Biology subjects

Outreman, Y.

Publications and source records attributed to Outreman, Y..

2 recordsLinked to original sources

bioRxiv2024

Insights into the triggering factors and determination mechanisms of host alternation in aphids

The bird cherry-oat aphid Rhopalosiphum padi, is one of the ten percent of aphids that are host alternating. The annual life cycle of R. padi entails an obligatory migration between a primary woody host, Prunus padus (Rosaceae), where sexual reproduction occurs, and many secondary hosts of the Poaceae family, where successive generations reproduce parthenogenetically. Migration between the two types of host plants is achieved by specialized migrant morphs. Very little is known about the cues that trigger migrant development, host alternation establishment and the underlying mechanisms. In this study, we aimed to elucidate the key steps involved in migrant induction and determination of host alternation, and to shed light on these intricate processes. We showed that a specific stage of leaf maturity triggers the development into a migrant morph when presented to R. padi at the first or second larval instar stages. We also demonstrated the gradual establishment of acclimation to the secondary hosts that precedes the migration step. Finally, we showed that the switch to feeding on the alternative hosts is irreversible once emigrants have reached adulthood. These results not only allowed us to define the critical periods of the leaf stage associated with morph induction and determination, but also to pinpoint the emigrants developmental stages when acclimation to secondary hosts begins. These novel insights of these critical periods will facilitate the investigation of molecular changes associated with host alternation in aphids.

ecology↗

bioRxiv2022

Pea-adapted biotype of the aphid Acyrthosiphon pisum induces susceptibility of pea to non-adapted biotype enabling improved feeding and performance

Most insect herbivores are adapted to feed on a few host plants only, but the mechanisms underlying plant specialization are poorly understood. One of the dominant hypotheses is that insects inject an oral secretion into the plant that manipulates the plants defences resulting in induced susceptibility. We tested this hypothesis on the pea aphid (Acyrthosiphon pisum), which forms multiple biotypes, each specialized on specific legume hosts. In particular, we tested whether a pea-adapted biotype can induce host susceptibility on pea, which should positively affect the fitness of a non-pea-adapted biotype. We found that survival and fecundity of an alfalfa-adapted biotype on pea were enhanced by co-infestation but not pre-infestation with a pea-adapted biotype. The electrical penetration graph (EPG) method was then used to dissect the components of alfalfa biotype feeding behaviour on pea with and without co-infestation by the pea biotype. While probing time did not differ between these two conditions, differences were observed in most other EPG parameters. When co-infested with the pea-adapted biotype, the alfalfa-adapted biotype was more likely to establish a phloem feeding and exhibited a longer ingestion time on pea. Our results clearly indicated that the pea-adapted biotype induced pea susceptibility by increasing the accessibility of non-pea-adapted aphids to the host phloem sap, and as a result, the alfalfa biotype increased its survival rate and fecundity. These results contribute to understanding how aphids manipulate their specific host plants.

ecology↗