Role of plastid signals in modulating Arabidopsis responses to Cucumber mosaic virus

Chloroplasts can serve as sensors for detecting perturbations in the subcellular environment and actively communicate these signals to other organelles. They also play a critical role in plant immunity. Previous studies have indicated that some plastid-signaling deficient mutants have impaired abiotic stresses tolerance. However, whether plastid signals are involved in biotic stress response is rarely reported. In this study, the relationship between plastid signals and Cucumber mosaic virus (CMV) stress response was investigated in Arabidopsis thaliana. Our results showed that plastid-signaling defective mutants were more susceptible to CMV infection and showed more serious stress damages [higher oxidative damages, more compromised in PSII photochemistry and more reactive oxygen species accumulation] compared with the wild-type plants. Furthermore, the induction of defense-associated genes and antioxidant enzymes activity in plastid-signaling defective mutants gun1 and abi4 were lesser than that observed in the wild-type plants after CMV infection. Collectively, our reports provide evidences that plastid signals are necessary for defense responses to CMV in A. thaliana. Moreover, the present study contributes to the understanding of the signaling pathway mediated by chloroplast in response to virus pathogens.