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PubMed2005

Positive genetic correlations among major life-history traits related to ecological success in the aphid Myzus persicae.

Life-history theory is based on the assumption that evolution is constrained by trade-offs among different traits that contribute to fitness. Such trade-offs should be evident from negative genetic correlations among major life-history traits. However, this expectation is not always met. Here I report the results of a life-table experiment designed to measure the broad-sense heritabilities of life-history traits and their genetic correlations in 19 different clones of the aphid Myzus persicae from Victoria, Australia. Most individual traits, as well as fitness calculated as the finite rate of increase from the life table, exhibited highly significant heritabilities. The pattern of genetic correlations revealed absolutely no evidence for life-history trade-offs. Rather, life histories were arranged along an axis from better to worse. Clones with shorter development times tended to have larger body sizes, higher fecundities, and larger offspring. The fitness of clones estimated from the life table in the laboratory tended to be positively associated with their abundance in the field. Fitness also increased significantly with heterozygosity at the seven microsatellite loci that were used to distinguish clones and estimate their frequencies in the field. I discuss these findings in light of a recent proposition that positive genetic correlations among life-history traits for which trade-offs are expected can be explained by genetic variation for resource acquisition ability that is maintained in populations by a cost of acquisition, and I propose ways to test for such a cost in M. persicae.

Adaptation, Physiological↗
PubMed1991

Aphid derived sugars in the neotropical sandfly--Lutzomyia peruensis.

It is known that a sugar meal is a prerequisite for the transmission of Leishmania by sandflies in the laboratory. Lutzomyia peruensis the proven vector of Leishmania peruviana, was caught by aspiration from crevices in rocks near Chaute in the Rimac Valley, Peru, cryopreserved and analysed for sugars using HPLC. The major sugars present are glucose and fructose as well as smaller amounts of sucrose, maltose, melibiose, turanose and a trisaccharide, probably raffinose. The results indicate that the major carbohydrate sugar meal of Lutzomyia peruensis is aphid honeydew. This is the first report of such behaviour in Neotropical sandflies.

Animals↗
PubMed1983

[Multiple molecular forms of esterases from grass aphids inhibitory identification and stereospecificity].

Nine esterase fractions hydrolyzing 1-naphthylacetate were revealed in Triton X-100-solubilized extracts from aphides homogenates by polyacrylamide gel electrophoresis. The less mobile fractions 1-4 were identified as cholinesterases, using specific inhibitors--eserine and the cationic phosphoorganic inhibitor Gd-42; fractions 5-7 were related to carboxylesterases, using specific inhibition by triorthocresylphosphate and O,O-dimethyl (2,2-dichlorvinyl)phosphate. The most mobile fractions 8-9 which were resistant to the inhibitors, were classified as arylesterases. The aphis cholinesterase fractions revealed the highest mobility; the activity of carboxylesterase fractions was lower. Thiophosphonate--C8H17O(CH3)P(O)-SCH2SCH2COOCH3 was found to be a highly efficient selective inhibitor of aphis carboxylesterase, i. e. the kII values for carboxylesterase and cholinesterase were equal to 10(8) and 10(5) M-1 min-1, respectively. The thiophosphoorganic derivatives containing a beta-alanine residue in the cleaved part are more specific to acetylcholinesterase and carboxylesterase than those containing a valine residue. Studies with enanthiomers--C2H5O(CH3)P(O)SCH2CONHCH2CH2COOC2H5 and (C2H5O)2P(O)SCH2CONHCH(iC3H7)COOC2H5 have demonstrated that the asymmetry due to the central phosphorus atom is more essential for the acetylcholinesterase and carboxylesterase activities than that connected with the carbon atom in the cleaved part of the inhibitor molecule. During the interaction of the enanthiomers with the asymmetric phosphorus the stereospecificity of acetylcholinesterase is much higher than that of carboxylesterase. In terms of stereospecificity of the esterase site aphis acetylcholinesterase is is similar to its mammalian counterpart, while carboxylesterase from the same source is rather close to mammalian butyrylcholinesterase.

Animals↗
PubMed1994

Cowpea aphid borne mosaic virus-Morocco and South African Passiflora virus are strains of the same potyvirus.

High performance liquid chromatography (HPLC) profiles of tryptic peptides and partial amino acid sequence analysis have been employed to establish the taxonomic status of the Moroccan isolate of cowpea aphid-borne mosaic virus (CABMV). Some previous reports have suggested CABMV to be very closely related to blackeye cowpea mosaic virus (B1CMV) while other reports have concluded that this relationship is distant. In this report a tryptic digest of the coat protein of CABMV-Morocco was compared with those of the coat proteins of B1CMV-Type, B1CMV-W, the mild mottle strain of peanut stripe virus (PStV-MM) and the NY15 strain of bean common mosaic virus (BCMV-NY15), all of which are now recognised as strains of BCMV. The comparisons also included the NL-3 strain of bean necrosis mosaic virus (BNMV-NL3), which had previously been classified as a strain of BCMV. The HPLC peptide profiles indicated that CABMV-Morocco was distinct from BCMV and BNMV. Amino acid sequence analysis of peptides accounting for more than half of the coat protein confirmed that CABMV-Morocco was not a strain of BNMV or BCMV but was a distinct member of the BCMV subset of viruses that previously has been shown to include BCMV, BNMV, soybean mosaic virus, zucchini yellow mosaic virus, passionfruit woodiness virus and South African Passiflora virus (SAPV). Comparison of the partial sequence data with these and other published sequences revealed that the coat protein of CABMV-Morocco is very similar to that of SAPV suggesting that they are strains of the same virus. Since CABMV was described over 25 years earlier than SAPV, the name CABMV should take precedence and SAPV should be renamed CABMV-SAP, the South African Passiflora strain of CABMV.

Amino Acid Sequence↗
PubMed1996

Sequence of the 3'-terminal region of a Zimbabwe isolate of cowpea aphid-borne mosaic virus (CABMV).

The 3'-terminal 1221 nucleotides of a Zimbabwe isolate of cowpea aphid-borne mosaic potyvirus (CABMV) genome have been sequenced. The sequence comprises an open reading frame (ORF) of 990 nucleotides and a 3' non-coding-region of 231 nucleotides followed by a poly-A. The ORF has high similarity to NIb and coat proteins (CP) of potyviruses. A potential CP Q/S cleavage site was identified, yielding a CP of 30.5 kDa containing 275 amino acids. The CABMV sequence is closely related to that of South African passiflora virus (SAPV) which should therefore be regarded as a strain of CABMV.

Amino Acid Sequence↗
PubMed2002

Identification of microsatellite markers linked to Russian wheat aphid resistance genes Dn4 and Dn6.

The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), is a serious economic pest of wheat worldwide. Host plant resistance is the preferred method to control RWA infestations. The identification and mapping of RWA-resistant genes and the development of resistant wheat cultivars can be facilitated through the use of molecular markers. In the present study, microsatellite (SSR) markers linked to the RWA-resistant genes Dn4 and Dn6 were identified using several F(2) mapping populations derived from crosses of susceptible wheat cultivars and resistant sources. Two flanking microsatellite markers Xgwm106 and Xgwm337 are linked in coupling phase with Dn4 on the short arm of wheat chromosome 1D at 7.4 cM and 12.9 cM, respectively. Two other microsatellite markers Xgwm44 and Xgwm111 are linked to Dn6 in coupling phase near the centromere on the short arm of chromosome 7D at 14.6 cM and 3.0 cM, respectively. This is the first report on the chromosomal location of Dn6, which proved to be either allelic or tightly linked to Dn1, Dn2 and Dn5. This result of Dn6 location contradicts previous reports that Dn6 was independent of Dn1, Dn2 and Dn5. The linked markers can be conveniently used for marker-assisted selection in wheat breeding programs for the identification and/or pyramiding of Dn4 and Dn6 genes.

Journal Article↗
PubMed1997

The (F1F0) ATP synthase of Buchnera aphidicola (endosymbiont of aphids): genetic analysis of the putative ATP operon.

Buchnera aphidicola is an intracellular, non-cultivable prokaryotic symbiont of the aphid Schizaphis graminum. A 6.8-kilobase fragment from B. aphidicola was cloned and sequenced and was found to contain genes encoding for proteins of the ATP synthase. The order of the genes, atpBEFHAGDC, is identical to that found inEscherichia coli and many other prokaryotes. This genetic organization is different from that observed in organelles such as mitochondria and chloroplasts, in which the genes are partitioned between the organellar and nuclear genomes. One difference between B. aphidicola and E. coli was the absence of atpI, a gene of unknown function, which in E. coli precedes atpB. As is the case of many other prokaryotes, atpBEFHAGDC appears to constitute a single transcription unit. The detection in B. aphidicola of the genes encoding the ATP synthase as well as past observations indicating that this organism is capable of respiration are consistent with the utilization byB. aphidicola of a proton gradient for the generation of ATP.

Amino Acid Sequence↗
PubMed1998

Sequence analysis of a DNA fragment from buchnera aphidicola (Aphid endosymbiont) containing the genes dapD-htrA-ilvI-ilvH-ftsL-ftsI-murE

Buchnera aphidicola is a prokaryotic endosymbiont of the aphid Schizaphis graminum. One of the endosymbiont's functions is the synthesis of branched-chain amino acids. A 9.7-kilobase B. aphidicola chromosomal DNA fragment was cloned and sequenced and found to contain genes encoding acetohydroxy acid synthase (ilvIH), the first enzyme of the parallel pathway of isoleucine and valine biosynthesis. Previously we have detected ilvC and ilvD, encoding the two other enzymes of this pathway. In addition the DNA fragment contained genes for cell division (ftsL, ftsI), murein biosynthesis (murE), lysine biosynthesis (dapD) and a periplasmic protease (htrA). In these properties B. aphidicola resembles free-living bacteria.

Journal Article↗
PubMed2002

The genomic sequence of cowpea aphid-borne mosaic virus and its similarities with other potyviruses.

The genomic sequence of a Zimbabwe isolate of Cowpea aphid-borne mosaic virus (CABMV-Z) was determined by sequencing overlapping viral cDNA clones generated by RT-PCR using degenerate and/or specific primers. The sequence is 9465 nucleotides in length excluding the 3' terminal poly (A) tail and contains a single open reading frame (ORF) of 9159 nucleotides encoding a large polyprotein of 3,053 amino acids and predicted Mr of 348. The size of the genome and the encoded polyprotein is in agreement with other potyviruses and contains nine putative proteolytic cleavage sites and motifs conserved in homologous proteins of other potyviruses. The P1 and P3 were the most variable proteins while CI, NIb and CP were the most conserved.

Cloning, Molecular↗
PubMed2006

Cowpea aphid-borne mosaic virus (CABMV) is widespread in passionfruit in Brazil and causes passionfruit woodiness disease.

Leaf samples of yellow passionfruit (Passiflora edulis f. flavicarpa) displaying fruit woodiness symptoms were collected in seven Brazilian states and the Federal District. Viral infection was confirmed by host range and ELISA, and fourteen viral isolates were obtained. All isolates were capable of infecting several leguminous host species, although differences in symptom severity were noticeable. Woodiness symptoms were reproduced in yellow passionfruit, and mosaic symptoms were induced in common bean. All isolates infected cowpea, reported as a non-host of passion fruit woodiness virus (PWV). Indirect ELISA demonstrated that all isolates were serologically related to each other and also to cowpea aphid-borne mosaic virus (CABMV). The complete sequence of the capsid protein was determined for all isolates. Comparison of these sequences with those of other potyviruses indicated the highest identity with CABMV isolates (85 to 94%). Identity with PWV isolates ranged from 54 to 70%. Phylogenetic analysis grouped all of the Brazilian isolates in a monophyletic cluster with the CABMV isolates, clearly distinct from the PWV isolates. Furthermore, this analysis demonstrated that a group of previously characterized isolates from Brazil that had been designated as PWV should be reclassified as CABMV. Together, these results provide unequivocal evidence that, in Brazil, passionfruit woodiness disease is primarily caused by CABMV. The presence of PWV in Brazil has yet to be confirmed.

Brazil↗
PubMed1993

Conifer aphids in an air-polluted environment. II. Host plant quality.

Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) seedlings were transported to five forest sites at increasing distances from a pulp mill emitting mainly SO(2). Levels of compounds which may have nutritional or defensive value for aphids on pine and spruce seedlings were studied. Glucose and fructose concentrations were significantly increased in pine and spruce needles near the pulp mill. There were no changes in sucrose and starch concentrations. In pine shoots, total free amino acid concentration and the concentrations of ornithine, lysine, histidine and arginine were significantly negatively correlated with the distance from the pulp mill, while in spruce only the individual amino acids glycine, ornithine, lysine and histidine showed a significant negative correlation with distance. There were no changes in total phenolic, catechin, total monoterpene and total resin acid concentrations. However, in pine seedlings monoterpenes beta-pinene and sabinene and in spruce seedlings resin acid palustric acid were significantly correlated with the distance from the pulp mill. The results indicate that SO(2) disturbs carbohydrate metabolism in spruce and pine seedlings. The elevated concentrations of arginine may be the result of the combinations of SO(2), NO(3) and NH(3) emissions of the pulp mill. The emissions did not have any impact on total amounts of defensive substances in trees. Thus, the possible susceptibility of conifers to herbivores appears to be due to changes in nutritive value rather than to reduced chemical resistance.

Journal Article↗
PubMed1994

The response of spruce shoot aphid Cinara pilicornis hartig to ambient and filtered air at two elevations and pollution climates.

The effects of ambient air compared to filtered air on the reproduction of females and mean relative growth rate (MRGR) of nymphs of C. pilicornis on Norway spruce was determined in open-top chambers at Wengernalp in the Swiss Alps (1900 m a.s.l.) and at Schönenbuch near the city of Basle (400 m a.s.l.). The ambient concentration of O(3), the main pollutant at both sites, varied between 45 and 120 microg m(-3) (24-h mean) at both sites. A 5-8 day exposure of spruce saplings to ambient compared to filtered air enhanced the MRGR of nymphs of C. pilicornis of local and northern origins at Schönenbuch. The cumulative numbers of offspring of C. pilicornis were higher in ambient air chambers than in filtered air chambers at Schönenbuch, but not at Wengernalp. Filtration of ambient air did not affect significantly the levels of total free amino acids or reducing sugars in phloem sap or concentration of total phenolics in needles at the end of the growing season. The results suggest that ambient air with elevated O(3) and with high daily fluctuations, as it can be observed in Schönenbuch, affects aphid performance on conifers more than ambient air with also elevated, but rather constant levels of O(3), as it can be observed in mountain forest areas.

Journal Article↗
PubMed2000

Lipid composition in long-day and short-day forms of the black bean aphid, Aphis fabae.

Long-day reared winged (alate) virginoparae from laboratory stock cultures which had been reared throughout larval development on bean stipules were significantly smaller (0.46+/-0.02 mg; mean+/-SEM) than short-day-reared gynoparae (0.69+/-0.04 mg; the winged autumn migrant) which completed development on intact beans. When winged virginoparae were raised from the third stadium on bean seedlings they grew larger (0.86+/-0.02 mg) but the gynoparae contained proportionally more total lipid (12.1+/-0.4%, gynoparae; 7.4+/-0.6%, stipule-reared virginoparae; 9.2+/-0.8%, seedling-reared virginoparae). Wingless aphids (apterae) were heavier, whether reared in short (0.99+/-0.03 mg) or long days (0.95+/-0.04 mg) but the lipid content was low (4.5+/-0.7% and 4.9+/-0.6%, respectively). The triacyl-, diacylglycerol and the phospholipid contents followed this trend but analysis of the fatty acid moieties of the triacylglycerides showed phenotypic differences. The ratios of myristic acid:palmitic acid were significantly higher in the winged forms than the wingless forms and were much higher in the gynoparae than the winged virginoparae. Short-day-reared wingless females also had a higher myristic acid:palmitic acid ratio than long-day-reared apterae, possibly reflecting the embryonic gynoparae maturing in their ovaries.

Journal Article↗
PubMed2000

Overwintering strategies and cold hardiness of two aphid parasitoid species (Hymenoptera: Braconidae: Aphidiinae).

The role of winter diapause in two aphid parasitoid species, Aphidius ervi Haliday and Aphidius rhopalosiphi DeStefani-Peres (Hymenoptera: Braconidae: Aphidiinae), in host synchronization and the induction of cold hardiness was investigated. Parasitoids were reared during three successive generations on Sitobion avenae Fabricius, at 15 degrees C under a photoperiod of 9 h light 15 h dark. Although these conditions are known to be strongly diapause inducing, neither parasitoids showed an incidence of diapause above 65% over the three generations; the rest of the population underwent quiescence. In both parasitoid species, diapausing mummies exhibited greater cold hardiness than non-diapausing mummies, resulting in significantly lower supercooling points (SCP) and in a higher survival rate during long-term exposures at 0 and -10 degrees C. The induction of increased cold hardiness in parasitoids was thus associated with the diapause state. SCPs of third instar larvae of S. avenae were similar to those of non-diapausing mummies of both parasitoid species, but significantly higher than those of diapausing mummies. The effect of winter climate on the stability of the host-parasitoid interaction is discussed.

Journal Article↗
PubMed2000

Overwintering adaptations in the lettuce root aphid Pemphigus bursarius (L.).

Pemphigus bursarius (L.) is a host alternating root-feeding aphid with a proportion of the population overwintering as asexual hiemalis in the soil. These hiemalis must be sufficiently cold tolerant to survive at the temperatures they would experience in winter, and also be able to overcome a period of prolonged starvation brought about by the absence of secondary host plants. Cold tolerance experiments showed field collected hiemalis to be considerably more cold hardy than laboratory summer apterae, with an LTemp(50) of -13.1 degrees C compared with 2.3 degrees C. In a constant exposure at 0 degrees C some field collected hiemalis survived for 18 days, while no summer apterae survived more than 8 h. Hiemalis, collected from the field in winter and induced in the laboratory, had significantly higher levels of triglycerides, 12.8% fresh weight (39.9% dry wt.) and 11.4% fresh weight (43.7% dry wt.), respectively, compared with summer apterae with a value of 7.1% fresh weight (32.5% dry wt.). These two adaptations of increased cold tolerance and accumulation of energy reserves confirm that the hiemalis morph is adapted for overwintering and hence physiologically distinct from summer morphs, and in turn, contribute to the success of the asexual life cycle strategy in this species.

Journal Article↗
PubMed1996

The aphid transmission factor of cauliflower mosaic virus forms a stable complex with microtubules in both insect and plant cells.

We analyzed the distribution of the cauliflower mosaic virus (CaMV) aphid transmission factor (ATF), produced via a baculovirus recombinant, within Sf9 insect cells. Immunogold labeling revealed that the ATF colocalizes with an atypical cytoskeletal network. Detailed observation by electron microscopy demonstrated that this network was composed of microtubules decorated with paracrystalline formations, characteristic of the CaMV ATF. A derivative mutant of the ATF, unable to self-assemble into paracrystals, was also analyzed. This mutant formed a net-like structure, with a mesh of four nanometers, tightly sheathing microtubules. Both the ATF- and the derivative mutant-microtubule complexes were highly stable. They resisted dilution-, cold-, and calcium-induced microtubule disassembly as well as a combination of all three for over 6 hr. CaMV ATF cosedimented with microtubules and, surprisingly, it bound to Taxol-stabilized microtubules at high ionic strength, thus suggesting an atypical interaction when compared with that usually described for microtubule-binding proteins. Using immunofluorescence double labeling we also demonstrated that the CaMV ATF colocalizes with the microtubule network when expressed in plant cells.

Animals↗