show Abstracthide AbstractA pseudometallophyte Arabidopsis halleri is frequently found to be infected with cucumber mosaic virus (CMV) in its natural habitat. The purpose of this study is to elucidate the effect of CMV infection on its natural hosts. The CMV(Ho) strain isolated from A. halleri was inoculated into clonal A. halleri plants that were obtained from runners of mother plants, and the pathosystem consisting of CMV(Ho) and its natural host A. halleri was established.In low heavy metal environment, the CMV(Ho) infection caused growth retardation in the above-ground part (stems and leaves) of host plants, and thereby conferred strong drought tolerance on host plants. On the other hand, in high heavy metal environment, which simulates a natural habitat for A halleri, the CMV(Ho) infection did not cause any symptoms to host plants and conferred mild drought tolerance. And the result of transcriptome analysis suggests that CMV(Ho) is recognized as a symbiont rather than a pathogen by its host plant. These results indicate a resilient mutualistic interaction between CMV(Ho) and its natural host A. halleri to adapt to an environmental change. Overall design: RNA-seq is perfomed using three CMV-free, three CMV-infected, three CMV-free zinc excess and three CMV-infected zinc excess leaves of Arabidopsis halleri.