Biology subjects

Vallat, A.

Publications and source records attributed to Vallat, A..

4 recordsLinked to original sources

bioRxiv2026

Exposure to herbivore-induced plant volatiles directly induces jasmonic acid and primes chemical defences in cotton plants

Plants can deploy alternative defensive strategies in response to airborne signals from damaged neighbours to prepare for incoming attack: a straightaway response up-regulating their defences (induction), or a primed state, leading to a faster/stronger defence response after herbivory. However, it is unclear which mechanisms are involved in each response. We used a monophagous and a polyphagous leafworm species to specifically dissect induction and priming effects of exposure to herbivore-induced plant volatiles (HIPVs). Exposure to HIPVs directly elevated jasmonate levels in undamaged receivers but did not induce defensive terpenoids or volatiles. However, HIPV-primed plants accumulated high levels of toxic terpenoids (e.g. gossypol) and emitted high quantities of volatile sesquiterpenes, when damaged by either species of caterpillars. This comprehensive study demonstrates that both defence induction and priming can be detected in cotton but occur as different, linked responses which are robust to herbivore identity, providing insights into a generalised plant communication strategy.

ecology↗

bioRxiv2024

Mosquitoes self-medicate according to the dynamics of a microsporidian infection

Immune responses protect against infectious diseases but often incur physiological costs, such as oxidative stress. In mosquitoes, these costs may shape behaviours that help regulate oxidative balance, potentially including the consumption of nectar containing bioactive substances like prooxidants and antioxidants. We investigated whether Anopheles gambiae adjust their preferences for diets with such substances when they are infected with the microsporidian parasite Vavraia culicis. Using sugar solutions supplemented with hydrogen peroxide (a prooxidant) or ascorbic acid (an antioxidant), we assessed the feeding preferences of uninfected and infected mosquitoes at different ages and measured the effects of these diets on oxidative homeostasis, parasite load, and lifespan. Infected mosquitoes initially preferred the prooxidant diet, which reduced parasite load and extended lifespan, before shifting their preference towards the antioxidant diet as infection progressed. In contrast, uninfected mosquitoes consistently preferred the unsupplemented sugar, likely to avoid oxidative stress induced by the supplemented diets, which, surprisingly, also increased their lifespan. These results suggest a form of self-medication, despite benefits in uninfected individuals, where mosquitoes dynamically adjust their dietary choices throughout infection. We propose that such dietary strategies may be widespread among mosquitoes, helping them manage oxidative stress, with potential implications for vector-pathogen interactions and the success of biological control programmes.

evolutionary biology↗

bioRxiv2024

Mechanisms of host exploitation by a microsporidian parasite

Parasites exploit their hosts to enhance their growth and reproduction, yet the mechanisms underlying host manipulation remain understudied for many taxa. The microsporidian Vavraia culicis, a potential biological control agent for mosquitoes, serves as an excellent model to explore such mechanisms. In this study, we investigate how infection by V. culicis lines that vary in virulence alters resource dynamics within the mosquito host Anopheles gambiae. Using metallomics and quantification of protein, carbohydrate, and lipid content, we show that infection alters host resource concentrations in ways that depend on parasite virulence. More virulent parasites led to increased protein levels and greater energy demands, evidenced by higher carbohydrate reserves. Additionally, infection with V. culicis impacted host metal content, particularly zinc and manganese, used by V. culicis independently of its evolutionary background. Iron availability, a key nutrient for parasite growth, enhanced spore production, with selected parasite lines better able to exploit host iron than unselected. These findings provide insight into the mechanisms by which V. culicis manipulates host resources, shedding light on the role of host exploitation in parasite virulence and the potential use of microsporidia as biological control agents in vector biology.

evolutionary biology↗

bioRxiv2020

Exploiting oxalotrophic bacteria to control Aspergillus niger lung infections

Aspergillus fungi are opportunistic pathogens that affect a large number of people worldwide. Many aspects of Aspergillus spp. pathogenesis toward humans are known, but their ability to enhance their infectious potential by manipulating the environmental pH of its host has not been considered yet. In this study, we tested the hypothesis that by producing oxalic acid, Aspergillus niger can manipulate pH during lung infection and thus, interfering with this process could limit pathogenicity. To test this hypothesis, we co-cultured A. niger with oxalotrophic bacteria in increasingly complex testing systems (Petri dishes and 3D-cell cultures systems). In in vitro tests, oxalotrophic bacteria limit oxalic acid production and suppressed the pH shift induced by A. niger. In 3D-cell cultures (Transwells(R) and Bronchioles-on-a-chip), A. niger also modified pH, Ca2+ and oxalic acid concentrations. Co-inoculation with as little as 10 cells of the oxalatrophic bacterium strongly inhibited the germination and development of A. niger and returned each of the three parameters to the baseline physiological values of uninfected cells. This biocontrol interaction between oxalotrophic bacteria and oxalate-producing A. niger could represent a paradigm shift in the fight against opportunistic fungal pathogens, where the host environment is rendered less permissive to fungal development.

microbiology↗