| 1. |
- Gao, Jie, et al.
(författare)
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Demography and speciation history of the homoploid hybrid pine Pinus densata on the Tibetan Plateau
- 2012
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Ingår i: Molecular Ecology. - : John Wiley & Sons. - 0962-1083 .- 1365-294X. ; 21:19, s. 4811-4827
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Tidskriftsartikel (refereegranskat)abstract
- Pinus densata is an ecologically successful homoploid hybrid that inhabits vast areas of heterogeneous terrain on the south-eastern Tibetan Plateau as a result of multiple waves of colonization. Its region of origin, route of colonization onto the plateau and the directions of introgression with its parental species have previously been defined, but little is known about the isolation and divergence history of its populations. In this study, we surveyed nucleotide polymorphism over eight nuclear loci in 19 representative populations of P. densata and its parental species. Using this information and coalescence simulations, we assessed the historical changes in its population size, gene flow and divergence in time and space. The results indicate a late Miocene origin for P. densata associated with the recent uplift of south-eastern Tibet. The subsequent differentiation between geographical regions of this species began in the late Pliocene and was induced by regional topographical changes and Pleistocene glaciations. The ancestral P. densata population had a large effective population size but the central and western populations were established by limited founders, suggesting that there were severe bottlenecks during the westward migration out of the ancestral hybrid zone. After separating from their ancestral populations, population expansion occurred in all geographical regions especially in the western range. Gene flow in P. densata was restricted to geographically neighbouring populations, resulting in significant differentiation between regional groups. The new information on the divergence and demographic history of P. densata reported herein enhances our understanding of its speciation process on the Tibetan Plateau.
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| 2. |
- Ren, Lin-Ling, et al.
(författare)
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Subcellular relocalization and positive selection play key Roles in the retention of duplicate genes of populus class III peroxidase family
- 2014
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Ingår i: The Plant Cell. - : Oxford University Press (OUP). - 1040-4651 .- 1532-298X. ; 26:6, s. 2404-2419
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Tidskriftsartikel (refereegranskat)abstract
- Gene duplication is the primary source of new genes and novel functions. Over the course of evolution, many duplicate genes lose their function and are eventually removed by deletion. However, some duplicates have persisted and evolved diverse functions. A particular challenge is to understand how this diversity arises and whether positive selection plays a role. In this study, we reconstructed the evolutionary history of the class III peroxidase (PRX) genes from the Populus trichocarpa genome. PRXs are plant-specific enzymes that play important roles in cell wall metabolism and in response to biotic and abiotic stresses. We found that two large tandem-arrayed clusters of PRXs evolved from an ancestral cell wall type PRX to vacuole type, followed by tandem duplications and subsequent functional specification. Substitution models identified seven positively selected sites in the vacuole PRXs. These positively selected sites showed significant effects on the biochemical functions of the enzymes. We also found that positive selection acts more frequently on residues adjacent to, rather than directly at, a critical active site of the enzyme, and on flexible regions rather than on rigid structural elements of the protein. Our study provides new insights into the adaptive molecular evolution of plant enzyme families.
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| 3. |
- Wang, Baosheng, 1983-, et al.
(författare)
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Colonization of the Tibetan Plateau by the homoploid hybrid pine Pinus densata
- 2011
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Ingår i: Molecular Ecology. - Leicester : Blackwell Scientific Publications. - 0962-1083 .- 1365-294X. ; 20:18, s. 3796-3811
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Tidskriftsartikel (refereegranskat)abstract
- Pinus densata is an intriguingly successful homoploid hybrid species that occupies vast areas of the southeastern Tibetan Plateau in which neither of its parental species are present, but the colonization processes involved are poorly understood. To shed light on how this species colonized and became established on the plateau, we surveyed paternally inherited chloroplast (cp) and maternally inherited mitochondrial (mt) DNA variation within and among 54 populations of P. densata and its putative parental species throughout their respective ranges. Strong spatial genetic structure of both cp and mtDNA were detected in P. densata populations. Mitotypes specific to P. densata were likely generated by complex recombination events. A putative ancestral hybrid zone in the northeastern periphery of P. densata was identified, and we propose that the species then colonized the plateau by migrating westwards. Along the colonization route, consecutive bottlenecks and surfing of rare alleles caused a significant reduction in genetic diversity and strong population differentiation. The direction and intensity of introgression from parental species varied among geographic regions. In western parts of its range, the species seems to have been isolated from seed and pollen flow from its parent species for a long time. The observed spatial distribution of genetic diversity in P. densata also appears to reflect the persistence of this species on the plateau during the last glaciation. Our results indicate that both ancient and contemporary population dynamics have contributed to the spatial distribution of genetic diversity in P. densata, which accordingly reflects its evolutionary history.
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| 4. |
- Wang, Baosheng, et al.
(författare)
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Extremely low nucleotide polymorphism in Pinus krempfii Lecomte, a unique flat needle pine endemic to Vietnam
- 2014
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 4:11, s. 2228-2238
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Tidskriftsartikel (refereegranskat)abstract
- Pinus krempfii Lecomte is a morphologically and ecologically unique pine, endemic to Vietnam. It is regarded as vulnerable species with distribution limited to just two provinces: Khanh Hoa and Lam Dong. Although a few phylogenetic studies have included this species, almost nothing is known about its genetic features. In particular, there are no studies addressing the levels and patterns of genetic variation in natural populations of P.krempfii. In this study, we sampled 57 individuals from six natural populations of P.krempfii and analyzed their sequence variation in ten nuclear gene regions (approximately 9kb) and 14 mitochondrial (mt) DNA regions (approximately 10kb). We also analyzed variation at seven chloroplast (cp) microsatellite (SSR) loci. We found very low haplotype and nucleotide diversity at nuclear loci compared with other pine species. Furthermore, all investigated populations were monomorphic across all mitochondrial DNA (mtDNA) regions included in our study, which are polymorphic in other pine species. Population differentiation at nuclear loci was low (5.2%) but significant. However, structure analysis of nuclear loci did not detect genetically differentiated groups of populations. Approximate Bayesian computation (ABC) using nuclear sequence data and mismatch distribution analysis for cpSSR loci suggested recent expansion of the species. The implications of these findings for the management and conservation of P.krempfii genetic resources were discussed.
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| 5. |
- Wang, Baosheng, 1983-
(författare)
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Hybridization and Evolution in the Genus Pinus
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Gene flow and hybridization are pervasive in nature, and can lead to different evolutionary outcomes. They can either accelerate divergence and promote speciation or reverse differentiation. The process of divergence and speciation are strongly influenced by both neutral and selective forces. Disentangling the interplay between these processes in natural systems is important for understanding the general importance of interspecific gene flow in generating novel biodiversity in plants. This thesis first examines the importance of introgressive hybridization in the evolution of the genus Pinus as a whole, and then focusing on specific pine species, investigates the role of geographical, environmental and demographical factors in driving divergence and adaptation.By examining the distribution of cytoplasmic DNA variation across the wide biogeographic range of the genus Pinus, I revealed historical introgression and mtDNA capture events in several groups of different pine species. This finding suggests that introgressive hybridization was common during past species’ range contractions and expansions and thus has played an important role in the evolution of the genus. To understand the cause and process of hybrid speciation, I focused on the significant case of hybrid speciation in Pinus densata. I established the hybridization, colonization and differentiation processes that defined the origin of this species. I found P. densata originated via multiple hybridization events in the late Miocene. The direction and intensity of introgression with two parental species varied among geographic regions of this species. During the colonization on Tibetan Plateau from the ancestral hybrid zone, consecutive bottlenecks and surfing of rare alleles caused a significant reduction in genetic diversity and strong population differentiation. Divergence within P. densata started from the late Pliocene onwards, induced by regional topographic changes and Pleistocene glaciations. To address the role of neutral and selective forces on genetic divergence, I examined the association of ecological and geographical distance with genetic distance in Pinus yunnanensis populations. I found both neutral and selective forces have contributed to population structure and differentiation in P. yunnanensis, but their relative contributions varied across the complex landscape. Finally, I evaluated genetic diversity in the Vietnamese endemic Pinus krempfii. I found extremely low genetic diversity in this species, which is explained by a small ancestral population, short-term population expansion and recent population decline and habitat fragmentation.These findings highlight the role of hybridization in generating novel genetic diversity and the different mechanisms driving divergence and adaptation in the genus Pinus.
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| 6. |
- Wang, Baosheng, 1983-, et al.
(författare)
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Impact of Geography and Climate on the Genetic Differentiation of the Subtropical Pine Pinus yunnanensis
- 2013
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Ingår i: PLOS ONE. - : plosone. - 1932-6203. ; 8:6, s. e67345-
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Tidskriftsartikel (refereegranskat)abstract
- Southwest China is a biodiversity hotspot characterized by complex topography, heterogeneous regional climates and rich flora. The processes and driving factors underlying this hotspot remain to be explicitly tested across taxa to gain a general understanding of the evolution of biodiversity and speciation in the region. In this study, we examined the role played by historically neutral processes, geography and environment in producing the current genetic diversity of the subtropical pine Pinus yunnanensis. We used genetic and ecological methods to investigate the patterns of genetic differentiation and ecological niche divergence across the distribution range of this species. We found both continuous genetic differentiation over the majority of its range, and discrete isolated local clusters. The discrete differentiation between two genetic groups in the west and east peripheries is consistent with niche divergence and geographical isolation of these groups. In the central area of the species' range, population structure was shaped mainly by neutral processes and geography rather than by ecological selection. These results show that geographical and environmental factors together created stronger and more discrete genetic differentiation than isolation by distance alone, and illustrate the importance of ecological factors in forming or maintaining genetic divergence across a complex landscape. Our findings differ from other phylogenetic studies that identified the historical drainage system in the region as the primary factor shaping population structure, and highlight the heterogeneous contributions that geography and environment have made to genetic diversity among taxa in southwest China.
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| 7. |
- Wang, Baosheng, et al.
(författare)
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Mitochondrial DNA capture and divergence in Pinus provide new insights into the evolution of the genus
- 2014
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Ingår i: Molecular Phylogenetics and Evolution. - : Elsevier BV. - 1055-7903 .- 1095-9513. ; 80, s. 20-30
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Tidskriftsartikel (refereegranskat)abstract
- The evolution of the mitochondrial (mt) genome is far from being fully understood. Systematic investigations into the modes of inheritance, rates and patterns of recombination, nucleotide substitution, and structural changes in the mt genome are still lacking in many groups of plants. In this study, we sequenced >11 kbp mtDNA segments from multiple accessions of 36 pine species to characterize the evolutionary patterns of mtDNA in the genus Pious. We found extremely low substitution rates and complex repetitive sequences scattered across different genome regions, as well as chimeric structures that were probably generated by multiple intergenomic recombinations. The mtDNA-based phylogeny of the genus differed from that based on chloroplast and nuclear DNA in the placement of several groups of species. Such discordances suggest a series of mtDNA capture events during past range shifts of the pine species and that both vertical and horizontal inheritance are implicated in the evolution of mtDNA in Pinus. MtDNA dating revealed that most extant lineages of the genus originated during Oligocene-Miocene radiation and subgenus Strobus diversified earlier than subgenus Pinus. Our findings illustrate a reticular evolutionary pathway for the mt genome through capture and recombination in the genus Pinus, and provide new insights into the evolution of the genus.
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| 8. |
- Wei, Tao, et al.
(författare)
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Molecular and catalytic characterization of a phi class glutathione transferase from Cathaya argyrophylla
- 2012
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Ingår i: Biochemical Systematics and Ecology. - Oxford : Pergamon Press. - 0305-1978 .- 1873-2925. ; 40, s. 75-85
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Tidskriftsartikel (refereegranskat)abstract
- Plant phi class glutathione transferases (GSTs) play important roles in stress tolerance and detoxification metabolism. This study reports the cloning, expression and biochemical characteristics of a phi GST gene (CaGSTF) from the endemic and endangered conifer Cathaya argyrophylla. The recombinant CaGSTF showed GSH-conjugating activity towards the substrate NED-Cl and CDNB. Kinetic analysis revealed low catalytic efficiency with a k(cat)/K-m(GSH) value of 9.82 mM(-1)S(-1). The CaGSTF proved to be a thermolabile enzyme, at 40 degrees C the enzyme's activity was nearly abolished. Site-directed mutagenesis revealed that Ser12, Lys42, Ile55, Glu67 and Ser68 of CaGSTF are critical components of glutathione-binding sites that contribute to the enzyme's catalytic activity. Compared to other plant phi GSTs and conifer tau GSTs, CaGSTF showed a narrow substrate spectrum, low catalytic efficiency and thermolability. These atypical properties suggest the enzyme may have a limited functional role in the organism's adaptation to environmental stresses in the subtropical regions. (C) 2011 Elsevier Ltd. All rights reserved.
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| 9. |
- Zhao, Wei, et al.
(författare)
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Weak Crossability Barrier but Strong Juvenile Selection Supports Ecological Speciation of the Hybrid Pine Pinus Densata on the Tibetan Plateau
- 2014
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Ingår i: Evolution. - : John Wiley & Sons. - 0014-3820 .- 1558-5646. ; 68:11, s. 3120-3133
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Tidskriftsartikel (refereegranskat)abstract
- Determining how a new hybrid lineage can achieve reproductive isolation is a key to understanding the process and mechanisms of homoploid hybrid speciation. Here, we evaluated the degree and nature of reproductive isolation between the ecologically successful hybrid species Pinus densata and its parental species P. tabuliformis and P. yunnanensis. We performed interspecific crosses among the three species to assess their crossability. We then conducted reciprocal transplantation experiments to evaluate their fitness differentiation, and to examine how natural populations representing different directions of introgression differ in adaptation. The crossing experiments revealed weak genetic barriers among the species. The transplantation trials showed manifest evidence of local adaptation as the three species all performed best in their native habitats. Pinus densata populations from the western edge of its distribution have evolved a strong local adaptation to the specific habitat in that range; populations representing different directions of introgressants with the two parental species all showed fitness disadvantages in this P. densata habitat. These observations illustrate that premating isolation through selection against immigrants from other habitat types or postzygotic isolation through selection against backcrosses between the three species is strong. Thus, ecological selection in combination with endogenous components and geographic isolation has likely played a significant role in the speciation of P. densata.
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| 10. |
- Lan, Ting, et al.
(författare)
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Structural and Functional Evolution of Positively Selected Sites in Pine Glutathione S-Transferase Enzyme Family
- 2013
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 288:34, s. 24441-24451
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Tidskriftsartikel (refereegranskat)abstract
- Phylogenetic analyses have identified positive selection as an important driver of protein evolution, both structural and functional. However, the lack of appropriate combined functional and structural assays has generally hindered attempts to elucidate patterns of positively selected sites and their effects on enzyme activity and substrate specificity. In this study we investigated the evolutionary divergence of the glutathione S-transferase (GST) family in Pinus tabuliformis, a pine that is widely distributed from northern to central China, including cold temperate and drought-stressed regions. GSTs play important roles in plant stress tolerance and detoxification. We cloned 44 GST genes from P. tabuliformis and found that 26 of the 44 belong to the largest (Tau) class of GSTs and are differentially expressed across tissues and developmental stages. Substitution models identified five positively selected sites in the Tau GSTs. To examine the functional significance of these positively selected sites, we applied protein structural modeling and site-directed mutagenesis. We found that four of the five positively selected sites significantly affect the enzyme activity and specificity; thus their variation broadens the GST family substrate spectrum. In addition, positive selection has mainly acted on secondary substrate binding sites or sites close to (but not directly at) the primary substrate binding site; thus their variation enables the acquisition of new catalytic functions without compromising the protein primary biochemical properties. Our study sheds light on selective aspects of the functional and structural divergence of the GST family in pine and other organisms.
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