Eric C. H. Chen

Ancient eudicot hexaploidy meets ancestral eurosid gene order

BackgroundA hexaploidization event over 125 Mya underlies the evolutionary lineage of the majority of flowering plants, including very many species of agricultural importance. Half of these belong to the rosid subgrouping, containing severals whose genome sequences have been published. Although most duplicate and triplicate genes have been lost in all descendants, clear traces of the original chromosome triples can be discerned, their internal contiguity highly conserved in some genomes and very fragmented in others. To understand the particular evolutionary patterns of plant genomes, there is a need to systematically survey the fate of the subgenomes of polyploids, including the retention of a small proportion of the duplicate and triplicate genes and the reconstruction of putative ancestral intermediates between the original hexaploid and modern species, in this case the ancestor of the eurosid clade.ResultsWe quantitatively trace the fate of gene triples originating in the hexaploidy across seven core eudicot flowering plants, and fit this to a two-stage model, pre- and post-radiation. We also measure the simultaneous dynamics of duplicate orthologous gene loss in three rosids, as influenced by biological functional class. We propose a new protocol for reconstructing ancestral gene order using only gene adjacency data from pairwise genomic analyses, based on repeating MAXIMUM WEIGHT MATCHING at two levels of resolution, an approach designed to transcend limitations on reconstructed contig size, while still avoiding the ambiguities of a multiplicity of solutions. Applied to three high-quality rosid genomes without subsequent polyploidy events, our automated procedure reconstructs the ancestor of the eurosid clade.ConclusionsThe gene loss analysis and the ancestor reconstruction present complementary assessments of post-hexaploidization evolution, the first at the level of individual gene families within and across sister genomes and the second at the chromosome level. Despite the loss of more than 95% of gene duplicates and triplicates, and despite major structural rearrangement, our reconstructed eurosid ancestor clearly identifies the three regions corresponding to each of the seven original chromosomes of the earlier pre-hexaploid ancestor. Functional analysis confirmed trends reported for more recent plant polyploidy events: genes involved with regulation and responses were retained in multiple copies, while genes involved with metabolic processes were lost.

The dynamics of functional classes of plant genes in rediploidized ancient polyploids

BackgroundTo understand the particular evolutionary patterns of plant genomes, there is a need to systematically survey the fate of the subgenomes of polyploids fixed as whole genome duplicates, including patterns of retention of duplicate, triplicate, etc. genes.ResultsWe measure the simultaneous dynamics of duplicate orthologous gene loss in rosids, in asterids, and in monocots, as influenced by biological functional class. This pan-angiosperm view confirms common tendencies and consistency through time for both ancient and more recent whole genome polyploidization events.ConclusionsThe gene loss analysis represents an assessment of post-polyploidization evolution, at the level of individual gene families within and across sister genomes. Functional analysis confirms universal trends previously reported for more recent plant polyploidy events: genes involved with regulation and responses were retained in multiple copies, while genes involved with metabolic and catalytic processes tended to lose copies, across all three groups of plants.

Gene expression and fractionation resistance

BackgroundPrevious work on whole genome doubling in plants established the importance of gene functional category in provoking or suppressing duplicate gene loss, or fractionation. Other studies, particularly in Paramecium have correlated levels of gene expression with vulnerability or resistance to duplicate loss.ResultsHere we analyze the simultaneous effect of function category and expression in two plant data sets, rosids and asterids.ConclusionWe demonstrate function category and expression level have independent effects, though expression does not play the dominant role it does in Paramecium.

The kernel of maximum agreement subtrees

A Maximum Agreement SubTree (MAST) is a largest subtree common to a set of trees and serves as a summary of common substructure in the trees. A single MAST can be misleading, however, since there can be an exponential number of MASTs, and two MASTs for the same tree set do not even necessarily share any leaves. In this paper we introduce the notion of the Kernel Agreement SubTree (KAST), which is the summary of the common substructure in all MASTs, and show that it can be calculated in polynomial time (for trees with bounded degree). Suppose the input trees represent competing hypotheses for a particular phylogeny. We show the utility of the KAST as a method to discern the common structure of confidence, and as a measure of how confident we are in a given tree set.

An ethnobotany of the Lukomir Highlanders of Bosnia & Herzegovina

BackgroundThis aim of this study is to report upon traditional knowledge and use of wild medicinal plants by the Highlanders of Lukomir, Bjelašnica, Bosnia and Herzegovina (B&H). The Highlanders are an indigenous community of approximately 60 transhumant pastoralist families who speak Bosnian (Bosanski) and inhabit a highly biodiverse region of Europe. This paper adds to the growing record of traditional use of wild plants within isolated communities in the Balkans.MethodsAn ethnobotanical study using consensus methodology was conducted in Lukomir in Bjelašnica’s mountains and canyons. Field work involved individual semi-structured interviews during which informants described plants, natural product remedies, and preparation methods on field trips, garden tours, while shepherding, or in settings of their choice. Plant use categories were ranked with informant consensus factor and incorporated into a phylogenetic tree. Plants cited were compared to other ethnobotanical surveys of the country.ResultsTwenty five people were interviewed, resulting in identification of 58 species (including two subspecies) from 35 families, which were cited in 307 medicinal, 40 food, and seven material use reports. Individual plant uses had an average consensus of five and a maximum consensus of 15 out of 25. There were a number of rare and endangered species used as poisons or medicine that are endemic to Flora Europaea and found in Lukomir. Ten species (including subspecies) cited in our research have not previously been reported in the systematic ethnobotanical surveys of medicinal plant use in B&H: (Elymus repens (L.) Gould, Euphorbia myrsinites L., Jovibarba hirta (L.) Opiz, Lilium bosniacum (Beck) Fritsch, Matricaria matricarioides (Less.) Porter ex Britton, Phyllitis scolopendrium (L.) Newman, Rubus saxatilis L., Silene uniflora Roth ssp. glareosa (Jord.) Chater & Walters, Silene uniflora Roth ssp. prostrata (Gaudin) Chater & Walters, Smyrnium perfoliatum L.). New uses not reported in any of the aforementioned systematic surveys were cited for a total of 28 species. Thirteen percent of medicinal plants cited are endemic: Helleborus odorus Waldst. et Kit., Gentiana lutea L., Lilium bosniacum (Beck) Fritsch, Silene uniflora Roth ssp. glareosa (Jord.) Chater & Walters., Silene uniflora Roth ssp. prostrata (Gaudin) Chater & Walters, Salvia officinalis L., Jovibarba hirta (L.) Opiz, and Satureja montana L.ConclusionsThese results report on the cohesive tradition of medicinal plant use among healers in Lukomir, Bosnia and Herzegovina. This work facilitates the community’s development by facilitating local and international conversations about their traditional medicine and sharing insight for conservation in one of Europe’s most diverse endemic floristic regions, stewarded by one of Europe’s last traditional Highland peoples.

The Kernel of Maximum Agreement Subtrees

A Maximum Agreement SubTree (MAST) is a largest subtree common to a set of trees and serves as a summary of common substructure in the trees. A single MAST can be misleading, however, since there can be an exponential number of MASTs, and two MASTs for the same tree set do not even necessarily share any leaves. In this paper, we introduce the notion of the Kernel Agreement SubTree (KAST), which is the summary of the common substructure in all MASTs, and show that it can be calculated in polynomial time (for trees with bounded degree). Suppose the input trees represent competing hypotheses for a particular phylogeny. We explore the utility of the KAST as a method to discern the common structure of confidence, and as a measure of how confident we are in a given tree set. We also show the trend of the KAST, as compared to other consensus methods, on the set of all trees visited during a Bayesian analysis of flatworm genomes.

Ways the Lukomir Highlanders of Bosnia and Herzegovina Treat Diabetes

In a Bosnia and Herzegovina (B&H) and Canada postwar development research collaboration, health authorities have identified type 2 diabetes (T2D) as a top health concern for the mountain community of Lukomir, B&H, located in the Bjelasnica of the Dinaric Alps. Lukomir lacks a health-care facility but is home to many traditional healers. A consensus ethnobotanical survey of plants was conducted with Lukomir Highlanders to identify plants used to treat diabetes and highly associated symptoms. Twenty-five people were interviewed, resulting in 41 species from 26 families. Physicians determined diabetes symptom association rank values, which were used to evaluate the syndromic importance value (SIV) function. SIVs were determined for families and species. Caryophyllaceae, Equisetaceae, Asteraceae, Ericaceae were the top-ranked antidiabetic families, and Matricaria matricarioides (Less.) Porter ex Britton, Silene spp., Achillea millefolium L., and Equisetum arvense L. were the top species. Five species were endemic, and Gentiana lutea L. is considered endangered. A cross-cultural comparison with the Cree of James Bay, Canada, revealed that Vaccinium was the only consensus genus. Extracts of Vaccinium myrtillus L. and V. vitis-idaea L. leaves were potent inhibitors of advanced glycation end products (AGEs) and demonstrated concentration-dependent inhibition, with a half maximal inhibitory concentration (IC50) ranging from 12.43 to 44.09 µg mL−1. High-performance liquid chromatography–mass spectrometry (HPLC–MS) confirmed the presence of (+)-catechin, chlorogenic acid, para coumaric acid, taxifolin, quercetin-3-O-galactoside, quercetin-3-O-glucoside, rutin, quercetin-3-O-rhamnoside, and myricetin. Rutin was absent in both species. This work provides a baseline study of available complimentary medicines for the T2D problem in the Lukomir community.

Ultra-low input transcriptomics reveal the spore functional content and phylogenetic affiliations of poorly studied arbuscular mycorrhizal fungi

Abstract Arbuscular mycorrhizal fungi (AMF) are a group of soil microorganisms that establish symbioses with the vast majority of land plants. To date, generation of AMF coding information has been limited to model genera that grow well axenically; Rhizoglomus and Gigaspora. Meanwhile, data on the functional gene repertoire of most AMF families is non-existent. Here, we provide primary large-scale transcriptome data from eight poorly studied AMF species (Acaulospora morrowiae, Diversispora versiforme, Scutellospora calospora, Racocetra castanea, Paraglomus brasilianum, Ambispora leptoticha, Claroideoglomus claroideum and Funneliformis mosseae) using ultra-low input ribonucleic acid (RNA)-seq approaches. Our analyses reveals that quiescent spores of many AMF species harbour a diverse functional diversity and solidify known evolutionary relationships within the group. Our findings demonstrate that RNA-seq data obtained from low-input RNA are reliable in comparison to conventional RNA-seq experiments. Thus, our methodology can potentially be used to deepen our understanding of fungal microbial function and phylogeny using minute amounts of RNA material.

Statistical analysis of fractionation resistance by functional category and expression

BackgroundThe current literature establishes the importance of gene functional category and expression in promoting or suppressing duplicate gene loss after whole genome doubling in plants, a process known as fractionation. Inspired by studies that have reported gene expression to be the dominating factor in preventing duplicate gene loss, we analyzed the relative effect of functional category and expression.MethodsWe use multivariate methods to study data sets on gene retention, function and expression in rosids and asterids to estimate effects and assess their interaction.ResultsOur results suggest that the effect on duplicate gene retention fractionation by functional category and expression are independent and have no statistical interaction.ConclusionIn plants, functional category is the more dominant factor in explaining duplicate gene loss.

Statistical analysis of fractionation resistance by functional category and expression level

In Table I, the effect size, measured in partial eta squared, supports the conjecture in the Chen et al. paper [5] that functional category carries more weight in determining retention rates than expression levels. Our results also suggest that the effect on duplicate gene retention fractionation by functional category and expression are independent and have no interaction. At least in plants, functional category appears to be the more dominant factor.