Biotic stress in plants frequently induces a hypersensitive response (HR). This distinctive reaction has been studied intensively in several pathosystems and has shed light on the biology of defence signalling. Compared with microbial pathogens, relatively little is known about the role of the HR in defence against insects. Reference genotype A17 of Medicago truncatula Gaertn., a model legume, ...

Interactions among predators can a have substantial effect on the total impact of the predator complex. We investigated the interaction between foliar-foraging (Coccinella septempunctata) and ground-foraging (Harpalus pennsylvanicus) predators of the pea aphid (Acyrthosiphon pisum) in a series of laboratory and field experiments. The intensity and direction of the interaction were determined by...

The nutrition and metabolism of aphids are of interest to biochemists, since these important pests depend upon leaf cell sap for their nutrition and excrete large amounts of carbohydrate and amino acids (1, 2). This suggests that they may have some special nutritional requirements (3), and that their carbohydrate metabolism may possess unusual features. The evidence obtained to date indicates t...

The morphology and fine structure of the ocelli of Acanthosiphon pisum have been analyzed by means of light and electron microscopy. The three ocelli of this species are located near the compound eyes. Externally, the ocelli are marked by the corneal lenses virtually spherical in form. A single layer of corneagen cells lies below the cuticular lens. The corneagen and retinal cells are arranged ...

The genetic basis of color polymorphism is explored in the pea aphid, Acyrthosiphon pisum (Harris) (Homoptera: Sternorrhyncha), in which two color morphs have been described (pink or green). Laboratory crosses and a Mendelian genetic analysis reveal that color polymorphism in pea aphids is determined by a single biallelic locus, which we name colorama, with alleles P and p, pink being dominant ...

In the face of global climate change, understanding how aphid-symbiont relationships are affected by heat shock is critical. We evaluated effects on pea aphid, Acyrthosiphon pisum Harris (Hemiptera: Aphididae), and its obligate endosymbiont Buchnera aphidicola Munson et al. means quantitative PCR in treated aphids their offspring. First-instar received a single (35 °C for 6 h), repetitive shock...

Evolutionary theory predicts that sexually antagonistic mutations accumulate differentially on the X chromosome and autosomes in species with an XY sex-determination system, with effects (masculinization or feminization of the X) depending on the dominance of mutations. Organisms with alternative modes of inheritance of sex chromosomes offer interesting opportunities for studying sexual conflic...

In aphids, clonal individuals can show distinct morphologic traits in response to environmental cues. Such phenotypic plasticity cannot be studied with classical genetic model organisms such as Caenorhabditis elegans or Drosophila melanogaster. The genetic basis of this biological process remain unknown, as mutations affecting this process are not available in aphids. Here, we describe a protoc...

Although evolutionary transitions from sexual to asexual reproduction are frequent in eukaryotes, the genetic bases of such shifts toward asexuality remain largely unknown. We addressed this issue in an aphid species where both sexual and obligate asexual lineages coexist in natural populations. These sexual and asexual lineages may occasionally interbreed because some asexual lineages maintain...

Symbiotic associations play a pivotal role in multicellular life by facilitating acquisition of new traits and expanding the ecological capabilities of organisms. In insects that are obligatorily dependent on intracellular bacterial symbionts, novel host cells (bacteriocytes) or organs (bacteriomes) have evolved for harboring beneficial microbial partners. The processes regulating the cellular ...