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

Plants emit volatile organic compounds (VOCs) in response to biotic and abiotic stimuli that provide information about their physiological status to other individuals in the community. Nearby receivers adjust their own defenses in response to these chemical cues. The majority of studies to date has concentrated on the communication of abiotic stressors (e.g. salinity or drought) or herbivory. Less attention had received the role of VOCs during microbial infections and almost nothing has been done for viruses. Here we investigated the function of VOCs during turnip mosaic virus infection of Arabidopsis thaliana. First, we looked at the influence of two factors on the kinetics of symptoms progression in receivers, namely the prevalence of infection in the population and the growth stage of the receiver plants at inoculation. We found that young plants were more sensitive to the protective effect of VOCs than older ones, and that high infection prevalence results in a slower disease progression in receivers. Second, we tested the possibility that jasmonates could be VOC candidates. To do this, we examined the kinetics of symptoms progression in jasmonate-insensitive and wild-type plants, and the results showed that the protective effect vanished in the mutant plants. Third, we investigated the possibility that root communication would be also relevant. We found that the kinetics of symptom progression across receivers was further slowed down in an age-dependent manner 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 VOCs.