Virus-mediated suppression of host non-self recognition facilitates horizontal transmission of heterologous viruses

Non-self recognition is a common phenomenon among organisms; it often leads to innate immunity to prevent the invasion of parasites and maintain the genetic polymorphism of organisms. fungal vegetative incompatibility is a type of non-self recognition which often induces programmed cell death (pcd) and restricts the spread of molecular parasites. it is not clearly known whether virus infection could attenuate non-self recognition among host individuals to facilitate its spread. here,we report that a hypovirulence-associated mycoreovirus,named sclerotinia sclerotiorum mycoreovirus 4 (ssmyrv4),could suppress host non-self recognition and facilitate horizontal transmission of heterologous viruses. we found that cell death in intermingled colony regions between ssmyrv4-infected sclerotinia sclerotiorum strain and other tested vegetatively incompatible strains was markedly reduced and inhibition barrage lines were not clearly observed. vegetative incompatibility,which involves heterotrimeric guanine nucleotide-binding proteins (g proteins) signaling pathway,is controlled by specific loci termed het (heterokaryon incompatibility) loci. reactive oxygen species (ros) plays a key role in vegetative incompatibility-mediated pcd. the expression of g protein subunit genes,het genes,and ros-related genes were significantly down-regulated,and cellular production of ros was suppressed in the presence of ssmyrv4. furthermore,ssmyrv4-infected strain could easily accept other viruses through hyphal contact and these viruses could be efficiently transmitted from ssmyrv4-infected strain to other vegetatively incompatible individuals. thus,we concluded that ssmyrv4 is capable of suppressing host non-self recognition and facilitating heterologous viruses transmission among host individuals. these findings may enhance our understanding of virus ecology,and provide a potential strategy to utilize hypovirulence-associated mycoviruses to control fungal diseases. © 2017 wu et al.