Molecular characterization and genome sequence analysis of Dichroa emaravirus, a putative novel member of the genus Emaravirus.

Hydrangea febrifuga (syn. Dichroa febrifuga) is a traditional medicinal plant distributed in China and Southeast Asia, and febrifugine, one of its principal bioactive constituents, has served as an important lead compound for antimalarial drug development. Viral infections may adversely affect the quality of medicinal plants; however, no emaravirus has previously been reported from H. febrifuga. Here, high-throughput sequencing was performed on H. febrifuga leaves exhibiting mosaic symptoms collected in Yunnan Province, China. Combined with RT-PCR, Sanger sequencing, and 5'/3' rapid amplification of cDNA ends (RACE), five full-length genomic RNA segments of a putative novel emaravirus, tentatively designated Dichroa emaravirus (DEV), were identified and characterized. The five negative-sense single-stranded RNA (-ssRNA) segments have a combined length of 12,971 nt and encode an RNA-dependent RNA polymerase (RdRp), glycoprotein precursor (GP), nucleocapsid protein (NP), movement protein (MP), and an uncharacterized accessory protein, P5. The maximum amino acid sequence identities of DEV P1-P4 with recognized emaraviruses were 73.90%, 51.82%, 65.60%, and 81.30%, respectively, whereas P5 showed a maximum identity of 49.16% with its closest homolog. Thus, three of the four core proteins had maximum identities below 80%, consistent with the current ICTV species demarcation criterion for the genus Emaravirus. Maximum-likelihood phylogenetic analyses based on the four core proteins further supported the placement of DEV within the genus Emaravirus (family Fimoviridae). These results support DEV as a putative novel emaravirus and represent the first report of an emaravirus associated with H. febrifuga.