Complete Genome Sequence of a Phycodnavirus, Heterosigma Akashiwo Virus Strain 53

We report the complete genome sequence of Heterosigma akashiwo virus strain 53. The virus is a member of the Phycodnaviridae, one of the families regarded as giant double-stranded DNA viruses. The 274,793-bp genome contained 246 protein-coding and 3 tRNA-coding sequences.

Here, we report the complete genome sequence of HaV strain 53, originally isolated from the Itsukaichi Fishing Port in Hiroshima Bay, Japan (27). HaV53 was propagated on H. akashiwo, and viral particles were collected by adding polyethylene glycol 8000 at a final concentration of 6% to the culture medium containing lysed hosts, followed by centrifugation of the mixture at 21,000 ϫ g. The HaV53 DNA was extracted from the purified HaV53 particles by proteinase K digestion, followed by chloroform-isoamyl alcohol treatment and ethanol precipitation. A genomic DNA library was prepared using a Nextera XT DNA sample prep kit (Illumina), and 24 million reads were generated by HiSeq 2500 using the 100-bp paired-end mode. Reads with high-quality scores (Ͼ28) were assembled using Platanus (28), yielding five high-sequence-coverage contigs (73.2, 58.5, 57.6, 41.2, and 33.2 kb) derived from HaV and numerous low-coverage contigs derived from the host DNA. Gaps between the contigs were filled by sequencing of gap-spanning PCR products using ABI3130xl and Illumina MiSeq sequencers. The accuracy of assembly was confirmed by mapping the paired-end reads to the final assemblage using BWA (29).
The genome of HaV53 was 274,792 bp in size, and the AϩT content was 69.6%. It was predicted to contain 247 open reading frames (ORFs) by GeneMarkS (30) and 3 tRNAs by tRNAscan-SE (31). Among the 246 ORFs, 105 had significant hits in the NCBI nonredundant protein database (BlastX, searched with E value Ͻ10 -5 ); 4 had best hits to the sequences previously reported for HaV strain 01 (accession numbers BAE06835.1, BAE06251.1, BAB69884.1, and BAB69883.1) and 23 has best hits to other Phycodnaviridae members. The 105 ORFs coded for polypeptides with a variety of functions, including gene regulation, metabolism, signal transduction, and ubiquitin-related protein regulation. As the sequence of HaV53 reported here is the first complete genome sequence of HaV, it would help advance research on Phycodnaviridae.
Accession number(s). The annotated genome sequence of HaV53 has been deposited in DDBJ/EMBL/GenBank under the accession number KX008963.

ACKNOWLEDGMENTS
This work was supported by KAKENHI (grant 26291092), and Priority Areas "Comprehensive Genomics" (grant 221S0002) provided by the Ministry of Education, Culture, Sports, Science and Technology of Japan to S.U.
We thank Keizo Nagasaki (currently in Kochi University) and Fisheries Research Agency for providing us with HaV53 and its host H. akashiwo strain H93616.

FUNDING INFORMATION
This work, including the efforts of Shoko Ueki, was funded by the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) (26291092).
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.