| 1. |
- Apuli, Rami-Petteri, et al.
(författare)
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Inferring the Genomic Landscape of Recombination Rate Variation in European Aspen (Populus tremula)
- 2020
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Ingår i: G3. - : GENETICS SOCIETY AMERICA. - 2160-1836. ; 10:1, s. 299-309
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Tidskriftsartikel (refereegranskat)abstract
- The rate of meiotic recombination is one of the central factors determining genome-wide levels of linkage disequilibrium which has important consequences for the efficiency of natural selection and for the dissection of quantitative traits. Here we present a new, high-resolution linkage map for Populus tremula that we use to anchor approximately two thirds of the P. tremula draft genome assembly on to the expected 19 chromosomes, providing us with the first chromosome-scale assembly for P. tremula (Table 2). We then use this resource to estimate variation in recombination rates across the P. tremula genome and compare these results to recombination rates based on linkage disequilibrium in a large number of unrelated individuals. We also assess how variation in recombination rates is associated with a number of genomic features, such as gene density, repeat density and methylation levels. We find that recombination rates obtained from the two methods largely agree, although the LD-based method identifies a number of genomic regions with very high recombination rates that the map-based method fails to detect. Linkage map and LD-based estimates of recombination rates are positively correlated and show similar correlations with other genomic features, showing that both methods can accurately infer recombination rate variation across the genome. Recombination rates are positively correlated with gene density and negatively correlated with repeat density and methylation levels, suggesting that recombination is largely directed toward gene regions in P. tremula.
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| 2. |
- Bernhardsson, Carolina, et al.
(författare)
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Geographic structure in metabolome and herbivore community co-occurs with genetic structure in plant defence genes
- 2013
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Ingår i: Ecology Letters. - Hoboken : Wiley-Blackwell. - 1461-023X .- 1461-0248. ; 16:6, s. 791-798
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Tidskriftsartikel (refereegranskat)abstract
- Plantherbivore interactions vary across the landscape and have been hypothesised to promote local adaption in plants to the prevailing herbivore regime. Herbivores that feed on European aspen (Populus tremula) change across regional scales and selection on host defence genes may thus change at comparable scales. We have previously observed strong population differentiation in a set of inducible defence genes in Swedish P. tremula. Here, we study the geographic patterns of abundance and diversity of herbivorous insects, the untargeted metabolome of the foliage and genetic variation in a set of wound-induced genes and show that the geographic structure co-occurs in all three data sets. In response to this structure, we observe local maladaptation of herbivores, with fewer herbivores on local trees than on trees originated from more distant localities. Finally, we also identify 28 significant associations between single nucleotide polymorphisms SNPs from defence genes and a number of the herbivore traits and metabolic profiles.
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| 3. |
- Bernhardsson, Carolina, et al.
(författare)
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Population differentiation in arthropod community structure and phenotypic association with inducible defense genes in European Aspen (Populus tremula L., salicaceae)
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Plant-herbivore interactions are known to vary across a landscape due to both variation in abiotic and biotic factors. Such spatial variation tends to promoting local adaption of plants to the prevailing herbivore regime. Here we use data from a common garden to look for patterns across populations in the abundance and diversity of herbivorous insects. We also screen for variation in the untargeted metabolome of the foliage of a subset of the same trees. We also search for phenotypic associations between genetic variation in a number of wound-induced genes and phenotypic variation in herbivore abundance, diversity and in metabolomes. We observe significant genetic variation in a number of herbivore-related traits but low correlations between traits. We do observe substantial genetic structure in both herbivore community structure and in metabolic profiles and this structure is aligned with genetic structure we have previously documented for a set of defense genes. We also identify a number of significant associations between SNPs from wound-induced defense genes and a number of the herbivore traits and metabolic profiles. However, these associations are likely not causal, but are rather caused by the underlying population structure we observe. These results highlight to the importance of historical processes and the need to better understand both the current-day geographic distribution of different herbivore species as well as the post-glacial colonization history of both plants and herbivores.
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| 4. |
- de La Torre, Amanda R, et al.
(författare)
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Insights into conifer giga-genomes
- 2014
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Ingår i: Plant Physiology. - : American Society of Plant Biologists. - 0032-0889 .- 1532-2548. ; 166:4, s. 1724-1732
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Tidskriftsartikel (refereegranskat)abstract
- Insights from sequenced genomes of major land plant lineages have advanced research in almost every aspect of plant biology. Until recently, however, assembled genome sequences of gymnosperms have been missing from this picture. Conifers of the pine family (Pinaceae) are a group of gymnosperms that dominate large parts of the world's forests. Despite their ecological and economic importance, conifers seemed long out of reach for complete genome sequencing, due in part to their enormous genome size (20-30 Gb) and the highly repetitive nature of their genomes. Technological advances in genome sequencing and assembly enabled the recent publication of three conifer genomes: white spruce (Picea glauca), Norway spruce (Picea abies), and loblolly pine (Pinus taeda). These genome sequences revealed distinctive features compared with other plant genomes and may represent a window into the past of seed plant genomes. This Update highlights recent advances, remaining challenges, and opportunities in light of the publication of the first conifer and gymnosperm genomes.
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| 5. |
- Fataftah, Nazeer, et al.
(författare)
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GIGANTEA influences leaf senescence in trees in two different ways
- 2021
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Ingår i: Plant Physiology. - : Oxford University Press. - 0032-0889 .- 1532-2548. ; 187:4, s. 2435-2450
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Tidskriftsartikel (refereegranskat)abstract
- GIGANTEA (GI) genes have a central role in plant development and influence several processes. Hybrid aspen T89 (Populus tremula x tremuloides) trees with low GI expression engineered through RNAi show severely compromised growth. To study the effect of reduced GI expression on leaf traits with special emphasis on leaf senescence, we grafted GI-RNAi scions onto wild-type rootstocks and successfully restored growth of the scions. The RNAi line had a distorted leaf shape and reduced photosynthesis, probably caused by modulation of phloem or stomatal function, increased starch accumulation, a higher carbon-to-nitrogen ratio, and reduced capacity to withstand moderate light stress. GI-RNAi also induced senescence under long day (LD) and moderate light conditions. Furthermore, the GI-RNAi lines were affected in their capacity to respond to “autumn environmental cues” inducing senescence, a type of leaf senescence that has physiological and biochemical characteristics that differ from those of senescence induced directly by stress under LD conditions. Overexpression of GI delayed senescence under simulated autumn conditions. The two different effects on leaf senescence under LD or simulated autumn conditions were not affected by the expression of FLOWERING LOCUS T. GI expression regulated leaf senescence locally-the phenotype followed the genotype of the branch, independent of its position on the tree-and trees with modified gene expression were affected in a similar way when grown in the field as under controlled conditions. Taken together, GI plays a central role in sensing environmental changes during autumn and determining the appropriate timing for leaf senescence in Populus.
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| 6. |
- Ismail, Mohamed, et al.
(författare)
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Comparative Nucleotide Diversity Across North American and European Populus Species
- 2012
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Ingår i: Journal of Molecular Evolution. - : Springer Science and Business Media LLC. - 0022-2844 .- 1432-1432. ; 74:5-6, s. 257-272
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Tidskriftsartikel (refereegranskat)abstract
- Nucleotide polymorphisms in two North American balsam poplars (Populus trichocarpa Torr. & Gray and P. balsamifera L.; section Tacamahaca), and one Eurasian aspen (P. tremula L.; section Populus) were compared using nine loci involved in defense, stress response, photoperiodism, freezing tolerance, and housekeeping. Nucleotide diversity varied among species and was highest for P. tremula (theta (w) = 0.005, pi (T) = 0.007) as compared to P. balsamifera (theta (w) = 0.004, pi (T) = 0.005) or P. trichocarpa (theta (w) = 0.002, pi (T) = 0.003). Across species, the defense and the stress response loci accounted for the majority of the observed level of nucleotide diversity. In general, the studied loci did not deviate from neutral expectation either at the individual locus (non-significant normalized Fay and Wu's H) or at the multi-locus level (non-significant HKA test). Using molecular clock analysis, section Tacamahaca probably shared a common ancestor with section Populus approximately 4.5 million year ago. Divergence between the two closely related balsam poplars was about 0.8 million years ago, a pattern consistent with an isolation-with-migration (IM) model. As expected, P. tremula showed a five-fold higher substitution rate (2 x 10(-8) substitution/site/year) compared to the North American species (0.4 x 10(-8) substitution/site/year), probably reflecting its complex demographic history. Linkage disequilibrium (LD) varied among species with a more rapid decay in the North American species (< 400 bp) in comparison to P. tremula (a parts per thousand << 400 bp). The similarities in nucleotide diversity pattern and LD decay of the two balsam poplar species likely reflects the recent time of their divergence.
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| 7. |
- Jansson, Stefan, 1959-, et al.
(författare)
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Cohort-structured tree populations
- 2010
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Ingår i: Heredity. - : Springer Science and Business Media LLC. - 0018-067X .- 1365-2540. ; 105:4, s. 331-332
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Tidskriftsartikel (refereegranskat)
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| 8. |
- Lin, Yao-Cheng, et al.
(författare)
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Functional and evolutionary genomic inferences in Populus through genome and population sequencing of American and European aspen
- 2018
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : NATL ACAD SCIENCES. - 0027-8424 .- 1091-6490. ; 115:46, s. E10970-E10978
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Tidskriftsartikel (refereegranskat)abstract
- The Populus genus is one of the major plant model systems, but genomic resources have thus far primarily been available for poplar species, and primarily Populus trichocarpa (Torr. & Gray), which was the first tree with a whole-genome assembly. To further advance evolutionary and functional genomic analyses in Populus, we produced genome assemblies and population genetics resources of two aspen species, Populus tremula L. and Populus tremuloides Michx. The two aspen species have distributions spanning the Northern Hemisphere, where they are keystone species supporting a wide variety of dependent communities and produce a diverse array of secondary metabolites. Our analyses show that the two aspens share a similar genome structure and a highly conserved gene content with P. trichocarpa but display substantially higher levels of heterozygosity. Based on population resequencing data, we observed widespread positive and negative selection acting on both coding and noncoding regions. Furthermore, patterns of genetic diversity and molecular evolution in aspen are influenced by a number of features, such as expression level, coexpression network connectivity, and regulatory variation. To maximize the community utility of these resources, we have integrated all presented data within the PopGenIE web resource (PopGenIE.org).
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| 9. |
- Ma, Xiao-Fei, et al.
(författare)
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Genetic differentiation, clinal variation and phenotypic associations with growth cessation across the Populus tremula Photoperiodic Pathway
- 2010
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Ingår i: Genetics. - : Oxford University Press (OUP). - 0016-6731 .- 1943-2631. ; 186, s. 1033-1044
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Tidskriftsartikel (refereegranskat)abstract
- Perennial plants monitor seasonal changes through changes inenvironmental conditions such as the quantity and quality oflight. To ensure a correct initiation of critical developmentalprocesses, such as the initiation and cessation of growth, plantshave adapted to a spatially variable light regime and genesin the photoperiodic pathway have been implicated as likelysources for these adaptations. Here we examine genetic variationin genes from the photoperiodic pathway in Populus tremula (Salicaceae)for signatures diversifying selection in response to varyinglight regimes across a latitudinal gradient. We fail to identifyany loci with unusually high levels of genetic differentiationamong populations despite identifying four SNPs that show significantallele frequency clines with latitude. We do, however, observelarge covariance in allelic effects across populations for growthcessation, a highly adaptive trait in P. tremula. High covariancein allelic effects is a signature compatible with diversifyingselection along an environmental gradient. We also observe significantlyhigher heterogeneity in genetic differentiation among SNPs fromthe photoperiod genes than among SNPs from randomly chosen genes.This suggests that spatially variable selection could be affectinggenes from the photoperiod pathway even if selection is notstrong enough to cause individual loci to be identified as outliers.SNPs from three genes in the photoperiod pathway (PHYB2, LHY1,and LHY2) show significant associations with natural variationin growth cessation. Collectively these SNPs explain 10–15%of the phenotypic variation in growth cessation. Covariancesin allelic effects across populations help explain an additional5–7% of the phenotypic variation in growth cessation.
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| 10. |
- Michelson, Ingrid H., et al.
(författare)
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Autumn senescence in aspen is not triggered by day length
- 2018
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Ingår i: Physiologia Plantarum. - : John Wiley & Sons. - 0031-9317 .- 1399-3054. ; 162:1, s. 123-134
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Tidskriftsartikel (refereegranskat)abstract
- Autumn senescence in mature aspens, grown under natural conditions, is initiated at almost the same date every year. The mechanism of such precise timing is not understood but we have previously shown that the signal must be derived from light. We studied variation in bud set and autumn senescence in a collection of 116 natural Eurasian aspen (Populus tremula) genotypes, from 12 populations in Sweden and planted in one northern and one southern common garden, to test the hypothesis that onset of autumn senescence is triggered by day length. We confirmed that, although bud set seemed to be triggered by a critical photoperiod/day length, other factors may influence it. The data on initiation of autumn senescence, on the other hand, were incompatible with the trigger being the day length per se, hence the trigger must be some other light-dependent factor.
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