Characterization of a newly identified RNA segment derived from the genome of Sclerotinia sclerotiorum reovirus 1.

Sclerotinia sclerotiorum reovirus 1 (SsReV1) was previously reported to infect hypovirulent strain SCH941 of the phytopathogenic fungus Sclerotinia sclerotiorum and to contain 11 double-stranded RNA (dsRNA) segments (S1-S11). Here, we report that SsReV1 is actually composed of 12 dsRNA segments instead of 11. The full-length nucleotide sequence of the twelfth segment (S12) was determined using a combination of RACE and high-throughput sequencing methods. S12 is 1217 nucleotides in length and has highly conserved terminal sequences that resemble those of the other 11 segments of SsReV1. S12 contains a single open reading frame encoding a protein (VP12) of 311 amino acids. Although regular BLAST analysis did not reveal any similarity of VP12 to known sequences, it was found to be homologous to the VP11 of Colorado tick fever virus of the genus Coltivirus when a hidden-Markov-model-based HHpred analysis was performed. A single-protoplast regeneration experiment suggested that S12 and S2 were maintained or lost in parallel. In summary, the SsReV1 genome consists of 12 dsRNA segments.