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At least 19 recordsLinked to original sources
PubMed1977

Effect of dietary cholesterol on the pattern of osmium deposition in the symbiote-containing cells of the pea aphid.

Pea aphids left for 48 h in unbuffered osmium tetroxide show heavy staining of many organelles in the symbiote-containing cells (mycetocytes and sheath), embryos and oenocytes very similar to that characteristic of mammalian sterol-synthesizing cells. However, the staining of the per-aphid cells is, to a large extent, dependent on the presence of cholesterol benzoate, or free cholesterol, in the aphid's diet. In aphids cultured in vitro with 3H mevalonate in the presence of added cholesterol, the incorporation of label into the cholesterol and lanosterol fractions is significantly reduced. If the dietary cholesterol effects a similar inhibition in vivo, the cholesterol-dependent osmium staining could be due to precursors(s) of cholesterol accumulating in the intracellular sites described. There is also osmium staining of large (normally electron-transparent) vacuoles in mycetocytes, gut and fat body, irrespective of dietary cholesterol.

Animals↗
PubMed1994

Mitochondrial DNA diversity in the pea aphid Acyrthosiphon pisum.

The pea aphid Acyrthosiphon pisum has been established in North America for at least a century and occurs on a broad range of host plants. Despite its importance as a crop pest, there is little understanding of the genetic structure of its populations or the extent of genetic divergence associated with different host plant utilization. This study examined the extent of mitochondrial DNA (mtDNA) diversity among 35 clones of pea aphids from alfalfa. Polymorphisms were detected at only 2 of 126 restriction sites, suggesting the same impoverished level of genetic diversity found in prior allozyme studies. However, length variation was common and apparently arose as a result of tandem repeats in two regions of the mtDNA molecule. Region 1 occurred in proximity to the control region of the molecule, while region 2 was close to a cluster of tRNA genes flanking the NAD-dehydrogenase subunit 3 gene on the opposite side of the mtDNA molecule. Each of the aphid clones was homoplasmic for a single length variant in region 1, which varied with respect to the number of copies of a 120-bp repeat. By contrast, one-third of the clones were heteroplasmic at region 2, where they possessed a variable number of copies of a 210-bp repeat. Reanalysis of clones after 30 generations of parthenogenetic reproduction established the stability of length variants over this interval, suggesting their value in studies of the genetic structure of aphid populations.

Animals↗
PubMed2025

Analysis of Duplication and Potential Functional Divergence of Wing Gene Network Components in Pea Aphids.

A fundamental focus of evolutionary developmental biology is uncovering the genetic mechanisms responsible for the gain and loss of characters. One approach to this question is to investigate changes in the coordinated expression of a group of genes important for the development of a character of interest (a gene regulatory network). Here we consider the possibility that modifications to the wing gene regulatory network (wGRN), as defined by work primarily done in Drosophila melanogaster, were involved in the evolution of wing dimorphisms of the pea aphid (Acyrthosiphon pisum). We hypothesize that this may have occurred via changes in expression levels or by duplication followed by divergence of wGRN components. To test this, we annotated members of the wGRN in the pea aphid genome and assessed their expression levels in first and third nymphal instars of winged and wingless morphs of males and asexual females. We find that only 2 of the 32 assessed genes exhibit morph-biased expression. We also find that three wing genes (apterous (ap), warts (wts), and decapentaplegic (dpp)) have undergone gene duplication. In each case, the resulting paralogs show signs consistent with functional divergence, exhibiting either sex-, morph-, or stage-specific expression. Two gene duplicates, wts2 and dpp3, are of particular interest with respect to wing dimorphism, as they exhibit male morph-specific isoforms and wingless male-biased expression, respectively. These gene expression results provide an important first step toward identifying members of the pea aphid wGRN that may play a causative role in differentiating winged from wingless morphs. These findings supplement our understanding of trends in developmental gene network evolution, such as side-stepping pleiotropic constraint via duplication and sub-functionalization, underlying the emergence of novel phenotypes.

Animals↗
PubMed2025

Analysis of duplication and possible sub-functionalization of wing gene network components in pea aphids.

A fundamental focus of evolutionary-developmental biology is uncovering the genetic mechanisms responsible for the gain and loss of characters. One approach to this question is to investigate changes in the coordinated expression of a group of genes important for the development of a character of interest (a gene regulatory network). Here we consider the possibility that modifications to the wing gene regulatory network (wGRN), as defined by work primarily done in Drosophila melanogaster, were involved in the evolution of wing dimorphisms of the pea aphid (Acyrthosiphon pisum). We hypothesize that this may have occurred via changes in expression levels or duplication followed by sub-functionalization of wGRN components. To test this, we annotated members of the wGRN in the pea aphid genome and assessed their expression levels in first and third nymphal instars of winged and wingless morphs of males and asexual females. We find that only two of the 32 assessed genes exhibit morph-biased expression. We also find that three wing genes (apterous (ap), warts (wts), and decapentaplegic (dpp)) have undergone gene duplication. In each case, the resulting paralogs show signs of functional divergence, exhibiting either sex-, morph-, or stage-specific expression. Two gene duplicates, wts2 and dpp3, are of particular interest with respect to wing dimorphism, as they exhibit a wingless male-specific isoform and wingless male-biased expression, respectively. These results supplement our understanding of trends in developmental gene network evolution, such as side-stepping pleiotropic constraint via duplication and sub-functionalization, underlying the emergence of novel phenotypes.

dimorphism↗
PubMed1977

In vivo sterol biosynthesis by pea aphid symbiotes as determined by digitonin and electron microscopic autoradiography.

Pea aphid primary symbiotes have previously been shown to synthesize cholesterol in vitro. Two electron microscopic techniques were used here to determine whether the symbiotes also synthesize cholesterol in vivo and whether this cholesterol is made available to the aphid. We also inquired into a possible role of secondary symbiotes in chosesterol biosynthesis. Treatment of aphids with digitonin resulted in significant alteration of ultrastructural sites in primary and secondary symbiote membranes. We concluded that these sites are areas of high cholesterol concentration in the symbiotes. Electron microscopic autoradiography with 3H-mevalonate precursor indicated that both primary and secondary symbiotes synthesize cholesterol; in both cases, the majority of grains were associated with the symbiote membranes. While the frequency of grains on the symbiotes remained constant, irrespective of incubation time in labelled media, the frequency of grains over surrounding tissues increased exponentially as the time of incubation was increased from 30 min to 8 h, indicating that symbiote cholesterol is transported to other tissues. High voltage electron microscopic autoradiography permitted thick section autoradiography, reducing the time of emulsion exposure from 54 days (thin section) to 12 days (0.5 mum sections).

Animals↗
PubMed1994

Cloning and characterization of the ribosomal protein genes in the spc operon of a prokaryotic endosymbiont of the pea aphid, Acyrthosiphon kondoi.

To correlate a prokaryotic endosymbiont in the pea aphid, Acyrthosiphon kondoi, with the endosymbionts in related aphid species as well as with free-living bacteria and subcellular organelles, and to study the mode of its gene expression within aphid cells, we have cloned and characterized the genes encoding ribosomal proteins S3, L16, L29, S17, L14, L24, L5, S14, S8, L6, L18, S5, L30, L15 and secretion protein Y (Sec Y) from the S10 and spc ribosomal protein gene operons of this endosymbiont. The organization of these genes is identical to that in Escherichia coli, and their nucleotide sequences are highly similar (87% identity) to the corresponding E. coli genes. They are much less similar to the corresponding chloroplast and mitochondrial genes. The guanine plus cytosine G+C content of the genes of the A. kondoi endosymbiont is much higher than those of the endosymbionts in related aphid species reported so far. It appears either that the A. kondoi endosymbiont is derived from an ancestral bacterium different from those in other aphids or that its G+C content increased in a relatively short time after the evolutionary divergence of its host.

Amino Acid Sequence↗
PubMed1989

Pea aphid symbiont relationships established by analysis of 16S rRNAs.

The pea aphid (Acyrthosiphon pisum Harris) harbors two morphologically distinct procaryotic intracellular symbionts. The genes for the 16S rRNA from these symbionts have been cloned and sequenced. Comparisons with sequences of 16S rRNAs from selected procaryotes indicate that the two symbionts are evolutionarily distinct from each other and are members of the gamma-3 subdivision of the class Proteobacteria. One of the symbionts is a member of the family Enterobacteriaceae, while the other constitutes a lineage distinct from these organisms. Both symbionts appear to have only one copy of their rRNA operon.

Animals↗
PubMed1980

Intraspecies variability in transmission efficiency of stylet-borne viruses by the pea aphid (Acyrthosiphon pisum).

The efficiency of bean yellow mosaic virus (BYMV; Potyvirus group) tranasmission from pea to pea plants by 36 clones of the pea aphid (Acyrthosiphon pisum) was studied. The efficiency of the clones varied; it was not related to the aphid colour form (green, red or yellow) or the origin of the clone (host plant, geographic area). With alfalfa mosaic virus, the virus-vector relationships concerning transmission efficiency were, in general, similar to those found with BYMV. The behaviour of the clones to the circulative pea enation mosaic virus was, however, different.

Aphids↗
PubMed1975

Ultrastructure of pea aphid mycetocytes: evidence for symbiote secretion.

A detailed investigation into the ultrastructure of the pea aphid mycetocytes and their contained symbiotes and organelles was carried out with the transmission electron microscope. The most striking observation was the presence of small vesicles in the space between the primary symbiote cell wall and membrane envelope (outer membrane space). The vesicles appear to form by a budding process at the outer cell wall layer. Subsequently, the vesicles, we suggest, may move out into the mycetocyte cytoplasm via a similar budding of the membrane envelope; The Golgi apparatus was found to be an important structural component of the primary mycetocyte; it is continuous with the rough endoplasmic reticulum and the latter, in turn, appears to be closely connected to the primary symbiote membrane envelope. This may be of functional significance. A number of other organelles not previously described in mycetocytes were found, including transparent vacuoles, granular bodies, multi-vesicular bodies and microfilaments. The chemical composition of the various vesicles and organelles is unknown at present.

Animals↗
PubMed1992

Nucleotide sequence and presumed secondary structure of the internal transcribed spacers of rDNA of the pea aphid, Acyrthosiphon pisum.

1. Internal transcribed spacer (ITS) 1 and ITS 2 of rDNA of the pea aphid, Acyrthosiphon pisum consisted of 229 and 280 nucleotides, whose G+C contents were 70 and 74%, respectively. 2. Secondary structure models constructed for the ITS 1 and ITS 2 suggested that certain structural motifs have been conserved in these regions despite extensive divergence in nucleotide sequence due to species.

Animals↗