Phylogenomics and diversification drivers of the Eastern Asian - Eastern North American disjunct Podophylloideae.

Evolutionary and biogeographic processes determine species richness patterns of vascular plants between Eastern Asia (EA) and Eastern North America (ENA). However, the strikingly higher species richness of EA relative to ENA remains poorly understood from this perspective. Here, we studied the relative importance of biogeographical, evolutionary and ecological factors underlying differences in species richness between EA and ENA in Podophylloideae (Berberidaceae, Ranunculales; in total 10 spp. in EA vs. 2 spp. in ENA). Based on large-scale transcriptome data, our phylogenomic analyses strongly supported Podophylloideae and its two multi-species genera, i.e. Dysosma (EA) and Diphylleia (EA/ENA), as monophyletic groups. Sinopodophyllum hexandrum (EA) was identified as sister to the remainder of Podophylloideae. Dysosma (7 spp.) was recovered as sister to Podophyllum peltatum (ENA), forming an EA-ENA disjunct pair with a strong bias of species diversity in the EA counterpart. Our biogeographic analyses support the 'out-of-Tibet' hypothesis, suggesting that Podophylloideae started to diversify in the Himalaya-Hengduan Mountains (Mid-Miocene) and migrated eastward (since the Late Miocene) into Central-eastern China, Japan, and ENA (only P. peltatum and Diphylleia cymosa). Overall, we conclude that the striking species diversity anomaly between EA and ENA in Podophylloideae may be explained by a combination of (1) a longer period of time available to accumulate species in EA; and (2) a greater diversification rate in EA, which might have been promoted by greater physiographic and environmental heterogeneity in this region.

Plastome phylogenomics of the early-diverging eudicot family Berberidaceae.

The relationships among the genera of the early-diverging eudicot family Berberidaceae have long been controversial. To resolve these relationships and to better understand plastome evolution within the family, we sequenced the complete plastome sequences of ten Berberidaceae genera, combined these with six existing plastomes for the family, and conducted a series of phylogenomic analyses on the resulting data set. Five of the newly sequenced plastomes were found to possess the typical angiosperm plastome complement of 79 protein-coding genes, 4 rRNA genes, and 30 tRNA genes. The infA gene was found to be pseudogenized in Bongardia, Diphylleia, Dysosma and Vancouveria; rps7 was found to be severely truncated in Diphylleia, Dysosma and Podophyllum; clpP was found to be highly divergent in Vancouveria; and a ∼19 kb inversion was detected in Bongardia. Maximum likelihood phylogenetic analyses of a 79-gene, 24-taxon data set including nearly all genera of Berberidaceae recovered four chromosome groups (x = 6, 7, 8, 10), resolved the x = 8 group as the sister to the x = 10 group, and supported the monophyly of the clade comprising x = 7, 8, 10. The generic relationships within each group were all resolved with high support. Based on gene presence within the Inverted Repeat (IR), a total of seven plastome IR types were identified within Berberidaceae. Biogeographical analysis indicated the origin and diversification of Berberidaceae has likely been strongly influenced by the distribution of its favored habitat: temperate forests.

Plastome organization, genome-based phylogeny and evolution of plastid genes in Podophylloideae (Berberidaceae).

Species of Podophylloideae (Berberidaceae, Ranunculales) are of great pharmacogenetic importance and represent the classic biogeographic disjunction between eastern Asia (EA; 10 ssp.) and eastern North America (ENA; 2 ssp.). However, previous molecular studies of this group suffered from low phylogenetic resolution and/or insufficient marker variability. This study is the first to report whole-plastome sequence data for all 12 species of Podophylloideae (14 individuals) and a close relative, Achlys triphylla. These 15 plastomes proved highly similar in overall size (156,240-157,370 bp), structure, gene order and content, also when compared to other Ranunculales, but also revealed some structural variations caused by the expansion or contraction of the inverted repeats (IRs) into or out of adjacent single-copy regions. Our phylogenomic analysis, based on 63 plastome-derived protein-coding genes (CDS), supported the monophyly of Podophylloideae and its two major genera (EA: Dysosma, EA/ENA: Diphylleia), with Podophyllum peltatum L. (ENA) being more closely related to Diphylleia than to the group's earliest diverging species, Sinopodophyllum hexandrum (EA). Furthermore, within this subfamily/dataset, matK was identified as the fastest evolving gene, which proved to be under positive selection especially in more recently derived, lower-elevation lineages of Dysosma, possibly reflecting an adaptive response to novel environmental (i.e. subtropical compared to higher-elevation/alpine) conditions. Finally, several highly variable noncoding regions were identified in the plastomes of Podophylloideae and Ranunculales. These highly variable loci should be the best choices for future phylogenetic, phylogeographic, and population-level genetic studies. Overall, our results demonstrate the power of plastid phylogenomics to improve phylogenetic resolution, and contribute to a better understanding of plastid gene evolution in Podophylloideae.

Conservation implications of the genetic diversity of Gymnospermium microrrhynchum in Korea.

Gymnospermium microrrhynchum (Berberidaceae) is an ephemeral perennial herb with a limited distributional range in the Baekdudaegan mountain areas of the Korean Peninsula, and is designated a rare plant by the Korean Forest Service. Information about its genetic variation and structure is important for developing successful conservation strategies. To investigate the genetic variation within and among seven G. microrrhynchum populations, random amplified polymorphic DNA data were obtained for 207 individuals. The populations exhibited relatively low genetic diversity: the percentage of polymorphic bands (PPB) ranged from 32.1 to 66.7% (mean = 51.4%) and Nei's gene diversity (HE) ranged from 0.116 to 0.248 (mean = 0.188). However, genetic diversity at the species level was relatively high (PPB = 98.7%, HE = 0.349). An analysis of molecular variance revealed high differentiation among populations (ΦST = 0.6818), but the low gene flow value (Nm = 0.117) suggests a low level of gene exchange occurs among populations. Principal coordinates analysis revealed that individuals were separated according to population. The high level of genetic differentiation and restricted gene flow among G. microrrhynchum populations, which resulted from their isolation in alpine areas after the Ice Age, indicates that it is essential to protect and manage all populations, rather than focus on specific populations, in order to maintain the genetic diversity of this species.

Genetic diversity and structure of the threatened species Sinopodophyllum hexandrum (Royle) Ying.

Sinopodophyllum hexandrum is an important medicinal plant that has been listed as an endangered species, making the conservation of its genetic diversity a priority. Therefore, the genetic diversity and population structure of S. hexandrum was investigated through inter-simple sequence repeat analysis of eight natural populations. Eleven selected primers generated 141 discernible fragments. The percentage of polymorphic bands was 37.59% at the species level, and 7.66-24.32% at the population level. Genetic diversity of S. hexandrum was low within populations (average HE = 0.0366), but higher at the species level (HE = 0.0963). Clear structure and high genetic differentiation were detected between populations using unweighted pair groups mean arithmetic and principle coordinate analysis. Clustering approaches clustered the eight sampled populations into three major groups, and AMOVA confirmed there to be significant variation between populations (63.27%). Genetic differentiation may have arisen through limited gene flow (Nm = 0.3317) in this species. Isolation by distance among populations was determined by comparing genetic distance versus geographical distance using the Mantel test. The results revealed no correlation between spatial pattern and geographic location. Given the low within-population genetic diversity, high differentiation among populations, and the increasing anthropogenic pressure on this species, in situ conservation measures, in addition to sampling and ex situ preservation, are recommended to preserve S. hexandrum populations and to retain their genetic diversity.

[Cloning,expression and functional identification of secoisolariciresinol dehydrogenase gene from Dysosma versipellis callus].

Secoisolariciresinol dehydrogenase (SDH) is a key enzyme involved in the biosynthetic pathway of podophyllotoxin.In this study, two SDH candidate genes,SO282 and SO1223, were cloned from callus of Dysosma versipellis by homology-based PCR and rapid amplification of cDNA end (RACE).The SDH candidate genes were expressed in Escherichia coli and the subsequent enzyme assay in vitro showed that recombinant SO282 had the SDH activity. These results pave the way to the follow-up investigation of the biosynthetic of podophyllotoxin.

Metabolome analysis of 20 taxonomically related benzylisoquinoline alkaloid-producing plants.

BACKGROUND: Recent progress toward the elucidation of benzylisoquinoline alkaloid (BIA) metabolism has focused on a small number of model plant species. Current understanding of BIA metabolism in plants such as opium poppy, which accumulates important pharmacological agents such as codeine and morphine, has relied on a combination of genomics and metabolomics to facilitate gene discovery. Metabolomics studies provide important insight into the primary biochemical networks underpinning specialized metabolism, and serve as a key resource for metabolic engineering, gene discovery, and elucidation of governing regulatory mechanisms. Beyond model plants, few broad-scope metabolomics reports are available for the vast number of plant species known to produce an estimated 2500 structurally diverse BIAs, many of which exhibit promising medicinal properties. RESULTS: We applied a multi-platform approach incorporating four different analytical methods to examine 20 non-model, BIA-accumulating plant species. Plants representing four families in the Ranunculales were chosen based on reported BIA content, taxonomic distribution and importance in modern/traditional medicine. One-dimensional (1)H NMR-based profiling quantified 91 metabolites and revealed significant species- and tissue-specific variation in sugar, amino acid and organic acid content. Mono- and disaccharide sugars were generally lower in roots and rhizomes compared with stems, and a variety of metabolites distinguished callus tissue from intact plant organs. Direct flow infusion tandem mass spectrometry provided a broad survey of 110 lipid derivatives including phosphatidylcholines and acylcarnitines, and high-performance liquid chromatography coupled with UV detection quantified 15 phenolic compounds including flavonoids, benzoic acid derivatives and hydroxycinnamic acids. Ultra-performance liquid chromatography coupled with high-resolution Fourier transform mass spectrometry generated extensive mass lists for all species, which were mined for metabolites putatively corresponding to BIAs. Different alkaloids profiles, including both ubiquitous and potentially rare compounds, were observed. CONCLUSIONS: Extensive metabolite profiling combining multiple analytical platforms enabled a more complete picture of overall metabolism occurring in selected plant species. This study represents the first time a metabolomics approach has been applied to most of these species, despite their importance in modern and traditional medicine. Coupled with genomics data, these metabolomics resources serve as a key resource for the investigation of BIA biosynthesis in non-model plant species.

Transcriptome analysis of 20 taxonomically related benzylisoquinoline alkaloid-producing plants.

BACKGROUND: Benzylisoquinoline alkaloids (BIAs) represent a diverse class of plant specialized metabolites sharing a common biosynthetic origin beginning with tyrosine. Many BIAs have potent pharmacological activities, and plants accumulating them boast long histories of use in traditional medicine and cultural practices. The decades-long focus on a select number of plant species as model systems has allowed near or full elucidation of major BIA pathways, including those of morphine, sanguinarine and berberine. However, this focus has created a dearth of knowledge surrounding non-model species, which also are known to accumulate a wide-range of BIAs but whose biosynthesis is thus far entirely unexplored. Further, these non-model species represent a rich source of catalyst diversity valuable to plant biochemists and emerging synthetic biology efforts. RESULTS: In order to access the genetic diversity of non-model plants accumulating BIAs, we selected 20 species representing 4 families within the Ranunculales. RNA extracted from each species was processed for analysis by both 1) Roche GS-FLX Titanium and 2) Illumina GA/HiSeq platforms, generating a total of 40 deep-sequencing transcriptome libraries. De novo assembly, annotation and subsequent full-length coding sequence (CDS) predictions indicated greater success for most species using the Illumina-based platform. Assembled data for each transcriptome were deposited into an established web-based BLAST portal ( www.phytometasyn.ca) to allow public access. Homology-based mining of libraries using BIA-biosynthetic enzymes as queries yielded ~850 gene candidates potentially involved in alkaloid biosynthesis. Expression analysis of these candidates was performed using inter-library FPKM normalization methods. These expression data provide a basis for the rational selection of gene candidates, and suggest possible metabolic bottlenecks within BIA metabolism. Phylogenetic analysis was performed for each of 15 different enzyme/protein groupings, highlighting many novel genes with potential involvement in the formation of one or more alkaloid types, including morphinan, aporphine, and phthalideisoquinoline alkaloids. Transcriptome resources were used to design and execute a case study of candidate N-methyltransferases (NMTs) from Glaucium flavum, which revealed predicted and novel enzyme activities. CONCLUSIONS: This study establishes an essential resource for the isolation and discovery of 1) functional homologues and 2) entirely novel catalysts within BIA metabolism. Functional analysis of G. flavum NMTs demonstrated the utility of this resource and underscored the importance of empirical determination of proposed enzymatic function. Publically accessible, fully annotated, BLAST-accessible transcriptomes were not previously available for most species included in this report, despite the rich repertoire of bioactive alkaloids found in these plants and their importance to traditional medicine. The results presented herein provide essential sequence information and inform experimental design for the continued elucidation of BIA metabolism.

Transcriptome sequencing of rhizome tissue of Sinopodophyllum hexandrum at two temperatures.

BACKGROUND: Sinopodophyllum hexandrum is an endangered medicinal herb, which is commonly present in elevations ranging between 2,400-4,500 m and is sensitive to temperature. Medicinal property of the species is attributed to the presence of podophyllotoxin in the rhizome tissue. The present work analyzed transcriptome of rhizome tissue of S. hexandrum exposed to 15°C and 25°C to understand the temperature mediated molecular responses including those associated with podophyllotoxin biosynthesis. RESULTS: Deep sequencing of transcriptome with an average coverage of 88.34X yielded 60,089 assembled transcript sequences representing 20,387 unique genes having homology to known genes. Fragments per kilobase of exon per million fragments mapped (FPKM) based expression analysis revealed genes related to growth and development were over-expressed at 15°C, whereas genes involved in stress response were over-expressed at 25°C. There was a decreasing trend of podophyllotoxin accumulation at 25°C; data was well supported by the expression of corresponding genes of the pathway. FPKM data was validated by quantitative real-time polymerase chain reaction data using a total of thirty four genes and a positive correlation between the two platforms of gene expression was obtained. Also, detailed analyses yielded cytochrome P450s, methyltransferases and glycosyltransferases which could be the potential candidate hitherto unidentified genes of podophyllotoxin biosynthesis pathway. CONCLUSIONS: The present work revealed temperature responsive transcriptome of S. hexandrum on Illumina platform. Data suggested expression of genes for growth and development and podophyllotoxin biosynthesis at 15°C, and prevalence of those associated with stress response at 25°C.

[Genetic diversity and genetic structure of endangered wild Sinopodophyllum emodi by start codon targeted polymorphism].

OBJECTIVE: Revealed the genetic diversity level and genetic structure characteristics in Sinopodophyllum emodi, a rare and endangered species in China. METHOD: We detected the genetic polymorphism within and among six wild populations (45 individuals) by the approach of Start Codon Targeted (SCoT) Polymorphism. The associated genetic parameters were calculated by POP-GENE1.31 and the relationship was constructed based on UPGMA method. RESULT: A total of 350 bands were scored by 27 primers and 284 bands of them were polymorphic. The average polymorphic bands of each primer were 10.52. At species level, there was a high level of genetic diversity among six populations (PPB = 79.27%, N(e) = 1.332 7, H = 0.210 9 and H(sp) = 0.328 6). At population level, the genetic diversity level was low (PPB = 10.48% (4.00% -23.71%), N(e) = 1.048 7 (1.020 7-1.103 7), H = 0.029 7 (0.012 9-0.063 1), H(pop) = 0.046 2 (0.019 9-0.098 6). The Nei's coefficient of genetic differentiation was 0.841 1, which was consistent with the Shannon's coefficient of genetic differentiation (0.849 4). Two calculated methods all showed that most of the genetic variation existed among populations. The gene flow (N(m) = 0.094 4) was less among populations, indicating that the degree of genetic differentiation was higher. Genetic similarity coefficient were changed from 0.570 8 to 0.978 7. By clustering analysis, the tested populations were divided into two classes and had a tendency that the same geographical origin or material of similar habitats clustered into one group. CONCLUSION: The genetic diversity of samples of S. emodi is high,which laid a certain foundation for effective protection and improvement of germplasm resources.

Transcriptome analysis reveals differentially expressed genes involved in somatic embryogenesis and podophyllotoxin biosynthesis of Sinopodophyllum hexandrum (Royle) T. S. Ying.

Sinopodophyllum hexandrum (Royle) T. S. Ying, an important source of podophyllotoxin (PTOX), has become a rare and endangered plant because of over-harvesting. Somatic embryogenesis (SE) is the main way of seedling rapid propagation and germplasm enhancement, but the regeneration of S. hexandrum has not been well established, and the PTOX biosynthesis abilities at different SE stages remain unclear. Therefore, it is extremely important to elucidate the SE mechanism of S. hexandrum and clarify the biosynthesis variation of PTOX. In this study, the transcriptomes of S. hexandrum at different SE stages were sequenced, the contents of PTOX and 4'-demethylepipodophyllotoxin were assayed, and the transcript expression patterns were validated by qRT-PCR. The results revealed that plant hormone (such as auxins, abscisic acid, zeatin, and gibberellins) related pathways were significantly enriched among different SE stages, indicating these plant hormones play important roles in SE of S. hexandrum; the expression levels of a series of PTOX biosynthesis related genes as well as PTOX and 4'-demethylepipodophyllotoxin contents were much higher in embryogenic callus stage than in the other stages, suggesting embryogenic callus stage has the best PTOX biosynthesis ability among different SE stages. This study will contribute to germplasm conservation and fast propagation of S. hexandrum, and facilitate the production of PTOX.

Plastid genome data provide new insights into the phylogeny and evolution of the genus Epimedium.

INTRODUCTION: Epimedium L., the largest herbaceous genus of Berberidaceae, is one of the most taxonomically difficult representatives. The classification and phylogenetic relationships within Epimedium are controversial and unresolved. OBJECTIVES: For the first time, we systematically studied the phylogeny and evolution of Epimedium based on plastid genome (plastome) data for better understanding this enigmatic genus. METHODS: We explored the molecular phylogeny, assessed the infrageneric classification, estimated the divergence times, and inferred the ancestral states for flower traits of Epimedium based on 45 plastomes from 32 species. RESULTS: The Epimedium plastome length ranged from 156,635 bp to 159,956 bp. Four types of plastome organization with different inverted repeat boundary changes were identified. Phylogenetic analysis revealed a strong support for the sister relationship of sect. Macroceras and sect. Diphyllon but did not provide a distinct route for petal evolution in sect. Diphyllon. Disharmony between phylogenetic relationships and traditional classification of sect. Diphyllon was observed. Results from divergence time analysis showed that Epimedium diverged in the early Pleistocene (~2.11 Ma, 95% HPD = 1.88-2.35 Ma). Ancestral character state reconstructions indicated transitions from long spur (large-flowered group) to other petal types (small-flowered group) in Epimedium. CONCLUSION: These findings provide new insights into the relationships among Epimedium species and pave the way for better elucidation of the classification and evolution of this genus.

Glacial survival east and west of the 'Mekong-Salween Divide' in the Himalaya-Hengduan Mountains region as revealed by AFLPs and cpDNA sequence variation in Sinopodophyllum hexandrum (Berberidaceae).

Molecular phylogeographic studies have recently begun to elucidate how plant species from the Qinghai-Tibetan Plateau (QTP) and adjacent regions responded to the Quaternary climatic oscillations. In this regard, however, far less attention has been paid to the southern and south-eastern declivities of the QTP, i.e. the Himalaya-Hengduan Mountains (HHM) region. Here, we report a survey of amplified fragment length polymorphisms (AFLPs) and chloroplast DNA (cpDNA) sequence variation in the HHM endemic Sinopodophyllum hexandrum, a highly selfing alpine perennial herb with mainly gravity-dispersed berries (105 individuals, 19 localities). We specifically aimed to test a vicariant evolutionary hypothesis across the 'Mekong-Salween Divide', a known biogeographic and phytogeographic boundary of north-to-south trending river valleys separating the East Himalayas and Hengduan Mts. Both cpDNA and AFLPs identified two divergent phylogroups largely congruent with these mountain ranges. There was no genetic depauperation in the more strongly glaciated East Himalayas (AFLPs: H(E)=0.031; cpDNA: h(S)=0.133) compared to the mainly ice-free Hengduan Mts. (AFLPs: H(E)=0.037; cpDNA: h(S)=0.082), while population differentiation was consistently higher in the former region (AFLPs: Φ(ST)=0.522 vs. 0.312; cpDNA: Φ(ST)=0.785 vs. 0.417). Our results suggest that East Himalayan and Hengduan populations of S. hexandrum were once fragmented, persisted in situ during glacials in both areas, and have not merged again, except for a major instance of inter-lineage chloroplast capture identified at the MSD boundary. Our coalescent time estimate for all cpDNA haplotypes (c. 0.37-0.48 mya), together with paleogeological evidence, strongly rejects paleo-drainage formation as a mechanism underlying allopatric fragmentation, whereas mountain glaciers following the ridges of the MSD during glacials (and possible interglacials) could have been responsible. This study thus indicates an important role for mountain glaciers in driving (incipient) allopatric speciation across the MSD in the HHM region by causing vicariant lineage divergence and acting as barriers to post-divergence gene flow.

Development and characterization of polymorphic microsatellite markers in Dysosma pleiantha (Berberidaceae).

PREMISE OF THE STUDY: The development of compound microsatellite markers was conducted in Dysosma pleiantha to investigate genetic diversity and population genetic structure of this threatened medicinal plant. METHODS AND RESULTS: Using the compound microsatellite marker technique, 14 microsatellite markers that were successfully amplified showed polymorphism when tested on 38 individuals from three populations in eastern China. Overall, the number of alleles per locus ranged from 2 to 14, with an average of 7.71 alleles per locus. CONCLUSIONS: These results indicate that these microsatellite markers are adequate for detecting and characterizing population genetic structure and genetic diversity in Dysosma pleiantha.

Did glacials and/or interglacials promote allopatric incipient speciation in East Asian temperate plants? Phylogeographic and coalescent analyses on refugial isolation and divergence in Dysosma versipellis.

To explore the evolutionary consequences of climate-induced fluctuations in presently fragmented temperate forest habitats in continental East Asia we investigated the phylogeography and demographic history of the temperate-deciduous forest endemic Dysosma versipellis from disjunct montane sites in Central-Southeast China. Based on a survey of chloroplast (cp) DNA sequence variation, our analyses show that this perennial herb consists of morphologically indistinguishable western and central/eastern cpDNA lineages. Coalescent analyses under the 'isolation with migration' (IM) model support an ancient (Mid-Pleistocene) divergence between these lineages, with the western lineage having persisted without significant population growth in a long-term refuge just east of the Tibetan (Qinghai-Xizang) Plateau. In contrast, for the central/eastern lineage, we found strong evidence for population expansion from a refuge located south of the middle and lower reaches of the Yangtze River, and likely coinciding with the last or penultimate interglacial, followed by considerable population isolation and divergence in situ over (at least) the latest glacial-interglacial cycle. In line with recent evidence from palaeomodeling of East Asian forest biomes, our results suggest that the same vicariance factor, i.e. climate-induced eco-geographic isolation through (a)biotic displacement of temperate-deciduous forested habitats, promoted the divergence of D. versipellis lineages and populations at different spatial-temporal scales and over glacial and interglacial periods. Thus, there is no evidence that populations of D. versipellis merged at lower elevations during the last glacial(s). As such, D. versipellis accords with the premise that Late Quaternary refugial isolation is likely to have enhanced allopatric (incipient) species formation of temperate plants in East Asia.

[Cloning and sequence analysis of full-length cDNA of secoisolariciresinol dehydrogenase of Dysosma versipellis].

OBJECTIVES: To obtain the full-length cDNA sequence of Secoisolariciresinol Dehydrogenase gene from Dysosma versipellis by RACE PCR,then investigate the character of Secoisolariciresinol Dehydrogenase gene. METHODS: The full-length cDNA sequence of Secoisolariciresinol Dehydrogenase gene was obtained by 3'-RACE and 5'-RACE from Dysosma versipellis. RESULTS: We first reported the full cDNA sequences of Secoisolariciresinol Dehydrogenase in Dysosma versipellis. The acquired gene was 991bp in full length, including 5' untranslated region of 42bp, 3' untranslated region of 112bp with Poly (A). The open reading frame (ORF) encoding 278 amino acid with molecular weight 29253.3 Daltons and isolectric point 6.328. The gene accession nucleotide sequence number in GeneBank was EU573789. Semi-quantitative RT-PCR analysis revealed that the Secoisolariciresinol Dehydrogenase gene was highly expressed in stem. Alignment of the amino acid sequence of Secoisolariciresinol Dehydrogenase indicated there may be some significant amino acid sequence difference among different species. CONCLUSION: Obtain the full-length cDNA sequence of Secoisolariciresinol Dehydrogenase gene from Dysosma versipellis.

Quaternary climate change drives allo-peripatric speciation and refugial divergence in the Dysosma versipellis-pleiantha complex from different forest types in China.

Subtropical China harbours the world's most diverse temperate flora, but little is known about the roles of geographical and eco-climatic factors underlying the region's exceptionally high levels of species diversity and endemism. Here we address this key question by investigating the spatio-temporal and ecological processes of divergence within the Dysosma versipellis-pleiantha species complex, endemic to subtropical China. Our cpDNA phylogeny showed that this monophyletic group of understory herbs is derived from a Late Pliocene ancestor of the Qinghai-Tibetan Plateau (QTP)/Southwest China. Genetic and ENM data in conjunction with niche differentiation analyses support that the early divergence of D. versipellis and D. pleiantha proceeded through allo-peripatric speciation, possibly triggered by Early Pleistocene climate change, while subsequent climate-induced cycles of range contractions/expansions enhanced the eco-geographical isolation of both taxa. Furthermore, modelling of population-genetic data indicated that major lineage divergences within D. versipellis likely resulted from long-term allopatric population isolation in multiple localized refugia over the last glacial/interglacial periods, and which in turn fostered endemic species formation (D. difformis, D. majoensis) from within D. versipellis in Southwest China. These findings point to an overriding role of Quaternary climate change in triggering essentially allopatric (incipient) speciation in this group of forest-restricted plant species in subtropical China.

The complete chloroplast genome of Sinopodophyllum hexandrum Ying (Berberidaceae).

The complete nucleotide sequence of the Sinopodophyllum hexandrum Ying chloroplast genome (cpDNA) was determined based on next-generation sequencing technologies in this study. The genome was 157 203 bp in length, containing a pair of inverted repeat (IRa and IRb) regions of 25 960 bp, which were separated by a large single-copy (LSC) region of 87 065 bp and a small single-copy (SSC) region of 18 218 bp, respectively. The cpDNA contained 148 genes, including 96 protein-coding genes, 8 ribosomal RNA genes, and 44 tRNA genes. In these genes, eight harbored a single intron, and two (ycf3 and clpP) contained a couple of introns. The cpDNA AT content of S. hexandrum cpDNA is 61.5%.

The complete chloroplast genome of Sinopodophyllum hexandrum (Berberidaceae).

The complete chloroplast (cp) genome of the Sinopodophyllum hexandrum (Berberidaceae) was determined in this study. The circular genome is 157,940 bp in size, and comprises a pair of inverted repeat (IR) regions of 26,077 bp each, a large single-copy (LSC) region of 86,460 bp and a small single-copy (SSC) region of 19,326 bp. The GC content of the whole cp genome was 38.5%. A total of 133 genes were identified, including 88 protein-coding genes, 37 tRNA genes and eight rRNA genes. The whole cp genome consists of 114 unique genes, and 19 genes are duplicated in the IR regions. The phylogenetic analysis revealed that S. hexandrum is closely related to Nandina domestica within the family Berberidaceae.

Comparative transcriptome resources of two Dysosma species (Berberidaceae) and molecular evolution of the CYP719A gene in Podophylloideae.

Dysosma species (Berberidaceae, Podophylloideae) are of great medicinal pharmacogenetic importance and used as model systems to study the drivers and mechanisms of species diversification of temperate plants in East Asia. Recently, we have sequenced the transcriptome of the low-elevation D. versipellis. In this study, we sequenced the transcriptome of the high-elevation D. aurantiocaulis and used comparative genomic approaches to investigate the transcriptome evolution of the two species. We retrieved 53,929 unigenes from D. aurantiocaulis by de novo transcriptome assemblies using the Illumina HiSeq 2000 platform. Comparing the transcriptomes of both species, we identified 4593 orthologs. Estimation of Ka/Ks ratios for 3126 orthologs revealed that none had a Ka/Ks significantly greater than 1, whereas 1273 (Ka/Ks < 0.5, P < 0.05) were inferred to be under purifying selection. A total of 51 primer pairs were successfully designed from 461 EST-SSRs contained in 4593 orthologs. Marker validation assay revealed that 26 (51%) and 41 (80.4%) produced clear fragments with the expected sizes in all Podophylloideae species. Specifically, 19 different sequences of CYP719A were identified from PCR-amplified genomic DNA of all 12 species of Podophylloideae using primers designed from the assembled transcripts. The data further indicated that CYP719A was likely subject to strong selective constraints maintaining only one copy per genome. In Dysosma, there was relaxed purifying selection or more positive selection for high-elevation species. Overall, this study has generated a wealth of molecular resources potentially useful for pharmacogenetic and evolutionary studies in Dysosma and allied taxa.