title: High interaction variability of the bivalve-killing dinoflagellate Heterocapsa circularisquama strains and their single-stranded RNA virus HcRNAV isolates.
abstract: HcRNAV is a single-stranded RNA (ssRNA) virus that specifically infects the bivalve-killing dinoflagellate, Heterocapsa circularisquama. HcRNAV strains are grouped into 2 types (UA and CY), based on intra-species host specificity and the amino acid sequence of the major capsid protein (MCP). In the present study, we report the isolation of novel HcRNAV clones (n=51) lytic to the H. circularisquama strains, HU9433-P, HCLG-1, 05HC05 and 05HC06. HcRNAV34, HcRNAV109, HcRNAV641, and HcRNAV659, which displayed lytic activity against the strains, HU9433-P, HCLG-1, 05HC05, and 05HC06, respectively, were selected as typical virus clones and were intensively examined. The infection intensity of each host-virus combination was analyzed by examining the algicidal activity, detecting the intracellular replication of the viral RNA as well as the appearance of host cells with a morphologically abnormal nucleus post-infection. Interestingly, the strains, 05HC05 and 05HC06, were markedly sensitive to HcRNAV641 and HcRNAV659, respectively. Tertiary structural modeling predicted 4 unique amino acid (aa) substitutions in HcRNAV659-MCP to be exposed to an ambient water environment, which contributed towards determining its infection specificity. Neighbor-joining analysis of MCP aa sequences from HcRNAV clones revealed 3 clades, namely, the CY type and the UA1 and UA2 subtypes. The HcRNAV clones lytic to HCLG-1 (ex. HcRNAV109), HU9433-P and 05HC05 (ex. HcRNAV34), and 05HC06 (ex. HcRNAV659) were categorized into CY type, UA1 and UA2 subtypes, respectively. The present study highlights the complexity of the H. circularisquama-HcRNAV host-virus system, i.e., clonal variation, microbial control, and ecology in a natural algal population.
authors.affiliation: National Research Institute of Fisheries and Environment of Inland Sea, Hiroshima, Japan.
authors.forename: Natsuko
authors.initials: N
authors.lastname: Nakayama
authors.forename: Akihiro
authors.initials: A
authors.lastname: Fujimoto
authors.forename: Hisae
authors.initials: H
authors.lastname: Kawami
authors.forename: Yuji
authors.initials: Y
authors.lastname: Tomaru
authors.forename: Naotsugu
authors.initials: N
authors.lastname: Hata
authors.forename: Keizo
authors.initials: K
authors.lastname: Nagasaki
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D049872:Bivalvia / Q000469:parasitology*; D036022:Capsid Proteins / Q000737:chemistry / Q000235:genetics; D004141:Dinoflagellida / Q000502:physiology* / Q000821:virology*; D054884:Host-Pathogen Interactions; D008969:Molecular Sequence Data; D010802:Phylogeny; D012328:RNA Viruses / Q000235:genetics / Q000502:physiology*; D016415:Sequence Alignment
chemical_list: D036022:Capsid Proteins