Date |
2:00pm Jul 23, 2019 |
Speaker |
Dr. Nigel Grimsley
CNRS UMR 7232, BIOM, Avenue du Fontaulé, 66650 Banyuls-sur-Mer, France |
Title |
Prasinovirus infection is firstly furtive, then furious, but phytoplankton fight
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Abstract |
Prasinoviruses are large dsDNA viruses commonly found in aquatic systems
worldwide, where they can infect and lyse unicellular prasinophyte algae
such as Ostreococcus. In diurnal 12 h day ? 12 h dark cultures,
transcriptome analyses revealed that prasinovirus gene expression was
low in the day but much higher in the night, the majority of cells
lysing the following morning. Host susceptibility is virus
strain-specific, but resistance of susceptible Ostreococcus tauri
strains to a virulent virus arises frequently. In clonal resistant lines
that re-grew, viruses were usually present for many generations, and
genes in a 150 kb-long chromosome 19 region were strongly
over-expressed. Here, by serial dilutions of cultures at the time of
inoculation, we estimated the frequency of resistant cells arising in
virus-challenged O. tauri cultures to be 10E-3-10E-4 of the inoculated
population. Regrowth of virus-resistant cells in O. tauri cultures that
had been inoculated with OtV5 showed visible re-greening in less than 5
days, and by 8 days post-inoculation karyotypic changes in the host
chromosome 19 were detectable. Virus adsorption to host cells was
strain-specific and resistant cell lines showed a modified spectrum of
host-virus specificities.
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