1
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Advances in Novel Animal Vitamin C Biosynthesis Pathways and the Role of Prokaryote-Based Inferences to Understand Their Origin. Genes (Basel) 2022; 13:genes13101917. [PMID: 36292802 PMCID: PMC9602106 DOI: 10.3390/genes13101917] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 10/17/2022] [Accepted: 10/18/2022] [Indexed: 11/04/2022] Open
Abstract
Vitamin C (VC) is an essential nutrient required for the optimal function and development of many organisms. VC has been studied for many decades, and still today, the characterization of its functions is a dynamic scientific field, mainly because of its commercial and therapeutic applications. In this review, we discuss, in a comparative way, the increasing evidence for alternative VC synthesis pathways in insects and nematodes, and the potential of myo-inositol as a possible substrate for this metabolic process in metazoans. Methodological approaches that may be useful for the future characterization of the VC synthesis pathways of Caenorhabditis elegans and Drosophila melanogaster are here discussed. We also summarize the current distribution of the eukaryote aldonolactone oxidoreductases gene lineages, while highlighting the added value of studies on prokaryote species that are likely able to synthesize VC for both the characterization of novel VC synthesis pathways and inferences on the complex evolutionary history of such pathways. Such work may help improve the industrial production of VC.
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2
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Caro L, Raman P, Steiner FA, Ailion M, Malik HS. Recurrent but Short-Lived Duplications of Centromeric Proteins in Holocentric Caenorhabditis Species. Mol Biol Evol 2022; 39:6731087. [PMID: 36173809 PMCID: PMC9577544 DOI: 10.1093/molbev/msac206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Centromeric histones (CenH3s) are essential for chromosome inheritance during cell division in most eukaryotes. CenH3 genes have rapidly evolved and undergone repeated gene duplications and diversification in many plant and animal species. In Caenorhabditis species, two independent duplications of CenH3 (named hcp-3 for HoloCentric chromosome-binding Protein 3) were previously identified in C. elegans and C. remanei. Using phylogenomic analyses in 32 Caenorhabditis species, we find strict retention of the ancestral hcp-3 gene and 10 independent duplications. Most hcp-3L (hcp-3-like) paralogs are only found in 1-2 species, are expressed in both males and females/hermaphrodites, and encode histone fold domains with 69-100% identity to ancestral hcp-3. We identified novel N-terminal protein motifs, including putative kinetochore protein-interacting motifs and a potential separase cleavage site, which are well conserved across Caenorhabditis HCP-3 proteins. Other N-terminal motifs vary in their retention across paralogs or species, revealing potential subfunctionalization or functional loss following duplication. An N-terminal extension in the hcp-3L gene of C. afra revealed an unprecedented protein fusion, where hcp-3L fused to duplicated segments from hcp-4 (nematode CENP-C). By extending our analyses beyond CenH3, we found gene duplications of six inner and outer kinetochore genes in Caenorhabditis, which appear to have been retained independent of hcp-3 duplications. Our findings suggest that centromeric protein duplications occur frequently in Caenorhabditis nematodes, are selectively retained for short evolutionary periods, then degenerate or are lost entirely. We hypothesize that unique challenges associated with holocentricity in Caenorhabditis may lead to this rapid "revolving door" of kinetochore protein paralogs.
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Affiliation(s)
- Lews Caro
- Molecular and Cellular Biology Program, University of Washington, Seattle, WA 98195, USA.,Department of Biochemistry, University of Washington, Seattle, WA 98195, USA
| | - Pravrutha Raman
- Division of Basic Sciences, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
| | - Florian A Steiner
- Department of Molecular Biology and Cellular Biology, Section of Biology, Faculty of Sciences, University of Geneva, Geneva, Switzerland
| | - Michael Ailion
- Molecular and Cellular Biology Program, University of Washington, Seattle, WA 98195, USA.,Department of Biochemistry, University of Washington, Seattle, WA 98195, USA
| | - Harmit S Malik
- Division of Basic Sciences, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA.,Howard Hughes Medical Institute, Fred Hutchinson Cancer Center, Seattle, WA 98109, USA
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3
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Abstract
Diversity within the fungal kingdom is evident from the wide range of morphologies fungi display as well as the various ecological roles and industrial purposes they serve. Technological advances, particularly in long-read sequencing, coupled with the increasing efficiency and decreasing costs across sequencing platforms have enabled robust characterization of fungal genomes. These sequencing efforts continue to reveal the rampant diversity in fungi at the genome level. Here, we discuss studies that have furthered our understanding of fungal genetic diversity and genomic evolution. These studies revealed the presence of both small-scale and large-scale genomic changes. In fungi, research has recently focused on many small-scale changes, such as how hypermutation and allelic transmission impact genome evolution as well as how and why a few specific genomic regions are more susceptible to rapid evolution than others. High-throughput sequencing of a diverse set of fungal genomes has also illuminated the frequency, mechanisms, and impacts of large-scale changes, which include chromosome structural variation and changes in chromosome number, such as aneuploidy, polyploidy, and the presence of supernumerary chromosomes. The studies discussed herein have provided great insight into how the architecture of the fungal genome varies within species and across the kingdom and how modern fungi may have evolved from the last common fungal ancestor and might also pave the way for understanding how genomic diversity has evolved in all domains of life.
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Affiliation(s)
- Shelby J. Priest
- Department of Molecular Genetics and Microbiology, Duke University Medical Centre, Durham, NC, USA
| | - Vikas Yadav
- Department of Molecular Genetics and Microbiology, Duke University Medical Centre, Durham, NC, USA
| | - Joseph Heitman
- Department of Molecular Genetics and Microbiology, Duke University Medical Centre, Durham, NC, USA
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4
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Kan SL, Shen TT, Gong P, Ran JH, Wang XQ. The complete mitochondrial genome of Taxus cuspidata (Taxaceae): eight protein-coding genes have transferred to the nuclear genome. BMC Evol Biol 2020; 20:10. [PMID: 31959109 PMCID: PMC6971862 DOI: 10.1186/s12862-020-1582-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Accepted: 01/13/2020] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Gymnosperms represent five of the six lineages of seed plants. However, most sequenced plant mitochondrial genomes (mitogenomes) have been generated for angiosperms, whereas mitogenomic sequences have been generated for only six gymnosperms. In particular, complete mitogenomes are available for all major seed plant lineages except Conifer II (non-Pinaceae conifers or Cupressophyta), an important lineage including six families, which impedes a comprehensive understanding of the mitogenomic diversity and evolution in gymnosperms. RESULTS Here, we report the complete mitogenome of Taxus cuspidata in Conifer II. In comparison with previously released gymnosperm mitogenomes, we found that the mitogenomes of Taxus and Welwitschia have lost many genes individually, whereas all genes were identified in the mitogenomes of Cycas, Ginkgo and Pinaceae. Multiple tRNA genes and introns also have been lost in some lineages of gymnosperms, similar to the pattern observed in angiosperms. In general, gene clusters could be less conserved in gymnosperms than in angiosperms. Moreover, fewer RNA editing sites were identified in the Taxus and Welwitschia mitogenomes than in other mitogenomes, which could be correlated with fewer introns and frequent gene losses in these two species. CONCLUSIONS We have sequenced the Taxus cuspidata mitogenome, and compared it with mitogenomes from the other four gymnosperm lineages. The results revealed the diversity in size, structure, gene and intron contents, foreign sequences, and mutation rates of gymnosperm mitogenomes, which are different from angiosperm mitogenomes.
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Affiliation(s)
- Sheng-Long Kan
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Ting-Ting Shen
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
| | - Ping Gong
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
| | - Jin-Hua Ran
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China.
- University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Xiao-Quan Wang
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
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5
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Kuitche E, Jammali S, Ouangraoua A. SimSpliceEvol: alternative splicing-aware simulation of biological sequence evolution. BMC Bioinformatics 2019; 20:640. [PMID: 31842741 PMCID: PMC6916212 DOI: 10.1186/s12859-019-3207-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Background It is now well established that eukaryotic coding genes have the ability to produce more than one type of transcript thanks to the mechanisms of alternative splicing and alternative transcription. Because of the lack of gold standard real data on alternative splicing, simulated data constitute a good option for evaluating the accuracy and the efficiency of methods developed for splice-aware sequence analysis. However, existing sequence evolution simulation methods do not model alternative splicing, and so they can not be used to test spliced sequence analysis methods. Results We propose a new method called SimSpliceEvol for simulating the evolution of sets of alternative transcripts along the branches of an input gene tree. In addition to traditional sequence evolution events, the simulation also includes gene exon-intron structure evolution events and alternative splicing events that modify the sets of transcripts produced from genes. SimSpliceEvol was implemented in Python. The source code is freely available at https://github.com/UdeS-CoBIUS/SimSpliceEvol. Conclusions Data generated using SimSpliceEvol are useful for testing spliced RNA sequence analysis methods such as methods for spliced alignment of cDNA and genomic sequences, multiple cDNA alignment, orthologous exons identification, splicing orthology inference, transcript phylogeny inference, which requires to know the real evolutionary relationships between the sequences.
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Affiliation(s)
- Esaie Kuitche
- Department of Computer Science, University of Sherbrooke, 2500 Boulevard de l'Université, Quebec, J1K2R1, Canada.
| | - Safa Jammali
- Department of Computer Science, University of Sherbrooke, 2500 Boulevard de l'Université, Quebec, J1K2R1, Canada.,Department of Biochemistry, University of Sherbrooke, 3001 12e avenue Nord, Quebec, J1H5N4, Canada
| | - Aïda Ouangraoua
- Department of Computer Science, University of Sherbrooke, 2500 Boulevard de l'Université, Quebec, J1K2R1, Canada
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6
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Wang Y, Youssef NH, Couger MB, Hanafy RA, Elshahed MS, Stajich JE. Molecular Dating of the Emergence of Anaerobic Rumen Fungi and the Impact of Laterally Acquired Genes. mSystems 2019; 4:e00247-19. [PMID: 31455637 PMCID: PMC6712302 DOI: 10.1128/msystems.00247-19] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Accepted: 08/01/2019] [Indexed: 01/01/2023] Open
Abstract
The anaerobic gut fungi (AGF), or Neocallimastigomycota, inhabit the rumen and alimentary tract of herbivorous mammals, where they play important roles in the degradation of plant fiber. Comparative genomic and phylogenomic analyses of the AGF have long been hampered by their fastidious growth condition, as well as their large (up to 200 Mb) and AT-biased (78 to 84%) genomes. We sequenced 21 AGF transcriptomes and combined them with 5 available AGF genome sequences to explore their evolutionary relationships, time their divergence, and characterize gene gain/loss patterns associated with their evolution. We estimate that the most recent common ancestor of the AGF diverged 66 (±10) million years ago, a time frame that coincides with the evolution of grasses (Poaceae), as well as the mammalian transition from insectivory to herbivory. The concordance of independent estimations suggests that AGF have been important in shaping the success of mammalian herbivory transition by improving the efficiency of energy acquisition from recalcitrant plant materials. Comparative genomics identified multiple lineage-specific genes in the AGF, two of which were acquired from rumen gut bacteria and animal hosts via horizontal gene transfer (HGT). A third AGF domain, plant-like polysaccharide lyase, represents a novel gene in fungi that potentially aids AGF to degrade pectin. Analysis of genomic and transcriptomic sequences confirmed both the presence and expression of these lineage-specific genes in nearly all AGF clades. These genetic elements may contribute to the exceptional abilities of AGF to degrade plant biomass and enable metabolism of the rumen microbes and animal hosts.IMPORTANCE Anaerobic fungi living in the rumen of herbivorous mammals possess an extraordinary ability to degrade plant biomass. We examined the origin and genomic composition of these poorly characterized anaerobic gut fungi using both transcriptome and genomic data. Phylogenomics and molecular dating analyses found remarkable concurrence of the divergence times of the rumen fungi, the forage grasses, and the dietary shift of ancestral mammals from primarily insectivory to herbivory. Comparative genomics identified unique machinery in these fungi to utilize plant polysaccharides. The rumen fungi were also identified with the ability to code for three protein domains with putative functions in plant pectin degradation and microbial defense, which were absent from all other fungal organisms (examined over 1,000 fungal genomes). Two of these domains were likely acquired from rumen gut bacteria and animal hosts separately via horizontal gene transfer. The third one is a plant-like polysaccharide lyase, representing a unique fungal enzyme with potential pectin breakdown abilities.
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Affiliation(s)
- Yan Wang
- Department of Microbiology and Plant Pathology, University of California-Riverside, Riverside, California, USA
- Institute for Integrative Genome Biology, University of California-Riverside, Riverside, California, USA
| | - Noha H Youssef
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, Oklahoma, USA
| | - Matthew Brian Couger
- High Performance Computing Center, Oklahoma State University, Stillwater, Oklahoma, USA
| | - Radwa A Hanafy
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, Oklahoma, USA
| | - Mostafa S Elshahed
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, Oklahoma, USA
| | - Jason E Stajich
- Department of Microbiology and Plant Pathology, University of California-Riverside, Riverside, California, USA
- Institute for Integrative Genome Biology, University of California-Riverside, Riverside, California, USA
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7
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Intron-mediated regulation of β-tubulin genes expression affects the sensitivity to carbendazim in Fusarium graminearum. Curr Genet 2019; 65:1057-1069. [DOI: 10.1007/s00294-019-00960-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 03/13/2019] [Accepted: 03/26/2019] [Indexed: 12/20/2022]
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8
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Pogoda CS, Keepers KG, Nadiadi AY, Bailey DW, Lendemer JC, Tripp EA, Kane NC. Genome streamlining via complete loss of introns has occurred multiple times in lichenized fungal mitochondria. Ecol Evol 2019; 9:4245-4263. [PMID: 31016002 PMCID: PMC6467859 DOI: 10.1002/ece3.5056] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 02/12/2019] [Accepted: 02/22/2019] [Indexed: 12/22/2022] Open
Abstract
Reductions in genome size and complexity are a hallmark of obligate symbioses. The mitochondrial genome displays clear examples of these reductions, with the ancestral alpha-proteobacterial genome size and gene number having been reduced by orders of magnitude in most descendent modern mitochondrial genomes. Here, we examine patterns of mitochondrial evolution specifically looking at intron size, number, and position across 58 species from 21 genera of lichenized Ascomycete fungi, representing a broad range of fungal diversity and niches. Our results show that the cox1gene always contained the highest number of introns out of all the mitochondrial protein-coding genes, that high intron sequence similarity (>90%) can be maintained between different genera, and that lichens have undergone at least two instances of complete, genome-wide intron loss consistent with evidence for genome streamlining via loss of parasitic, noncoding DNA, in Phlyctis boliviensisand Graphis lineola. Notably, however, lichenized fungi have not only undergone intron loss but in some instances have expanded considerably in size due to intron proliferation (e.g., Alectoria fallacina and Parmotrema neotropicum), even between closely related sister species (e.g., Cladonia). These results shed light on the highly dynamic mitochondrial evolution that is occurring in lichens and suggest that these obligate symbiotic organisms are in some cases undergoing recent, broad-scale genome streamlining via loss of protein-coding genes as well as noncoding, parasitic DNA elements.
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Affiliation(s)
- Cloe S. Pogoda
- Department of Ecology and Evolutionary BiologyUniversity of ColoradoBoulderColorado
| | - Kyle G. Keepers
- Department of Ecology and Evolutionary BiologyUniversity of ColoradoBoulderColorado
| | - Arif Y. Nadiadi
- Department of Ecology and Evolutionary BiologyUniversity of ColoradoBoulderColorado
| | - Dustin W. Bailey
- Department of Ecology and Evolutionary BiologyUniversity of ColoradoBoulderColorado
| | - James C. Lendemer
- Institute of Systematic BotanyThe New York Botanical GardenBronxNew York
| | - Erin A. Tripp
- Department of Ecology and Evolutionary BiologyUniversity of ColoradoBoulderColorado
- Museum of Natural HistoryUniversity of ColoradoBoulderColorado
| | - Nolan C. Kane
- Department of Ecology and Evolutionary BiologyUniversity of ColoradoBoulderColorado
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9
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Abstract
In Cryptococcus neoformans, nearly all genes are interrupted by small introns. In recent years, genome annotation and genetic analysis have illuminated the major roles these introns play in the biology of this pathogenic yeast. Introns are necessary for gene expression and alternative splicing can regulate gene expression in response to environmental cues. In addition, recent studies have revealed that C. neoformans introns help to prevent transposon dissemination and protect genome integrity. These characteristics of cryptococcal introns are probably not unique to Cryptococcus, and this yeast likely can be considered as a model for intron-related studies in fungi.
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Affiliation(s)
- Guilhem Janbon
- Unité Biologie des ARN des Pathogènes Fongiques, Département de Mycologie, Institut Pasteur, Paris, France
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10
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Comparative Analysis of Four Calypogeia Species Revealed Unexpected Change in Evolutionarily-Stable Liverwort Mitogenomes. Genes (Basel) 2017; 8:genes8120395. [PMID: 29257096 PMCID: PMC5748713 DOI: 10.3390/genes8120395] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 12/08/2017] [Accepted: 12/12/2017] [Indexed: 11/17/2022] Open
Abstract
Liverwort mitogenomes are considered to be evolutionarily stable. A comparative analysis of four Calypogeia species revealed differences compared to previously sequenced liverwort mitogenomes. Such differences involve unexpected structural changes in the two genes, cox1 and atp1, which have lost three and two introns, respectively. The group I introns in the cox1 gene are proposed to have been lost by two-step localized retroprocessing, whereas one-step retroprocessing could be responsible for the disappearance of the group II introns in the atp1 gene. These cases represent the first identified losses of introns in mitogenomes of leafy liverworts (Jungermanniopsida) contrasting the stability of mitochondrial gene order with certain changes in the gene content and intron set in liverworts.
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11
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Phylogenetic relationships of ascomycetes and basidiomycetes based on comparative genomics analysis. Genes Genomics 2017. [DOI: 10.1007/s13258-017-0595-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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12
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Catania F. From intronization to intron loss: How the interplay between mRNA-associated processes can shape the architecture and the expression of eukaryotic genes. Int J Biochem Cell Biol 2017; 91:136-144. [PMID: 28673893 DOI: 10.1016/j.biocel.2017.06.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Revised: 06/25/2017] [Accepted: 06/30/2017] [Indexed: 12/29/2022]
Abstract
Transcription-coupled processes such as capping, splicing, and cleavage/polyadenylation participate in the journey from genes to proteins. Although they are traditionally thought to serve only as steps in the generation of mature mRNAs, a synthesis of available data indicates that these processes could also act as a driving force for the evolution of eukaryotic genes. A theoretical framework for how mRNA-associated processes may shape gene structure and expression has recently been proposed. Factors that promote splicing and cleavage/polyadenylation in this framework compete for access to overlapping or neighboring signals throughout the transcription cycle. These antagonistic interactions allow mechanisms for intron gain and splice site recognition as well as common trends in eukaryotic gene structure and expression to be coherently integrated. Here, I extend this framework further. Observations that largely (but not exclusively) revolve around the formation of DNA-RNA hybrid structures, called R loops, and promoter directionality are integrated. Additionally, the interplay between splicing factors and cleavage/polyadenylation factors is theorized to also affect the formation of intragenic DNA double-stranded breaks thereby contributing to intron loss. The most notable prediction in this proposition is that RNA molecules can mediate intron loss by serving as a template to repair DNA double-stranded breaks. The framework presented here leverages a vast body of empirical observations, logically extending previous suggestions, and generating verifiable predictions to further substantiate the view that the intracellular environment plays an active role in shaping the structure and the expression of eukaryotic genes.
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Affiliation(s)
- Francesco Catania
- Institute for Evolution and Biodiversity, University of Münster, Hüfferstraße 1, 48149 Münster, Germany.
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13
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Effects of sub-culturing on genetic and physiological parameters in different Beauveria bassiana isolates. J Invertebr Pathol 2017; 145:62-67. [DOI: 10.1016/j.jip.2017.03.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 03/09/2017] [Accepted: 03/19/2017] [Indexed: 11/20/2022]
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14
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Roy SW. Is Genome Complexity a Consequence of Inefficient Selection? Evidence from Intron Creation in Nonrecombining Regions. Mol Biol Evol 2016; 33:3088-3094. [DOI: 10.1093/molbev/msw172] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
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15
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Collemare J, Beenen HG, Crous PW, de Wit PJGM, van der Burgt A. Novel Introner-Like Elements in fungi Are Involved in Parallel Gains of Spliceosomal Introns. PLoS One 2015; 10:e0129302. [PMID: 26046656 PMCID: PMC4457414 DOI: 10.1371/journal.pone.0129302] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 05/08/2015] [Indexed: 01/08/2023] Open
Abstract
Spliceosomal introns are key components of the eukaryotic gene structure. Although they contributed to the emergence of eukaryotes, their origin remains elusive. In fungi, they might originate from the multiplication of invasive introns named Introner-Like Elements (ILEs). However, so far ILEs have been observed in six fungal species only, including Fulvia fulva and Dothistroma septosporum (Dothideomycetes), arguing against ILE insertion as a general mechanism for intron gain. Here, we identified novel ILEs in eight additional fungal species that are phylogenetically related to F. fulva and D. septosporum using PCR amplification with primers derived from previously identified ILEs. The ILE content appeared unique to each species, suggesting independent multiplication events. Interestingly, we identified four genes each containing two gained ILEs. By analysing intron positions in orthologues of these four genes in Ascomycota, we found that three ILEs had inserted within a 15 bp window that contains regular spliceosomal introns in other fungal species. These three positions are not the result of intron sliding because ILEs are newly gained introns. Furthermore, the alternative hypothesis of an inferred ancestral gain followed by independent losses contradicts the observed degeneration of ILEs. These observations clearly indicate three parallel intron gains in four genes that were randomly identified. Our findings suggest that parallel intron gain is a phenomenon that has been highly underestimated in ILE-containing fungi, and likely in the whole fungal kingdom.
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Affiliation(s)
- Jérôme Collemare
- Laboratory of Phytopathology, Wageningen University, Wageningen, The Netherlands
- Present address: UMR1345 IRHS-INRA, Beaucouzé, France
- * E-mail:
| | - Henriek G. Beenen
- Laboratory of Phytopathology, Wageningen University, Wageningen, The Netherlands
- Present address: Dyadic, Wageningen, The Netherlands
| | - Pedro W. Crous
- Evolutionary Phytopathology, CBS-KNAW Fungal Biodiversity Centre, Utrecht, The Netherlands
| | | | - Ate van der Burgt
- Laboratory of Phytopathology, Wageningen University, Wageningen, The Netherlands
- Present address: Dyadic, Wageningen, The Netherlands
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16
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Chen J, Xu Y, San M, Cao Z, Li W, Wu Y, Chen Z. Cloning and Genomic Characterization of a Natural Insecticidal Peptide LaIT1 with Unique DDH Structural Fold. J Biochem Mol Toxicol 2015; 29:207-12. [DOI: 10.1002/jbt.21686] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Revised: 11/14/2014] [Accepted: 12/10/2014] [Indexed: 11/10/2022]
Affiliation(s)
- Jing Chen
- Department of Biochemistry and Molecular Biology; Institute of Basic Medical Sciences; Hubei University of Medicine; Hubei People's Republic of China
- State Key Laboratory of Virology; College of Life Sciences; Wuhan University; Hubei People's Republic of China
| | - Yue Xu
- Department of Biochemistry and Molecular Biology; Institute of Basic Medical Sciences; Hubei University of Medicine; Hubei People's Republic of China
| | - Mingkui San
- Department of Biochemistry and Molecular Biology; Institute of Basic Medical Sciences; Hubei University of Medicine; Hubei People's Republic of China
| | - Zhijian Cao
- State Key Laboratory of Virology; College of Life Sciences; Wuhan University; Hubei People's Republic of China
| | - Wenxin Li
- State Key Laboratory of Virology; College of Life Sciences; Wuhan University; Hubei People's Republic of China
| | - Yingliang Wu
- State Key Laboratory of Virology; College of Life Sciences; Wuhan University; Hubei People's Republic of China
| | - Zongyun Chen
- Department of Biochemistry and Molecular Biology; Institute of Basic Medical Sciences; Hubei University of Medicine; Hubei People's Republic of China
- State Key Laboratory of Virology; College of Life Sciences; Wuhan University; Hubei People's Republic of China
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17
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Merkin JJ, Chen P, Alexis MS, Hautaniemi SK, Burge CB. Origins and impacts of new mammalian exons. Cell Rep 2015; 10:1992-2005. [PMID: 25801031 DOI: 10.1016/j.celrep.2015.02.058] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Revised: 01/09/2015] [Accepted: 02/23/2015] [Indexed: 02/08/2023] Open
Abstract
Mammalian genes are composed of exons, but the evolutionary origins and functions of new internal exons are poorly understood. Here, we analyzed patterns of exon gain using deep cDNA sequencing data from five mammals and one bird, identifying thousands of species- and lineage-specific exons. Most new exons derived from unique rather than repetitive intronic sequence. Unlike exons conserved across mammals, species-specific internal exons were mostly located in 5' UTRs and alternatively spliced. They were associated with upstream intronic deletions, increased nucleosome occupancy, and RNA polymerase II pausing. Genes containing new internal exons had increased gene expression, but only in tissues in which the exon was included. Increased expression correlated with the level of exon inclusion, promoter proximity, and signatures of cotranscriptional splicing. Altogether, these findings suggest that increased splicing at the 5' ends of genes enhances expression and that changes in 5' end splicing alter gene expression between tissues and between species.
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Affiliation(s)
- Jason J Merkin
- Departments of Biology and Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| | - Ping Chen
- Research Programs Unit, Genome-Scale Biology and Institute of Biomedicine, University of Helsinki, 00014 Helsinki, Finland
| | - Maria S Alexis
- Departments of Biology and Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02142, USA; Program in Computational and Systems Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| | - Sampsa K Hautaniemi
- Research Programs Unit, Genome-Scale Biology and Institute of Biomedicine, University of Helsinki, 00014 Helsinki, Finland
| | - Christopher B Burge
- Departments of Biology and Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02142, USA; Program in Computational and Systems Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA.
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Dey G, Jaimovich A, Collins SR, Seki A, Meyer T. Systematic Discovery of Human Gene Function and Principles of Modular Organization through Phylogenetic Profiling. Cell Rep 2015; 10:993-1006. [PMID: 25683721 DOI: 10.1016/j.celrep.2015.01.025] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Revised: 12/17/2014] [Accepted: 01/09/2015] [Indexed: 01/17/2023] Open
Abstract
Functional links between genes can be predicted using phylogenetic profiling, by correlating the appearance and loss of homologs in subsets of species. However, effective genome-wide phylogenetic profiling has been hindered by the large fraction of human genes related to each other through historical duplication events. Here, we overcame this challenge by automatically profiling over 30,000 groups of homologous human genes (orthogroups) representing the entire protein-coding genome across 177 eukaryotic species (hOP profiles). By generating a full pairwise orthogroup phylogenetic co-occurrence matrix, we derive unbiased genome-wide predictions of functional modules (hOP modules). Our approach predicts functions for hundreds of poorly characterized genes. The results suggest evolutionary constraints that lead components of protein complexes and metabolic pathways to co-evolve while genes in signaling and transcriptional networks do not. As a proof of principle, we validated two subsets of candidates experimentally for their predicted link to the actin-nucleating WASH complex and cilia/basal body function.
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Affiliation(s)
- Gautam Dey
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA 94305, USA
| | - Ariel Jaimovich
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA 94305, USA
| | - Sean R Collins
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA 94305, USA
| | - Akiko Seki
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA 94305, USA
| | - Tobias Meyer
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA 94305, USA.
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Wang H, Devos KM, Bennetzen JL. Recurrent loss of specific introns during angiosperm evolution. PLoS Genet 2014; 10:e1004843. [PMID: 25474210 PMCID: PMC4256211 DOI: 10.1371/journal.pgen.1004843] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Accepted: 10/22/2014] [Indexed: 11/18/2022] Open
Abstract
Numerous instances of presence/absence variations for introns have been documented in eukaryotes, and some cases of recurrent loss of the same intron have been suggested. However, there has been no comprehensive or phylogenetically deep analysis of recurrent intron loss. Of 883 cases of intron presence/absence variation that we detected in five sequenced grass genomes, 93 were confirmed as recurrent losses and the rest could be explained by single losses (652) or single gains (118). No case of recurrent intron gain was observed. Deep phylogenetic analysis often indicated that apparent intron gains were actually numerous independent losses of the same intron. Recurrent loss exhibited extreme non-randomness, in that some introns were removed independently in many lineages. The two larger genomes, maize and sorghum, were found to have a higher rate of both recurrent loss and overall loss and/or gain than foxtail millet, rice or Brachypodium. Adjacent introns and small introns were found to be preferentially lost. Intron loss genes exhibited a high frequency of germ line or early embryogenesis expression. In addition, flanking exon A+T-richness and intron TG/CG ratios were higher in retained introns. This last result suggests that epigenetic status, as evidenced by a loss of methylated CG dinucleotides, may play a role in the process of intron loss. This study provides the first comprehensive analysis of recurrent intron loss, makes a series of novel findings on the patterns of recurrent intron loss during the evolution of the grass family, and provides insight into the molecular mechanism(s) underlying intron loss. The spliceosomal introns are nucleotide sequences that interrupt coding regions of eukaryotic genes and are removed by RNA splicing after transcription. Recent studies have reported several examples of possible recurrent intron loss or gain, i.e., introns that are independently removed from or inserted into the identical sites more than once in an investigated phylogeny. However, the frequency, evolutionary patterns or other characteristics of recurrent intron turnover remain unknown. We provide results for the first comprehensive analysis of recurrent intron turnover within a plant family and show that recurrent intron loss represents a considerable portion of all intron losses identified and intron loss events far outnumber intron gain events. We also demonstrate that recurrent intron loss is non-random, affecting only a small number of introns that are repeatedly lost, and that different lineages show significantly different rates of intron loss. Our results suggest a possible role of DNA methylation in the process of intron loss. Moreover, this study provides strong support for the model of intron loss by reverse transcriptase mediated conversion of genes by their processed mRNA transcripts.
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Affiliation(s)
- Hao Wang
- Department of Genetics, University of Georgia, Athens, Georgia, United States of America
| | - Katrien M. Devos
- Department of Crop and Soil Sciences, and Department of Plant Biology, University of Georgia, Athens, Georgia, United States of America
| | - Jeffrey L. Bennetzen
- Department of Genetics, University of Georgia, Athens, Georgia, United States of America
- Germplasm Bank of Wild Species in Southwestern China, Kunming Institute of Botany, Kunming, Yunnan, P.R. China
- * E-mail:
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20
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Abstract
We used comparative and population genomics to study intron evolutionary dynamics in the fungal model genus Neurospora. For our investigation, we used well-annotated genomes of N. crassa, N. discreta, and N. tetrasperma, and 92 resequenced genomes of N. tetrasperma from natural populations. By analyzing the four well-annotated genomes, we identified 9495 intron sites in 7619 orthologous genes. Our data supports nonhomologous end joining (NHEJ) and tandem duplication as mechanisms for intron gains in the genus and the RT-mRNA process as a mechanism for intron loss. We found a moderate intron gain rate (5.78–6.89 × 10−13 intron gains per nucleotide site per year) and a high intron loss rate (7.53–13.76 × 10−10 intron losses per intron sites per year) as compared to other eukaryotes. The derived intron gains and losses are skewed to high frequencies, relative to neutral SNPs, in natural populations of N. tetrasperma, suggesting that selection is involved in maintaining a high intron turnover. Furthermore, our analyses of the association between intron population-level frequency and genomic features suggest that selection is involved in shaping a 5′ intron position bias and a low intron GC content. However, intron sequence analyses suggest that the gained introns were not exposed to recent selective sweeps. Taken together, this work contributes to our understanding of the importance of mutational bias and selection in shaping the intron distribution in eukaryotic genomes.
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Reichman JR, Vize PD. Separate introns gained within short and long soluble peridinin-chlorophyll a-protein genes during radiation of Symbiodinium (Dinophyceae) clade A and B lineages. PLoS One 2014; 9:e110608. [PMID: 25330037 PMCID: PMC4201569 DOI: 10.1371/journal.pone.0110608] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Accepted: 09/22/2014] [Indexed: 11/18/2022] Open
Abstract
Here we document introns in two Symbiodinium clades that were most likely gained following divergence of this genus from other peridinin-containing dinoflagellate lineages. Soluble peridinin-chlorophyll a-proteins (sPCP) occur in short and long forms in different species. Duplication and fusion of short sPCP genes produced long sPCP genes. All short and long sPCP genes characterized to date, including those from free living species and Symbiodinium sp. 203 (clade C/type C2) are intronless. However, we observed that long sPCP genes from two Caribbean Symbiodinium clade B isolates each contained two introns. To test the hypothesis that introns were gained during radiation of clade B, we compared sPCP genomic and cDNA sequences from 13 additional distinct Caribbean and Pacific Symbiodinium clade A, B, and F isolates. Long sPCP genes from all clade B/B1 and B/B19 descendants contain orthologs of both introns. Short sPCP genes from S. pilosum (A/A2) and S. muscatinei (B/B4) plus long sPCP genes from S. microadriaticum (A/A1) and S. kawagutii (F/F1) are intronless. Short sPCP genes of S. microadriaticum have a third unique intron. Symbiodinium clade B long sPCP sequences are useful for assessing divergence among B1 and B19 descendants. Phylogenetic analyses of coding sequences from four dinoflagellate orders indicate that introns were gained independently during radiation of Symbiodinium clades A and B. Long sPCP introns were present in the most recent common ancestor of Symbiodinium clade B core types B1 and B19, which apparently diverged sometime during the Miocene. The clade A short sPCP intron was either gained by S. microadriaticum or possibly by the ancestor of Symbiodinium types A/A1, A3, A4 and A5. The timing of short sPCP intron gain in Symbiodinium clade A is less certain. But, all sPCP introns were gained after fusion of ancestral short sPCP genes, which we confirm as occurring once in dinoflagellate evolution.
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Affiliation(s)
- Jay R. Reichman
- US Environmental Protection Agency, Western Ecology Division, Corvallis, Oregon, United States of America
- Oregon State University, Department of Botany and Plant Pathology, Corvallis, Oregon, United States of America
- * E-mail:
| | - Peter D. Vize
- University of Calgary, Department of Biological Sciences, Calgary, Alberta, Canada
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Junges Â, Boldo JT, Souza BK, Guedes RLM, Sbaraini N, Kmetzsch L, Thompson CE, Staats CC, de Almeida LGP, de Vasconcelos ATR, Vainstein MH, Schrank A. Genomic analyses and transcriptional profiles of the glycoside hydrolase family 18 genes of the entomopathogenic fungus Metarhizium anisopliae. PLoS One 2014; 9:e107864. [PMID: 25232743 PMCID: PMC4169460 DOI: 10.1371/journal.pone.0107864] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Accepted: 08/16/2014] [Indexed: 12/26/2022] Open
Abstract
Fungal chitin metabolism involves diverse processes such as metabolically active cell wall maintenance, basic nutrition, and different aspects of virulence. Chitinases are enzymes belonging to the glycoside hydrolase family 18 (GH18) and 19 (GH19) and are responsible for the hydrolysis of β-1,4-linkages in chitin. This linear homopolymer of N-acetyl-β-D-glucosamine is an essential constituent of fungal cell walls and arthropod exoskeletons. Several chitinases have been directly implicated in structural, morphogenetic, autolytic and nutritional activities of fungal cells. In the entomopathogen Metarhizium anisopliae, chitinases are also involved in virulence. Filamentous fungi genomes exhibit a higher number of chitinase-coding genes than bacteria or yeasts. The survey performed in the M. anisopliae genome has successfully identified 24 genes belonging to glycoside hydrolase family 18, including three previously experimentally determined chitinase-coding genes named chit1, chi2 and chi3. These putative chitinases were classified based on domain organization and phylogenetic analysis into the previously described A, B and C chitinase subgroups, and into a new subgroup D. Moreover, three GH18 proteins could be classified as putative endo-N-acetyl-β-D-glucosaminidases, enzymes that are associated with deglycosylation and were therefore assigned to a new subgroup E. The transcriptional profile of the GH18 genes was evaluated by qPCR with RNA extracted from eight culture conditions, representing different stages of development or different nutritional states. The transcripts from the GH18 genes were detected in at least one of the different M. anisopliae developmental stages, thus validating the proposed genes. Moreover, not all members from the same chitinase subgroup presented equal patterns of transcript expression under the eight distinct conditions studied. The determination of M. anisopliae chitinases and ENGases and a more detailed study concerning the enzymes’ roles in morphological or nutritional functions will allow comprehensive insights into the chitinolytic potential of this highly infective entomopathogenic fungus.
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Affiliation(s)
- Ângela Junges
- Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | | | - Bárbara Kunzler Souza
- Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | | | - Nicolau Sbaraini
- Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Lívia Kmetzsch
- Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | | | | | | | | | | | - Augusto Schrank
- Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
- * E-mail:
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Verhelst B, Van de Peer Y, Rouzé P. The complex intron landscape and massive intron invasion in a picoeukaryote provides insights into intron evolution. Genome Biol Evol 2014; 5:2393-401. [PMID: 24273312 PMCID: PMC3879977 DOI: 10.1093/gbe/evt189] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Genes in pieces and spliceosomal introns are a landmark of eukaryotes, with intron invasion usually assumed to have happened early on in evolution. Here, we analyze the intron landscape of Micromonas, a unicellular green alga in the Mamiellophyceae lineage, demonstrating the coexistence of several classes of introns and the occurrence of recent massive intron invasion. This study focuses on two strains, CCMP1545 and RCC299, and their related individuals from ocean samplings, showing that they not only harbor different classes of introns depending on their location in the genome, as for other Mamiellophyceae, but also uniquely carry several classes of repeat introns. These introns, dubbed introner elements (IEs), are found at novel positions in genes and have conserved sequences, contrary to canonical introns. This IE invasion has a huge impact on the genome, doubling the number of introns in the CCMP1545 strain. We hypothesize that each IE class originated from a single ancestral IE that has been colonizing the genome after strain divergence by inserting copies of itself into genes by intron transposition, likely involving reverse splicing. Along with similar cases recently observed in other organisms, our observations in Micromonas strains shed a new light on the evolution of introns, suggesting that intron gain is more widespread than previously thought.
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Affiliation(s)
- Bram Verhelst
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Belgium
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24
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Abstract
In this work we review the current knowledge on the prehistory, origins, and evolution of spliceosomal introns. First, we briefly outline the major features of the different types of introns, with particular emphasis on the nonspliceosomal self-splicing group II introns, which are widely thought to be the ancestors of spliceosomal introns. Next, we discuss the main scenarios proposed for the origin and proliferation of spliceosomal introns, an event intimately linked to eukaryogenesis. We then summarize the evidence that suggests that the last eukaryotic common ancestor (LECA) had remarkably high intron densities and many associated characteristics resembling modern intron-rich genomes. From this intron-rich LECA, the different eukaryotic lineages have taken very distinct evolutionary paths leading to profoundly diverged modern genome structures. Finally, we discuss the origins of alternative splicing and the qualitative differences in alternative splicing forms and functions across lineages.
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Affiliation(s)
- Manuel Irimia
- The Donnelly Centre, University of Toronto, Toronto, Ontario M5S3E1, Canada
| | - Scott William Roy
- Department of Biology, San Francisco State University, San Francisco, California 94132
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25
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van der Burgt A, Severing E, Collemare J, de Wit PJGM. Automated alignment-based curation of gene models in filamentous fungi. BMC Bioinformatics 2014; 15:19. [PMID: 24433567 PMCID: PMC3898260 DOI: 10.1186/1471-2105-15-19] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Accepted: 01/11/2014] [Indexed: 11/16/2022] Open
Abstract
Background Automated gene-calling is still an error-prone process, particularly for the highly plastic genomes of fungal species. Improvement through quality control and manual curation of gene models is a time-consuming process that requires skilled biologists and is only marginally performed. The wealth of available fungal genomes has not yet been exploited by an automated method that applies quality control of gene models in order to obtain more accurate genome annotations. Results We provide a novel method named alignment-based fungal gene prediction (ABFGP) that is particularly suitable for plastic genomes like those of fungi. It can assess gene models on a gene-by-gene basis making use of informant gene loci. Its performance was benchmarked on 6,965 gene models confirmed by full-length unigenes from ten different fungi. 79.4% of all gene models were correctly predicted by ABFGP. It improves the output of ab initio gene prediction software due to a higher sensitivity and precision for all gene model components. Applicability of the method was shown by revisiting the annotations of six different fungi, using gene loci from up to 29 fungal genomes as informants. Between 7,231 and 8,337 genes were assessed by ABFGP and for each genome between 1,724 and 3,505 gene model revisions were proposed. The reliability of the proposed gene models is assessed by an a posteriori introspection procedure of each intron and exon in the multiple gene model alignment. The total number and type of proposed gene model revisions in the six fungal genomes is correlated to the quality of the genome assembly, and to sequencing strategies used in the sequencing centre, highlighting different types of errors in different annotation pipelines. The ABFGP method is particularly successful in discovering sequence errors and/or disruptive mutations causing truncated and erroneous gene models. Conclusions The ABFGP method is an accurate and fully automated quality control method for fungal gene catalogues that can be easily implemented into existing annotation pipelines. With the exponential release of new genomes, the ABFGP method will help decreasing the number of gene models that require additional manual curation.
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Affiliation(s)
| | | | | | - Pierre J G M de Wit
- Laboratory of Phytopathology, Wageningen University & Research Centre, P,O, Box 16, 6700 AA Wageningen, The Netherlands.
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26
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Abstract
How introns are lost from eukaryotic genomes during evolution remains an enigmatic question in biology. By comparative genome analysis of five Caenorhabditis and eight Drosophila species, we found that the likelihood of intron loss is highly influenced by the degree of sequence homology at exon–intron junctions: a significant elevated degree of microhomology was observed for sequences immediately flanking those introns that were eliminated from the genome of one or more subspecies. This determinant was significant even at individual nucleotides. We propose that microhomology-mediated DNA repair underlies this phenomenon, which we termed microhomology-mediated intron loss. This hypothesis is further supported by the observations that in both species 1) smaller introns are preferentially lost over longer ones and 2) genes that are highly transcribed in germ cells, and are thus more prone to DNA double strand breaks, display elevated frequencies of intron loss. Our data also testify against a prominent role for reverse transcriptase-mediated intron loss in metazoans.
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Affiliation(s)
- Robin van Schendel
- Department of Toxicogenetics, Leiden University Medical Center, The Netherlands
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Collemare J, van der Burgt A, de Wit PJGM. At the origin of spliceosomal introns: Is multiplication of introner-like elements the main mechanism of intron gain in fungi? Commun Integr Biol 2013; 6:e23147. [PMID: 23750299 PMCID: PMC3609843 DOI: 10.4161/cib.23147] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The recent discovery of introner-like elements (ILEs) in six fungal species shed new light on the origin of regular spliceosomal introns (RSIs) and the mechanism of intron gains. These novel spliceosomal introns are found in hundreds of copies, are longer than RSIs and harbor stable predicted secondary structures. Yet, they are prone to degeneration in sequence and length to become undistinguishable from RSIs, suggesting that ILEs are predecessors of most RSIs. In most fungi, other near-identical introns were found duplicated in lower numbers in the same gene or in unrelated genes, indicating that intron duplication is a widespread phenomenon. However, ILEs are associated with the majority of intron gains, suggesting that the other types of duplication are of minor importance to the overall gains of introns. Our data support the hypothesis that ILEs’ multiplication corresponds to the main mechanism of intron gain in fungi.
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Affiliation(s)
- Jérôme Collemare
- Laboratory of Phytopathology; Wageningen University; Wageningen, The Netherlands
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Lefebvre F, Joly DL, Labbé C, Teichmann B, Linning R, Belzile F, Bakkeren G, Bélanger RR. The transition from a phytopathogenic smut ancestor to an anamorphic biocontrol agent deciphered by comparative whole-genome analysis. THE PLANT CELL 2013; 25:1946-59. [PMID: 23800965 PMCID: PMC3723605 DOI: 10.1105/tpc.113.113969] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Pseudozyma flocculosa is related to the model plant pathogen Ustilago maydis yet is not a phytopathogen but rather a biocontrol agent of powdery mildews; this relationship makes it unique for the study of the evolution of plant pathogenicity factors. The P. flocculosa genome of ~23 Mb includes 6877 predicted protein coding genes. Genome features, including hallmarks of pathogenicity, are very similar in P. flocculosa and U. maydis, Sporisorium reilianum, and Ustilago hordei. Furthermore, P. flocculosa, a strict anamorph, revealed conserved and seemingly intact mating-type and meiosis loci typical of Ustilaginales. By contrast, we observed the loss of a specific subset of candidate secreted effector proteins reported to influence virulence in U. maydis as the singular divergence that could explain its nonpathogenic nature. These results suggest that P. flocculosa could have once been a virulent smut fungus that lost the specific effectors necessary for host compatibility. Interestingly, the biocontrol agent appears to have acquired genes encoding secreted proteins not found in the compared Ustilaginales, including necrosis-inducing-Phytophthora-protein- and Lysin-motif- containing proteins believed to have direct relevance to its lifestyle. The genome sequence should contribute to new insights into the subtle genetic differences that can lead to drastic changes in fungal pathogen lifestyles.
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Affiliation(s)
| | - David L. Joly
- Agriculture and Agri-Food Canada, Pacific Agri-Food Research Centre, Summerland V0H 1Z0, Canada
| | - Caroline Labbé
- Département de Phytologie, Université Laval, Quebec G1V 0A6, Canada
| | - Beate Teichmann
- Département de Phytologie, Université Laval, Quebec G1V 0A6, Canada
| | - Rob Linning
- Agriculture and Agri-Food Canada, Pacific Agri-Food Research Centre, Summerland V0H 1Z0, Canada
| | - François Belzile
- Département de Phytologie, Université Laval, Quebec G1V 0A6, Canada
| | - Guus Bakkeren
- Agriculture and Agri-Food Canada, Pacific Agri-Food Research Centre, Summerland V0H 1Z0, Canada
| | - Richard R. Bélanger
- Département de Phytologie, Université Laval, Quebec G1V 0A6, Canada
- Address correspondence to
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Zhu T, Niu DK. Mechanisms of intron loss and gain in the fission yeast Schizosaccharomyces. PLoS One 2013; 8:e61683. [PMID: 23613904 PMCID: PMC3629103 DOI: 10.1371/journal.pone.0061683] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2013] [Accepted: 03/13/2013] [Indexed: 11/24/2022] Open
Abstract
The fission yeast, Schizosaccharomyces pombe, is an important model species with a low intron density. Previous studies showed extensive intron losses during its evolution. To test the models of intron loss and gain in fission yeasts, we conducted a comparative genomic analysis in four Schizosaccharomyces species. Both intronization and de-intronization were observed, although both were at a low frequency. A de-intronization event was caused by a degenerative mutation in the branch site. Four cases of imprecise intron losses were identified, indicating that genomic deletion is not a negligible mechanism of intron loss. Most intron losses were precise deletions of introns, and were significantly biased to the 3′ sides of genes. Adjacent introns tended to be lost simultaneously. These observations indicated that the main force shaping the exon-intron structures of fission yeasts was precise intron losses mediated by reverse transcriptase. We found two cases of intron gains caused by tandem genomic duplication, but failed to identify the mechanisms for the majority of the intron gain events observed. In addition, we found that intron-lost and intron-gained genes had certain similar features, such as similar Gene Ontology categories and expression levels.
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Affiliation(s)
- Tao Zhu
- MOE Key Laboratory for Biodiversity Science and Ecological Engineering and Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
| | - Deng-Ke Niu
- MOE Key Laboratory for Biodiversity Science and Ecological Engineering and Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
- * E-mail:
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30
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Frequency of intron loss correlates with processed pseudogene abundance: a novel strategy to test the reverse transcriptase model of intron loss. BMC Biol 2013; 11:23. [PMID: 23497167 PMCID: PMC3652778 DOI: 10.1186/1741-7007-11-23] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Accepted: 03/05/2013] [Indexed: 11/23/2022] Open
Abstract
Background Although intron loss in evolution has been described, the mechanism involved is still unclear. Three models have been proposed, the reverse transcriptase (RT) model, genomic deletion model and double-strand-break repair model. The RT model, also termed mRNA-mediated intron loss, suggests that cDNA molecules reverse transcribed from spliced mRNA recombine with genomic DNA causing intron loss. Many studies have attempted to test this model based on its predictions, such as simultaneous loss of adjacent introns, 3'-side bias of intron loss, and germline expression of intron-lost genes. Evidence either supporting or opposing the model has been reported. The mechanism of intron loss proposed in the RT model shares the process of reverse transcription with the formation of processed pseudogenes. If the RT model is correct, genes that have produced more processed pseudogenes are more likely to undergo intron loss. Results In the present study, we observed that the frequency of intron loss is correlated with processed pseudogene abundance by analyzing a new dataset of intron loss obtained in mice and rats. Furthermore, we found that mRNA molecules of intron-lost genes are mostly translated on free cytoplasmic ribosomes, a feature shared by mRNA molecules of the parental genes of processed pseudogenes and long interspersed elements. This feature is likely convenient for intron-lost gene mRNA molecules to be reverse transcribed. Analyses of adjacent intron loss, 3'-side bias of intron loss, and germline expression of intron-lost genes also support the RT model. Conclusions Compared with previous evidence, the correlation between the abundance of processed pseudogenes and intron loss frequency more directly supports the RT model of intron loss. Exploring such a correlation is a new strategy to test the RT model in organisms with abundant processed pseudogenes.
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Da Lage JL, Binder M, Hua-Van A, Janeček S, Casane D. Gene make-up: rapid and massive intron gains after horizontal transfer of a bacterial α-amylase gene to Basidiomycetes. BMC Evol Biol 2013; 13:40. [PMID: 23405862 PMCID: PMC3584928 DOI: 10.1186/1471-2148-13-40] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2012] [Accepted: 01/30/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Increasing genome data show that introns, a hallmark of eukaryotes, already existed at a high density in the last common ancestor of extant eukaryotes. However, intron content is highly variable among species. The tempo of intron gains and losses has been irregular and several factors may explain why some genomes are intron-poor whereas other are intron-rich. RESULTS We studied the dynamics of intron gains and losses in an α-amylase gene, whose product breaks down starch and other polysaccharides. It was transferred from an Actinobacterium to an ancestor of Agaricomycotina. This gene underwent further duplications in several species. The results indicate a high rate of intron insertions soon after the gene settled in the fungal genome. A number of these oldest introns, regularly scattered along the gene, remained conserved. Subsequent gains and losses were lineage dependent, with a majority of losses. Moreover, a few species exhibited a high number of both specific intron gains and losses in recent periods. There was little sequence conservation around insertion sites, then probably little information for splicing, whereas splicing sites, inside introns, showed typical and conserved patterns. There was little variation of intron size. CONCLUSIONS Since most Basidiomycetes have intron-rich genomes and this richness was ancestral in Fungi, long before the transfer event, we suggest that the new gene was shaped to comply with requirements of the splicing machinery, such as short exon and intron sizes, in order to be correctly processed.
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Affiliation(s)
- Jean-Luc Da Lage
- Laboratoire Evolution, génomes et spéciation UPR 9034 CNRS, 91198 Gif-sur-Yvette, and Université Paris-Sud, Orsay, 91405, France.
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Yenerall P, Zhou L. Identifying the mechanisms of intron gain: progress and trends. Biol Direct 2012; 7:29. [PMID: 22963364 PMCID: PMC3443670 DOI: 10.1186/1745-6150-7-29] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Accepted: 08/22/2012] [Indexed: 12/22/2022] Open
Abstract
Abstract Continued improvements in Next-Generation DNA/RNA sequencing coupled with advances in gene annotation have provided researchers access to a plethora of annotated genomes. Subsequent analyses of orthologous gene structures have identified numerous intron gain and loss events that have occurred both recently and in the very distant past. This research has afforded exceptional insight into the temporal and lineage-specific rates of intron gain and loss among various species throughout evolution. Numerous studies have also attempted to identify the molecular mechanisms of intron gain and loss. However, even after considerable effort, very little is known about these processes. In particular, the mechanism(s) of intron gain have proven exceptionally enigmatic and remain topics of considerable debate. Currently, there exists no definitive consensus as to what mechanism(s) may generate introns. Because many introns are known to affect gene expression, it is necessary to understand the molecular process(es) by which introns may be gained. Here we review the seven most commonly purported mechanisms of intron gain and, when possible, summarize molecular evidence for or against the occurrence of each of these mechanisms. Furthermore, we catalogue indirect evidence that supports the occurrence of each mechanism. Finally, because these proposed mechanisms fail to explain the mechanistic origin of many recently gained introns, we also look at trends that may aid researchers in identifying other potential mechanism(s) of intron gain. Reviewers This article was reviewed by Eugene Koonin, Scott Roy (nominated by W. Ford Doolittle), and John Logsdon.
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Affiliation(s)
- Paul Yenerall
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
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Ellwood SR, Syme RA, Moffat CS, Oliver RP. Evolution of three Pyrenophora cereal pathogens: recent divergence, speciation and evolution of non-coding DNA. Fungal Genet Biol 2012; 49:825-9. [PMID: 22850609 DOI: 10.1016/j.fgb.2012.07.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Revised: 06/05/2012] [Accepted: 07/19/2012] [Indexed: 12/22/2022]
Abstract
Three of the most important fungal pathogens of cereals are Pyrenophora tritici-repentis, the cause of tan spot on wheat, and Pyrenophora teres f. teres and Pyrenophora teres f. maculata, the cause of spot form and net form of net blotch on barley, respectively. Orthologous intergenic regions were used to examine the genetic relationships and divergence times between these pathogens. Mean divergence times were calculated at 519 kya (±30) between P. teresf. teres and P. teresf. maculata, while P. tritici-repentis diverged from both Pyrenophora teresforms 8.04 Mya (±138 ky). Individual intergenic regions showed a consistent pattern of co-divergence of the P. teresforms from P. tritici-repentis, with the pattern supported by phylogenetic analysis of conserved genes. Differences in calculated divergence times between individual intergenic regions suggested that they are not entirely under neutral selection, a phenomenon shared with higher Eukaryotes. P. tritici-repentis regions varied in divergence time approximately 5-12 Mya from the P. teres lineage, compared to the separation of wheat and barley some 12 Mya, while the P. teresf. teres and P. teresf. maculata intergenic region divergences correspond to the middle Pleistocene. The data suggest there is no correlation between the divergence of these pathogens the domestication of wheat and barley, and show P. teresf. teres and P. teresf. maculata are closely related but autonomous. The results are discussed in the context of speciation and the evolution of intergenic regions.
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Affiliation(s)
- Simon R Ellwood
- Department of Environment and Agriculture, Curtin University, Bentley, Perth, Western Australia 6102, Australia.
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van der Burgt A, Severing E, de Wit PJGM, Collemare J. Birth of new spliceosomal introns in fungi by multiplication of introner-like elements. Curr Biol 2012; 22:1260-5. [PMID: 22658596 DOI: 10.1016/j.cub.2012.05.011] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Revised: 04/12/2012] [Accepted: 05/03/2012] [Indexed: 11/25/2022]
Abstract
Spliceosomal introns are noncoding sequences that separate exons in eukaryotic genes and are removed from pre-messenger RNAs by the splicing machinery. Their origin has remained a mystery in biology since their discovery because intron gains seem to be infrequent in many eukaryotic lineages. Although a few recent intron gains have been reported, none of the proposed gain mechanisms can convincingly explain the high number of introns in present-day eukaryotic genomes. Here we report on particular spliceosomal introns that share high sequence similarity and are reminiscent of introner elements. These elements multiplied in unrelated genes of six fungal genomes and account for the vast majority of intron gains in these fungal species. Such introner-like elements (ILEs) contain all typical characteristics of regular spliceosomal introns (RSIs) but are longer and predicted to harbor more stable secondary structures. However, dating of multiplication events showed that they degenerate in sequence and length within 100,000 years to eventually become indistinguishable from RSIs. We suggest that ILEs not only account for intron gains in six fungi but also in ancestral eukaryotes to give rise to most RSIs by a yet unknown multiplication mechanism.
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Affiliation(s)
- Ate van der Burgt
- Laboratory of Phytopathology, Wageningen University, 6708PB Wageningen, The Netherlands.
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What Can Domesticated Genes Tell Us about the Intron Gain in Mammals? INTERNATIONAL JOURNAL OF EVOLUTIONARY BIOLOGY 2012; 2012:278981. [PMID: 22693680 PMCID: PMC3369469 DOI: 10.1155/2012/278981] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Accepted: 04/06/2012] [Indexed: 01/21/2023]
Abstract
Domesticated genes, originating from retroelements or from DNA-transposons, constitute an ideal system for testing the hypothesis on the absence of intron gain in mammals. Since single-copy domesticated genes originated from the intronless multicopy transposable elements, the ancestral intron state for domesticated genes is zero. A phylogenomic approach has been used to analyse all domesticated genes in mammals and chordates that originated from the coding parts of transposable elements. A significant amount of intron gain was found only in domesticated genes of placental mammals, where more than 70 cases were identified. De novo gained introns show clear positional bias, since they are distributed mainly in 5′ UTR and coding regions, while 3′ UTR introns are very rare. In the coding regions of some domesticated genes up to 8 de novo gained introns have been found. Surprisingly, the majority of intron gains have occurred in the ancestor of placental mammals. Domesticated genes could constitute an excellent system on which to analyse the mechanisms of intron gain. This paper summarizes the current understanding of intron gain in mammals.
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Rogozin IB, Carmel L, Csuros M, Koonin EV. Origin and evolution of spliceosomal introns. Biol Direct 2012; 7:11. [PMID: 22507701 PMCID: PMC3488318 DOI: 10.1186/1745-6150-7-11] [Citation(s) in RCA: 224] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Accepted: 03/15/2012] [Indexed: 12/31/2022] Open
Abstract
Evolution of exon-intron structure of eukaryotic genes has been a matter of long-standing, intensive debate. The introns-early concept, later rebranded ‘introns first’ held that protein-coding genes were interrupted by numerous introns even at the earliest stages of life's evolution and that introns played a major role in the origin of proteins by facilitating recombination of sequences coding for small protein/peptide modules. The introns-late concept held that introns emerged only in eukaryotes and new introns have been accumulating continuously throughout eukaryotic evolution. Analysis of orthologous genes from completely sequenced eukaryotic genomes revealed numerous shared intron positions in orthologous genes from animals and plants and even between animals, plants and protists, suggesting that many ancestral introns have persisted since the last eukaryotic common ancestor (LECA). Reconstructions of intron gain and loss using the growing collection of genomes of diverse eukaryotes and increasingly advanced probabilistic models convincingly show that the LECA and the ancestors of each eukaryotic supergroup had intron-rich genes, with intron densities comparable to those in the most intron-rich modern genomes such as those of vertebrates. The subsequent evolution in most lineages of eukaryotes involved primarily loss of introns, with only a few episodes of substantial intron gain that might have accompanied major evolutionary innovations such as the origin of metazoa. The original invasion of self-splicing Group II introns, presumably originating from the mitochondrial endosymbiont, into the genome of the emerging eukaryote might have been a key factor of eukaryogenesis that in particular triggered the origin of endomembranes and the nucleus. Conversely, splicing errors gave rise to alternative splicing, a major contribution to the biological complexity of multicellular eukaryotes. There is no indication that any prokaryote has ever possessed a spliceosome or introns in protein-coding genes, other than relatively rare mobile self-splicing introns. Thus, the introns-first scenario is not supported by any evidence but exon-intron structure of protein-coding genes appears to have evolved concomitantly with the eukaryotic cell, and introns were a major factor of evolution throughout the history of eukaryotes. This article was reviewed by I. King Jordan, Manuel Irimia (nominated by Anthony Poole), Tobias Mourier (nominated by Anthony Poole), and Fyodor Kondrashov. For the complete reports, see the Reviewers’ Reports section.
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Affiliation(s)
- Igor B Rogozin
- National Center for Biotechnology Information NLM/NIH, 8600 Rockville Pike, Bldg, 38A, Bethesda, MD 20894, USA
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Croll D, McDonald BA. Intron gains and losses in the evolution of Fusarium and Cryptococcus fungi. Genome Biol Evol 2012; 4:1148-61. [PMID: 23054310 PMCID: PMC3514964 DOI: 10.1093/gbe/evs091] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/02/2012] [Indexed: 12/15/2022] Open
Abstract
The presence of spliceosomal introns in eukaryotic genes poses a major puzzle for the study of genome evolution. Intron densities vary enormously among distant lineages. However, the mechanisms driving intron gains are poorly understood and very few intron gains and losses have been documented over short evolutionary time spans. Fungi emerged recently as excellent models to study intron evolution and "reverse splicing" was found to be a major driver of recent intron gains in a clade of ascomycete fungi. We screened a total of 38 genomes from two fungal clades important in medicine and agriculture to identify intron gains and losses both within and between species. We detected 86 and 198 variable intron positions in the Cryptococcus and Fusarium clades, respectively. Some genes underwent extensive changes in their exon-intron structure, with up to six variable intron positions per gene. We identified a very recently gained intron in a group of tomato-infecting strains belonging to the F. oxysporum species complex. In the human pathogen C. gattii, we found recent intron losses in subtypes of the species. The two studied fungal clades provided evidence for extensive changes in their exon-intron structure within and among closely related species. We show that both intronization of previously coding DNA and insertion of exogenous DNA are the major drivers of intron gains.
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Affiliation(s)
- Daniel Croll
- Plant Pathology, Institute of Integrative Biology, ETH Zurich, Switzerland.
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Guida A, Lindstädt C, Maguire SL, Ding C, Higgins DG, Corton NJ, Berriman M, Butler G. Using RNA-seq to determine the transcriptional landscape and the hypoxic response of the pathogenic yeast Candida parapsilosis. BMC Genomics 2011; 12:628. [PMID: 22192698 PMCID: PMC3287387 DOI: 10.1186/1471-2164-12-628] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Accepted: 12/22/2011] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND Candida parapsilosis is one of the most common causes of Candida infection worldwide. However, the genome sequence annotation was made without experimental validation and little is known about the transcriptional landscape. The transcriptional response of C. parapsilosis to hypoxic (low oxygen) conditions, such as those encountered in the host, is also relatively unexplored. RESULTS We used next generation sequencing (RNA-seq) to determine the transcriptional profile of C. parapsilosis growing in several conditions including different media, temperatures and oxygen concentrations. We identified 395 novel protein-coding sequences that had not previously been annotated. We removed > 300 unsupported gene models, and corrected approximately 900. We mapped the 5' and 3' UTR for thousands of genes. We also identified 422 introns, including two introns in the 3' UTR of one gene. This is the first report of 3' UTR introns in the Saccharomycotina. Comparing the introns in coding sequences with other species shows that small numbers have been gained and lost throughout evolution. Our analysis also identified a number of novel transcriptional active regions (nTARs). We used both RNA-seq and microarray analysis to determine the transcriptional profile of cells grown in normoxic and hypoxic conditions in rich media, and we showed that there was a high correlation between the approaches. We also generated a knockout of the UPC2 transcriptional regulator, and we found that similar to C. albicans, Upc2 is required for conferring resistance to azole drugs, and for regulation of expression of the ergosterol pathway in hypoxia. CONCLUSION We provide the first detailed annotation of the C. parapsilosis genome, based on gene predictions and transcriptional analysis. We identified a number of novel ORFs and other transcribed regions, and detected transcripts from approximately 90% of the annotated protein coding genes. We found that the transcription factor Upc2 role has a conserved role as a major regulator of the hypoxic response in C. parapsilosis and C. albicans.
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Affiliation(s)
- Alessandro Guida
- School of Medicine and Medical Science, Conway Institute, UniversityCollege Dublin, Belfield, Dublin 4, Ireland
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39
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Yenerall P, Krupa B, Zhou L. Mechanisms of intron gain and loss in Drosophila. BMC Evol Biol 2011; 11:364. [PMID: 22182367 PMCID: PMC3296678 DOI: 10.1186/1471-2148-11-364] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Accepted: 12/19/2011] [Indexed: 12/02/2022] Open
Abstract
Background It is widely accepted that orthologous genes have lost or gained introns throughout evolution. However, the specific mechanisms that generate these changes have proved elusive. Introns are known to affect nearly every level of gene expression. Therefore, understanding their mechanism of evolution after their initial fixation in eukaryotes is pertinent to understanding the means by which organisms develop greater regulation and complexity. Results To investigate possible mechanisms of intron gain and loss, we identified 189 intron gain and 297 intron loss events among 11 Drosophila species. We then investigated these events for signatures of previously proposed mechanisms of intron gain and loss. This work constitutes the first comprehensive study into the specific mechanisms that may generate intron gains and losses in Drosophila. We report evidence of intron gain via transposon insertion; the first intron loss that may have occurred via non-homologous end joining; intron gains via the repair of a double strand break; evidence of intron sliding; and evidence that internal or 5' introns may not frequently be deleted via the self-priming of reverse transcription during mRNA-mediated intron loss. Our data also suggest that the transcription process may promote or result in intron gain. Conclusion Our findings support the occurrence of intron gain via transposon insertion, repair of double strand breaks, as well as intron loss via non-homologous end joining. Furthermore, our data suggest that intron gain may be enabled by or due to transcription, and we shed further light on the exact mechanism of mRNA-mediated intron loss.
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Affiliation(s)
- Paul Yenerall
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
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40
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Extensive intron gain in the ancestor of placental mammals. Biol Direct 2011; 6:59. [PMID: 22112745 PMCID: PMC3257199 DOI: 10.1186/1745-6150-6-59] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2011] [Accepted: 11/23/2011] [Indexed: 01/29/2023] Open
Abstract
Background Genome-wide studies of intron dynamics in mammalian orthologous genes have found convincing evidence for loss of introns but very little for intron turnover. Similarly, large-scale analysis of intron dynamics in a few vertebrate genomes has identified only intron losses and no gains, indicating that intron gain is an extremely rare event in vertebrate evolution. These studies suggest that the intron-rich genomes of vertebrates do not allow intron gain. The aim of this study was to search for evidence of de novo intron gain in domesticated genes from an analysis of their exon/intron structures. Results A phylogenomic approach has been used to analyse all domesticated genes in mammals and chordates that originated from the coding parts of transposable elements. Gain of introns in domesticated genes has been reconstructed on well established mammalian, vertebrate and chordate phylogenies, and examined as to where and when the gain events occurred. The locations, sizes and amounts of de novo introns gained in the domesticated genes during the evolution of mammals and chordates has been analyzed. A significant amount of intron gain was found only in domesticated genes of placental mammals, where more than 70 cases were identified. De novo gained introns show clear positional bias, since they are distributed mainly in 5' UTR and coding regions, while 3' UTR introns are very rare. In the coding regions of some domesticated genes up to 8 de novo gained introns have been found. Intron densities in Eutheria-specific domesticated genes and in older domesticated genes that originated early in vertebrates are lower than those for normal mammalian and vertebrate genes. Surprisingly, the majority of intron gains have occurred in the ancestor of placentals. Conclusions This study provides the first evidence for numerous intron gains in the ancestor of placental mammals and demonstrates that adequate taxon sampling is crucial for reconstructing intron evolution. The findings of this comprehensive study slightly challenge the current view on the evolutionary stasis in intron dynamics during the last 100 - 200 My. Domesticated genes could constitute an excellent system on which to analyse the mechanisms of intron gain in placental mammals. Reviewers: this article was reviewed by Dan Graur, Eugene V. Koonin and Jürgen Brosius.
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Torriani SFF, Stukenbrock EH, Brunner PC, McDonald BA, Croll D. Evidence for extensive recent intron transposition in closely related fungi. Curr Biol 2011; 21:2017-22. [PMID: 22100062 DOI: 10.1016/j.cub.2011.10.041] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Revised: 10/26/2011] [Accepted: 10/26/2011] [Indexed: 11/30/2022]
Abstract
Though spliceosomal introns are a major structural component of most eukaryotic genes and intron density varies by more than three orders of magnitude among eukaryotes [1-3], the origins of introns are poorly understood, and only a few cases of unambiguous intron gain are known [4-8]. We utilized population genomic comparisons of three closely related fungi to identify crucial transitory phases of intron gain and loss. We found 74 intron positions showing intraspecific presence-absence polymorphisms (PAPs) for the entire intron. Population genetic analyses identified intron PAPs at different stages of fixation and showed that intron gain or loss was very recent. We found direct support for extensive intron transposition among unrelated genes. A substantial proportion of highly similar introns in the genome either were recently gained or showed a transient phase of intron PAP. We also identified an intron transfer among paralogous genes that created a new intron. Intron loss was due mainly to homologous recombination involving reverse-transcribed mRNA. The large number of intron positions in transient phases of either intron gain or loss shows that intron evolution is much faster than previously thought and provides an excellent model to study molecular mechanisms of intron gain.
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Affiliation(s)
- Stefano F F Torriani
- Institute of Integrative Biology, Swiss Federal Institute of Technology (ETH Zurich), 8092 Zurich, Switzerland
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42
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Da Lage JL, Maczkowiak F, Cariou ML. Phylogenetic distribution of intron positions in alpha-amylase genes of bilateria suggests numerous gains and losses. PLoS One 2011; 6:e19673. [PMID: 21611157 PMCID: PMC3096672 DOI: 10.1371/journal.pone.0019673] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2010] [Accepted: 04/03/2011] [Indexed: 11/19/2022] Open
Abstract
Most eukaryotes have at least some genes interrupted by introns. While it is well accepted that introns were already present at moderate density in the last eukaryote common ancestor, the conspicuous diversity of intron density among genomes suggests a complex evolutionary history, with marked differences between phyla. The question of the rates of intron gains and loss in the course of evolution and factors influencing them remains controversial. We have investigated a single gene family, alpha-amylase, in 55 species covering a variety of animal phyla. Comparison of intron positions across phyla suggests a complex history, with a likely ancestral intronless gene undergoing frequent intron loss and gain, leading to extant intron/exon structures that are highly variable, even among species from the same phylum. Because introns are known to play no regulatory role in this gene and there is no alternative splicing, the structural differences may be interpreted more easily: intron positions, sizes, losses or gains may be more likely related to factors linked to splicing mechanisms and requirements, and to recognition of introns and exons, or to more extrinsic factors, such as life cycle and population size. We have shown that intron losses outnumbered gains in recent periods, but that "resets" of intron positions occurred at the origin of several phyla, including vertebrates. Rates of gain and loss appear to be positively correlated. No phase preference was found. We also found evidence for parallel gains and for intron sliding. Presence of introns at given positions was correlated to a strong protosplice consensus sequence AG/G, which was much weaker in the absence of intron. In contrast, recent intron insertions were not associated with a specific sequence. In animal Amy genes, population size and generation time seem to have played only minor roles in shaping gene structures.
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Affiliation(s)
- Jean-Luc Da Lage
- Laboratoire Evolution, génomes et spéciation, UPR 9034 CNRS, Gif sur Yvette, France.
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43
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Feau N, Decourcelle T, Husson C, Desprez-Loustau ML, Dutech C. Finding single copy genes out of sequenced genomes for multilocus phylogenetics in non-model fungi. PLoS One 2011; 6:e18803. [PMID: 21533204 PMCID: PMC3076447 DOI: 10.1371/journal.pone.0018803] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Accepted: 03/18/2011] [Indexed: 11/17/2022] Open
Abstract
Historically, fungal multigene phylogenies have been reconstructed based on a small number of commonly used genes. The availability of complete fungal genomes has given rise to a new wave of model organisms that provide large number of genes potentially useful for building robust gene genealogies. Unfortunately, cross-utilization of these resources to study phylogenetic relationships in the vast majority of non-model fungi (i.e. “orphan” species) remains an unexamined question. To address this problem, we developed a method coupled with a program named “PHYLORPH” (PHYLogenetic markers for ORPHans). The method screens fungal genomic databases (107 fungal genomes fully sequenced) for single copy genes that might be easily transferable and well suited for studies at low taxonomic levels (for example, in species complexes) in non-model fungal species. To maximize the chance to target genes with informative regions, PHYLORPH displays a graphical evaluation system based on the estimation of nucleotide divergence relative to substitution type. The usefulness of this approach was tested by developing markers in four non-model groups of fungal pathogens. For each pathogen considered, 7 to 40% of the 10–15 best candidate genes proposed by PHYLORPH yielded sequencing success. Levels of polymorphism of these genes were compared with those obtained for some genes traditionally used to build fungal phylogenies (e.g. nuclear rDNA, β-tubulin, γ-actin, Elongation factor EF-1α). These genes were ranked among the best-performing ones and resolved accurately taxa relationships in each of the four non-model groups of fungi considered. We envision that PHYLORPH will constitute a useful tool for obtaining new and accurate phylogenetic markers to resolve relationships between closely related non-model fungal species.
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Affiliation(s)
- Nicolas Feau
- INRA, UMR1202, BIOGECO (Biodiversité Gènes et Communautés), Cestas, France.
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44
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DNA double-strand break repair and the evolution of intron density. Trends Genet 2010; 27:1-6. [PMID: 21106271 PMCID: PMC3020277 DOI: 10.1016/j.tig.2010.10.004] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Revised: 10/18/2010] [Accepted: 10/18/2010] [Indexed: 01/23/2023]
Abstract
The density of introns is both an important feature of genome architecture and a highly variable trait across eukaryotes. This heterogeneity has posed an evolutionary puzzle for the last 30 years. Recent evidence is consistent with novel introns being the outcome of the error-prone repair of DNA double-stranded breaks (DSBs) via non-homologous end joining (NHEJ). Here we suggest that deletion of pre-existing introns could occur via the same pathway. We propose a novel framework in which species-specific differences in the activity of NHEJ and homologous recombination (HR) during the repair of DSBs underlie changes in intron density.
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45
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Zhang LY, Yang YF, Niu DK. Evaluation of models of the mechanisms underlying intron loss and gain in Aspergillus fungi. J Mol Evol 2010; 71:364-73. [PMID: 20862581 DOI: 10.1007/s00239-010-9391-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Accepted: 09/08/2010] [Indexed: 11/26/2022]
Abstract
Although intron loss and gain have been widely observed, their mechanisms are still to be determined. In four Aspergillus genomes, we found 204 cases of intron loss and 84 cases of intron gain. Using this data, we tested common hypotheses of intron loss or gain. Statistical analysis showed that adjacent introns tend to be lost simultaneously and small introns were preferentially lost, supporting the model of mRNA-mediated intron loss. The lost introns reside in internal regions of genes, which is inconsistent with the traditional version of the model (partial length cDNAs are reverse transcribed from 3' ends of mRNAs), but consistent with an alternate version (partial length cDNAs are produced by self-primed reverse transcription). The latter version was not supported by examination of the abundance of T-rich segments in mRNAs. Preferential loss of internal introns might be explained by highly efficient recombination at internal regions of genes. Among the 84 cases of intron gain, we found a significantly higher frequency of short direct repeats near exon-intron boundary than in conserved introns, supporting the double-strand break repair model. We also found possible source sequences for two cases of intron gain, one by gene conversion and one by insertion of a mitochondrial sequence during double-strand break repair. Source sequences for most gained introns could not be identified and the possible reasons were discussed. In the four Aspergillus genomes studied, we did not find evidence of frequent parallel intron gains.
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Affiliation(s)
- Lei-Ying Zhang
- MOE Key Laboratory for Biodiversity Sciences and Ecological Engineering, College of Life Sciences, Beijing Normal University, Beijing, 100875, China
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46
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Martins M, Dairou J, Rodrigues-Lima F, Dupret JM, Silar P. Insights into the Phylogeny or Arylamine N-Acetyltransferases in Fungi. J Mol Evol 2010; 71:141-52. [DOI: 10.1007/s00239-010-9371-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2010] [Accepted: 07/16/2010] [Indexed: 11/28/2022]
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47
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Nonsense-mediated decay enables intron gain in Drosophila. PLoS Genet 2010; 6:e1000819. [PMID: 20107520 PMCID: PMC2809761 DOI: 10.1371/journal.pgen.1000819] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Accepted: 12/18/2009] [Indexed: 12/03/2022] Open
Abstract
Intron number varies considerably among genomes, but despite their fundamental importance, the mutational mechanisms and evolutionary processes underlying the expansion of intron number remain unknown. Here we show that Drosophila, in contrast to most eukaryotic lineages, is still undergoing a dramatic rate of intron gain. These novel introns carry significantly weaker splice sites that may impede their identification by the spliceosome. Novel introns are more likely to encode a premature termination codon (PTC), indicating that nonsense-mediated decay (NMD) functions as a backup for weak splicing of new introns. Our data suggest that new introns originate when genomic insertions with weak splice sites are hidden from selection by NMD. This mechanism reduces the sequence requirement imposed on novel introns and implies that the capacity of the spliceosome to recognize weak splice sites was a prerequisite for intron gain during eukaryotic evolution. The surprising observation 30 years ago that genes are interrupted by non-coding introns changed our view of gene architecture. Intron number varies dramatically among species; ranging from nine introns/gene in humans to less than one in some simple eukyarotes. Here we ask where new introns come from and how they are maintained in a population. We find that novel introns do not arise from pre-existing introns, although the mechanisms that generate novel introns remain unclear. We also show that novel introns carry only weak signals for their identification and removal, and therefore depend on nonsense-mediated decay (NMD). NMD maintains RNA quality control by degrading transcripts that have not been spliced properly. We propose that NMD shelters novel introns from natural selection. This increases the likelihood that a novel intron will rise in frequency and be maintained within a population, thus increasing the rate of intron gain.
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Abstract
Rates and mechanisms of intron gain and loss have traditionally been inferred from alignments of highly conserved genes sampled from phylogenetically distant taxa. We report a population-genomic approach that detected 24 discordant intron/exon boundaries between the whole-genome sequences of two Daphnia pulex isolates. Sequencing of presence/absence loci across a collection of D. pulex isolates and outgroup Daphnia species shows that most polymorphisms are a consequence of recent gains, with parallel gains often occurring at the same locations in independent allelic lineages. More than half of the recent gains are associated with short sequence repeats, suggesting an origin via repair of staggered double-strand breaks. By comparing the allele-frequency spectrum of intron-gain alleles with that for derived single-base substitutions, we also provide evidence that newly arisen introns are intrinsically deleterious and tend to accumulate in population-genetic settings where random genetic drift is a relatively strong force.
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Affiliation(s)
- Wenli Li
- Biology Department, Indiana University, Bloomington, IN 47405, USA
| | | | - Way Sung
- Hubbard Center for Genome Studies, University of New Hampshire, Durham, NH 03824, USA
| | - W. Kelley Thomas
- Hubbard Center for Genome Studies, University of New Hampshire, Durham, NH 03824, USA
| | - Michael Lynch
- Biology Department, Indiana University, Bloomington, IN 47405, USA
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Bryant MK, Schardl CL, Hesse U, Scott B. Evolution of a subtilisin-like protease gene family in the grass endophytic fungus Epichloë festucae. BMC Evol Biol 2009; 9:168. [PMID: 19615101 PMCID: PMC2717940 DOI: 10.1186/1471-2148-9-168] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2008] [Accepted: 07/19/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Subtilisin-like proteases (SLPs) form a superfamily of enzymes that act to degrade protein substrates. In fungi, SLPs can play either a general nutritive role, or may play specific roles in cell metabolism, or as pathogenicity or virulence factors. RESULTS Fifteen different genes encoding SLPs were identified in the genome of the grass endophytic fungus Epichloë festucae. Phylogenetic analysis indicated that these SLPs belong to four different subtilisin families: proteinase K, kexin, pyrolysin and subtilisin. The pattern of intron loss and gain is consistent with this phylogeny. E. festucae is exceptional in that it contains two kexin-like genes. Phylogenetic analysis in Hypocreales fungi revealed an extensive history of gene loss and duplication. CONCLUSION This study provides new insights into the evolution of the SLP superfamily in filamentous fungi.
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Affiliation(s)
- Michelle K Bryant
- Institute of Molecular Biosciences, Massey University, Private Bag 11222, Palmerston North, New Zealand.
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Meyer M, Vilardell J. The quest for a message: budding yeast, a model organism to study the control of pre-mRNA splicing. BRIEFINGS IN FUNCTIONAL GENOMICS AND PROTEOMICS 2009; 8:60-7. [PMID: 19279072 DOI: 10.1093/bfgp/elp002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Removal of introns during pre-mRNA splicing is a critical process in gene expression, and understanding its control at both single-gene and genomic levels is one of the great challenges in Biology. Splicing takes place in a dynamic, large ribonucleoprotein complex known as the spliceosome. Combining Genetics and Biochemistry, Saccharomyces cerevisiae provides insights into its mechanisms, including its regulation by RNA-protein interactions. Recent genome-wide analyses indicate that regulated splicing is broad and biologically relevant even in organisms with a relatively simple intronic structure, such as yeast. Furthermore, the possibility of coordination in splicing regulation at genomic level is becoming clear in this model organism. This should provide a valuable system to approach the complex problem of the role of regulated splicing in genomic expression.
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Affiliation(s)
- Markus Meyer
- Gene Regulation Program, Centre de Regulació Genòmica, Dr Aiguader 88, Barcelona, Spain
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