Effect of disease prevalence and growth stage on symptom severity in the Turnip mosaic virus-Arabidopsis thaliana pathosystem

In response to stresses, plants are capable of communicating their physiological status to other individuals in the community using several chemical cues. Nearby receivers then ad-just their own homeostasis to increase resilience. The majority of studies to date have con-centrated on the communication of abiotic stressors (e.g., salinity or drought) or herbivory. Less attention has been paid to the role of communication during microbial infections and almost nothing has focused on viruses. Here we investigated the effect that the prevalence of a turnip mosaic virus in a community of Arabidopsis thaliana has on the severity of symptoms developed in a group of receivers. First, we looked at the influence of two factors on the kinetics of symptom progression in the receivers, namely the prevalence of infection among emitters and the growth stage of the receiver plants at inoculation. We found that young receiver plants developed milder symptoms than older ones, and that high infection prevalence resulted in slower disease progression in receivers. Second, we tested the pos-sibility that jasmonates could act as chemical signaling cues. To do this, we examined the kinetics of symptom progression in jasmonate-insensitive and wild-type plants. The results showed that the protective effect vanished in the mutant plants. Third, we investigated the possibility that root communication could also be relevant. We found that the kinetics of symptom progression across receivers was further slowed down in an age-dependent man-ner when plants were planted in the same pot. Together, these preliminary findings point to a potential function for disease prevalence in plant communities in regulating the severity of symptoms, this effect being mediated by some volatile organic compounds.