Host response of Agaricus bisporus to mushroom virus X infection

Abstract

Commercial mushroom crops (Agaricus bisporus) are susceptible to a disease causedby a complex of 18 viruses known collectively as mushroom virus X (MVX). Symptoms of MVX infection vary from bare patches in crops to mushroom discolouration (browning). To understand the dynamic interaction between A. bisporus and MVX, we have studied five strains; including the globally-cultivated commercial strain, one wild strain, and one commercial-wild hybrid strain. Our transmission experiments using ‘healthy’ mycelium challenged with MVX-infected mycelium, detected MVX in the first day of hyphal anastomosis in all five strains. However, our commercial-scale crop experiment revealed varying degrees of disease tolerance in the fruiting body, the commercial strain being most susceptible and the hybrid strain most resistant to MVX. LC-MS/MS proteomics and RNA-seq analyses have elucidated key differences in response to both early and late crop inoculation of MVX. Quantitative shotgun proteomics of the susceptible commercial strain at late MVX inoculation revealed striking levels of proteins relating to mechanical membrane damage via detection of myo-inositol-associated biosynthetic proteins. Defense proteins relating to chalcone isomerase activity were also detected exclusively in the MVX-infected commercial strain. MVX-infected wild strain isolates showed significantly greater abundance of proteins related to fundamental cellular processes such as RNA polymerase activity and cell-redox homeostasis. Our findings show that although vegetative transmission of MVX is prevalent in all five strains, the fruiting body may oppose the infection in certain strains. Our findings of dynamic host response of A. bisporus to MVX, provides novel insights for this economically important, globally cultivated crop.