copies in an allopolyploid tracks the divergence of diploid species, not the origin of the polyploid. Estimating the date of origin of a polyploid is difficult, and in some circumstances impossible. Skepticism about dates of polyploid origins is clearly warranted.
Two groups independently and seemingly simultaneously published the new combination of Pediomelum pariense, the Paria River breadroot. Both names were published in the second-quarter issues of ...separate journals in 1986. Same issue dates have led to confusion over which name takes precedence and is thus accepted. However, one issue was delayed in printing. Evidence is provided herein for acceptance of Pediomelum pariense (S.L. Welsh & N.D. Atwood) J.W. Grimes over Pediomelum pariense (S.L. Welsh & N.D. Atwood) S.L. Welsh & N.D. Atwood.
As a first step in innate immunity, pattern recognition receptors (PRRs) recognize the distinct pathogen and herbivore-associated molecular patterns and mediate activation of immune responses, but ...specific steps in the evolution of new PRR sensing functions are not well understood. We employed comparative genomic and functional analyses to define evolutionary events leading to the sensing of the herbivore-associated peptide inceptin (In11) by the PRR inceptin receptor (INR) in legume plant species. Existing and de novo genome assemblies revealed that the presence of a functional
gene corresponded with ability to respond to In11 across ~53 million years (my) of evolution. In11 recognition is unique to the clade of Phaseoloid legumes, and only a single clade of INR homologs from Phaseoloids was functional in a heterologous model. The syntenic loci of several non-Phaseoloid outgroup species nonetheless contain non-functional INR-like homologs, suggesting that an ancestral gene insertion event and diversification preceded the evolution of a specific INR receptor function ~28 my ago. Chimeric and ancestrally reconstructed receptors indicated that 16 amino acid differences in the C1 leucine-rich repeat domain and C2 intervening motif mediate gain of In11 recognition. Thus, high PRR diversity was likely followed by a small number of mutations to expand innate immune recognition to a novel peptide elicitor. Analysis of INR evolution provides a model for functional diversification of other germline-encoded PRRs.
The medicinal legume Mucuna pruriens (L.) DC. has attracted attention worldwide as a source of the anti-Parkinson's drug L-Dopa. It is also a popular green manure cover crop that offers many ...agronomic benefits including high protein content, nitrogen fixation and soil nutrients. The plant currently lacks genomic resources and there is limited knowledge on gene expression, metabolic pathways, and genetics of secondary metabolite production. Here, we present transcriptomic resources for M. pruriens, including a de novo transcriptome assembly and annotation, as well as differential transcript expression analyses between root, leaf, and pod tissues. We also develop microsatellite markers and analyze genetic diversity and population structure within a set of Indian germplasm accessions.
One-hundred ninety-one million two hundred thirty-three thousand two hundred forty-two bp cleaned reads were assembled into 67,561 transcripts with mean length of 626 bp and N50 of 987 bp. Assembled sequences were annotated using BLASTX against public databases with over 80% of transcripts annotated. We identified 7,493 simple sequence repeat (SSR) motifs, including 787 polymorphic repeats between the parents of a mapping population. 134 SSRs from expressed sequenced tags (ESTs) were screened against 23 M. pruriens accessions from India, with 52 EST-SSRs retained after quality control. Population structure analysis using a Bayesian framework implemented in fastSTRUCTURE showed nearly similar groupings as with distance-based (neighbor-joining) and principal component analyses, with most of the accessions clustering per geographical origins. Pair-wise comparison of transcript expression in leaves, roots and pods identified 4,387 differentially expressed transcripts with the highest number occurring between roots and leaves. Differentially expressed transcripts were enriched with transcription factors and transcripts annotated as belonging to secondary metabolite pathways.
The M. pruriens transcriptomic resources generated in this study provide foundational resources for gene discovery and development of molecular markers. Polymorphic SSRs identified can be used for genetic diversity, marker-trait analyses, and development of functional markers for crop improvement. The results of differential expression studies can be used to investigate genes involved in L-Dopa synthesis and other key metabolic pathways in M. pruriens.
Horizontal gene transfer (HGT) involves the nonsexual transmission of genetic material across species boundaries. Although often detected in prokaryotes, examples of HGT involving animals are ...relatively rare, and any evolutionary advantage conferred to the recipient is typically obscure. We identified a gene (HhMAN1) from the coffee berry borer beetle, Hypothenemus hampei, a devastating pest of coffee, which shows clear evidence of HGT from bacteria. HhMAN1 encodes a mannanase, representing a class of glycosyl hydrolases that has not previously been reported in insects. Recombinant HhMAN1 protein hydrolyzes coffee berry galactomannan, the major storage polysaccharide in this species and the presumed food of H. hampei. HhMAN1 was found to be widespread in a broad biogeographic survey of H. hampei accessions, indicating that the HGT event occurred before radiation of the insect from West Africa to Asia and South America. However, the gene was not detected in the closely related species H. obscurus (the tropical nut borer or "false berry borer"), which does not colonize coffee beans. Thus, HGT of HhMAN1 from bacteria represents a likely adaptation to a specific ecological niche and may have been promoted by intensive agricultural practices.
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