The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
Craig H Carlson - One of the best experts on this subject based on the ideXlab platform.
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integrative genomics reveals paths to sex dimorphism in Salix purpurea l
bioRxiv, 2021Co-Authors: B Hyden, Craig H Carlson, Laura Sandor, Gerald A Tuskan, Kerrie Barry, Jeremy Schmutz, Fred E Gouker, Anna Lipzen, Anupma Sharma, Guanqiao FengAbstract:Sex dimorphism and gene expression were studied in developing catkins in 159 F2 individuals from the bioenergy crop Salix purpurea, and potential mechanisms and pathways for regulating sex development were explored. Differential expression, eQTL, bisulfite sequencing, and network analysis were used to characterize sex dimorphism, detect candidate master regulator genes, and identify pathways through which the sex determination region (SDR) may mediate sex dimorphism. Eleven genes are presented as candidates for master regulators of sex, supported by gene expression and network analyses. These include genes putatively involved in hormone signaling, epigenetic modification, and regulation of transcription. eQTL analysis revealed a suite of transcription factors and genes involved in secondary metabolism and floral development that were predicted to be under direct control of the sex determination region. Furthermore, data from bisulfite sequencing and small RNA sequencing revealed strong differences in expression between males and females that would implicate both of these processes in sex dimorphism pathways. These data indicate that the mechanism of sex determination in Salix purpurea is likely different from that observed in the related genus Populus. This further demonstrates the dynamic nature of SDRs in plants, which involves a multitude of mechanisms of sex determination and a high rate of turnover.
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transcriptome analysis of contrasting resistance to herbivory by empoasca fabae in two shrub willow species and their hybrid progeny
PLOS ONE, 2020Co-Authors: Wanyan Wang, Craig H Carlson, Lawrence B Smart, John E CarlsonAbstract:Short rotation woody biomass cultivars developed from fast-growing shrub species of willow (Salix spp.) have superior properties as perennial energy crops for the Northeast and Midwest US. However, the insect pest potato leafhopper (PLH) Empoasca fabae (Harris) can cause serious damage and reduce yield of susceptible genotypes. Currently, the willow cultivars in use display varying levels of susceptibility under PLH infestation. However, genes and markers for resistance to PLH are not yet available for marker-assisted selection in breeding. In this study, transcriptome differences between a resistant genotype 94006 (S. purpurea) and a susceptible cultivar 'Jorr' (S. viminalis), and their hybrid progeny were determined. Over 600 million RNA-Seq reads were generated and mapped to the Salix purpurea reference transcriptome. Gene expression analyses revealed the unique defense mechanism in resistant genotype 94006 that involves PLH-induced secondary cell wall modification. In the susceptible genotypes, genes involved in programed cell death were highly expressed, explaining the necrosis symptoms after PLH feeding. Overall, the discovery of resistance genes and defense mechanisms provides new resources for shrub willow breeding and research in the future.
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sexual dimorphism and sex ratio bias in the dioecious willow Salix purpurea l
bioRxiv, 2020Co-Authors: Fred E Gouker, Craig H Carlson, Stephen P Difazio, Junzhu Zou, Luke M Evans, Chase R Crowell, Christine D Smart, Lawrence B SmartAbstract:Premise: Sexual dimorphism in dioecious plant species is often not obvious or is absent. Dioecious species populations also often exhibit deviations from expected sex ratios. Previous studies on members of the Salicaceae family have shown strong, partial, and no sexual dimorphism. Some studies have shown sex-biased ratios in several Salix spp., however, S. purpurea has never been examined for evidence of sexual dimorphism or for the presence of sex-ratio bias, and therefore a comprehensive phenotypic study is needed to fill this knowledge gap. Methods: This study examined a suite of morphological, phenological, physiological and wood composition traits from multi-environment and multi-year replicated field trials in a diversity panel of unrelated S. purpurea accessions and in full-sib F1 and F2 families produced through controlled cross pollinations to test for sexual dimorphism and sex ratio bias. Key Results: Significant evidence of sexual dimorphism was found in vegetative traits with greater means for many traits in male genotypes compared to females across three populations of S. purpurea, measured across multiple years that were highly predictive of biomass yield. Male plants exhibited greater nitrogen accumulation under fertilizer amendment as measured by SPAD in the diversity panel, and males showed greater susceptibility to fungal infection by Melampsora spp in the F2 family. There were also consistent female-biased sex ratios in both the F1 and F2 families. Conclusions: These results provide the first evidence of sexual dimorphism in S. purpurea and also confirm the prevalence of female-biased sex ratios previously found in other Salix species.
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a willow sex chromosome reveals convergent evolution of complex palindromic repeats
Genome Biology, 2020Co-Authors: Ran Zhou, David Macayasanz, Craig H Carlson, Jerry Jenkins, Laura Sandor, David A Kudrna, Kerrie Barry, Jeremy Schmutz, Aditi Sharma, Gerald A TuskanAbstract:Sex chromosomes have arisen independently in a wide variety of species, yet they share common characteristics, including the presence of suppressed recombination surrounding sex determination loci. Mammalian sex chromosomes contain multiple palindromic repeats across the non-recombining region that show sequence conservation through gene conversion and contain genes that are crucial for sexual reproduction. In plants, it is not clear if palindromic repeats play a role in maintaining sequence conservation in the absence of homologous recombination. Here we present the first evidence of large palindromic structures in a plant sex chromosome, based on a highly contiguous assembly of the W chromosome of the dioecious shrub Salix purpurea. The W chromosome has an expanded number of genes due to transpositions from autosomes. It also contains two consecutive palindromes that span a region of 200 kb, with conspicuous 20-kb stretches of highly conserved sequences among the four arms that show evidence of gene conversion. Four genes in the palindrome are homologous to genes in the sex determination regions of the closely related genus Populus, which is located on a different chromosome. These genes show distinct, floral-biased expression patterns compared to paralogous copies on autosomes. The presence of palindromes in sex chromosomes of mammals and plants highlights the intrinsic importance of these features in adaptive evolution in the absence of recombination. Convergent evolution is driving both the independent establishment of sex chromosomes as well as their fine-scale sequence structure.
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joint linkage and association mapping of complex traits in shrub willow Salix purpurea l
Annals of Botany, 2019Co-Authors: Craig H Carlson, Fred E Gouker, Stephen P Difazio, Luke M Evans, Chase R Crowell, Christine D Smart, Lawrence B SmartAbstract:Background and aims Increasing energy demands and the necessity to reduce greenhouse gas emissions are key motivating factors driving the development of lignocellulosic crops as an alternative to non-renewable energy sources. The effects of global climate change will require a better understanding of the genetic basis of complex adaptive traits to breed more resilient bioenergy feedstocks, like willow (Salix spp.). Shrub willow is a sustainable and dedicated bioenergy crop, bred to be fast-growing and high-yielding on marginal land without competing with food crops. In a rapidly changing climate, genomic advances will be vital for the sustained improvement of willow and other non-model bioenergy crops. Here, joint genetic mapping was used to exploit genetic variation garnered from both recent and historical recombination events in S. purpurea. Methods A panel of North American naturalized S. purpurea accessions and full-sib F2S. purpurea population were genotyped and phenotyped for a suite of morphological, physiological, pest and disease resistance, and wood chemical composition traits, collected from multi-environment and multi-year replicated field trials. Controlling for population stratification and kinship in the association panel and spatial variation in the F2, a comprehensive mixed model analysis was used to dissect the complex genetic architecture and plasticity of these important traits. Key results Individually, genome-wide association (GWAS) models differed in terms of power, but the combined approach, which corrects for yearly and environmental co-factors across datasets, improved the overall detection and resolution of associated loci. Although there were few significant GWAS hits located within support intervals of QTL for corresponding traits in the F2, many large-effect QTL were identified, as well as QTL hotspots. Conclusions This study provides the first comparison of linkage analysis and linkage disequilibrium mapping approaches in Salix, and highlights the complementarity and limits of these two methods for elucidating the genetic architecture of complex bioenergy-related traits of a woody perennial breeding programme.
Lawrence B Smart - One of the best experts on this subject based on the ideXlab platform.
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transcriptome analysis of contrasting resistance to herbivory by empoasca fabae in two shrub willow species and their hybrid progeny
PLOS ONE, 2020Co-Authors: Wanyan Wang, Craig H Carlson, Lawrence B Smart, John E CarlsonAbstract:Short rotation woody biomass cultivars developed from fast-growing shrub species of willow (Salix spp.) have superior properties as perennial energy crops for the Northeast and Midwest US. However, the insect pest potato leafhopper (PLH) Empoasca fabae (Harris) can cause serious damage and reduce yield of susceptible genotypes. Currently, the willow cultivars in use display varying levels of susceptibility under PLH infestation. However, genes and markers for resistance to PLH are not yet available for marker-assisted selection in breeding. In this study, transcriptome differences between a resistant genotype 94006 (S. purpurea) and a susceptible cultivar 'Jorr' (S. viminalis), and their hybrid progeny were determined. Over 600 million RNA-Seq reads were generated and mapped to the Salix purpurea reference transcriptome. Gene expression analyses revealed the unique defense mechanism in resistant genotype 94006 that involves PLH-induced secondary cell wall modification. In the susceptible genotypes, genes involved in programed cell death were highly expressed, explaining the necrosis symptoms after PLH feeding. Overall, the discovery of resistance genes and defense mechanisms provides new resources for shrub willow breeding and research in the future.
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sexual dimorphism and sex ratio bias in the dioecious willow Salix purpurea l
bioRxiv, 2020Co-Authors: Fred E Gouker, Craig H Carlson, Stephen P Difazio, Junzhu Zou, Luke M Evans, Chase R Crowell, Christine D Smart, Lawrence B SmartAbstract:Premise: Sexual dimorphism in dioecious plant species is often not obvious or is absent. Dioecious species populations also often exhibit deviations from expected sex ratios. Previous studies on members of the Salicaceae family have shown strong, partial, and no sexual dimorphism. Some studies have shown sex-biased ratios in several Salix spp., however, S. purpurea has never been examined for evidence of sexual dimorphism or for the presence of sex-ratio bias, and therefore a comprehensive phenotypic study is needed to fill this knowledge gap. Methods: This study examined a suite of morphological, phenological, physiological and wood composition traits from multi-environment and multi-year replicated field trials in a diversity panel of unrelated S. purpurea accessions and in full-sib F1 and F2 families produced through controlled cross pollinations to test for sexual dimorphism and sex ratio bias. Key Results: Significant evidence of sexual dimorphism was found in vegetative traits with greater means for many traits in male genotypes compared to females across three populations of S. purpurea, measured across multiple years that were highly predictive of biomass yield. Male plants exhibited greater nitrogen accumulation under fertilizer amendment as measured by SPAD in the diversity panel, and males showed greater susceptibility to fungal infection by Melampsora spp in the F2 family. There were also consistent female-biased sex ratios in both the F1 and F2 families. Conclusions: These results provide the first evidence of sexual dimorphism in S. purpurea and also confirm the prevalence of female-biased sex ratios previously found in other Salix species.
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joint linkage and association mapping of complex traits in shrub willow Salix purpurea l
Annals of Botany, 2019Co-Authors: Craig H Carlson, Fred E Gouker, Stephen P Difazio, Luke M Evans, Chase R Crowell, Christine D Smart, Lawrence B SmartAbstract:Background and aims Increasing energy demands and the necessity to reduce greenhouse gas emissions are key motivating factors driving the development of lignocellulosic crops as an alternative to non-renewable energy sources. The effects of global climate change will require a better understanding of the genetic basis of complex adaptive traits to breed more resilient bioenergy feedstocks, like willow (Salix spp.). Shrub willow is a sustainable and dedicated bioenergy crop, bred to be fast-growing and high-yielding on marginal land without competing with food crops. In a rapidly changing climate, genomic advances will be vital for the sustained improvement of willow and other non-model bioenergy crops. Here, joint genetic mapping was used to exploit genetic variation garnered from both recent and historical recombination events in S. purpurea. Methods A panel of North American naturalized S. purpurea accessions and full-sib F2S. purpurea population were genotyped and phenotyped for a suite of morphological, physiological, pest and disease resistance, and wood chemical composition traits, collected from multi-environment and multi-year replicated field trials. Controlling for population stratification and kinship in the association panel and spatial variation in the F2, a comprehensive mixed model analysis was used to dissect the complex genetic architecture and plasticity of these important traits. Key results Individually, genome-wide association (GWAS) models differed in terms of power, but the combined approach, which corrects for yearly and environmental co-factors across datasets, improved the overall detection and resolution of associated loci. Although there were few significant GWAS hits located within support intervals of QTL for corresponding traits in the F2, many large-effect QTL were identified, as well as QTL hotspots. Conclusions This study provides the first comparison of linkage analysis and linkage disequilibrium mapping approaches in Salix, and highlights the complementarity and limits of these two methods for elucidating the genetic architecture of complex bioenergy-related traits of a woody perennial breeding programme.
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genetic diversity and population structure of native naturalized and cultivated Salix purpurea
Tree Genetics & Genomes, 2019Co-Authors: Stephen P Difazio, Fred E Gouker, Ben Bubner, Matthias Zander, Lawrence B SmartAbstract:Salix purpurea is a woody perennial that is bred as a high-yielding bioenergy crop in North America. To gain an understanding of the genotypic variation associated with phenotypic diversity, this study characterized the population structure and genetic diversity of S. purpurea from its native range of Europe and naturalized range of the Northeastern United States (US). A total of 273 genotypes of S. purpurea were analyzed, which included 95 naturalized accessions and 19 horticultural cultivars from the US and 159 accessions collected from the native range of four European countries. All individuals were evaluated using a filtered set of 2287 genotyping-by-sequencing (GBS) single nucleotide polymorphism (SNP) markers. Using five clustering techniques (PCA, neighbor joining, STRUCTURE, DAPC, and affinity propagation), population structure was resolved into three broadly classified groups. Further analysis revealed seven to eight subpopulations which corresponded to geographical collection sites, where performance of the DAPC and affinity propagation methods was superior to STRUCTURE analysis for the purposes of characterizing population structure and performing population assignment. The native European accessions exhibited greater diversity and subpopulation structure than the US naturalized accessions, where there was a clear geographical delineation between the alpine/subalpine collections and the lowland collections at the Baltic Sea and Oder River. We also show that a subset of the horticultural cultivars had a higher likelihood of similarity to US naturalized populations which display hybrid ancestry, where both naturalized and cultivated genotypes appear to share a common ancestor. Additionally, several accessions collected from different sites were found to be clonal. Ongoing and future conservation and association studies will benefit from these known substructures and diversity assessments.
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dominance and sexual dimorphism pervade the Salix purpurea l transcriptome
Genome Biology and Evolution, 2017Co-Authors: Craig H Carlson, Yongwook Choi, Agnes P Chan, Michelle J Serapiglia, Christopher D Town, Lawrence B SmartAbstract:The heritability of gene expression is critical in understanding heterosis and is dependent on allele-specific regulation by local and remote factors in the genome. We used RNA-Seq to test whether variation in gene expression among F1 and F2 intraspecific Salix purpurea progeny is attributable to cis- and trans-regulatory divergence. We assessed the mode of inheritance based on gene expression levels and allele-specific expression for F1 and F2 intraspecific progeny in two distinct tissue types: shoot tip and stem internode. In addition, we explored sexually dimorphic patterns of inheritance and regulatory divergence among F1 progeny individuals. We show that in S. purpurea intraspecific crosses, gene expression inheritance largely exhibits a maternal dominant pattern, regardless of tissue type or pedigree. A significantly greater number of cis- and trans-regulated genes coincided with upregulation of the maternal parent allele in the progeny, irrespective of the magnitude, whereas the paternal allele was higher expressed for genes showing cis × trans or compensatory regulation. Importantly, consistent with previous genetic mapping results for sex in shrub willow, we have delimited sex-biased gene expression to a 2 Mb pericentromeric region on S. purpurea chr15 and further refined the sex determination region. Altogether, our results offer insight into the inheritance of gene expression in S. purpurea as well as evidence of sexually dimorphic expression which may have contributed to the evolution of dioecy in Salix.
Gerald A Tuskan - One of the best experts on this subject based on the ideXlab platform.
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integrative genomics reveals paths to sex dimorphism in Salix purpurea l
bioRxiv, 2021Co-Authors: B Hyden, Craig H Carlson, Laura Sandor, Gerald A Tuskan, Kerrie Barry, Jeremy Schmutz, Fred E Gouker, Anna Lipzen, Anupma Sharma, Guanqiao FengAbstract:Sex dimorphism and gene expression were studied in developing catkins in 159 F2 individuals from the bioenergy crop Salix purpurea, and potential mechanisms and pathways for regulating sex development were explored. Differential expression, eQTL, bisulfite sequencing, and network analysis were used to characterize sex dimorphism, detect candidate master regulator genes, and identify pathways through which the sex determination region (SDR) may mediate sex dimorphism. Eleven genes are presented as candidates for master regulators of sex, supported by gene expression and network analyses. These include genes putatively involved in hormone signaling, epigenetic modification, and regulation of transcription. eQTL analysis revealed a suite of transcription factors and genes involved in secondary metabolism and floral development that were predicted to be under direct control of the sex determination region. Furthermore, data from bisulfite sequencing and small RNA sequencing revealed strong differences in expression between males and females that would implicate both of these processes in sex dimorphism pathways. These data indicate that the mechanism of sex determination in Salix purpurea is likely different from that observed in the related genus Populus. This further demonstrates the dynamic nature of SDRs in plants, which involves a multitude of mechanisms of sex determination and a high rate of turnover.
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a willow sex chromosome reveals convergent evolution of complex palindromic repeats
Genome Biology, 2020Co-Authors: Ran Zhou, David Macayasanz, Craig H Carlson, Jerry Jenkins, Laura Sandor, David A Kudrna, Kerrie Barry, Jeremy Schmutz, Aditi Sharma, Gerald A TuskanAbstract:Sex chromosomes have arisen independently in a wide variety of species, yet they share common characteristics, including the presence of suppressed recombination surrounding sex determination loci. Mammalian sex chromosomes contain multiple palindromic repeats across the non-recombining region that show sequence conservation through gene conversion and contain genes that are crucial for sexual reproduction. In plants, it is not clear if palindromic repeats play a role in maintaining sequence conservation in the absence of homologous recombination. Here we present the first evidence of large palindromic structures in a plant sex chromosome, based on a highly contiguous assembly of the W chromosome of the dioecious shrub Salix purpurea. The W chromosome has an expanded number of genes due to transpositions from autosomes. It also contains two consecutive palindromes that span a region of 200 kb, with conspicuous 20-kb stretches of highly conserved sequences among the four arms that show evidence of gene conversion. Four genes in the palindrome are homologous to genes in the sex determination regions of the closely related genus Populus, which is located on a different chromosome. These genes show distinct, floral-biased expression patterns compared to paralogous copies on autosomes. The presence of palindromes in sex chromosomes of mammals and plants highlights the intrinsic importance of these features in adaptive evolution in the absence of recombination. Convergent evolution is driving both the independent establishment of sex chromosomes as well as their fine-scale sequence structure.
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a willow sex chromosome reveals convergent evolution of complex palindromic repeats
bioRxiv, 2019Co-Authors: Ran Zhou, David Macayasanz, Craig H Carlson, Jerry Jenkins, Laura Sandor, David A Kudrna, Kerrie Barry, Jeremy Schmutz, Aditi Sharma, Gerald A TuskanAbstract:Background: Sex chromosomes in a wide variety of species share common characteristics, including the presence of suppressed recombination surrounding sex determination loci. They have arisen independently in numerous lineages, providing a conclusive example of convergent evolution. Mammalian sex chromosomes contain multiple palindromic repeats across the non-recombining region that facilitate sequence conservation through gene conversion, and contain genes that are crucial for sexual reproduction. Plant sex chromosomes are less well understood, and in particular it is not clear how coding sequence conservation is maintained in the absence of homologous recombination. Results: Here we present the first evidence of large palindromic structures in a plant sex chromosome, based on a highly contiguous assembly of the W chromosome of the dioecious shrub Salix purpurea. Two consecutive palindromes span over a region of 200 kb, with conspicuous 20 kb stretches of highly conserved sequences among the four arms. The closely-related species S. suchowensis also has two copies of a portion of the palindrome arm and provides strong evidence for gene conversion. Four genes in the palindrome are homologous to genes in the SDR of the closely-related genus Populus, which is located on a different chromosome. These genes show distinct, floral-biased expression patterns compared to paralogous copies on autosomes. Conclusion: The presence of palindromic structures in sex chromosomes of mammals and plants highlights the intrinsic importance of these features in adaptive evolution in the absence of recombination. Convergent evolution is driving both the independent establishment of sex chromosomes as well as their fine-scale sequence structure.
Fred E Gouker - One of the best experts on this subject based on the ideXlab platform.
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integrative genomics reveals paths to sex dimorphism in Salix purpurea l
bioRxiv, 2021Co-Authors: B Hyden, Craig H Carlson, Laura Sandor, Gerald A Tuskan, Kerrie Barry, Jeremy Schmutz, Fred E Gouker, Anna Lipzen, Anupma Sharma, Guanqiao FengAbstract:Sex dimorphism and gene expression were studied in developing catkins in 159 F2 individuals from the bioenergy crop Salix purpurea, and potential mechanisms and pathways for regulating sex development were explored. Differential expression, eQTL, bisulfite sequencing, and network analysis were used to characterize sex dimorphism, detect candidate master regulator genes, and identify pathways through which the sex determination region (SDR) may mediate sex dimorphism. Eleven genes are presented as candidates for master regulators of sex, supported by gene expression and network analyses. These include genes putatively involved in hormone signaling, epigenetic modification, and regulation of transcription. eQTL analysis revealed a suite of transcription factors and genes involved in secondary metabolism and floral development that were predicted to be under direct control of the sex determination region. Furthermore, data from bisulfite sequencing and small RNA sequencing revealed strong differences in expression between males and females that would implicate both of these processes in sex dimorphism pathways. These data indicate that the mechanism of sex determination in Salix purpurea is likely different from that observed in the related genus Populus. This further demonstrates the dynamic nature of SDRs in plants, which involves a multitude of mechanisms of sex determination and a high rate of turnover.
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sexual dimorphism and sex ratio bias in the dioecious willow Salix purpurea l
bioRxiv, 2020Co-Authors: Fred E Gouker, Craig H Carlson, Stephen P Difazio, Junzhu Zou, Luke M Evans, Chase R Crowell, Christine D Smart, Lawrence B SmartAbstract:Premise: Sexual dimorphism in dioecious plant species is often not obvious or is absent. Dioecious species populations also often exhibit deviations from expected sex ratios. Previous studies on members of the Salicaceae family have shown strong, partial, and no sexual dimorphism. Some studies have shown sex-biased ratios in several Salix spp., however, S. purpurea has never been examined for evidence of sexual dimorphism or for the presence of sex-ratio bias, and therefore a comprehensive phenotypic study is needed to fill this knowledge gap. Methods: This study examined a suite of morphological, phenological, physiological and wood composition traits from multi-environment and multi-year replicated field trials in a diversity panel of unrelated S. purpurea accessions and in full-sib F1 and F2 families produced through controlled cross pollinations to test for sexual dimorphism and sex ratio bias. Key Results: Significant evidence of sexual dimorphism was found in vegetative traits with greater means for many traits in male genotypes compared to females across three populations of S. purpurea, measured across multiple years that were highly predictive of biomass yield. Male plants exhibited greater nitrogen accumulation under fertilizer amendment as measured by SPAD in the diversity panel, and males showed greater susceptibility to fungal infection by Melampsora spp in the F2 family. There were also consistent female-biased sex ratios in both the F1 and F2 families. Conclusions: These results provide the first evidence of sexual dimorphism in S. purpurea and also confirm the prevalence of female-biased sex ratios previously found in other Salix species.
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joint linkage and association mapping of complex traits in shrub willow Salix purpurea l
Annals of Botany, 2019Co-Authors: Craig H Carlson, Fred E Gouker, Stephen P Difazio, Luke M Evans, Chase R Crowell, Christine D Smart, Lawrence B SmartAbstract:Background and aims Increasing energy demands and the necessity to reduce greenhouse gas emissions are key motivating factors driving the development of lignocellulosic crops as an alternative to non-renewable energy sources. The effects of global climate change will require a better understanding of the genetic basis of complex adaptive traits to breed more resilient bioenergy feedstocks, like willow (Salix spp.). Shrub willow is a sustainable and dedicated bioenergy crop, bred to be fast-growing and high-yielding on marginal land without competing with food crops. In a rapidly changing climate, genomic advances will be vital for the sustained improvement of willow and other non-model bioenergy crops. Here, joint genetic mapping was used to exploit genetic variation garnered from both recent and historical recombination events in S. purpurea. Methods A panel of North American naturalized S. purpurea accessions and full-sib F2S. purpurea population were genotyped and phenotyped for a suite of morphological, physiological, pest and disease resistance, and wood chemical composition traits, collected from multi-environment and multi-year replicated field trials. Controlling for population stratification and kinship in the association panel and spatial variation in the F2, a comprehensive mixed model analysis was used to dissect the complex genetic architecture and plasticity of these important traits. Key results Individually, genome-wide association (GWAS) models differed in terms of power, but the combined approach, which corrects for yearly and environmental co-factors across datasets, improved the overall detection and resolution of associated loci. Although there were few significant GWAS hits located within support intervals of QTL for corresponding traits in the F2, many large-effect QTL were identified, as well as QTL hotspots. Conclusions This study provides the first comparison of linkage analysis and linkage disequilibrium mapping approaches in Salix, and highlights the complementarity and limits of these two methods for elucidating the genetic architecture of complex bioenergy-related traits of a woody perennial breeding programme.
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genetic diversity and population structure of native naturalized and cultivated Salix purpurea
Tree Genetics & Genomes, 2019Co-Authors: Stephen P Difazio, Fred E Gouker, Ben Bubner, Matthias Zander, Lawrence B SmartAbstract:Salix purpurea is a woody perennial that is bred as a high-yielding bioenergy crop in North America. To gain an understanding of the genotypic variation associated with phenotypic diversity, this study characterized the population structure and genetic diversity of S. purpurea from its native range of Europe and naturalized range of the Northeastern United States (US). A total of 273 genotypes of S. purpurea were analyzed, which included 95 naturalized accessions and 19 horticultural cultivars from the US and 159 accessions collected from the native range of four European countries. All individuals were evaluated using a filtered set of 2287 genotyping-by-sequencing (GBS) single nucleotide polymorphism (SNP) markers. Using five clustering techniques (PCA, neighbor joining, STRUCTURE, DAPC, and affinity propagation), population structure was resolved into three broadly classified groups. Further analysis revealed seven to eight subpopulations which corresponded to geographical collection sites, where performance of the DAPC and affinity propagation methods was superior to STRUCTURE analysis for the purposes of characterizing population structure and performing population assignment. The native European accessions exhibited greater diversity and subpopulation structure than the US naturalized accessions, where there was a clear geographical delineation between the alpine/subalpine collections and the lowland collections at the Baltic Sea and Oder River. We also show that a subset of the horticultural cultivars had a higher likelihood of similarity to US naturalized populations which display hybrid ancestry, where both naturalized and cultivated genotypes appear to share a common ancestor. Additionally, several accessions collected from different sites were found to be clonal. Ongoing and future conservation and association studies will benefit from these known substructures and diversity assessments.
Ran Zhou - One of the best experts on this subject based on the ideXlab platform.
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a willow sex chromosome reveals convergent evolution of complex palindromic repeats
Genome Biology, 2020Co-Authors: Ran Zhou, David Macayasanz, Craig H Carlson, Jerry Jenkins, Laura Sandor, David A Kudrna, Kerrie Barry, Jeremy Schmutz, Aditi Sharma, Gerald A TuskanAbstract:Sex chromosomes have arisen independently in a wide variety of species, yet they share common characteristics, including the presence of suppressed recombination surrounding sex determination loci. Mammalian sex chromosomes contain multiple palindromic repeats across the non-recombining region that show sequence conservation through gene conversion and contain genes that are crucial for sexual reproduction. In plants, it is not clear if palindromic repeats play a role in maintaining sequence conservation in the absence of homologous recombination. Here we present the first evidence of large palindromic structures in a plant sex chromosome, based on a highly contiguous assembly of the W chromosome of the dioecious shrub Salix purpurea. The W chromosome has an expanded number of genes due to transpositions from autosomes. It also contains two consecutive palindromes that span a region of 200 kb, with conspicuous 20-kb stretches of highly conserved sequences among the four arms that show evidence of gene conversion. Four genes in the palindrome are homologous to genes in the sex determination regions of the closely related genus Populus, which is located on a different chromosome. These genes show distinct, floral-biased expression patterns compared to paralogous copies on autosomes. The presence of palindromes in sex chromosomes of mammals and plants highlights the intrinsic importance of these features in adaptive evolution in the absence of recombination. Convergent evolution is driving both the independent establishment of sex chromosomes as well as their fine-scale sequence structure.
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a willow sex chromosome reveals convergent evolution of complex palindromic repeats
bioRxiv, 2019Co-Authors: Ran Zhou, David Macayasanz, Craig H Carlson, Jerry Jenkins, Laura Sandor, David A Kudrna, Kerrie Barry, Jeremy Schmutz, Aditi Sharma, Gerald A TuskanAbstract:Background: Sex chromosomes in a wide variety of species share common characteristics, including the presence of suppressed recombination surrounding sex determination loci. They have arisen independently in numerous lineages, providing a conclusive example of convergent evolution. Mammalian sex chromosomes contain multiple palindromic repeats across the non-recombining region that facilitate sequence conservation through gene conversion, and contain genes that are crucial for sexual reproduction. Plant sex chromosomes are less well understood, and in particular it is not clear how coding sequence conservation is maintained in the absence of homologous recombination. Results: Here we present the first evidence of large palindromic structures in a plant sex chromosome, based on a highly contiguous assembly of the W chromosome of the dioecious shrub Salix purpurea. Two consecutive palindromes span over a region of 200 kb, with conspicuous 20 kb stretches of highly conserved sequences among the four arms. The closely-related species S. suchowensis also has two copies of a portion of the palindrome arm and provides strong evidence for gene conversion. Four genes in the palindrome are homologous to genes in the SDR of the closely-related genus Populus, which is located on a different chromosome. These genes show distinct, floral-biased expression patterns compared to paralogous copies on autosomes. Conclusion: The presence of palindromic structures in sex chromosomes of mammals and plants highlights the intrinsic importance of these features in adaptive evolution in the absence of recombination. Convergent evolution is driving both the independent establishment of sex chromosomes as well as their fine-scale sequence structure.
