ABSTRACT
The Caulimoviridae is a family of double-stranded DNA viruses that infect plants. The genomes of most vascular plants contain endogenous caulimovirids (ECVs), a class of repetitive DNA elements that is abundant in some plant genomes, resulting from the integration of viral DNA in the chromosomes of germline cells during episodes of infection that have sometimes occurred millions of years ago. In this review, we reflect on 25 years of research on ECVs that has shown that members of the Caulimoviridae have occupied an unprecedented range of ecological niches over time and shed light on their diversity and macroevolution. We highlight gaps in knowledge and prospects of future research fueled by increased access to plant genome sequence data and new tools for genome annotation for addressing the extent, impact, and role of ECVs on plant biology and the origin and evolutionary trajectories of the Caulimoviridae.
Subject(s)
Caulimoviridae , Tracheophyta , Fossils , Caulimoviridae/genetics , Plants/genetics , Genome, Plant , PhylogenyABSTRACT
The complete genome sequence of a new caulimovirus in Pueraria montana was determined using high-throughput sequencing. The 7,572 nucleotide genome of pueraria virus A (PVA) contains genes that encode a movement protein, an aphid transmission factor, a virion-associated protein, a coat protein, a protease + reverse transcriptase + ribonuclease H, and a transactivator/viroplasmin protein, as well as two intergenic regions, which are all common features of members of the genus Caulimovirus. A sequence alignment revealed that the complete genome of PVA shares 66.82% nucleotide sequence identity with strawberry vein banding virus (GenBank accession no. KX249738.1). The results of phylogenetic analysis and the observation that the nucleotide sequence of the polymerase coding region differed by more than 20% indicated that PVA is a member of a new species the genus Caulimovirus, family Caulimoviridae.
Subject(s)
Caulimoviridae , Pueraria , Viruses, Unclassified , Caulimoviridae/genetics , Caulimovirus , Genome, Viral , High-Throughput Nucleotide Sequencing , Open Reading Frames , Phylogeny , Plant Diseases , Viruses, Unclassified/geneticsABSTRACT
In this work, a novel viral genomic sequence with a gene organization typical of members of the genus Soymovirus was identified using high-throughput sequencing data from common mallow. This species is a vigorous wild weed native to the Mediterranean region, commonly found in borders and edges of cultivated fields, making it a suitable reservoir for plant pests and pathogens. Indeed, plant viruses belonging to different genera have been previously found infecting common malva. This new viral genome consists of a single molecule of circular double-stranded DNA of 8391 base pairs and contains eight open reading frames encoding polymerase, movement, coat, translational transactivator protein typical of caulimoviruses, and four hypothetical proteins. Phylogenetic and pairwise distance analyses showed its close relationship with soybean chlorotic mottle virus. Interestingly, a small intergenic region was detected between ORFs Ib and II. Based on the demarcation criteria of the genus Soymovirus, the new virus, provisionally named malva-associated soymovirus 1, could be a member of a new species Soymovirus masolus. To our knowledge, this is the first report of a soymovirus infecting common mallow.
Subject(s)
Caulimoviridae , Malva , Caulimoviridae/genetics , Genome, Viral/genetics , High-Throughput Nucleotide Sequencing , Open Reading Frames , Phylogeny , Plant DiseasesABSTRACT
In 2019, plants of the genus Viola showing yellow mottling symptoms were collected in Liaoning, China. RNA sequencing and PCR both confirmed the presence of a reverse-transcribing DNA virus. The novel virus was named "viola yellow mottle virus" (VYMV), and its 9,872-bp genome was found to contain eight open reading frames. The polymerase (RT + RNase H) gene shared the most similarity (31.6% nucleotide and 41.6% amino acid sequence identity) with that of rose yellow vein virus (RYVV, NC_020999), which is currently the only member of the genus Rosadnavirus. Phylogenetic analysis indicated a close relationship between these viruses, suggesting that VYMV should be considered a new member of the genus Rosadnavirus.
Subject(s)
Caulimoviridae , Viola , Caulimoviridae/genetics , China , Genome, Viral , Open Reading Frames , Phylogeny , Plant DiseasesABSTRACT
Endogenous viral elements (EVEs) have been for the most part described in animals and to a less extent in plants. The endogenization was proposed to contribute toward evolution of living organisms via horizontal gene transfer of novel genetic material and resultant genetic diversity. During the last two decades, several full-length and fragmented EVEs of pararetroviral and non-retroviral nature have been identified in different plant genomes, both monocots and eudicots. Prior to this work, no EVEs have been reported in alfalfa (Medicago sativa L.), the most cultivated forage legume in the world. In this study, taking advantage of the most recent developments in the field of alfalfa research, we have assessed alfalfa genome on the presence of viral-related sequences. Our analysis revealed segmented EVEs resembling two dsDNA reverse-transcribing virus species: Soybean chlorotic mottle virus (family Caulimoviridae, genus Soymovirus) and Figwort mosaic virus (family Caulimoviridae, genus Caulimovirus). The EVEs appear to be stable constituents of the host genome and in that capacity could potentially acquire functional roles in alfalfa's development and response to environmental stresses.
Subject(s)
Caulimoviridae/genetics , Caulimovirus/genetics , Medicago sativa , Genome, Plant , Medicago sativa/genetics , Medicago sativa/virologyABSTRACT
A putative new virus with sequence similarity to members of the genus Cavemovirus in the family Caulimoviridae was identified in wild chicory (Cichorium intybus) by next-generation sequencing (NGS). The putative new virus was tentatively named "chicory mosaic cavemovirus" (ChiMV), and its genome was determined to be 7,775 nucleotides (nt) long with the typical genome organization of cavemoviruses. ORF1 encodes a putative coat protein/movement polyprotein (1,278 aa), ORF2 encodes a putative replicase (650 aa), and ORF3 encodes a putative transactivator factor (384 aa). The first two putative proteins have 46.2% and 68.7% amino acid sequence identity to the CP/MP protein (YP_004347414) and replicase (YP_004347415), respectively, of sweet potato collusive virus (SPCV). ORF3 encodes a protein with 38.5% amino acid sequence identity to the putative transactivator factor (NP_056849) of cassava vein mosaic virus (CsVMV). The new putative viral genome and those of three cavemoviruses (epiphyllum virus 4 [EpV-4], SPCV, and CsVMV) differ by 24-27% in the nt sequence of the replicase gene, which exceeds the species demarcation cutoff (>20%) for the family.
Subject(s)
Caulimoviridae/genetics , Cichorium intybus/virology , Amino Acid Sequence , Caulimoviridae/classification , Genome, Viral/genetics , Open Reading Frames/genetics , Phylogeny , Plant Diseases/virology , Plant Leaves/virology , RNA, Viral/genetics , Species Specificity , Viral Proteins/geneticsABSTRACT
The genomes of three putative novel viruses, tentatively named "Bacopa monnieri virus 1" (BmV1), "Bacopa monnieri virus 2" (BmV2), and "Bacopa monnieri virus 3" (BmV3) were identified in the transcriptome dataset of a medicinally important herb - water hyssop (Bacopa monnieri (L.) Wettst.). The BmV1 and BmV2 genomes resemble those of plant rhabdoviruses. The 13.3-kb-long BmV1 genome contains eight antisense ORFs in the order 3' l-N-P2'-P-P3-M-G-P6-L-t 5', with P2' ORF overlapping with P, while the 13.2-kb BmV2 genome contains six interspersed ORFs in the antisense orientation (3' l-N-P-P3-M-G-L-t 5'). The 8-kb BmV3 genome possesses five overlapping ORFs, with ORFs 2 to 5 being similar to those of solendoviruses. Based on genome organization, sequence similarity, and phylogeny, BmV1, BmV2, and BmV3 can be regarded as new members of the genera Cytorhabdovirus, Betanucleorhabdovirus, and Solendovirus, respectively.
Subject(s)
Bacopa/genetics , Bacopa/virology , Caulimoviridae/genetics , Genome, Viral/genetics , Rhabdoviridae/genetics , Transcriptome/genetics , Open Reading Frames/genetics , Phylogeny , Plants, Medicinal/geneticsABSTRACT
Rubus yellow net virus (RYNV) infects Rubus spp., causing a severe decline when present in mixed infections with other viruses. RYNV belongs to the family Caulimoviridae, also known as plant pararetroviruses, which can exist as episomal or integrated elements (endogenous). Most of integrated pararetroviruses are noninfectious; however, a few cases have been reported where they excised from the plant genome and formed infectious particles. Graft transmission onto indicator plants R. occidentalis "Munger" has been the standard test method for RYNV detection in certification programs. Previously, it was noticed that some RYNV PCR-positive plants did not induce symptoms on "Munger", suggesting an integration event. In this study, bio-indexing and different molecular techniques were employed to differentiate between integrated and episomal RYNV sequences. Reverse transcription-PCR using RYNV-specific oligonucleotides after DNase treatment generated positive results for the virus in graft transmissible isolates (episomal) only. To confirm these results, rolling circle amplification on DNA preparations from the same samples resulted in amplicons identified as RYNV only from plants with graft transmissible RYNV. High-throughput sequencing was used to identify the RYNV-like sequences present in the host DNA. These results indicate the integration of RYNV into the red raspberry genome and highlight the necessity to recognize this phenomenon (integration) in future Rubus quarantine and certification programs.
Subject(s)
Caulimoviridae/genetics , Genome, Plant/genetics , Plant Viruses/genetics , Rubus/genetics , Rubus/virology , Virus Integration/genetics , Caulimoviridae/isolation & purification , Plant Diseases/genetics , Plant Diseases/prevention & control , Plant Diseases/virology , Plant Viruses/isolation & purification , Plasmids/geneticsABSTRACT
A new virus with sequence similarities to members of the genus Cavemovirus in the family Caulimoviridae was identified in an Epiphyllum hybrid. The complete genome of the virus, tentatively named "epiphyllum virus 4" (EpV-4), was determined to be 7,296 nucleotides long. Its circular genome organization is typical of cavemoviruses, containing four open reading frames. This virus and the two known cavemoviruses share 67-69% and 72-75% overall nucleotide sequence identity in the replicase gene. Phylogenetic analysis placed EpV-4 in a same cluster with the two recognized cavemoviruses. Thus, EpV-4 should be considered a representative of a third species of the genus Cavemovirus. The virus was transmitted by grafting.
Subject(s)
Cactaceae/virology , Caulimoviridae/isolation & purification , Plant Diseases/virology , Caulimoviridae/classification , Caulimoviridae/genetics , Genome, Viral , Open Reading Frames , Phylogeny , Viral Proteins/geneticsABSTRACT
White areas of star-type bicolour petals of petunia (Petunia hybrida) are caused by post-transcriptional gene silencing (PTGS) of the key enzyme of anthocyanin biosynthesis. We observed blotched flowers and a vein-clearing symptom in aged petunia plants. To determine the cause of blotched flowers, we focused on an endogenous pararetrovirus, petunia vein clearing virus (PVCV), because this virus may have a suppressor of PTGS (VSR). Transcripts and episomal DNAs derived from proviral PVCVs accumulated in aged plants, indicating that PVCV was activated as the host plant aged. Furthermore, DNA methylation of CG and CHG sites in the promoter region of proviral PVCV decreased in aged plants, suggesting that poor maintenance of DNA methylation activates PVCV. In parallel, de novo DNA methylation of CHH sites in its promoter region was also detected. Therefore, both activation and inactivation of PVCV occurred in aged plants. The accumulation of PVCV transcripts and episomal DNAs in blotched regions and the detection of VSR activity support a mechanism in which suppression of PTGS by PVCV causes blotched flowers.
Subject(s)
Caulimoviridae/metabolism , Flowers/virology , Petunia/virology , Caulimoviridae/genetics , Color , DNA Methylation , DNA, Viral/genetics , Flowers/anatomy & histology , Gene Expression Regulation, Plant , Petunia/anatomy & histology , Proviruses/genetics , RNA Interference , Real-Time Polymerase Chain ReactionABSTRACT
Petunia plants are used for urban landscaping in many parts of the world, including South Korea. In this study, we aimed to investigate the occurrence of petunia vein clearing virus (PVCV) infection in petunia plants in Seoul, South Korea. PVCV was detected from 23 of 79 petunia samples collected from Seoul. We obtained the complete genome sequences of the Korean isolates in this study (called PVCV-Kr, Kr2, and Kr3), which were compared with the genome sequence of the USA isolate of the virus (PVCV-USA). The genomic DNA of the three PVCV isolates was found to comprise 7210-7267 nucleotides (nts), which is 4-15 nts longer than the PVCV-USA genome. The genomes of the Kr and Kr2 isolates encode a large polyprotein of 252 kDa (2180 amino acids (aa)). The genome of the Kr3 isolate encodes a large polyprotein of 255 kDa (2203 aa). The polyprotein has six protein domains: a movement protein (MP; 72 aa), a coiled-coil domain (CC; 33 aa), an RNA-binding domain (RB; 18 aa), a protease (PR; 21 aa), a reverse transcriptase (RT; 196 aa), and an RNase H (RH; 121 aa). The large polyprotein and six domains of the three isolates showed 93.9-100.0% sequence homology with those of PVCV-USA. Furthermore, the polymerase polyprotein gene (PR, RT, and RH) of the four PVCV isolates containing the USA isolate grouped with those of Rice tungro bacilliform virus and Soybean chlorotic mottle virus, which belong to the same family (Caulimoviridae). Our findings suggested that the Korean isolates represent a new isolate of PVCV. To our knowledge, this is the first report of PVCV detection in South Korea.
Subject(s)
Caulimoviridae/genetics , Plant Diseases/virology , Base Sequence , Caulimoviridae/chemistry , Caulimoviridae/classification , Caulimoviridae/isolation & purification , Genetic Variation , Genome, Viral , Open Reading Frames , Petunia/virology , Protein Domains , Republic of Korea , United States , Viral Proteins/chemistry , Viral Proteins/geneticsABSTRACT
BACKGROUND: A disease of unknown etiology in water chestnut plants (Eleocharis dulcis) was reported in China between 2012 and 2014. High throughput sequencing of small RNA (sRNA) combined with bioinformatics, and molecular identification based on PCR detection with virus-specific primers and DNA sequencing is a desirable approach to identify an unknown infectious agent. In this study, we employed this approach to identify viral sequences in water chestnut plants and to explore the molecular interaction of the identified viral pathogen and its natural plant host. RESULTS: Based on high throughput sequencing of virus-derived small RNAs (vsRNA), we identified the sequence a new-to-science double-strand DNA virus isolated from water chestnut cv. 'Tuanfeng' samples, a widely grown cultivar in Hubei province, China, and analyzed its genomic organization. The complete genomic sequence is 7535 base-pairs in length, and shares 42-52% nucleotide sequence identity with viruses in the Caulimoviridae family. The virus contains nine predicated open reading frames (ORFs) encoding nine hypothetical proteins, with conserved domains characteristic of caulimoviruses. Phylogenetic analyses at the nucleotide and amino acid levels indicated that the virus belongs to the genus Soymovirus. The virus is tentatively named Water chestnut soymovirus-1 (WCSV-1). Phylogenetic analysis of the putative viral polymerase protein suggested that WCSV-1 is distinct to other well established species in the Soymovirus genus. This conclusion was supported by phylogenetic analyses of the amino acid sequences encoded by ORFs I, IV, VI, or VII. The sRNA bioinformatics showed that the majority of the vsRNAs are 22-nt in length with a preference for U at the 5'-terminal nucleotide. The vsRNAs are unevenly distributed over both strands of the entire WCSV-1 circular genome, and are clustered into small defined regions. In addition, we detected WCSV-1 in asymptomatic and symptomatic water chestnut samples collected from different regions of China by using PCR. RNA-seq assays further confirmed the presence of WCSV-1-derived viral RNA in infected plants. CONCLUSIONS: This is the first discovery of a dsDNA virus in the genus Soymovirus infecting water chestnuts. Data presented also add new information towards a better understanding of the co-evolutionary mechanisms between the virus and its natural plant host.
Subject(s)
Caulimoviridae/physiology , Eleocharis/virology , Amino Acid Motifs , Amino Acid Sequence , Base Sequence , Caulimoviridae/genetics , China , Computational Biology , Conserved Sequence , Eleocharis/genetics , Genome, Viral , High-Throughput Nucleotide Sequencing , Phylogeny , RNA, Viral/genetics , Transcriptome/genetics , Viral Proteins/chemistryABSTRACT
We have characterized the complete genome of a novel circular double-stranded DNA virus, tentatively named Dioscorea nummularia-associated virus (DNUaV), infecting Dioscorea nummularia originating from Samoa. The genome of DNUaV comprised 8139 bp and contained four putative open reading frames (ORFs). ORFs 1 and 2 had no identifiable conserved domains, while ORF 3 had conserved motifs typical of viruses within the family Caulimoviridae including coat protein, movement protein, aspartic protease, reverse transcriptase and ribonuclease H. A transactivator domain, similar to that present in members of several caulimoviridae genera, was also identified in the putative ORF 4. The genome size, organization, and presence of conserved amino acid domains are similar to other viruses in the family Caulimoviridae. However, based on nucleotide sequence similarity and phylogenetic analysis, DNUaV appears to be a distinct novel member of the family and may represent a new genus.
Subject(s)
Caulimoviridae/classification , Caulimoviridae/physiology , Dioscorea/virology , Amino Acid Sequence , Caulimoviridae/genetics , Genomics , Open Reading Frames/genetics , Pacific Ocean , Phylogeny , Viral Proteins/chemistry , Viral Proteins/geneticsABSTRACT
Recent metagenomic surveys have provided unprecedented amounts of data that have revolutionized our understanding of virus evolution and diversity. Infectious clones are powerful tools to aid the biological characterization of viruses. We recently described the pLX vectors, a set of mini binary T-DNA vectors (â¼3 kb) that includes strong bacterial terminators and a minimal replicon from the broad-host-range plasmid pBBR1, which replicate autonomously in both Escherichia coli and Agrobacterium. In this study, a workflow that encompassed pLX binary vectors, overlap-based assembly strategies, and sequencing-by-synthesis verification steps is described and applied for the streamlined generation of infectious clones suitable for Agrobacterium-mediated delivery. The pLX-based vectors herein assembled include the first infectious clone of Wasabi mottle virus, a crucifer-infecting tobamovirus, as well as binary vectors of positive-single-stranded RNA and single- and double-stranded DNA viruses from the Potyviridae, Geminiviridae and Caulimoviridae families, respectively. Finally, the clones generated were used to agro-inoculate the model plant Arabidopsis thaliana and infections were confirmed by a multiplex RT-PCR assay. This workflow facilitated the rapid generation of infectious clones which, together with agro-infection scalability, would allow the pursuit of systematic insights into virus biology and physiology of plant infections and the design of novel biotechnological applications.
Subject(s)
Genetic Vectors , Plant Viruses/genetics , Virology/methods , Agriculture , Arabidopsis/virology , Biotechnology/methods , Caulimoviridae/genetics , Geminiviridae/genetics , Genome, Viral , Potyviridae/geneticsABSTRACT
Endogenous viral elements (paleoviruses) provide "molecular fossils" for studying the deep history and macroevolution of viruses. Endogenous plant pararetroviruses (EPRVs) are widespread in angiosperms, but little is known about EPRVs in earlier-branching plants. Here we use a large-scale phylogenomic approach to investigate the diversity and macroevolution of plant pararetroviruses (formally known as Caulimoviridae). We uncover an unprecedented and unappreciated diversity of EPRVs within the genomes of gymnosperms and ferns. The known angiosperm viruses constitute only a minor part of the Caulimoviridae diversity. By characterizing the distribution of EPRVs, we show that no major euphyllophyte lineages escape the activity of Caulimoviridae, raising the possibility that many exogenous Caulimoviridae remain to be discovered in euphyllophytes. We find that the copy numbers of EPRVs are generally high, suggesting that EPRVs might define a unique group of repetitive elements and represent important components of euphyllophyte genomes. Evolutionary analyses suggest an ancient origin of Caulimoviridae and at least three independent origins of Caulimoviridae in angiosperms. Our findings reveal the remarkable diversity of Caulimoviridae and have important implications for understanding the origin and macroevolution of plant pararetroviruses.IMPORTANCE Few viruses have been documented in plants outside angiosperms. Viruses can occasionally integrate into host genomes, forming endogenous viral elements (EVEs). Endogenous plant pararetroviruses (EPRVs) are widespread in angiosperms. In this study, we performed comprehensive comparative and phylogenetic analyses of EPRVs and found that EPRVs are present in the genomes of gymnosperms and ferns. We identified numerous EPRVs in gymnosperm and fern genomes, revealing an unprecedented depth in the diversity of plant pararetroviruses. Plant pararetroviruses mainly underwent cross-species transmission, and angiosperm pararetroviruses arose at least three times. Our study provides novel insights into the diversity and macroevolution of plant pararetroviruses.
Subject(s)
Caulimoviridae/classification , Caulimoviridae/genetics , Cycadopsida/virology , Ferns/virology , Genome, Plant/genetics , Magnoliopsida/virology , Plant Viruses/genetics , Cycadopsida/genetics , DNA Copy Number Variations/genetics , DNA Transposable Elements/genetics , Endogenous Retroviruses/genetics , Evolution, Molecular , Ferns/genetics , Host-Pathogen Interactions/genetics , Magnoliopsida/genetics , PhylogenyABSTRACT
Endogenous viral elements (EVEs) are viral sequences that are integrated in the nuclear genomes of their hosts and are signatures of viral infections that may have occurred millions of years ago. The study of EVEs, coined paleovirology, provides important insights into virus evolution. The Caulimoviridae is the most common group of EVEs in plants, although their presence has often been overlooked in plant genome studies. We have refined methods for the identification of caulimovirid EVEs and interrogated the genomes of a broad diversity of plant taxa, from algae to advanced flowering plants. Evidence is provided that almost every vascular plant (tracheophyte), including the most primitive taxa (clubmosses, ferns and gymnosperms) contains caulimovirid EVEs, many of which represent previously unrecognized evolutionary branches. In angiosperms, EVEs from at least one and as many as five different caulimovirid genera were frequently detected, and florendoviruses were the most widely distributed, followed by petuviruses. From the analysis of the distribution of different caulimovirid genera within different plant species, we propose a working evolutionary scenario in which this family of viruses emerged at latest during Devonian era (approx. 320 million years ago) followed by vertical transmission and by several cross-division host swaps.
Subject(s)
Caulimoviridae/genetics , DNA, Viral/genetics , Sequence Analysis, DNA/methods , Tracheophyta/genetics , Evolution, Molecular , Genome, Plant , Host-Pathogen Interactions , Phylogeny , Tracheophyta/virologyABSTRACT
We report a new circular DNA virus identified from a Chinese jujube tree showing mosaic-like symptoms. The genome of this virus is 7194 bp in length and contains five putative open reading frames (ORFs), all on the plus-strand of the genome. The genomic organization, primer binding sites and the sizes of the ORFs were similar to those reported for other badnaviruses (family Caulimoviridae), except for ORF3, which was split into ORF3a and ORF3b with a 70-nt intergenic region. Furthermore, this new virus shares low nucleotide sequence identity (<50%) with other members of the family Caulimoviridae. Consequently, we propose this virus as a new member of the family Caulimoviridae and refer to it as jujube mosaic-associated virus (JuMaV).
Subject(s)
Caulimoviridae/genetics , Genome, Viral , Mosaic Viruses/genetics , Ziziphus/virology , PhylogenyABSTRACT
A disease of Rudbeckia hirta (Black-eyed Susan), characterized by severe flower deformation, was observed in Minnesota during 2010-2016. A previously undescribed virus species, named Rudbeckia flower distortion virus (RuFDV, family Caulimoviridae, genus unassigned), was determined to be the causal agent of the disease. Symptoms induced by RuFDV infection resemble those characteristic of phytoplasma-induced diseases, but no phytoplasmas were detected in RuFDV-infected R. hirta. The virus, and the disease were transmitted readily by mechanical inoculation and by the aphid Myzus persicae, but only to R. hirta. Virions of RuFDV are icosahedral, 42-45nm in diameter, and contain a circular 8222bp dsDNA genome containing seven open reading frames (ORFs). The ORFs 2-6 have 28-52% amino acid sequence identity to the movement protein (MP), coat protein (CP), aspartic protease (AP), reverse transcriptase (RT) and RNase H, and translational transactivator (TA) domains of known caulimoviruses. The two remaining ORFs (1 and 7) have no significant amino acid sequence similarity to known viruses. Although the RuFDV ORF 6 is significantly truncated relative to those of other known caulimoviruses, neither this nor the concomitant absence of characteristic virus-encoded cytoplasmic inclusion bodies appears to adversely affect aphid transmission of this virus. Phylogenetic analysis based on the sequence of the RT region revealed no close relationship to known members of the family Caulimoviridae. Based on sequence similarity, genome organization and phylogenetic relatedness, RuFDV appears to be distinct from any currently recognized taxonomic grouping in the family Caulimoviridae.
Subject(s)
Caulimoviridae/classification , Caulimoviridae/genetics , Flowers/virology , Plant Diseases/virology , Rudbeckia/virology , Amino Acid Sequence , Animals , Aphids/virology , Aspartic Acid Proteases/genetics , Capsid Proteins/genetics , Insect Vectors/virology , Plant Viral Movement Proteins/genetics , RNA-Directed DNA Polymerase/genetics , Ribonuclease H/genetics , Sequence Homology, Amino AcidABSTRACT
Long terminal repeat retrotransposons represent a major component of plant genomes and act as drivers of genome evolution and diversity. Musa is an important fruit crop and also used as a starchy vegetable in many countries. BAC sequence analysis by dot plot was employed to investigate the LTR retrotransposons from Musa genomes. Fifty intact LTR retrotransposons from selected Musa BACs were identified by dot plot analysis and further BLASTN searches retrieved 153 intact copies, 61 truncated, and a great number of partial copies/remnants from GenBank database. LARD-like elements were also identified with several copies dispersed among the Musa genotypes. The predominant elements were the LTR retrotransposons Copia and Gypsy, while Caulimoviridae (pararetrovirus) were rare in the Musa genome. PCR amplification of reverse transcriptase (RT) sequences revealed their abundance in almost all tested Musa accessions and their ancient nature before the divergence of Musa species. The phylogenetic analysis based on RT sequences of Musa and other retrotransposons clustered them into Gypsy, Caulimoviridae, and Copia lineages. Most of the Musa-related elements clustered in their respective groups, while some grouped with other elements indicating homologous sequences. The present work will be helpful to understand the LTR retrotransposons landscape, giving a complete picture of the nature of the elements, their structural features, annotation, and evolutionary dynamics in the Musa genome.
Subject(s)
Genome, Plant/genetics , Musa/genetics , Retroelements/genetics , Terminal Repeat Sequences/genetics , Base Sequence , Caulimoviridae/genetics , Chromosomes, Artificial, Bacterial/genetics , DNA, Plant/genetics , Phylogeny , Sequence Analysis, DNAABSTRACT
Here, we report the genome sequence and evidence for transcriptional activity of a virus-like element in the native Chilean berry tree Aristotelia chilensis. We propose to name the endogenous sequence as Aristotelia chilensis Virus 1 (AcV1). High-throughput sequencing of the genome of this tree uncovered an endogenous viral element, with a size of 7122 bp, corresponding to the complete genome of AcV1. Its sequence contains three open reading frames (ORFs): ORFs 1 and 2 shares 66%-73% amino acid similarity with members of the Caulimoviridae virus family, especially the Petunia vein clearing virus (PVCV), Petuvirus genus. ORF1 encodes a movement protein (MP); ORF2 a Reverse Transcriptase (RT) and a Ribonuclease H (RNase H) domain; and ORF3 showed no amino acid sequence similarity with any other known virus proteins. Analogous to other known endogenous pararetrovirus sequences (EPRVs), AcV1 is integrated in the genome of Maqui Berry and showed low viral transcriptional activity, which was detected by deep sequencing technology (DNA and RNA-seq). Phylogenetic analysis of AcV1 and other pararetroviruses revealed a closer resemblance with Petuvirus. Overall, our data suggests that AcV1 could be a new member of Caulimoviridae family, genus Petuvirus, and the first evidence of this kind of virus in a fruit plant.