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Transcriptomic and proteomic analyses of seasonal photoperiodism in the pea aphid

ABSTRACT: Aphid adaptation to harsh winter conditions is illustrated by an alternation of their reproductive mode. Aphids detect photoperiod shortening by sensing the length of the night and switch from viviparous parthenogenesis in spring and summer, to oviparous sexual reproduction in autumn. The photoperiodic signal is transduced from the head to the reproductive tract to change the fate of the future oocytes from mitotic diploid embryogenesis to haploid formation of gametes. Because of viviparous parthenogenesis, the whole process takes place in three consecutive generations. To understand the molecular basis of the switch in the reproductive mode, a transcriptomic approach was used to detect significantly regulated transcripts in the heads of the pea aphid Acyrthosiphon pisum. The transcriptomic profiles of the heads of the first generation were slightly affected by photoperiod shortening. This suggests that trans-generation signaling does not occur between the grand-mothers and the viviparous embryos they contain. By analogy, many of the genes regulated in the heads of the second generation are implicated in visual functions, photoreception and cuticle structure. The modification of the cuticle could decrease the storage of N-β-alanyldopamine and provoke an increase in free dopamine concentration. Based in results in Drosophila, modification of the insulin pathway could cause a decrease of juvenile hormones in short-day reared aphids.

ORGANISM(S): Acyrthosiphon pisum

PROVIDER: GSE15776 | GEO | 2009/04/25

SECONDARY ACCESSION(S): PRJNA116845

REPOSITORIES: GEO

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Project description:Aphid adaptation to harsh winter conditions is illustrated by an alternation of their reproductive mode. Aphids detect photoperiod shortening by sensing the length of the night and switch from viviparous parthenogenesis in spring and summer, to oviparous sexual reproduction in autumn. The photoperiodic signal is transduced from the head to the reproductive tract to change the fate of the future oocytes from mitotic diploid embryogenesis to haploid formation of gametes. Because of viviparous parthenogenesis, the whole process takes place in three consecutive generations. To understand the molecular basis of the switch in the reproductive mode, a transcriptomic approach was used to detect significantly regulated transcripts in the heads of the pea aphid Acyrthosiphon pisum. The transcriptomic profiles of the heads of the first generation were slightly affected by photoperiod shortening. This suggests that trans-generation signaling does not occur between the grand-mothers and the viviparous embryos they contain. By analogy, many of the genes regulated in the heads of the second generation are implicated in visual functions, photoreception and cuticle structure. The modification of the cuticle could decrease the storage of N-Î²-alanyldopamine and provoke an increase in free dopamine concentration. Based in results in Drosophila, modification of the insulin pathway could cause a decrease of juvenile hormones in short-day reared aphids. Biological material for microarray experiments was prepared under two dayly photoperiodic regimes both at constant temperature of 18Â°C: i) âShort Nightâ (SN) at 16h of light and ii) âLong Nightâ (LN) at 12h of light to induce the production of sexual morphs. To initiate the experiment, two groups of 105 L3 larvae were placed either under SN or LN condition. This corresponds to generation G0. At the middle of the photophase, 25 individual were frozen when they had reached both the L4 and the wingless adult (WA) stages, in the two photoperiod conditions. The 55 remaining WA individuals (still divided in two groups) were left on 55 plants to lay their offspring: one larva of the 1st stage (L1) was kept per WA. This larva was selected among the 20 first born larvae. This is the generation G1. At the middle of the photophase, 25 individual were frozen when they had reached both the L2 and the L4 stages, in the two photoperiodic conditions. Thus, 25 individuals from 4 different stages (L4-G0, WA-G0, L2-G1 and L4-G1) were collected in the two photoperiod conditions with 3 biological replicates, forming the 24 samples used for microarray experiments. RNAs from heads of aphids from the two photoperiodic conditions were hybridized one against the other for each stage with a dye-swap.The experimental design is thus 24 arrays which corresponds to the described samples of that series.

Project description:We have implemented an integrated Systems Biology approach to analyze overall transcriptomic reprogramming and systems level defense responses in the model plant Arabidopsis thaliana during an insect (Brevicoryne brassicae) and a bacterial (Pseudomonas syringae pv. tomato strain DC3000) attack. The main aim of this study was to identify the attacker-specific and general defense response signatures in the model plant Arabidopsis thaliana while attacked by phloem feeding aphids or pathogenic bacteria. Defense responses and networks, unique and specific for aphid or Pseudomonas stresses were identified. Our analysis revealed a probable link between biotic stress and microRNAs in Arabidopsis and thus opened up a new direction to conduct large-scale targeted experiments to explore detailed regulatory links among them. The presented results provide a first comprehensive understanding of Arabidopsis - B. brassicae and Arabidopsis - P. syringae interactions at a systems biology level. Arabidopsis thaliana (ecotype Colombia-0) seeds were grown in 6-cm-diameter pots filled with a sterile soil mix (1.0 part soil and 0.5 part horticultural perlite), 3 plants per pot. Plants were kept in growth chambers VM-CM-6tsch VB 1514 (VM-CM-6tsch Industrietechnik GmbH, Germany) under the following conditions: a 8/16 h (light/dark) photoperiod at 22M-BM-0C/18M-BM-0C, 40%/70% relative humidity, and 70/0 M-NM-<mol m-2s-1 light intensity. After 32 days plants had 8 fully developed leaves. Each plant was infested with 32 wingless aphids [Brevicoryne Brassicae] (4 per leaf), which were transferred to leaves with a fine paintbrush. Infested plants and aphid-free controls were kept in plexiglass cylinders. Plants were harvested 72 h after infestation between the 6th and 8th hour of the light photoperiod. Four biological replicates were prepared from aphid infested and control plants, each sampled from 15 individual plants. Whole rosettes were cut at the hypocotyls and aphids were removed by washing with Milli-Q-filtered water. Differences in transcriptional responses were measured by comparing genes expression of aphid infested plants against non-infested control plants.

Project description:In most aphid species, facultative parthenogenetic reproduction allows rapid growth and formation of large single-genotype colonies. Upon predator attack, individual aphids emit an alarm pheromone to warn the colony of this danger. (E)-beta-farnesene (EBF) is the predominant constituent of the alarm pheromone in Myzus persicae (green peach aphid) and many other aphid species. Continuous exposure to alarm pheromone in aphid colonies raised on transgenic Arabidopsis thaliana plants that produce EBF leads to habituation of the aphid population. Whereas naïve aphids are repelled by EBF, habituated aphids show no avoidance response. Individual aphids from the habituated colony can revert back to being EBF-sensitive in three generations, indicating that this behavioral change is not caused by a genetic mutation. Instead, DNA microarray experiments comparing gene expression in naïve and habituated aphids treated with EBF demonstrate an almost complete desensitization in the transcriptional response to EBF. Furthermore, EBF-responsive aphids, but not habituated aphids show significantly lower reproduction in the presence of EBF. Although both naïve and habituated aphids emit EBF upon damage, EBF-responsive aphids display a higher survival rate in the presence of coccinellid predators and thus outperform habituated aphids that do not show an avoidance response. These results provide direct evidence that aphid perception of conspecific alarm pheromone aids in predator avoidance and thereby bestows fitness benefits in survivorship and fecundity. Although habituated M. persicae have equal fecundity on control and EBF-producing plants, such transgenics may have practical applications in agriculture because of increased predation of habituated aphids. Log fold-changes (LogFC) were computed and contigs with P-values ≤ 0.05 were considered to be differentially expressed (see Supplementary file at foot of this record). Agilent 8x15K array previously reported by Ramsey et al., 2007 - BMC Genomics 8: 243. Two-condition experiment using Alexa Fluor 555 and 647 dyes. Biological replicates: 4 control replicates, 4 treated replicates.

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Transcriptomic and proteomic analyses of seasonal photoperiodism in the pea aphid

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