Full-length sequence and genome analysis of CHV1-CN280, a North China isolate of cryphonectria hypovirus 1.

CHV1-CN280 is a North China isolate of cryphonectria hypovirus 1 (CHV1), which has high horizontal transmission ability. The complete genomic sequence of CHV1-CN280 was determined and analyzed. Compared with other reported CHV1s, the genome of CHV1-CN280 shows some significantly different characteristics. The junction of the two open reading frames (ORFs) of CHV1-CN280 is AUGUAUAA, while in other reported CHV1s, it is UAAUG. The genomic sequence of CHV1-CN280 shows a high level of similarity to other reported CHV1s in the 3' portion, but in some sections of the 5' portion (the region around the start codon of ORFA, the region around the predicted cleavage site of p29 and p40, and the 5'-portion of p48 coding region), the nucleotide sequence identity is lower than 50%. The p29 of CHV1-CN280 shares only about 60% identity with other sequenced CHV1 isolates at the amino acid level. Full-length genomic recombination analysis suggests that several recombination events have occurred in the ORFB coding region between CHV1-CN280 and two subtype I CHV1 isolates (CHV1-Euro7 or CHV1-EP721). RT-PCR primers were designed according to the genomic sequence of CHV1-CN280 to study the genetic diversity of CHV1 in East Asia. Phylogenetic analysis showed that the East Asian CHV1s were quite different from the five assigned subtypes in Europe, and seven new CHV1 subtypes were identified in this study.