Plant viruses maintain intricate interactions with their vector and non-vector insects and can impact the fitness of insects. However, the details of their molecular and cellular mechanisms have not ...been studied well. We compared the transcriptome-level responses in vector and non-vector aphids (Schizaphis graminum and Rhopalosiphum padi, respectively) after feeding on wheat plants with viral infections (Barley Yellow Dwarf Virus (BYDV) and Wheat dwarf virus (WDV), respectively). We conducted differentially expressed gene (DEG) annotation analyses and observed DEGs related to immune pathway, growth, development, and reproduction. And we conducted cloning and bioinformatic analyses of the key DEG involved in immune.
For all differentially expressed gene analyses, the numbers of DEGs related to immune, growth, development, reproduction and cuticle were higher in vector aphids than in non-vector aphids. STAT5B (signal transducer and activator of transcription 5B), which is involved in the JAK-STAT pathway, was upregulated in R. padi exposed to WDV. The cloning and bioinformatic results indicated that the RpSTAT5B sequence contains a 2082 bp ORF encoding 693 amino acids. The protein molecular weight is 79.1 kD and pI is 8.13. Analysis indicated that RpSTAT5B is a non-transmembrane protein and a non-secreted protein. Homology and evolutionary analysis indicated that RpSTAT5B was closely related to R. maidis.
Unigene expression analysis showed that the total number of differentially expressed genes (DEGs) in the vector aphids was higher than that in the non-vector aphids. Functional enrichment analysis showed that the DEGs related to immunity, growth and reproduction in vector aphids were higher than those in non-vector aphids, and the differentially expressed genes related to immune were up-regulated. This study provides a basis for the evaluation of the response mechanisms of vector/non-vector insects to plant viruses.
Aphis craccivora Koch (Hemiptera: Aphididae) is an aphid pest which occurs in different crops and causes damages related to habit of sucking sap. In Brazil information about host weed species are ...rare, particulary in Rio Grande do Sul (RS) State. Weeds infested by aphids were found at an experimental area located at the Universidade Federal de Santa Maria, Santa Maria, RS, in two different dates, February 22nd and March 25th 2010. In the second record (March 25th), each weed plant was measured and evaluated on the number of aphids. The aphid species was identified as Aphis craccivora and the host weed as Amaranthus hybridus Linnaeus, 1 753 (Amaranthaceae), and Solanum americanum Mill, 1768 (Solanaceae). This is the first report of both A. hybridus and S. americanum hosting A. craccivora in Santa Maria, Rio Grande do Sul State. Key words: aphids, Amaranthus hybridus, Solanum americanum, aphid. Aphis craccivora Koch (Hemiptera: Aphididae) e um afideo-praga que ocorre em diferentes cultivos e causa danos relacionados ao habito da succao de seiva. No Brasil, sao raros os registros de plantas daninhas hospedeiras dessa especie, particularmente no Estado do Rio Grande do Sul (RS). Plantas daninhas infestadas com afideos foram encontradas em area experimental localizada no campus da Universidade Federal de Santa Maria (UFSM), RS, em duas datas, 22/02/2010 e 25/03/2010. No segundo registro (25/03/2010), cada planta daninha foi medida e avaliada quanto ao numero de afideos. A especie foi identificada como Aphis craccivora e as plantas daninhas hospedeiras, como Amaranthus hybridus Linnaeus, 1753 (Amaranthaceae), caruru-roxo, e Solanum americanum Mill, 1768 (Solanaceae), maria-pretinha. Este trabalho faz o primeiro registro de A. hybridus e S. americanum hospedando A. craccivora em Santa Maria, no Rio Grande do Sul. Palavras-chave: afideos, Amaranthus hybridus, Solanum americanum, pulgao.
Aphis craccivora Koch (Hemiptera: Aphididae) is an aphid pest which occurs in different crops and causes damages related to habit of sucking sap. In Brazil information about host weed species are ...rare, particulary in Rio Grande do Sul (RS) State. Weeds infested by aphids were found at an experimental area located at the Universidade Federal de Santa Maria, Santa Maria, RS, in two different dates, February 22nd and March 25th 2010. In the second record (March 25th), each weed plant was measured and evaluated on the number of aphids. The aphid species was identified as Aphis craccivora and the host weed as Amaranthus hybridus Linnaeus, 1 753 (Amaranthaceae), and Solanum americanum Mill, 1768 (Solanaceae). This is the first report of both A. hybridus and S. americanum hosting A. craccivora in Santa Maria, Rio Grande do Sul State.
•Absence of RNAi response by feeding and injection of dsRNA in pea aphids (Acyrthosiphon pisum).•Degradation of dsRNA by salivary secretions and aphid hemolymph.•Upon dsRNA injection, no effect in ...expression of RNA-related genes dicer-2, argonaute-2, r2d2 and sid-1.•Pea aphids contain an Eri-1-like endocellular nuclease as in nematodes.
Over the past decade, RNA interference (RNAi), the sequence-specific suppression of gene expression, has proven very promising for molecular research in many species, including model insects as Tribolium castaneum and Apis mellifera. It showed its usefulness to analyze gene function and its potential to manage pest populations and reduce disease pathogens. However, in several insects, the efficiency of RNAi is low or very variable at best. One of the factors that could influence RNAi efficiency in insects is degradation of dsRNA after administration to the insect. In this paper, we report on the importance of dsRNA breakdown in the pea aphid (Acyrthosiphon pisum) associated with the absence of an RNAi response upon oral feeding and injection with dsRNA targeting different genes such as the ecdysone hormone receptor and ultraspiracle. In essence, we discovered that both the salivary secretions of aphids and the hemolymph were able to degrade the dsRNA. In parallel, introduction of dsRNA in the aphid body was not able to provoke a response in the expression of the siRNA core machinery genes.
Biological invasion of aphids and other insects has been increased due to long distance commercial transportation of plant material. The bamboo-aphid-parasitoid association is strictly specific and ...even though it does not develop interactions with the local environment it should be listed as part of the fauna of southwestern Europe. On-going research regarding aphids and their aphidiine parasitoids in Spain has yielded a new association of Trioxys liui Chou & Chou, 1993 with an undescribed species of Takecallis aphids on bamboo, Phyllostachys spp. Here we present the first association of T. liui with aphids of the genus Takecallis that attack bamboos. Trioxys liui is known as a parasitoid of Cranaphis formosana (Takahashi, 1924) and Phyllaphoides bambusicola Takahashi, 1921 on bamboos in China and Russia. The accidental introduction of this parasitoid species to southwestern Europe has been probably realized through transportation of contaminated bamboo plant material. In the current study, a new host association is recorded for T. liui. Its potential to invade other bamboo-associated aphids and the significance of the tritrophic bamboo-aphid-parasitoid interactions in the new environments are also discussed. Keywords: Bamboo, invasive species, new association, parasitoid
Insect symbionts in food webs McLean, Ailsa H. C.; Parker, Benjamin J.; Hrček, Jan ...
Philosophical transactions of the Royal Society of London. Series B. Biological sciences,
09/2016, Letnik:
371, Številka:
1702
Journal Article
Recenzirano
Odprti dostop
Recent research has shown that the bacterial endosymbionts of insects are abundant and diverse, and that they have numerous different effects on their hosts' biology. Here we explore how insect ...endosymbionts might affect the structure and dynamics of insect communities. Using the obligate and facultative symbionts of aphids as an example, we find that there are multiple ways that symbiont presence might affect food web structure. Many symbionts are now known to help their hosts escape or resist natural enemy attack, and others can allow their hosts to withstand abiotic stress or affect host plant use. In addition to the direct effect of symbionts on aphid phenotypes there may be indirect effects mediated through trophic and non-trophic community interactions. We believe that by using data from barcoding studies to identify bacterial symbionts, this extra, microbial dimension to insect food webs can be better elucidated.
This article is part of the themed issue ‘From DNA barcodes to biomes’.
Heritable symbionts are common in insects with many contributing to host defence. Hamiltonella defensa is a facultative, bacterial symbiont of the pea aphid, Acyrthosiphon pisum that provides ...protection against the endoparasitoid wasp Aphidius ervi. Protection levels vary among strains of H. defensa that are differentially infected by bacteriophages named APSEs. By contrast, little is known about mechanism(s) of resistance owing to the intractability of host-restricted microbes for functional study. Here, we developed methods for culturing strains of H. defensa that varied in the presence and type of APSE. Most H. defensa strains proliferated at 27°C in co-cultures with the TN5 cell line or as pure cultures with no insect cells. The strain infected by APSE3, which provides high levels of protection in vivo, produced a soluble factor(s) that disabled development of A. ervi embryos independent of any aphid factors. Experimental transfer of APSE3 also conferred the ability to disable A. ervi development to a phage-free strain of H. defensa. Altogether, these results provide a critical foundation for characterizing symbiont-derived factor(s) involved in host protection and other functions. Our results also demonstrate that phage-mediated transfer of traits provides a mechanism for innovation in host restricted symbionts.
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•Thermal performance varied across developmental stages of an aphid.•A tradeoff may exist between plasticity and basal tolerance across stages.•Stress dosage, not proximity to adult ...stage, affected reproductive costs.•Ontogenetic variation may influence population persistence under climate change.
Heat responses can vary ontogenetically in many insects with complex life cycles, reflecting differences in thermal environments they experience. Such variation has rarely been considered in insects that develop incrementally and experience common microclimates across stages. To test if there is a low level of ontogenetic variation for heat responses in one such species, the English grain aphid Sitobion avenae, basal tolerance upper lethal temperature (ULT50) and maximum critical temperature (CTmax), hardening capacity (CTmax) and hardening costs (adult longevity and fecundity) were measured across five stages (1st, 2nd, 3rd and 4th-instar nymphs and newly moulted adults). We found large tolerance differences among stages of this global pest species, and a tendency for the stage with lower heat tolerance to show a stronger hardening response. There were also substantial reproductive costs of hardening responses, with the level of stress experienced, and not the proximity of the exposed stage to the reproductive adult stage, influencing the magnitude of this cost. Hence hardening in this aphid may counter inherently low tolerance levels of some life stages but at a cost to adult longevity and fecundity. Our findings highlight the significance of ontogenetic variation in predicting responses of a species to climate change, even in species without a complex life cycle.
The development of insecticide-resistance mechanisms in aphids has been associated with inhibitory, pleiotropic fitness costs. Such fitness costs have not yet been examined in the UK's most damaging ...cereal aphid, Sitobion avenae (grain aphid) (Hemiptera: Aphididae). This study aimed to evaluate the fitness trade-offs of the insecticide-resistant S. avenae clone versus an insecticide-susceptible S. avenae clone. Additionally, the parasitoid, Aphidius ervi (Hymenoptera: Braconidae), was introduced to examine its potential as a biological control agent. This study found that insecticide-resistant clones had significantly lower population growth and individual relative growth rate. Furthermore, insecticide-resistant clones suffered from a significantly greater rate of parasitisation (mummification) compared to their insecticide-susceptible counterparts. The successfulness of the parasitoid as a biological control agent could prevent the spread of the insecticide-resistant genotype. However, for this to be possible, insecticide spraying regimes need to be moderated, and habitat modification and parasitoid manipulation must be considered.
RNA silencing is an important mechanism for regulation of endogenous gene expression and defense against genomic intruders in plants. This natural defense system was adopted to generate ...virus-resistant plants even before the mechanism of RNA silencing was unveiled. With the clarification of that mechanism, transgenic antiviral plants were developed that expressed artificial virus-specific hairpin RNAs (hpRNAs) or microRNAs (amiRNAs) in host plants. Previous works also showed that plant-mediated RNA silencing technology could be a practical method for constructing insect-resistant plants by expressing hpRNAs targeting essential genes of insects.
In this study, we chose aphid Myzus persicae of order Hemiptera as a target insect. To screen for aphid genes vulnerable to attack by plant-mediated RNA silencing to establish plant aphid resistance, we selected nine genes of M. persicae as silencing targets, and constructed their hpRNA-expressing vectors. For the acetylcholinesterase 2 coding gene (MpAChE2), two amiRNA-expressing vectors were also constructed. The vectors were transformed into tobacco plants (Nicotiana tabacum cv. Xanti). Insect challenge assays showed that most of the transgenic plants gained aphid resistance, among which those expressing hpRNAs targeting V-type proton ATPase subunit E-like (V-ATPaseE) or tubulin folding cofactor D (TBCD) genes displayed stronger aphicidal activity. The transgenic plants expressing amiRNAs targeting two different sites in the MpAChE2 gene exhibited better aphid resistance than the plants expressing MpAChE2-specific hpRNA.
Our results indicated that plant-mediated insect-RNA silencing might be an effective way to develop plants resistant to insects with piercing-sucking mouthparts, and both the selection of vulnerable target genes and the biogenetic type of the small RNAs were crucial for the effectiveness of aphid control. The expression of insect-specific amiRNA is a promising and preferable approach to engineer plants resistant to aphids and, possibly, to other plant-infesting insects.
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