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PubMed1993

Gene II product of an aphid-nontransmissible isolate of cauliflower mosaic virus expressed in a baculovirus system possesses aphid transmission factor activity.

A new baculovirus expression system was used to express the gene II which encodes the 18-kDa aphid transmission factor (ATF) protein of two isolates of cauliflower mosaic virus (CaMV), the aphid-transmissible (AT+) Cabb B-JI and the aphid-nontransmissible (AT-) CM1841 isolates. ATF activity was shown to be associated with the baculovirus expression product of CaMV gene II from both the AT+ and the AT- isolates. No differences could be detected in the stability of the P18s from AT+ and AT- isolates expressed in the baculovirus system. These results indicate that the AT- phenotype of CM1841 isolate might not be due to a defective P18 but to an insufficient concentration of it in infected plant tissue.

Animals↗
PubMed2005

Reduced response of insecticide-resistant aphids and attraction of parasitoids to aphid alarm pheromone; a potential fitness trade-off.

Response to the alarm pheromone, (E)-beta-farnesene, produced by many species of aphids, was assessed in laboratory bioassays using an aphid pest, Myzus persicae (Sulzer), and its primary endoparasitoid, Diaeretiella rapae (McIntosh). This was done in three separate studies, the first investigating responses of a large number of M. persicae clones carrying different combinations of metabolic (carboxylesterase) and target site (kdr) insecticide resistance mechanisms, and the other two investigating the responses of young virgin female adult parasitoids. In M. persicae, both insecticide resistance mechanisms were associated with reduced repellence suggesting that each has a pleiotropic effect on aphid behaviour. In contrast, D. rapae females were attracted to the alarm pheromone source. The implications of this apparent fitness trade-off for the evolution and dynamics of insecticide resistance, and the potential for using beneficial insects to combat resistance development are discussed.

Animals↗
PubMed1993

Reasons for the low accumulation level of aphid transmission factor protein in infected leaves with an aphid-non-transmissible cauliflower mosaic virus isolate, CM1841.

The synthesis and accumulation of aphid transmission factor protein (p18) in cauliflower mosaic virus (CaMV)-infected turnip protoplasts were examined in time course and pulse-labelling experiments, comparing an aphid-non-transmissible isolate (CM1841) with an in vitro recombinant aphid-transmissible CaMV (CMBX) generated from the CM1841 isolate. There was little difference in the synthesis and accumulation of p18 between CM1841- and CMBX-infected protoplasts. When the accumulation of p18 in infected leaves was monitored from 3 to 28 days post-symptom emergence (p.e.) by Western blotting, the amount of p18 accumulated in CM1841-infected leaves continuously decreased from 3 days p.e. throughout the experimental period, whereas the amount of p18 in CMBX-infected leaves was lowest at 3 days p.e. and increased thereafter. These results suggested that CM1841 differed from CMBX not in the synthesis of p18 but in the stability of p18 in infected leaves.

Animals↗
PubMed1996

Comparison of the nucleotide sequences of the 3'-terminal regions of one aphid and two non-aphid transmissible isolates of potato A potyvirus.

The sequences of the 3'-terminal 1145 nucleotides of two non-aphid transmissible (NAT) isolates (Ali and Juliniere) and one aphid transmissible (AT) isolate (Rouge) of potato virus A (PVA) RNA were determined. Those sequences contained the complete coding region of the coat protein (CP) followed by a 3'-nontranslated region (3'-NTR) of 225 (Ali and Juliniere) and 227 (Rouge) nucleotides. The obtained sequences were compared to those of the 3'-regions of four published PVA isolates and a virus described as tamarillo mosaic virus (TamMV) which on the basis of sequence data is a strain of PVA. The analysis of the 3'-terminal region of PVA isolates indicated that the CP N-terminal variable domain (32 residues) divides PVA isolates into two subgroups, where only tripeptide DAG correlates with aphid transmissibility. In addition to DAG/DAS sequence we found four other amino acids at the N-terminus of PVA CP, which are conserved in two subgroups. The central region (core part and C-termini) of CP is highly conserved among all PVA isolates (96.6 to 99.6%). 3'-NTR, separates PVA-isolates into two subgroups on the basis of its length and homology.

Amino Acid Sequence↗
PubMed2006

Aphid alarm pheromone produced by transgenic plants affects aphid and parasitoid behavior.

The alarm pheromone for many species of aphids, which causes dispersion in response to attack by predators or parasitoids, consists of the sesquiterpene (E)-beta-farnesene (Ebetaf). We used high levels of expression in Arabidopsis thaliana plants of an Ebetaf synthase gene cloned from Mentha x piperita to cause emission of pure Ebetaf. These plants elicited potent effects on behavior of the aphid Myzus persicae (alarm and repellent responses) and its parasitoid Diaeretiella rapae (an arrestant response). Here, we report the transformation of a plant to produce an insect pheromone and demonstrate that the resulting emission affects behavioral responses at two trophic levels.

Animals↗
PubMed1994

The peach-potato aphid Myzus persicae and the tobacco aphid Myzus nicotianae have the same esterase-based mechanisms of insecticide resistance.

Biochemical and molecular studies have established that in the peach-potato aphid, Myzus persicae, insecticide resistance is conferred by amplification of genes encoding the insecticide-detoxifying esterases E4 or FE4. Here we report that two insecticide-resistant clones of the closely related tobacco aphid Myzus nicotianae have elevated esterases indistinguishable from E4 and FE4 and amplified esterase DNA sequences, and flanking regions, with identical restriction maps to the M. persicae genes. Furthermore, the DNA sequences of c. 630 bp fragments of the E4 and FE4 genes of M. persicae are different from each other but identical to the fragment from corresponding M. nicotianae clones. The existence of apparently identical insecticide resistance genes in the two species can be best explained by the selection of the amplified genes in M. persicae, transfer to hybrids of M. persicae and M. nicotianae by sexual reproduction and subsequent spread through M. nicotianae populations.

Animals↗
PubMed2006

Molecular basis of plant gene expression during aphid invasion: wheat Pto- and Pti-like sequences are involved in interactions between wheat and Russian wheat aphid (Homoptera: Aphididae).

The Russian wheat aphid, Diuraphis noxia (Mordvilko) (Homoptera: Aphididae), is a major pest of bread wheat, Triticum aestivum L. (em Thell), in most wheat-growing areas worldwide. Aphid-resistant cultivars are used to combat this pest, but very little is known about the molecular basis of resistance. In this study, differential gene expression in D. noxia biotype 1-resistant wheat plants containing the Dnx gene and D. noxia biotype 1 feeding on Dnx plants was investigated using suppressive subtraction hybridization. The derived subtracted cDNA library includes sequences similar to Pto and Pti1, genes involved in gene-for-gene recognition of and resistance to bacterial speck disease in tomato, Lycopersicon esculentum (L.). Pto- and Pti1-like sequences contain an activation domain with conserved amino acid residues crucial for avr protein recognition and binding by Pto, and avr-Pto phosphorylation of Pti1. Wheat defense signaling is represented by sequences putatively involved in producing sterols, jasmonates, Ca2+, and abscisic and gibberellic acids. We suggest that reductions in populations of D. noxia fed Dnx plants are related to the expression of sequences involved in defensive chemical production, cellular transport, and exocytosis. Dnx plant tolerance of D. noxia feeding is proposed to be based on the expression of sequences putatively involved in self-defense against reactive oxygen species and toxins, and proteolysis; DNA, RNA, and protein synthesis; chloroplast and mitochondrial function; carbohydrate metabolism; and maintenance of cell homeostasis. D. noxia unsuccessfully counter Dnx by expressing sequences putatively involved in detoxification; proteolysis; DNA, RNA, protein, and lipid synthesis; carbohydrate metabolism; and mitochondrial function.

Amino Acid Sequence↗
PubMed2002

Composition of the volatiles from intact and mechanically pierced tea aphid-tea shoot complexes and their attraction to natural enemies of the tea aphid.

The volatile components from intact tea shoots (ITS), obtained by air entrainment, were identified by their mass spectra and retention times and confirmed by comparison with standard samples. They are E-2-hexenal, ocimene, Z-3-hexenyl acetate, Z-3-hexen-1-ol, butanoic acid-3-hexenyl ester, linalool, 1-octanol, geraniol, and indole. Volatiles from mechanically pierced tea shoots (MPTS) were identified as E-2-hexenal, ocimene, Z-3-hexen-1-ol, butanoic acid-3-hexenyl ester, linalool, geraniol, indole, E-2-hexenoic acid, Z-3-hexenyl formate, methyl salicylate, and benzyl alcohol, and volatiles from tea aphid-tea shoot complexes (TATSC) were identified as E-2-hexenal, ocimene, Z-3-hexenyl acetate, Z-3-hexen-1-ol, linalool, geraniol, indole, benzaldehyde, and E-2-hexenoic acid. Z-3-Hexen-1-ol is the main component in the three different types of volatiles, and the amount of benzaldehyde in TATSC volatiles is very ample. The attraction of the volatiles from ITS, MPTS, and TATSC, and the nine components of TATSC volatiles to the natural enemies, the coccinellid, Coccinella septempunctata, the parasite, Aphidius sp., and the lacewing, Chrysopa sinica, were determined by electroantennogram (EAG) and the wind tunnel bioassay. TATSC volatiles and benzaldehyde elicited much larger EAG responses and stronger upwind flight and arresting behavior from each natural enemy in the wind tunnel than other infochemicals.

Animals↗
PubMed1994

Capsid protein properties of cowpea aphid-borne mosaic virus and blackeye cowpea mosaic virus confirm the existence of two major subgroups of aphid-transmitted, legume-infecting potyviruses.

A study of the capsid proteins of different legume-infecting potyviruses using specific monoclonal antibodies on immunoblots of crude extracts from infected plants revealed that cowpea aphid-borne mosaic virus (CAMV) and blackeye cowpea mosaic virus (BICMV) have coat protein M(r) values of 32K and 35K, respectively. Immunoblot comparisons of BICMV, peanut stripe mosaic virus (PStV), bean common mosaic virus (BCMV) and azuki bean mosaic virus (AzMV) revealed equal reactivity of their 35K coat proteins. Similar comparisons between CAMV and the necrotic strain of BCMV (isolate NL3) showed a serological relationship between their 32K coat proteins, results providing the first evidence of a possible similarity between CAMV and BCMV NL3. Peptides from trypsin digests of the coat proteins of several of these legume-infecting potyviruses were analysed by HPLC. Comparison of the peptide profiles confirmed the serological results in distinguishing the two subgroups. Peptide profiles of coat protein from BICMV, PStV, AzMV and BCMV were almost identical, results suggesting that they could be considered as strains of one virus. In contrast, peptide profiles of various CAMV serotypes and BCMV NL3 were distinct from the first group and exhibited limited similarities to each other.

Animals↗
PubMed2004

Feeding and egg distribution studies of Heringia calcarata (Diptera: Syrphidae), a specialized predator of woolly apple aphid (Homoptera: Eriosomatidae) in Virginia apple orchards.

Predation by the aphidophagous syrphid fly Heringia calcarata (Loew) on woolly apple aphid, Eriosoma lanigerum (Hausmann), was studied in the laboratory and in Virginia apple orchards. Feeding studies compared the prey suitability of three temporally sympatric aphid pests of apple: spirea aphid, Aphis spiraecola Patch; rosy apple aphid, Dysaphis plantaginea (Passerini); and woolly apple aphid. Significantly more H. calcarata larvae survived and completed development on a pure diet of woolly apple aphid than on rosy apple aphid, and none survived on spirea aphid. Final larval weights were significantly greater, and the larval developmental period was significantly shorter on woolly apple aphid than on rosy apple aphid, but neither the duration of pupal development nor adult weight differed between diets. H. calcarata larvae consumed an average of 105 woolly apple aphids during their development. Naïve, neonate larvae given access to all possible pair combinations of woolly apple aphid, rosy apple aphid, and spirea aphid consumed significantly more woolly apple aphids in all pairings that included woolly apple aphid. When given a choice of rosy apple aphid and spirea aphid, significantly more rosy apple aphids were consumed. Weekly counts of syrphid eggs found in woolly apple aphid, rosy apple aphid, and spirea aphid colonies collected from apple trees showed that two generalist hover fly predators, Eupeodes americanus (Wiedemann) and Syrphus rectus Osten Sacken, were present in colonies of all three aphid species and that E. americanus was the most abundant syrphid predator in A. spiraecola and D. plantaginea colonies. H. calcarata eggs were found only in woolly apple aphid colonies and were more abundant there than E. americanus and S. rectus. These data suggest that H. calcarata is a specialized predator of woolly apple aphid in the apple ecosystem in Virginia.

Animals↗
PubMed1999

Fate of dietary sucrose and neosynthesis of amino acids in the pea aphid, acyrthosiphon pisum, reared on different diets

The fate of sucrose, the major nutrient of an aphid's natural food, was explored by radiolabeling in the pea aphid Acyrthosiphon pisum. To investigate the influence of nitrogen quality of food on amino acid neosynthesis, pea aphids were reared on two artificial diets differing in their amino acid composition. The first (diet A) had an equilibrated amino acid balance, similar to that derived from analysis of aphid carcass, and the other (diet B) had an unbalanced amino acid composition similar to that of legume phloem sap. Aphids grown on either diet expired the same quantity of sucrose carbon as CO(2), amounting to 25-30 % of the ingested sucrose catabolized in oxidation pathways. On diet A, the aphids excreted through honeydew about twice as much sucrose carbon as on diet B (amounting to 12.6 % of the ingested sucrose for diet A and 8.4 % for diet B), while amounts of sucrose carbons incorporated into exuviae were almost identical (1.9 % of the ingested sucrose on diet A and 2.7 % on diet B). There was also no difference in the amounts of sucrose carbon incorporated into the aphid tissues, which represented close to 50 % of the ingested sucrose. Sucrose carbons in the aphid tissues were mainly incorporated into lipids and the quantities involved were the same in aphids reared on either diet. On diet B, we observed neosynthesis of all protein amino acids from sucrose carbons and, for the first time in an aphid, we directly demonstrated the synthesis of the essential amino acids leucine, valine and phenylalanine. Amino acid neosynthesis from sucrose was significantly higher on diet B (11.5 % of ingested sucrose carbons) than on diet A (5.4 %). On diet A, neosynthesis of most of the amino acids was significantly diminished, and synthesis of two of them (histidine and arginine) was completely suppressed. The origin of amino acids egested through honeydew was determined from the specific activity of the free amino acid pool in the aphid. Aphids are able to adjust to variation in dietary amino acids by independent egestion of each amino acid. While more than 80 % of excreted nitrogen was from food amino acids, different amino acids were excreted in honeydew of aphids reared on the two diets. The conversion yields of dietary sucrose into aphid amino acids determined in this study were combined with those obtained previously by studying the fate of amino acids in pea aphids reared on diet A. The origin of all the amino acid carbons in aphid tissues was thus computed, and the metabolic abilities of aphid are discussed from an adaptive point of view, with respect to their symbiotic status.

Journal Article↗