Abstract:
Mycoviruses are ubiquitous and their infection has been reported from almost all major
fungal taxonomic groups. Numerous mycoviruses have been identified and characterized
so far, which revealed neo-lifestyles of mycoviruses. This study reports an extensive
screening survey on Pakistani filamentous fungal isolates for the identification of viral
infections. A total of 125 fungal samples were screened, 6 isolates were found positive for
double-stranded (ds) RNA elements when analyzed by a classical dsRNA isolation method
with an infection frequency of 4.8%. All six isolates (1NL, NFN, SP1, HK, E, L3) were
subjected to Next-generation sequencing for virome analysis. Obtained contigs sequences
were completed by 3′ RACE-PCR strategy and subsequent sequencing by a classical
Sanger sequencing method. A total of 28 mycoviruses were identified in the infected
isolates, belonging to the families Chrysoviridae, Polymycoviridae, Partitiviridae,
Totiviridae, Narnaviridae, Mitoviridae, Botourmiaviridae, Tombusviridae and a proposed
member of Hadakavirus genera. Based on the International Committee on Taxonomy of
Viruses (ICTV) demarcation criteria, the majority of the identified mycoviruses are
considered novel. Viruses from three isolates (1NL, NFN, SP1) were completely
characterized and sequences have been submitted in the NCBI database. Isolate SP1 was
found to harbor co-infection of 11 viruses which is among the largest number of viruses
infecting single fungal isolate. Isolates 1NL and NFN showed unique molecular features.
Following genomic characterization, the biological assessment was also conducted in
which curing mycoviral infection was attempted. HadV1-1NL infecting 1NL was easily
cured in aged mycelia however viruses of isolate SP1 and NFN showed persistent
infections. Artificial transfection of C. parasitica (model fungus) using virus particles
Abstract
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showed that some mycoviruses can infect and maintain a stable infection in experimental
host, whilst others can′t cope with host silencing machinery.
