Mycoviruses of an endophytic fungus can replicate in plant cells: Evolutionary implications

So far there is no record of a specific virus able to infect both fungal and plant hosts in nature. However, experimental evidence shows that some plant virus RdRPs are able to perform replication in trans of genomic or DI RNAs in the yeast Saccharomyces cerevisiae. Furthermore, tobacco mosaic virus was recently shown to replicate in a filamentous ascomycetous fungus. Thus, at least experimentally, some plant viruses can infect some fungi. Endophytic fungi have been reported from many plants and several of these fungi have been shown to contain viruses. Here we tested if mycoviruses derived from a marine plant endophyte can replicate in plant cells. For this purpose, we used partially purified viral particles from isolate MUT4330 of Penicillium aurantiogriseum var. viridicatum which harbors six virus species, some having dsRNA and some positive-strand ssRNA genomes. These were transfected into three distinct plant protoplast cell systems. Time-course analysis of absolute RNA accumulation provided for the first time evidence that viruses of two species belonging to the Partitiviridae and Totiviridae families, can replicate in plant cells without evidence of host adaptation, i.e, changes in their nucleotide sequence.