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Wilhelmsson PKI, Chandler JO, Fernandez-Pozo N, Graeber K, Ullrich KK, Arshad W, Khan S, Hofberger JA, Buchta K, Edger PP, Pires JC, Schranz ME, Leubner-Metzger G, Rensing SA. Usability of reference-free transcriptome assemblies for detection of differential expression: a case study on Aethionema arabicum dimorphic seeds. BMC Genomics 2019; 20:95. [PMID: 30700268 PMCID: PMC6354389 DOI: 10.1186/s12864-019-5452-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Accepted: 01/14/2019] [Indexed: 12/31/2022] Open
Abstract
Background RNA-sequencing analysis is increasingly utilized to study gene expression in non-model organisms without sequenced genomes. Aethionema arabicum (Brassicaceae) exhibits seed dimorphism as a bet-hedging strategy – producing both a less dormant mucilaginous (M+) seed morph and a more dormant non-mucilaginous (NM) seed morph. Here, we compared de novo and reference-genome based transcriptome assemblies to investigate Ae. arabicum seed dimorphism and to evaluate the reference-free versus -dependent approach for identifying differentially expressed genes (DEGs). Results A de novo transcriptome assembly was generated using sequences from M+ and NM Ae. arabicum dry seed morphs. The transcripts of the de novo assembly contained 63.1% complete Benchmarking Universal Single-Copy Orthologs (BUSCO) compared to 90.9% for the transcripts of the reference genome. DEG detection used the strict consensus of three methods (DESeq2, edgeR and NOISeq). Only 37% of 1533 differentially expressed de novo assembled transcripts paired with 1876 genome-derived DEGs. Gene Ontology (GO) terms distinguished the seed morphs: the terms translation and nucleosome assembly were overrepresented in DEGs higher in abundance in M+ dry seeds, whereas terms related to mRNA processing and transcription were overrepresented in DEGs higher in abundance in NM dry seeds. DEGs amongst these GO terms included ribosomal proteins and histones (higher in M+), RNA polymerase II subunits and related transcription and elongation factors (higher in NM). Expression of the inferred DEGs and other genes associated with seed maturation (e.g. those encoding late embryogenesis abundant proteins and transcription factors regulating seed development and maturation such as ABI3, FUS3, LEC1 and WRI1 homologs) were put in context with Arabidopsis thaliana seed maturation and indicated that M+ seeds may desiccate and mature faster than NM. The 1901 transcriptomic DEG set GO-terms had almost 90% overlap with the 2191 genome-derived DEG GO-terms. Conclusions Whilst there was only modest overlap of DEGs identified in reference-free versus -dependent approaches, the resulting GO analysis was concordant in both approaches. The identified differences in dry seed transcriptomes suggest mechanisms underpinning previously identified contrasts between morphology and germination behaviour of M+ and NM seeds. Electronic supplementary material The online version of this article (10.1186/s12864-019-5452-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Per K I Wilhelmsson
- Plant Cell Biology, Faculty of Biology, University of Marburg, 35043, Marburg, Germany
| | - Jake O Chandler
- School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK
| | - Noe Fernandez-Pozo
- Plant Cell Biology, Faculty of Biology, University of Marburg, 35043, Marburg, Germany
| | - Kai Graeber
- School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK
| | - Kristian K Ullrich
- Plant Cell Biology, Faculty of Biology, University of Marburg, 35043, Marburg, Germany.,Present Address: Max Planck Institute for Evolutionary Biology, August-Thienemann-Straße 2, 24306, Ploen, Germany
| | - Waheed Arshad
- School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK
| | - Safina Khan
- School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK
| | - Johannes A Hofberger
- Biosystematics Group, Wageningen University, Wageningen, 6708 PB, The Netherlands
| | - Karl Buchta
- Plant Cell Biology, Faculty of Biology, University of Marburg, 35043, Marburg, Germany
| | - Patrick P Edger
- Department of Horticulture, Michigan State University, East Lansing, MI, 48864, USA
| | - J Chris Pires
- Division of Biological Sciences, University of Missouri, Columbia, MO, 65211, USA
| | - M Eric Schranz
- Biosystematics Group, Wageningen University, Wageningen, 6708 PB, The Netherlands
| | - Gerhard Leubner-Metzger
- School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK. .,Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Palacký University and Institute of Experimental Botany, Academy of Sciences of the Czech Republic, 78371, Olomouc, Czech Republic.
| | - Stefan A Rensing
- Plant Cell Biology, Faculty of Biology, University of Marburg, 35043, Marburg, Germany. .,BIOSS Centre for Biological Signalling Studies, University of Freiburg, Freiburg, Germany.
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Wilhelmsson PKI, Chandler JO, Fernandez-Pozo N, Graeber K, Ullrich KK, Arshad W, Khan S, Hofberger JA, Buchta K, Edger PP, Pires JC, Schranz ME, Leubner-Metzger G, Rensing SA. Usability of reference-free transcriptome assemblies for detection of differential expression: a case study on Aethionema arabicum dimorphic seeds. BMC Genomics 2019. [PMID: 30700268 DOI: 10.1186/s12864-019-5452-5454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/10/2023] Open
Abstract
BACKGROUND RNA-sequencing analysis is increasingly utilized to study gene expression in non-model organisms without sequenced genomes. Aethionema arabicum (Brassicaceae) exhibits seed dimorphism as a bet-hedging strategy - producing both a less dormant mucilaginous (M+) seed morph and a more dormant non-mucilaginous (NM) seed morph. Here, we compared de novo and reference-genome based transcriptome assemblies to investigate Ae. arabicum seed dimorphism and to evaluate the reference-free versus -dependent approach for identifying differentially expressed genes (DEGs). RESULTS A de novo transcriptome assembly was generated using sequences from M+ and NM Ae. arabicum dry seed morphs. The transcripts of the de novo assembly contained 63.1% complete Benchmarking Universal Single-Copy Orthologs (BUSCO) compared to 90.9% for the transcripts of the reference genome. DEG detection used the strict consensus of three methods (DESeq2, edgeR and NOISeq). Only 37% of 1533 differentially expressed de novo assembled transcripts paired with 1876 genome-derived DEGs. Gene Ontology (GO) terms distinguished the seed morphs: the terms translation and nucleosome assembly were overrepresented in DEGs higher in abundance in M+ dry seeds, whereas terms related to mRNA processing and transcription were overrepresented in DEGs higher in abundance in NM dry seeds. DEGs amongst these GO terms included ribosomal proteins and histones (higher in M+), RNA polymerase II subunits and related transcription and elongation factors (higher in NM). Expression of the inferred DEGs and other genes associated with seed maturation (e.g. those encoding late embryogenesis abundant proteins and transcription factors regulating seed development and maturation such as ABI3, FUS3, LEC1 and WRI1 homologs) were put in context with Arabidopsis thaliana seed maturation and indicated that M+ seeds may desiccate and mature faster than NM. The 1901 transcriptomic DEG set GO-terms had almost 90% overlap with the 2191 genome-derived DEG GO-terms. CONCLUSIONS Whilst there was only modest overlap of DEGs identified in reference-free versus -dependent approaches, the resulting GO analysis was concordant in both approaches. The identified differences in dry seed transcriptomes suggest mechanisms underpinning previously identified contrasts between morphology and germination behaviour of M+ and NM seeds.
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Affiliation(s)
- Per K I Wilhelmsson
- Plant Cell Biology, Faculty of Biology, University of Marburg, 35043, Marburg, Germany
| | - Jake O Chandler
- School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK
| | - Noe Fernandez-Pozo
- Plant Cell Biology, Faculty of Biology, University of Marburg, 35043, Marburg, Germany
| | - Kai Graeber
- School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK
| | - Kristian K Ullrich
- Plant Cell Biology, Faculty of Biology, University of Marburg, 35043, Marburg, Germany
- Present Address: Max Planck Institute for Evolutionary Biology, August-Thienemann-Straße 2, 24306, Ploen, Germany
| | - Waheed Arshad
- School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK
| | - Safina Khan
- School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK
| | - Johannes A Hofberger
- Biosystematics Group, Wageningen University, Wageningen, 6708 PB, The Netherlands
| | - Karl Buchta
- Plant Cell Biology, Faculty of Biology, University of Marburg, 35043, Marburg, Germany
| | - Patrick P Edger
- Department of Horticulture, Michigan State University, East Lansing, MI, 48864, USA
| | - J Chris Pires
- Division of Biological Sciences, University of Missouri, Columbia, MO, 65211, USA
| | - M Eric Schranz
- Biosystematics Group, Wageningen University, Wageningen, 6708 PB, The Netherlands
| | - Gerhard Leubner-Metzger
- School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK.
- Laboratory of Growth Regulators, Centre of the Region Haná for Biotechnological and Agricultural Research, Palacký University and Institute of Experimental Botany, Academy of Sciences of the Czech Republic, 78371, Olomouc, Czech Republic.
| | - Stefan A Rensing
- Plant Cell Biology, Faculty of Biology, University of Marburg, 35043, Marburg, Germany.
- BIOSS Centre for Biological Signalling Studies, University of Freiburg, Freiburg, Germany.
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