Identification and characterization of circadian clock genes in the pea aphid Acyrthosiphon pisum

The molecular basis of circadian clocks is highly evolutionarily conserved and has been best characterized in Drosophila and mouse. Analysis of the Acyrthosiphon pisum genome revealed the presence of orthologs of the following genes constituting the core of the circadian clock in Drosophila: period (per), timeless (tim), Clock, cycle, vrille, and Pdp1. However, the presence in A. pisum of orthologs of a mammal-type in addition to a Drosophila-type cryptochrome places the putative aphid clockwork closer to the ancestral insect system than to the Drosophila one. Most notably, five of these putative aphid core clock genes are highly divergent and exhibit accelerated rates of change (especially…

Characterisation, analysis of expression and localisation of the opsin gene repertoire from the perspective of photoperiodism in the aphid Acyrthosiphon pisum

Organisms exhibit a wide range of seasonal responses as adaptions to predictable annual changes in their environment. These changes are originally caused by the effect of the Earth's cycles around the sun and its axial tilt. Examples of seasonal responses include floration, migration, reproduction and diapause. In temperate climate zones, the most robust variable to predict seasons is the length of the day (i.e. the photoperiod). The first step to trigger photoperiodic driven responses involves measuring the duration of the light-dark phases, but the molecular clockwork performing this task is poorly characterized. Photopigments such as opsins are known to participate in light perception, b…

Molecular systematics of aphids (Homoptera: Aphididae): new insights from the long-wavelength opsin gene.

Viviparous aphids (Aphididae) constitute a monophyletic group within the Homoptera with more than 4000 extant species worldwide but higher diversity in temperate regions. Several aspects of their biology account for attention paid to this group of insects. Their plant-sap-sucking way of feeding with many species transmitting viruses to crop plants has important implications on crop management strategies. Cyclical parthenogenesis associated in many groups to host alternation and elaborate polyphenisms is of special interests for evolutionists. Finally, the ancient association of most aphid species with intracellular endosymbiotic bacteria (Buchnera sp.) has also received much attention from …

Molecular phylogeny of Iberian Fordini (Aphididae: Eriosomatinae): implications for the taxonomy of generaFordaandParacletus

Mediterranean representatives of the galling aphid tribe Fordini (Hemiptera: Aphididae: Eriosomatinae) are usually grouped under the subtribe term Fordina. Aphids within Fordina display two-year life cycles, alternating between Pistacia shrubs, where they induce conspicuous galls, and roots of Poaceae species. The high number of morphs present in a given species, the lack of knowledge of the complete cycle in some species, and the similarity between homologous morphs observed in different species pose many taxonomic problems in this group. We present results of a survey to elucidate the phylogenetic relationships among Fordini species present in the Iberian Peninsula and the Canary Islands.…

A new Aphid genus and species (Hemiptera: Aphididae: Macrosiphini) living on ferns in Costa Rica and Mexico

AbstractAphid species colonising ferns belong to the subfamily Aphidinae (Hemiptera: Aphididae) and the majority of these to the tribe Macrosiphini. A new genus in this tribe and its type species: Gibbomyzus pteridophytorumnew genus, new species, are established. Apterous and alate viviparous females are described from specimens collected on Blechnum buchtienii Rosenstock (Blechnaceae) in Costa Rica and on Pteridium aquilinum (Linnaeus) Kuhn (Dennstaedtiaceae) and an unidentified fern in Mexico. The taxonomic validity of the two new taxa is discussed based on morphological and molecular data. Morphologically, the new genus is compared with genera with swollen siphunculi recorded in the New …

Geographic distribution and seasonal variation of mitochondrial DNA haplotypes in the aphidRhopalosiphum padi(Hemiptera: Aphididae)

AbstractThis study examines the spatial and seasonal patterning of mitochondrial DNA diversity in French populations of the bird cherry-oat aphid,Rhopalosiphum padi(Linnaeus), on both its primary and secondary hosts. Our results confirm the presence of two major mitochondrial lineages that are generally associated with the breeding system variation (cyclic and obligate parthenogenesis) shown by this species. The strength of this relationship varies regionally, being most evident in the south and west. Cyclically parthenogenetic populations show no significant regional or seasonal genetic divergence reflecting high levels of gene flow, possibly promoted by their obligate host-alternation. Ho…

Insulin-like peptides involved in photoperiodism in the aphid Acyrthosiphon pisum

Aphids were the first animals reported as photoperiodic as their life cycles are strongly determined by the photoperiod. During the favourable seasons (characterised by long days) aphid populations consist exclusively of viviparous parthenogenetic females (known as virginoparae). Shortening of the photoperiod in autumn is perceived by aphids as the signal that anticipates the harsh season, leading to a switch in the reproductive mode giving place to the sexual morphs (oviparae females and males) that mate and lay winter-resistant (diapause-like) eggs. The molecular and cellular basis governing the switch between the two reproductive modes are far from being understood. Classical experiments…

Mapping and quantification of cryptochrome expression in the brain of the pea aphid Acyrthosiphon pisum.

Aphids are paradigmatic photoperiodic animals often used to study the role of the circadian clock in the seasonal response. Previously, we described some elements of the circadian clock core (genes period and timeless) and output (melatonin, AANATs and PTTH) that could have a role in the regulation of the aphid seasonal response. More recently we identified two opsins (C-ops and SWO4) as candidate input photoperiodic receptors. In the present report, we focus on the study of cryptochromes (cry) as photoreceptors of the circadian clock and discuss their involvement in the seasonal response. We analyze the expression of cry1 and cry2 genes in a circadian and seasonal context, and map their ex…

Aggressive mimicry coexists with mutualism in an aphid

Understanding the evolutionary transition from interspecific exploitation to cooperation is a major challenge in evolutionary biology. Ant-aphid relationships represent an ideal system to this end because they encompass a coevolutionary continuum of interactions ranging from mutualism to antagonism. In this study, we report an unprecedented interaction along this continuum: aggressive mimicry in aphids. We show that two morphs clonally produced by the aphid Paracletus cimiciformis during its root-dwelling phase establish relationships with ants at opposite sides of the mutualism-antagonism continuum. Although one of these morphs exhibits the conventional trophobiotic (mutualistic) relations…

Seasonal photoperiodism regulates the expression of cuticular and signalling protein genes in the pea aphid

International audience; Seasonal photoperiodism in aphids is responsible for the spectacular switch from asexual to sexual reproduction. However, little is known on the molecular and physiological mechanisms involved in reproductive mode shift through the action of day length. Earlier works showed that aphid head, but not eyes, directly perceives the photoperiodic signal through the cuticle. In order to identify genes regulating the photoperiodic response, a 3321 cDNA microarray developed for the pea aphid, Acyrthosiphon pisum was used to compare RNA populations extracted from heads of short- and long-day reared aphids. Microarray analyses revealed that 59 different transcripts were signifi…

Additional file 1 of The genome sequence of the grape phylloxera provides insights into the evolution, adaptation, and invasion routes of an iconic pest

Additional file 1: Figures. S1-S22, Table S1-S20, Methods and Results. Figure S1. Mitochondrial genome view of grape phylloxera. Figure S2. Proportion of transposable elements (TE) in the genome. Figure S3. GO terms of phylloxera-specific genes. Figure S4. Enriched GO terms in the phylloxera genome with and without TEs. Figure S5. Gene gain/loss at different nodes or branches. Figure S6. Species phylogenetic tree based on insect genomes and the transcriptomes of Planoccoccus citri and Adelges tsugae. Figure S7. Diagram of the gap-filling and annotation process. Figure S8. Urea cycle in D. vitifoliae and A. pisum. Figure S9. IMD immune pathway in D. vitifoliae.Figure S10. Phylogenetic tree o…

Combination of molecular data support the existence of three main lineages in the phylogeny of aphids (Hemiptera: Aphididae) and the basal position of the subfamily Lachninae

Abstract The first molecular studies on the phylogeny of aphids (Hemiptera: Aphididae) bumped into a striking lack of phylogenetic structure for taxa levels higher than tribe, probably as a consequence of the rapid adaptive radiation that this group of insects went through during the Late Cretaceous. Here we present a new attempt to infer the relationships between major aphid taxa by the separate and combined analysis of two nuclear sequences (the long-wavelength opsin gene and the elongation factor 1α gene) and two mitochondrial sequences (the genes encoding the subunit 6 of the F-ATPase and the subunit II of the cytochrome oxidase). Our results confirm previous results with the grouping o…

Genetic variation in natural populations of the aphid Rhopalosiphum padi as revealed by maternally inherited markers

A survey on 148 clones of the aphid Rhopalosiphum padi from 11 widespread localities has been carried out to study the genetic structure of populations of this species as revealed by mitochondrial DNA restriction site and length polymorphisms as well as by restriction site analysis of a maternally inherited plasmid carried by the aphid eubacterial endosymbiont Buchnera aphidicola. Our results support the existence in the area under study of two main aphid maternal lineages strikingly coincidental with the two main reproductive categories displayed by this species. Those aphid clones possessing an incomplete life cycle that lacks the sexual phase (anholocyclic or androcyclic clones) show mit…

Morphological stasis of two species belonging to the L-morphotype in the Brachionus plicatilis species complex

Detection and characterization of sibling species complexes in zooplankton are critical to understanding their ecological responses and patterns of evolution. The taxon Brachionus plicatilis is a complex of at least 14 species with three major, deeply diverged clades, which are morphologically distinct. We studied morphometric differences between two species — B. plicatilis sensu stricto and B. ‘Manjavacas’ — which belong to the L-(large) morphotype and often co-occur in ponds or lakes. B. plicatilis s.s. was on average 6% longer than B. ‘Manjavacas’. They differed significantly in the measurements related to lorica spines. A significant discriminant function relating spine measurements was…

Assessing the nucleotide diversity of three aphid species by RAPD

A method is presented for the estimation of nucleotide diversity and genetic structure of populations from RAPD (random amplified polymorphic DNA) data. It involves a modification of the technique developed by Lynch and Crease (1990) for the case of restriction sites as survey data. As new elements the method incorporates (i) dominance correction, (ii) values of asexual reproduction of the populations sampled, and (iii) an analytical variance of the number of nucleotide substitutions per site. Sampling was carried out at two geographic scales for three aphid species. At a macrogeographic scale, populations of Rhopalosiphum padi did not show statistical genetic differentiation. Aphis gossypi…

Melatonin in the seasonal response of the aphid Acyrthosiphon pisum.

Aphids display life cycles largely determined by the photoperiod. During the warm long-day seasons, most aphid species reproduce by viviparous parthenogenesis. The shortening of the photoperiod in autumn induces a switch to sexual reproduction. Males and sexual females mate to produce overwintering resistant eggs. In addition to this full life cycle (holocycle), there are anholocyclic lineages that do not respond to changes in photoperiod and reproduce continuously by parthenogenesis. The molecular or hormonal events that trigger the seasonal response (i.e., induction of the sexual phenotypes) are still unknown. Although circadian synthesis of melatonin is known to play a key role in verteb…

A new genus and species of asteraceae-inhabiting aphid (hemiptera: aphididae) from Costa Rica and Mexico

P. 323-331 Ucrimyzus villalobosi Mier Durante & Pérez Hidalgo gen. n., sp. n. (Hemiptera: Aphididae: Macrosiphini) are described from apterous and alate viviparous females collected on species of genera Bidens, Schkuhria, Senecio and Stevia (Asteraceae: Asteroideae) in Costa Rica and Mexico. Principal components analysis (PCA) was done to verify that the studied aphids belong to a single species regardless of their geographical origin or host plant. Molecular analyses were carried out on the sequences of a fragment of the mitochondrial gene encoding for cytochrome c oxidase subunit 1 (COI) and of a fragment of the nuclear gene encoding elongation factor 1α (EF1α). The taxonomic discussion t…

Determination of melatonin in Acyrthosiphon pisum aphids by liquid chromatography-tandem mass spectrometry.

Melatonin is a hormone mainly involved in the regulation of circadian and seasonal rhythms in both invertebrates and vertebrates. Despite the identification of melatonin in many insects, its involvement in the insect seasonal response remains unclear. A liquid chromatography tandem mass spectrometry (LC-MS/MS) method has been developed for melatonin analysis in aphids (Acyrthosiphon pisum) for the first time. After comparing two different procedures and five extraction solvents, a sample preparation procedure with a mixture of methanol/water (50:50) was selected for melatonin extraction. The method was validated by analyzing melatonin recovery at three spiked concentrations (5, 50 and 100 p…

Additional file 1 of The genome sequence of the grape phylloxera provides insights into the evolution, adaptation, and invasion routes of an iconic pest

Additional file 1: Figures. S1-S22, Table S1-S20, Methods and Results. Figure S1. Mitochondrial genome view of grape phylloxera. Figure S2. Proportion of transposable elements (TE) in the genome. Figure S3. GO terms of phylloxera-specific genes. Figure S4. Enriched GO terms in the phylloxera genome with and without TEs. Figure S5. Gene gain/loss at different nodes or branches. Figure S6. Species phylogenetic tree based on insect genomes and the transcriptomes of Planoccoccus citri and Adelges tsugae. Figure S7. Diagram of the gap-filling and annotation process. Figure S8. Urea cycle in D. vitifoliae and A. pisum. Figure S9. IMD immune pathway in D. vitifoliae.Figure S10. Phylogenetic tree o…

Characterisation, analysis of expression and localisation of circadian clock genes from the perspective of photoperiodism in the aphid Acyrthosiphon pisum.

Aphids are typical photoperiodic insects that switch from viviparous parthenogenetic reproduction typical of long day seasons to oviparous sexual reproduction triggered by the shortening of photoperiod in autumn yielding an overwintering egg in which an embryonic diapause takes place. While the involvement of the circadian clock genes in photoperiodism in mammals is well established, there is still some controversy on their participation in insects. The availability of the genome of the pea aphid Acyrthosiphon pisum places this species as an excellent model to investigate the involvement of the circadian system in the aphid seasonal response. In the present report, we have advanced in the c…

Sex versus parthenogenesis: A transcriptomic approach of photoperiod response in the model aphid Acyrthosiphon pisum (Hemiptera: Aphididae)

International audience; Most aphids develop a cyclic parthenogenesis life-cycle. After several generations of viviparous parthenogenetic females, it follows a single annual generation of sexual individuals, usually in autumn, that mate and lay the sexual eggs. Shortening of photoperiod at the end of the summer is a key factor inducing the sexual response. With the survey here reported we aimed at identifying a collection of candidate genes to participate at some point in the cascade of events that lead to the sexual phenotypes. Following a suppression subtractive hybridization methodology (SSH) on the model aphid Acyrthosiphon pisum, we built and characterised two reciprocal cDNA libraries …

Identification of a gene overexpressed in aphids reared under short photoperiod.

Most aphids develop a cyclic parthenogenesis life-cycle. After several generations of viviparously produced parthenogenetic females, follows a single annual generation of sexual individuals, usually in autumn, that mate and lay the sexual eggs. Shortening of photoperiod at the end of the summer (together with temperature) is a key factor inducing the sexual response. Currently no genes involved in the cascade of events that lead to the appearance of sexual forms have been reported. After a Differential Display RT-PCR survey performed on Acyrthosiphon pisum aphids, we identified a gene that is overexpressed in aphids reared under short photoperiod conditions that induce sexuality in this spe…

The genome sequence of the grape phylloxera provides insights into the evolution, adaptation, and invasion routes of an iconic pest

Background: 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. Results: Using a combination of…

Plasmid-encoded anthranilate synthase (TrpEG) in Buchnera aphidicola from aphids of the family pemphigidae

Aphids are dependent on an intracellular symbiont (Buchnera aphidicola, Proteobacteria) for normal growth and reproduction (7, 19, 45). The bacteria reside in specialized cells in the aphid hemocele and are transmitted maternally through infection of eggs or embryos (11, 26). Phylogenetic studies have revealed two major characteristics of the evolutionary history of the association (37, 39); (i) the symbiosis had a single origin, dated about 150 million to 250 million years ago; and (ii) host and symbiont lineages have since diverged strictly in parallel. The association, like other symbioses in insects feeding on restricted and unbalanced diets, is thought to have a nutritional basis (5–7,…

A new species of Rhopalosiphum (Hemiptera, Aphididae) on Chusquea tomentosa (Poaceae, Bambusoideae) from Costa Rica

copyright 2012, Los autores y Zookeys. Datos incluidos por Lisela Moreira Carmona, responsable de depósitos del área de Patógenos y Plagas de Plantas (CIBCM-UCR). The new species Rhopalosiphum chusqueae Pérez Hidalgo & Villalobos Muller, is described from apterous viviparous females caught on Chusquea tomentosa in Cerro de la Muerte (Costa Rica). The identity of the species is supported both by the morphological features and by a molecular phylogenetic analysis based on a fragment of the mitochondrial DNA containing the 5’ region of the cytochrome c oxidase 1 (COI) and on the nuclear gene coding for the Elongation factor-1 alpha (EF1α). The taxonomic position of the new species is discussed…

Molecular characterization of cyclic and obligate parthenogens in the aphid Rhopalosiphum padi (L.)

Holocyclic clones of the aphid Rhopalosiphum padi (L.) reproduce by cyclic parthenogenesis, whereas anholocyclic individuals are obligate parthenogens. Mitochondrial DNA (mtDNA) and random amplified polymorphic DNA markers in R . padi as well as plasmid DNA markers of its bacterial endosymbiont, Buchnera aphidicola , were examined to determine the extent of genetic divergence between clones with these differing breeding systems. These analyses revealed that cyclically parthenogenetic lineages possessed differing mtDNA and plasmid haplotypes than most obligately asexual clones. The extent of sequence divergence between these maternally inherited molecules suggests a relatively ancient origin…

Progress in the characterization of insulin-like peptides in aphids: Immunohistochemical mapping of ILP4.

Aphids were the first animals described as photoperiodic due to their seasonal switch from viviparous parthenogenesis to sexual reproduction (cyclical parthenogenesis) caused by the shortening of the photoperiod in autumn. This switch produces a single sexual generation of oviparous females and males that mate and lay diapausing cold-resistant eggs that can overcome the unfavourable environmental conditions typical of winter in temperate regions. Previous studies have hinted at a possible implication of two insulin-like peptides (ILP1 and ILP4) in the aphid seasonal response, changing their expression levels between different photoperiodic conditions. Moreover, in situ localization of their…

Identification, characterization and analysis of expression of genes encoding arylalkylamine N-acetyltransferases in the pea aphidAcyrthosiphon pisum

Most organisms exhibit some kind of rhythmicity in their behaviour and/or physiology as an adaptation to the cyclical movements of the Earth. In addition to circadian rhythms, many organisms have an annual rhythmicity in certain activities, such as reproduction, migration or induction of diapause. Current knowledge of the molecular basis controlling seasonal rhythmicity, especially in insects, is scarce. One element that seems to play an essential role in the maintenance of both circadian and seasonal rhythms in vertebrates is the hormone melatonin. In vertebrates, the limiting enzyme in its synthesis is the arylalkylamine N-acetyltransferase (AANAT). Melatonin is also present in insects bu…

Molecular Systematics of Aphids and Their Primary Endosymbionts

Abstract Aphids constitute a monophyletic group within the order Homoptera (i.e., superfamily Aphidoidea). The Aphidoidea originated in the Jurassic about 150 my ago from some aphidiform ancestor whose origin can be traced back to about 250 my ago. They exhibit a mutualistic association with intracellular bacteria ( Buchnera sp.) related to Escherichia coli. Buchnera is usually considered the aphids' primary endosymbiont. The association is obligate for both partners. The 16S rDNA-based phylogeny of Buchnera from four aphid families showed complete concordance with the morphology-based phylogeny of their aphid hosts, which pointed to a single original infection in a common ancestor of aphid…

Aphids are the leading pests in agricultural crops. A large-scale sequencing of 40,904 ESTs from the pea aphid Acyrthosiphon pisum was carried out to define a catalog of 12,082 unique transcripts. A strong AT bias was found, indicating a compositional shift between Drosophila melanogaster and A. pisum. An in silico profiling analysis characterized 135 transcripts specific to pea-aphid tissues (relating to bacteriocytes and parthenogenetic embryos). This project is the first to address the genetics of the Hemiptera and of a hemimetabolous insect.

Identification of theprothoracicotropic hormone(Ptth) coding gene and localization of its site of expression in the pea aphidAcyrthosiphon pisum

Insect hormones control essential aspects of physiology, behaviour and development in insects. The majority of insect hormones are peptide hormones that perform a highly diverse catalogue of functions. Prothoracicotropic hormone (PTTH) is a brain neuropeptide hormone whose main function is to stimulate the secretion of ecdysone (the moulting hormone) by the prothoracic glands in insect larvae thus playing a key role in the control of moulting and metamorphosis. Moreover, both PTTH release or blockade have been reported to act as a switch to terminate or initiate larval and pupal diapauses. In insects, diapause is a prevalent response often regulated by the photoperiod. It has been shown tha…

Two mitochondrial haplotypes inPterochloroides persicae(Hemiptera: Aphididae: Lachninae) associated with different feeding sites

Pterochloroides persicae (Cholodkovsky) is an aphid species belonging to the subfamily Lachninae that uses different members of Rosaceae (specially Prunus spp.) as hosts. Partial sequences from the mitochondrial cytochrome c oxidase 1 (COI) and the nuclear long-wave opsin genes were obtained for approximately 100 P. persicae aphid individuals sampled from 34 colonies collected mainly in Tunisia and other Mediterranean locations. The variability found at the mitochondrial locus revealed the presence of two maternal haplotypes in the studied area that differed in a single nucleotide. The nuclear gene analyzed, however, failed to reveal any variability in this species. The variability found at…

Discovery and molecular characterization of a plasmid localized in Buchnera sp. bacterial endosymbiont of the aphid Rhopalosiphum padi

We have identified and completely sequenced a novel plasmid isolated from the aphid Rhopalosiphum padi. Evidence which suggests that the plasmid occurs localized within the bacterial endosymbionts is presented. The plasmid contains the four genes that constitute the entire leucine operon. This fact makes it really unique since most plasmids are dispensable and lack genes that encode essential anabolic functions. Four more phloem-feeding aphid species also seem to contain homologous plasmids. Although further work is necessary, we hypothesize that this plasmid has appeared during the evolution of the symbiotic association between the aphid and the bacterial endosymbiont. The fact that this p…