ORCID Profile
0000-0003-3722-9733
Current Organisation
University of Miami
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Publisher: Wiley
Date: 23-02-2010
Publisher: Proceedings of the National Academy of Sciences
Date: 23-07-2019
Abstract: Plant sap-feeding insects thrive despite feeding exclusively on a diet lacking in essential amino acids. This nutritional deficit is countered through endosymbiotic relationships with microbial symbionts. Nonessential amino acids, vital for microbial symbionts, are utilized by symbiont metabolic pathways and yield essential amino acids required by their eukaryotic hosts. Symbionts are completely dependent on their host to meet nutritional requirements. The endosymbionts are surrounded in idually by host-derived symbiosomal membranes and are housed within specialized host bacteriocyte cells. The transport capabilities of the symbiosomal membrane remain unknown. Here, we identify a transport system that mediates a crucial step in this metabolic complementarity: a transporter capable of transporting nonessential amino acids across the symbiosomal membrane of the pea aphid Acyrthosiphon pisum .
Publisher: Wiley
Date: 11-2000
DOI: 10.1046/J.1365-294X.2000.01084.X
Abstract: All genetic markers are estimators of DNA nucleotide sequence variation. Rather than obtaining DNA sequence data, it is cheaper and faster to use techniques that estimate sequence variation, although this usually results in the loss of some information. SSCP (single-stranded conformation polymorphism) offers a sensitive but inexpensive, rapid, and convenient method for determining which DNA s les in a set differ in sequence, so that only an informative subset need be sequenced. In short, most DNA sequence variation can be detected with relatively little sequencing. SSCP has been widely applied in medical diagnosis, yet few studies have been published in population genetics. The utility and convenience of SSCP is far from fully appreciated by molecular population biologists. We hope to help redress this by illustrating the application of a single simple SSCP protocol to mitochondrial genes, nuclear introns, microsatellites, and anonymous nuclear sequences, in a range of vertebrates and invertebrates.
Publisher: Cambridge University Press (CUP)
Date: 04-1999
DOI: 10.1017/S0007485399000498
Abstract: A prerequisite to studying the specific interactions involved in the persistent transmission of luteoviruses such as the potato leafroll virus (PLRV) is the characterization of both the virus and its vectors. A range of techniques was used to assess genetic differentiation among 27 clones belonging to the Myzus persicae complex ( M. persicae (Sulzer), M. antirrhinii (Macchiati) and M. nicotianae Blackman) and showing different efficiencies in transmitting PLRV isolates. All M. persicae / M. nicotianae clones belonged to one of two karyotypes, both 2n = 12, either normal or carrying an autosomal translocation (A1,3), and all M. antirrhinii clones had 13 or 14 chromosomes. Amplified esterase 4 genes were detected by PCR–REN assay in M. persicae / M. nicotianae taxa, with gene expression being modified by methylation. Similarly, lified E4 genes were revealed in M. antirrhinii but they all showed unmethylated. Two allozyme and 11 microsatellite loci discriminated 10 different genotypic classes among the 27 clones. Analysis of genetic relatedness between these genotypic classes revealed that M. nicotianae clones were very closely related to M. persicae clones, whereas the genetic differentiation between M. antirrhinii and M. persicae was greater. The implications of these results for the taxonomic status of these genotypes within the complex, and the transmission of PLRV, are discussed.
Publisher: Springer Science and Business Media LLC
Date: 07-07-2021
DOI: 10.1038/S42003-021-02373-X
Abstract: The aphid Myzus persicae is a destructive agricultural pest that displays an exceptional ability to develop resistance to both natural and synthetic insecticides. To investigate the evolution of resistance in this species we generated a chromosome-scale genome assembly and living panel of fully sequenced globally s led clonal lines. Our analyses reveal a remarkable ersity of resistance mutations segregating in global populations of M. persicae . We show that the emergence and spread of these mechanisms is influenced by host–plant associations, uncovering the widespread co‐option of a host-plant adaptation that also offers resistance against synthetic insecticides. We identify both the repeated evolution of independent resistance mutations at the same locus, and multiple instances of the evolution of novel resistance mechanisms against key insecticides. Our findings provide fundamental insights into the genomic responses of global insect populations to strong selective forces, and hold practical relevance for the control of pests and parasites.
Publisher: Springer Science and Business Media LLC
Date: 11-12-2019
DOI: 10.1038/S41598-019-54488-1
Abstract: Like all organisms, aphids, plant sap-sucking insects that house a bacterial endosymbiont called Buchnera , are members of a species interaction network. Ecological interactions across such networks can result in phenotypic change in network members mediated by molecular signals, like microRNAs. Here, we interrogated small RNA data from the aphid, Myzus persicae , to determine the source of reads that did not map to the aphid or Buchnera genomes. Our analysis revealed that the pattern was largely explained by reads that mapped to the host plant, Brassica oleracea , and a facultative symbiont, Regiella . To start elucidating the function of plant small RNA in aphid gut, we annotated 213 unique B. oleracea miRNAs 32/213 were present in aphid gut as mature and star miRNAs. Next, we predicted targets in the B. oleracea and M. persicae genomes for these 32 plant miRNAs. We found that plant targets were enriched for genes associated with transcription, while the distribution of targets in the aphid genome was similar to the functional distribution of all genes in the aphid genome. We discuss the potential of plant miRNAs to regulate aphid gene expression and the mechanisms involved in processing, export and uptake of plant miRNAs by aphids.
Publisher: Springer Science and Business Media LLC
Date: 10-11-2020
DOI: 10.1186/S13227-020-00168-5
Abstract: Host/symbiont integration is a signature of evolutionarily ancient, obligate endosymbioses. However, little is known about the cellular and developmental mechanisms of host/symbiont integration at the molecular level. Many insects possess obligate bacterial endosymbionts that provide essential nutrients. To advance understanding of the developmental and metabolic integration of hosts and endosymbionts, we track the localization of a non-essential amino acid transporter, ApNEAAT1, across asexual embryogenesis in the aphid, Acyrthosiphon pisum . Previous work in adult bacteriomes revealed that ApNEAAT1 functions to exchange non-essential amino acids at the A. pisum / Buchnera aphidicola symbiotic interface. Driven by amino acid concentration gradients, ApNEAAT1 moves proline, serine, and alanine from A. pisum to Buchnera and cysteine from Buchnera to A. pisum . Here, we test the hypothesis that ApNEAAT1 is localized to the symbiotic interface during asexual embryogenesis. During A. pisum asexual embryogenesis, ApNEAAT1 does not localize to the symbiotic interface. We observed ApNEAAT1 localization to the maternal follicular epithelium, the germline, and, in late-stage embryos, to anterior neural structures and insect immune cells (hemocytes). We predict that ApNEAAT1 provisions non-essential amino acids to developing oocytes and embryos, as well as to the brain and related neural structures. Additionally, ApNEAAT1 may perform roles related to host immunity. Our work provides further evidence that the embryonic and adult bacteriomes of asexual A. pisum are not equivalent. Future research is needed to elucidate the developmental time point at which the bacteriome reaches maturity.
Publisher: Springer Science and Business Media LLC
Date: 12-2013
Abstract: Myzus persicae , the green peach aphid, is a polyphagous herbivore that feeds from hundreds of species of mostly dicot crop plants. Like other phloem-feeding aphids, M. persicae rely on the endosymbiotic bacterium, Buchnera aphidicola ( Buchnera Mp), for biosynthesis of essential amino acids and other nutrients that are not sufficiently abundant in their phloem sap diet. Tobacco-specialized M. persicae are typically red and somewhat distinct from other lineages of this species. To determine whether the endosymbiotic bacteria of M. persicae could play a role in tobacco adaptation, we sequenced the Buchnera Mp genomes from two tobacco-adapted and two non-tobacco M. persicae lineages. With a genome size of 643.5 kb and 579 predicted genes, Buchnera Mp is the largest Buchnera genome sequenced to date. No differences in gene content were found between the four sequenced Buchnera Mp strains. Compared to Buchnera APS from the well-studied pea aphid, Acyrthosiphon pisum , Buchnera Mp has 21 additional genes. These include genes encoding five enzymes required for biosynthesis of the modified nucleoside queosine, the heme pathway enzyme uroporphyrinogen III synthase, and asparaginase. Asparaginase, which is also encoded by the genome of the aphid host, may allow Buchnera Mp to synthesize essential amino acids from asparagine, a relatively abundant phloem amino acid. Together our results indicate that the obligate intracellular symbiont Buchnera aphidicola does not contribute to the adaptation of Myzus persicae to feeding on tobacco.
Publisher: Proceedings of the National Academy of Sciences
Date: 26-05-2015
Abstract: The role of symbiosis in bacterial symbiont genome evolution is well understood, yet the ways that symbiosis shapes host genomes or more particularly, host/symbiont genome coevolution in the holobiont is only now being revealed. Here, we identify three coevolutionary signatures that characterize holobiont genomes. The first signature, host/symbiont collaboration, arises when completion of essential pathways requires host/endosymbiont genome complementarity. Metabolic collaboration has evolved numerous times in the pathways of amino acid and vitamin biosynthesis. Here, we highlight collaboration in branched-chain amino acid and pantothenate (vitamin B5) biosynthesis. The second coevolutionary signature is acquisition, referring to the observation that holobiont genomes acquire novel genetic material through various means, including gene duplication, lateral gene transfer from bacteria that are not their current obligate symbionts, and full or partial endosymbiont replacement. The third signature, constraint, introduces the idea that holobiont genome evolution is constrained by the processes governing symbiont genome evolution. In addition, we propose that collaboration is constrained by the expression profile of the cell lineage from which endosymbiont-containing host cells, called bacteriocytes, are derived. In particular, we propose that such differences in bacteriocyte cell lineage may explain differences in patterns of host/endosymbiont metabolic collaboration between the sap-feeding suborders Sternorrhyncha and Auchenorrhynca. Finally, we review recent studies at the frontier of symbiosis research that are applying functional genomic approaches to characterization of the developmental and cellular mechanisms of host/endosymbiont integration, work that heralds a new era in symbiosis research.
Publisher: Springer Science and Business Media LLC
Date: 21-11-2016
Publisher: Springer Science and Business Media LLC
Date: 25-03-2015
Publisher: Elsevier BV
Date: 06-2013
DOI: 10.1016/J.CELL.2013.05.040
Abstract: The smallest reported bacterial genome belongs to Tremblaya princeps, a symbiont of Planococcus citri mealybugs (PCIT). Tremblaya PCIT not only has a 139 kb genome, but possesses its own bacterial endosymbiont, Moranella endobia. Genome and transcriptome sequencing, including genome sequencing from a Tremblaya lineage lacking intracellular bacteria, reveals that the extreme genomic degeneracy of Tremblaya PCIT likely resulted from acquiring Moranella as an endosymbiont. In addition, at least 22 expressed horizontally transferred genes from multiple erse bacteria to the mealybug genome likely complement missing symbiont genes. However, none of these horizontally transferred genes are from Tremblaya, showing that genome reduction in this symbiont has not been enabled by gene transfer to the host nucleus. Our results thus indicate that the functioning of this three-way symbiosis is dependent on genes from at least six lineages of organisms and reveal a path to intimate endosymbiosis distinct from that followed by organelles.
Publisher: Frontiers Media SA
Date: 19-05-2022
DOI: 10.3389/FMICB.2022.816608
Abstract: Quantifying the size of endosymbiont populations is challenging because endosymbionts are typically difficult or impossible to culture and commonly polyploid. Current approaches to estimating endosymbiont population sizes include quantitative PCR (qPCR) targeting endosymbiont genomic DNA and flow-cytometry. While qPCR captures genome copy number data, it does not capture the number of bacterial cells in polyploid endosymbiont populations. In contrast, flow cytometry can capture accurate estimates of whole host-level endosymbiont population size, but it is not readily able to capture data at the level of endosymbiotic host cells. To complement these existing approaches for estimating endosymbiont population size, we designed and implemented an object detection/segmentation tool for counting the number of endosymbiont cells in micrographs of host tissues. The tool, called SymbiQuant, which makes use of recent advances in deep neural networks includes a graphic user interface that allows for human curation of tool output. We trained SymbiQuant for use in the model aphid/ Buchnera endosymbiosis and studied Buchnera population dynamics and phenotype over aphid postembryonic development. We show that SymbiQuant returns accurate counts of endosymbionts, and readily captures Buchnera phenotype. By replacing our training data with data composed of annotated microscopy images from other models of endosymbiosis, SymbiQuant has the potential for broad application. Our tool, which is available on GitHub, adds to the repertoire of methods researchers can use to study endosymbiosis at the organismal, genome, and now endosymbiotic host tissue or cell levels.
Publisher: Springer Science and Business Media LLC
Date: 14-09-2011
Abstract: A major goal of molecular evolutionary biology is to understand the fate and consequences of duplicated genes. In this context, aphids are intriguing because the newly sequenced pea aphid genome harbors an extraordinary number of lineage-specific gene duplications relative to other insect genomes. Though many of their duplicated genes may be involved in their complex life cycle, duplications in nutrient amino acid transporters appear to be associated rather with their essential amino acid poor diet and the intracellular symbiosis aphids rely on to compensate for dietary deficits. Past work has shown that some duplicated amino acid transporters are highly expressed in the specialized cells housing the symbionts, including a paralog of an aphid-specific expansion homologous to the Drosophila gene slimfast . Previous data provide evidence that these bacteriocyte-expressed transporters mediate amino acid exchange between aphids and their symbionts. We report that some nutrient amino acid transporters show male-biased expression. Male-biased expression characterizes three paralogs in the aphid-specific slimfast expansion, and the male-biased expression is conserved across two aphid species for at least two paralogs. One of the male-biased paralogs has additionally experienced an accelerated rate of non-synonymous substitutions. This is the first study to document male-biased slimfast expression. Our data suggest that the male-biased aphid slimfast paralogs erged from their ancestral function to fill a functional role in males. Furthermore, our results provide evidence that members of the slimfast expansion are maintained in the aphid genome not only for the previously hypothesized role in mediating amino acid exchange between the symbiotic partners, but also for sex-specific roles.
Publisher: Oxford University Press (OUP)
Date: 24-05-2011
Abstract: In insects, some of the most ecologically important symbioses are nutritional symbioses that provide hosts with novel traits and thereby facilitate exploitation of otherwise inaccessible niches. One such symbiosis is the ancient obligate intracellular symbiosis of aphids with the γ-proteobacteria, Buchnera aphidicola. Although the nutritional basis of the aphid/Buchnera symbiosis is well understood, the processes and structures that mediate the intimate interactions of symbiotic partners remain uncharacterized. Here, using a de novo approach, we characterize the complement of 40 amino acid polyamine organocation (APC) superfamily member amino acid transporters (AATs) encoded in the genome of the pea aphid, Acyrthosiphon pisum. We find that the A. pisum APC superfamily is characterized by extensive gene duplications such that A. pisum has more APC superfamily transporters than other fully sequenced insects, including a ten paralog aphid-specific expansion of the APC transporter slimfast. Detailed expression analysis of 17 transporters selected on the basis of their phylogenetic relationship to five AATs identified in an earlier bacteriocyte expressed sequence tag study distinguished a subset of eight transporters that have been recruited for amino acid transport in bacteriocyte cells at the symbiotic interface. These eight transporters include transporters that are highly expressed and/or highly enriched in bacteriocytes and intriguingly, the four AATs that show bacteriocyte-enriched expression are all members of gene family expansions, whereas three of the four that are highly expressed but not enriched in bacteriocytes retain one-to-one orthology with transporters in other genomes. Finally, analysis of evolutionary rates within the large A. pisum slimfast expansion demonstrated increased rates of molecular evolution coinciding with two major shifts in expression: 1) a loss of gut expression and possibly a gain of bacteriocyte expression and 2) loss of expression in all surveyed tissues in asexual females. Taken together, our characterization of nutrient AATs at the aphid/Buchnera symbiotic interface provides the first examination of the processes and structures operating at the interface of an obligate intracellular insect nutritional symbiosis, offering unique insight into the types of genomic change that likely facilitated evolutionary maintenance of the symbiosis.
Publisher: Elsevier BV
Date: 10-2015
Publisher: Proceedings of the National Academy of Sciences
Date: 16-10-2023
Publisher: Springer Science and Business Media LLC
Date: 13-02-2017
Publisher: Hindawi Limited
Date: 06-1997
DOI: 10.1017/S0016672397002747
Abstract: This paper reports the first direct molecular evidence that X chromosome loss during determination of male aphids (XO) is random. Clonal and sexual females, and males, of the species Sitobion near fragariae were screened using three polymorphic microsatellite loci. Two loci, Sm10 and Sm17, showed the same heterozygous genotypes in all three aphid morphs. The third, Sm11, was heterozygous for the same two alleles in clonal and sexual females, but of the 25 males screened 11 showed the ‘160’ allele and 14 showed the ‘156’ allele. This result indicates X-linkage of locus Sm11, with random loss of the X chromosome during the formation of male embryos. The possible implications of this result are discussed with respect to aphid sex determination, recombination and chromosome evolution.
Publisher: Wiley
Date: 07-10-2010
Publisher: CSIRO Publishing
Date: 2001
DOI: 10.1071/ZO00082
Abstract: Mitochondrial DNA (mtDNA) analysis was undertaken to resolve the systematic uncertainties surrounding the morphologically distinct purple-necked rock-wallaby (P. lateralis purpureicollis) of north-west Queensland, Australia. A comparison of mtDNA sequence ergence using both whole mtDNA restriction site and control-region sequence analyses revealed that P. l. purpureicollis was as well differentiated from other P. lateralis (black-footed rock-wallaby) taxa as P. lateralis was from P. penicillata (brush-tailed rock-wallaby) or P. assimilis (allied rock-wallaby). Phylogenetic analysis of the sequence data suggests thatP. lateralis (sensu lato) is paraphyletic, with P. l. purpureicollis being more closely aligned to P. penicillataand P. assimilis than to P. lateralis (sensu stricto). Data are also presented that demonstrate significant differences in the distribution of the telomeric repeat sequence (TTAGGG)n between the chromosomes of P. l. purpureicollis and the karyotypically similar MacDonnell Ranges race of P. lateralis. In addition, meiosis appears to be severely disrupted in the majority (73%) of oocytes examined from two P. l. purpureicollis MacDonnell Ranges race hybrids. In light of these findings we recommend that the purple-necked rock-wallaby be reinstated as a full species, P. purpureicollis Le Souef 1924.
Publisher: Proceedings of the National Academy of Sciences
Date: 22-07-2021
Publisher: Springer Science and Business Media LLC
Date: 11-01-2016
Publisher: Springer Science and Business Media LLC
Date: 23-07-2020
DOI: 10.1186/S12915-020-00820-5
Abstract: Although native to North America, the invasion of the aphid-like grape phylloxera Daktulosphaira vitifoliae across the globe altered the course of grape cultivation. For the past 150 years, viticulture relied on grafting-resistant North American Vitis species as rootstocks, thereby limiting genetic stocks tolerant to other stressors such as pathogens and climate change. Limited understanding of the insect genetics resulted in successive outbreaks across the globe when rootstocks failed. Here we report the 294-Mb genome of D. vitifoliae as a basic tool to understand host plant manipulation, nutritional endosymbiosis, and enhance global viticulture. Using a combination of genome, RNA, and population resequencing, we found grape phylloxera showed high duplication rates since its common ancestor with aphids, but similarity in most metabolic genes, despite lacking obligate nutritional symbioses and feeding from parenchyma. Similarly, no enrichment occurred in development genes in relation to viviparity. However, phylloxera evolved 2700 unique genes that resemble putative effectors and are active during feeding. Population sequencing revealed the global invasion began from the upper Mississippi River in North America, spread to Europe and from there to the rest of the world. The grape phylloxera genome reveals genetic architecture relative to the evolution of nutritional endosymbiosis, viviparity, and herbivory. The extraordinary expansion in effector genes also suggests novel adaptations to plant feeding and how insects induce complex plant phenotypes, for instance galls. Finally, our understanding of the origin of this invasive species and its genome provide genetics resources to alleviate rootstock bottlenecks restricting the advancement of viticulture.
Publisher: Springer Science and Business Media LLC
Date: 11-09-2020
DOI: 10.1186/S12915-020-00864-7
Abstract: An amendment to this paper has been published and can be accessed via the original article.
Publisher: Proceedings of the National Academy of Sciences
Date: 23-12-2013
Abstract: Nutritional bacterial endosymbionts are housed in specialized host cells and are partitioned from the host cell cytoplasm by a host-derived symbiosomal membrane. This cellular organization isolates bacterial symbionts from nutrient pools in the host cell and makes possible host control of nutrient supply to bacterial symbionts. Here, using the aphid– Buchnera nutritional endosymbiosis, we demonstrate that the most active host glutamine (precursor) transporter, Acyrthosiphon pisum glutamine transporter 1, is competitively inhibited by arginine (a Buchnera -synthesized end product). We propose a model of endosymbiosis regulation in which precursor transport is regulated by a symbiont-synthesized end product. Thus, we provide insights into the molecular mechanism of host control of bacterial endosymbiont essential nutrient biosynthesis.
Publisher: Springer Science and Business Media LLC
Date: 12-2014
Publisher: Hindawi Limited
Date: 06-2001
DOI: 10.1017/S0016672301005018
Abstract: Fifteen polymorphic microsatellite markers were used to establish linkage groups and relative rates of recombination in male and female Myzus persicae (Sulzer) (Hemiptera: Aphididae) (peach-potato aphid). We cloned nine markers from M. persicae and for these we report primer sequences and levels of allelic ersity and heterozygosity in four Australian M. persicae populations. Of the remaining six loci, four loci, also cloned from M. persicae, were obtained from G. Malarky (Natural History Museum, London) and two loci from Sitobion miscanthi were used. Additionally, the primer sequences of locus M77, a locus monomorphic in M. persicae but polymorphic in the closely related Myzus antirrhinii, are presented. Eleven of the 15 polymorphic markers were autosomal and four were X-linked. A linkage analysis was performed on a European pedigree of aphids containing five families with between seven and 11 offspring each. There was no linkage between any loci in females. In males, several pairwise comparisons yielded no recombinant offspring. With the exception of locus M40, these observations were supported in a linkage analysis performed on larger families produced from Australian M. persicae crosses. Locus M40 showed segregation consistent with involvement in a translocation between autosomes 1 and 3 in European s les but not in the Australian s les. From the Australian crosses we report an absence of recombination in males but high recombination rates in females. One X chromosome and four autosomal linkage groups were identified and tentatively assigned to chromosomes. The relevance of achiasmate meiosis to the evolution of sex is discussed.
Publisher: Wiley
Date: 05-2011
DOI: 10.1111/J.1365-294X.2011.05103.X
Abstract: Species interactions are fundamental to ecology. Classic studies of competition, predation, parasitism and mutualism between macroscopic organisms have provided a foundation for the discipline, but many of the most important and intimate ecological interactions are microscopic in scale. These microscopic interactions include those occurring between eukaryotic hosts and their microbial symbionts. Such symbioses, ubiquitous in nature, provide experimental challenges because the partners often cannot live outside the symbiosis. With respect to the symbionts, this precludes utilizing classical microbiological and genetic techniques that require in vitro cultivation. Genomics, however, has rapidly changed the study of symbioses. In this issue of Molecular Ecology, MacDonald et al. (2011), coupling symbiont whole-genome sequencing, experimental studies and metabolic modelling, provide novel insights into one of the best-studied symbioses, that between aphids and their obligate, nutrient-provisioning, intracellular bacteria, Buchnera aphidicola (Fig. 1). MacDonald and colleagues assessed variation in the ability of aphid–Buchnera pairs to thrive on artificial diets missing different amino acids. As shown previously (e.g. Wilkinson & Douglas 2003), aphid–Buchnera pairs can differ in their requirements for external sources of essential amino acids. Such phenotypic variation could result from differences in Buchnera’s amino acid biosynthetic capabilities or in the ability of aphids to interact with their symbionts. Whole-genome sequencing of the Buchnera genomes from four aphid lines with alternate nutritional phenotypes revealed that the environmental nutrients required by the aphid–Buchnera pairs could not be explained by sequence variation in the symbionts. Instead, a novel metabolic modelling approach suggested that much of the variation in nutritional phenotype could be explained by host variation in the capacity to provide necessary nutrient precursors to their symbionts. MacDonald et al.’s work complements a recent study by Vogel & Moran (2011), who through crossing experiments investigating the inheritance of a nutritional phenotype associated with a frameshift mutation in a Buchnera amino acid biosynthesis gene powerfully demonstrated that different host genotypes paired with the same symbiont genome could exhibit substantially different nutritional requirements.† Thus, while there is little doubt that Buchnera are evolutionarily central to the nutritional ecology of aphids, the current work by MacDonald et al. (2011) together with that of Vogel & Moran (2011) surprisingly demonstrates host dominance in defining and controlling the ecological niche of this particular symbiosis.
Publisher: Springer Science and Business Media LLC
Date: 16-11-2007
Abstract: The green peach aphid, Myzus persicae (Sulzer), is a world-wide insect pest capable of infesting more than 40 plant families, including many crop species. However, despite the significant damage inflicted by M. persicae in agricultural systems through direct feeding damage and by its ability to transmit plant viruses, limited genomic information is available for this species. Sequencing of 16 M. persicae cDNA libraries generated 26,669 expressed sequence tags (ESTs). Aphids for library construction were raised on Arabidopsis thaliana , Nicotiana benthamiana , Brassica oleracea, B. napus , and Physalis floridana (with and without Potato leafroll virus infection). The M. persicae cDNA libraries include ones made from sexual and asexual whole aphids, guts, heads, and salivary glands. In silico comparison of cDNA libraries identified aphid genes with tissue-specific expression patterns, and gene expression that is induced by feeding on Nicotiana benthamiana . Furthermore, 2423 genes that are novel to science and potentially aphid-specific were identified. Comparison of cDNA data from three aphid lineages identified single nucleotide polymorphisms that can be used as genetic markers and, in some cases, may represent functional differences in the protein products. In particular, non-conservative amino acid substitutions in a highly expressed gut protease may be of adaptive significance for M. persicae feeding on different host plants. The Agilent eArray platform was used to design an M. persicae oligonucleotide microarray representing over 10,000 unique genes. New genomic resources have been developed for M. persicae , an agriculturally important insect pest. These include previously unknown sequence data, a collection of expressed genes, molecular markers, and a DNA microarray that can be used to study aphid gene expression. These resources will help elucidate the adaptations that allow M. persicae to develop compatible interactions with its host plants, complementing ongoing work illuminating plant molecular responses to phloem-feeding insects.
Publisher: Springer Science and Business Media LLC
Date: 04-04-2017
Publisher: Oxford University Press (OUP)
Date: 09-2018
Abstract: Obligate nutritional endosymbioses are arguably the most intimate of all interspecific associations. While many insect nutritional endosymbioses are well studied, a full picture of how two disparate organisms, a bacterial endosymbiont and a eukaryotic host, are integrated is still lacking. The mTOR pathway is known to integrate nutritional conditions with cell growth and survival in eukaryotes. Characterization and localization of amino acid transporters in aphids suggest the mTOR pathway as a point of integration between an aphid host and its amino acid-provisioning endosymbiont Buchnera aphidicola. The mTOR pathway is unannotated in aphids and unstudied in any nutritional endosymbiosis. We annotated mTOR pathway genes in two aphid species, Acyrthosiphon pisum and Myzus persicae, using both BLASTp searches and Hidden Markov Models. Using previously collected RNAseq data we constructed new reference transcriptomes for bacteriocyte, gut, and whole insect tissue for three lines of M. persicae. Annotation of the mTOR pathway identified homologs of all known invertebrate mTOR genes in both aphid species with some duplications. Differential expression analysis showed that genes specific to the amino acid-sensitive mTOR Complex 1 were more highly expressed in bacteriocytes than genes specific to the amino acid-insensitive mTOR Complex 2. Almost all mTOR genes involved in sensing amino acids showed higher expression in bacteriocytes than in whole insect tissue. When compared to gut, the putative glutamine/arginine sensing transporter ACYPI000333, an ortholog of SLC38A9, showed 6.5 times higher expression in bacteriocytes. Our results suggest that the mTOR pathway may be functionally important in mediating integration of Buchnera into aphid growth and reproduction.
Publisher: Wiley
Date: 22-01-2018
DOI: 10.1111/MEC.14464
Abstract: Although many insects are associated with obligate bacterial endosymbionts, the mechanisms by which these host/endosymbiont associations are regulated remain mysterious. While microRNAs (miRNAs) have been recently identified as regulators of host/microbe interactions, including host athogen and host/facultative endosymbiont interactions, the role miRNAs may play in mediating host/obligate endosymbiont interactions is virtually unknown. Here, we identified conserved miRNAs that potentially mediate symbiotic interactions between aphids and their obligate endosymbiont, Buchnera aphidicola. Using small RNA sequence data from Myzus persicae and Acyrthosiphon pisum, we annotated 93 M. persicae and 89 A. pisum miRNAs, among which 69 were shared. We found 14 miRNAs that were either highly expressed in aphid bacteriome, the Buchnera-housing tissue, or differentially expressed in bacteriome vs. gut, a non-Buchnera-housing tissue. Strikingly, 10 of these 14 miRNAs have been implicated previously in other host/microbe interaction studies. Investigating the interaction networks of these miRNAs using a custom computational pipeline, we identified 103 miRNA::mRNA interactions shared between M. persicae and A. pisum. Functional annotation of the shared mRNA targets revealed only two over-represented cluster of orthologous group categories: amino acid transport and metabolism, and signal transduction mechanisms. Our work supports a role for miRNAs in mediating host/symbiont interactions between aphids and their obligate endosymbiont Buchnera. In addition, our results highlight the probable importance of signal transduction mechanisms to host/endosymbiont coevolution.
Publisher: Wiley
Date: 04-07-2000
Publisher: Wiley
Date: 10-1999
DOI: 10.1046/J.1365-294X.1999.00751.X
Abstract: In sharp contrast to their southeast Asian and European counterparts, Sitobion miscanthi and S. near fragariae aphids in Australia exhibit a complete absence of sexual reproduction. This demands an explanation within the context of the evolution and maintenance of sex and parthenogenesis. Accordingly, we executed a genetic analysis of the two species in neighbouring New Zealand. Microsatellites and single-stranded conformation polymorphism/sequence analysis of the nuclear gene elongation factor 1alpha were used to identify aphid clones and confirm species identification, respectively. Karyotypic variation was also investigated. The New Zealand fauna showed few (nonrecombining) genotypes and appears to have received migrants from both Australia and Asia. Other genotypes have apparently arisen in situ in New Zealand, exhibiting stepwise mutation of microsatellite alleles and also karyotypic change. Thus, these data represent rare evidence of evolution within wild-living parthenogenetic lineages. Karyotypic changes appear to occur at a rate even greater than that of microsatellite evolution. Strong geographical partitioning of genotypes/karyotypes was found, with certain ones predominating over large areas. These data suggest that clonal selection could be important in the distribution and patterning of genetic variation. We present a model to explain the genetic patterns, with particular reference to the absence of sexual reproduction in Sitobion aphids in New Zealand and Australia.
Publisher: Oxford University Press (OUP)
Date: 15-02-2016
DOI: 10.1093/GBE/EVW020
Publisher: Elsevier
Date: 2020
Publisher: Public Library of Science (PLoS)
Date: 30-12-2014
Publisher: Wiley
Date: 16-02-2014
DOI: 10.1111/MEC.12627
Abstract: Symbiosis is well known to influence bacterial symbiont genome evolution and has recently been shown to shape eukaryotic host genomes. Intriguing patterns of host genome evolution, including remarkable numbers of gene duplications, have been observed in the pea aphid, a sap‐feeding insect that relies on a bacterial endosymbiont for amino acid provisioning. Previously, we proposed that gene duplication has been important for the evolution of symbiosis based on aphid‐specific gene duplication in amino acid transporters ( AAT s), with some paralogs highly expressed in the cells housing symbionts (bacteriocytes). Here, we use a comparative approach to test the role of gene duplication in enabling recruitment of AAT s to bacteriocytes. Using genomic and transcriptomic data, we annotate AAT s from sap‐feeding and non sap‐feeding insects and find that, like aphids, AAT gene families have undergone independent large‐scale gene duplications in three of four additional sap‐feeding insects. RNA ‐seq differential expression data indicate that, like aphids, the sap‐feeding citrus mealybug possesses several lineage‐specific bacteriocyte‐enriched paralogs. Further, differential expression data combined with quantitative PCR support independent evolution of bacteriocyte enrichment in sap‐feeding insect AAT s. Although these data indicate that gene duplication is not necessary to initiate host/symbiont amino acid exchange, they support a role for gene duplication in enabling AAT s to mediate novel host/symbiont interactions broadly in the sap‐feeding suborder Sternorrhyncha. In combination with recent studies on other symbiotic systems, gene duplication is emerging as a general pattern in host genome evolution.
Publisher: Springer Science and Business Media LLC
Date: 10-03-2011
Publisher: Springer Science and Business Media LLC
Date: 30-09-2019
DOI: 10.1186/S13104-019-4665-6
Abstract: Aphids harbor a nutritional obligate endosymbiont in specialized cells called bacteriocytes, which aggregate to form an organ known as the bacteriome. Aphid bacteriomes display distinct gene expression profiles that facilitate the symbiotic relationship. Currently, the mechanisms that regulate these patterns of gene expression are unknown. Recently using computational pipelines, we identified miRNAs that are conserved in expression in the bacteriomes of two aphid species and proposed that they function as important regulators of bacteriocyte gene expression. Here using a dual luciferase assay in mouse NIH/3T3 cell culture, we aimed to experimentally validate the computationally predicted interaction between Myzus persicae miR-92a and the predicted target region of M. persicae bacteriocyte-specific secreted protein 1 (SP1) mRNA. In the dual luciferase assay, miR-92a interacted with the SP1 target region resulting in a significant downregulation of the luciferase signal. Our results demonstrate that miR-92a interacts with SP1 to alter expression in a heterologous expression system, thereby supporting our earlier assertion that miRNAs are regulators of the aphid/ Buchnera symbiotic interaction.
Publisher: Proceedings of the National Academy of Sciences
Date: 06-06-2011
Abstract: Plant sap-feeding insects and blood-feeding parasites are frequently depleted in 15 N relative to their diet. Unfortunately, most fluid-feeder/host nitrogen stable-isotope studies simply report stable-isotope signatures, but few attempt to elucidate the mechanism of isotopic trophic depletion. Here we address this deficit by investigating the nitrogen stable-isotope dynamics of a fluid-feeding herbivore-host plant system: the green peach aphid, Myzus persicae , feeding on multiple brassicaceous host plants. M. persicae was consistently more than 6‰ depleted in 15 N relative to their hosts, although aphid colonized plants were 1.5‰ to 2.0‰ enriched in 15 N relative to uncolonized control plants. Isotopic depletion of aphids relative to hosts was strongly related to host nitrogen content. We tested whether the concomitant aphid 15 N depletion and host 15 N enrichment was coupled by isotopic mass balance and determined that aphid 15 N depletion and host 15 N enrichment are uncoupled processes. We hypothesized that colonized plants would have higher nitrate reductase activity than uncolonized plants because previous studies had demonstrated that high nitrate reductase activity under substrate-limiting conditions can result in increased plant δ 15 N values. Consistent with our hypothesis, nitrate reductase activity in colonized plants was twice that of uncolonized plants. This study offers two important insights that are likely applicable to understanding nitrogen dynamics in fluid-feeder/host systems. First, isotopic separation of aphid and host depends on nitrogen availability. Second, aphid colonization alters host nitrogen metabolism and subsequently host nitrogen stable-isotope signature. Notably, this work establishes a metabolic framework for future hypothesis-driven studies focused on aphid manipulation of host nitrogen metabolism.
No related grants have been discovered for Alexandra Wilson.