Hosting certain facultative symbionts modulates the phenoloxidase activity and immune response of the pea aphid Acyrthosiphon pisum

Abstract

The pea aphid Acyrthosiphon pisum hosts different facultative symbionts (FS) which provide it with various benefits, such as tolerance to heat or protection against natural enemies (e.g., fungi, parasitoid wasps). Here, we investigated whether and how the presence of certain FS could affect phenoloxidase (PO) activity, a key component of insect innate immunity, under normal and stressed conditions. For this, we used clones of A. pisum of different genetic backgrounds (LL01, YR2 and T3-8V1) lacking FS or harboring one or two (Regiella insecticola, Hamiltonella defensa, Serratia symbiotica + Rickettsiella viridis). Gene expression and proteomics analyses of the aphid hemolymph indicated that the two A. pisum POs, PPO1 and PPO2, are expressed and translated into proteins. The level of PPO genes expression as well as the amount of PPO proteins and phenoloxidase activity in the hemolymph depended on both the aphid genotype and FS species. In particular, H. defensa and R. insecticola, but not S. symbiotica + R. viridis, caused a sharp decrease in PO activity by interfering with both transcription and translation. The microinjection of different types of stressors (yeast, Escherichia coli, latex beads) in the YR2 lines hosting different symbionts affected the survival rate of aphids and, in most cases, also decreased the expression of PPO genes after 24 h. The amount and activity of PPO proteins varied according to the type of FS and stressor, without clear corresponding changes in gene expression. These data demonstrate that the presence of certain FS influences an important component of pea aphid immunity.

Sustainable laser-based technology for insect pest control

“…While A. pisum LL01 and YR2 both have the obligatory symbiont Buchnera aphidicola which participates in their nutrition, only YR2 has a secondary symbiont Regiella insecticola that can provide the host with more resistance to biotic and abiotic stresses (temperature, parasitoid attack, etc.) 36 . The similar results of A. pisum LL01 and YR2 aphids indicate that despite the presence of the secondary symbiont, aphids are equally sensitive to the new stress caused by the CO 2 laser.…”

Variation in density, immune gene suppression, and co-infection outcomes among strains of the aphid endosymbiont Regiella insecticola

“…In particular, a sequenced strain (32) of Regiella that was isolated from another aphid species (Myzus persicae strain .515) ( 18) is harbored at extremely low densities (more than an order of magnitude below other strains) but has been nonetheless transmitted vertically over many years of laboratory propagation. The aphid immune system has been implicated in the regulation of vertically-transmitted symbioses in several studies, with two related symbionts (Regiella insecticola and Hamiltonella defensa) leading to decreased expression of key insect innate immune system genes and fewer circulating immune cells (22)(23)(24)(25). We have also found that knocking down expression of Phenoloxidase using RNAi leads to increased Regiella density over aphid development (24).…”

“…The aphid immune system has been implicated in the regulation of vertically-transmitted symbioses in several studies, with two related symbionts ( Regiella insecticola and Hamiltonella defensa ) leading to decreased expression of key insect innate immune system genes and fewer circulating immune cells (22-25). We have also found that knocking down expression of Phenoloxidase using RNAi leads to increased Regiella density over aphid development (24).…”

“…Several recent studies have found that some aphid facultative symbionts interact with the innate immune system (22). Specifically, aphids harboring Regiella have decreased numbers of circulating immune cells (23) and reduced expression (24) and protein levels of phenolxoidase (25), a critical component of the insect innate immune system. Suppression of phenoloxidase (PO) using RNAi leads to an increase in Regiella densities (24).…”

Cloning, Characterization, and Expression Prolife Analysis of Tyrosinase Genes: Insights into Black Shell Formation in Cyclina sinensis

“…Its expression controlling gene is a tyrosinase gene. Tyrosinase in plants is called polyphenol oxidase, in insects, it is called phenol oxidase, and in eukaryotes and microorganisms, it is known as tyrosinase [32,33]. A large number of studies have confrmed that tyrosinase gene mutations can cause abnormal body color in a variety of animals (mice, rabbits, Oryzias latipes, etc.)…”