Name: Yukari Takashima

Email: yukariyo@jamstec.go.jp

Author: Yukari Takashima 1

Author affiliation: Takashi Yoshida 2, Mitsuhiro Yoshida 3, Hiroyuki Ogata 4, Shingo Hiroishi 1, Keizo Nagasaki 5 1) Department of Marine Bioscience, Fukui Prefectural University, Fukui, Japan 2) Department of Agriculture, Kyoto University, Kyoto, Japan 3) National Research Institute of Fisheries Science, Fisheries Research Agency, Kanagawa, Japan 4) Information Génomique et Structule, CNRS, France 5) National Research Institute of Fisheries and Environment of Inland Sea, Fisheries Research Agency, Hiroshima, Japan

Abstract title: Transcription of the phycobilisome degradation gene in cyanophage Ma-LMM01 infecting Microcystis aeruginosa

Absstract:

Ma-LMM01 is a cyanophage infecting Microcystis aeruginosa that forms toxic blooms in eutrophic freshwaters. The linear, circularly permuted, 162,109 bp double-stranded DNA genome of Ma-LMM01 contains 184 open reading frames and 2 tRNAs. We found a homologue of the nblA gene involved in the degradation of the major light harvesting complex, the phycobilisomes (PBS). This is the first identification of a homologue of nblA in a viral genome. The Ma-LMM01 NblA sequence has two conserved amino acid residues involved in binding to phycobiliprotein, suggesting that Ma-LMM01 NblA is likely to be functional. In this study, we examined temporal transcription of Ma-LMM01-encoded nblA during an infection using quantitative real-time PCR. Transcripts of the phage nblA appeared at 1 h post infection, reached a maximum at 3 h, and remained at the same level until the end of the infection. No significant changes of host nblA transcripts in phage-infected cells were observed. We also found the absorption peak corresponding to phycocyanin (625 nm) that is major component of PBS decreased progressively during the infection. We hypothesize that the PBS degradation induced by the phage nblA may provide fitness advantages for the phage as follows: (i) the minimization of light absorption to prevent the host photodamage during phage replication and (ii) the PBS utilization as an important source of amino acids for phage protein synthesis.