Name: Assaf Vardi

Email: vardi@marine.rutgers.edu

Author: *Assaf Vardi1, Benjamin Van Mooy2, Helen Fredricks2, Kim Popendorf 2, Justin Ossolinski2, Liti Haramaty1, and Kay Bidle1

Author affiliation: 1. Environmental Biophysics and Molecular Ecology Group, Institute of Marine and Coastal Sciences, Rutgers University, 71 Dudley Road, New Brunswick, NJ 08901 USA. 2. Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, USA. * Presenting author

Abstract title: Viral Sphingolipids Biomimic Infection via induction of Coccolithophores Programmed Cell Death

Absstract:

Emiliania huxleyi is a cosmopolitan coccolithophore forming massive blooms, routinely infected and terminated by lytic viruses. Coccolithoviruses were recently shown to induce and regulate host programmed cell death (PCD) as part of their lytic pathway. The genome sequence of E. huxleyi virus 86 contains a cluster of biosynthetic genes for sphingolipids, never been described before in any known viral genome. Sphingolipids play a pivotal role in regulating signalling, defense and PCD in animals and plants. We characterized the lipidome of various susceptible and resistant E. huxleyi strains in response to viral infection. We detected a remarkable de novo production of cerebroside-like glycosphingolipids in the sensitive E. huxleyi strains during the lytic phase, using high performance liquid chromatography/mass spectrometry. These particular glycosphingolipids were not detected in resistant or uninfected strains. Addition of these purified cerebrosides from infected cells induced hallmarks of PCD in E. huxleyi, without the presence of the lytic viruses, biomimicking viral infection. Identical cerebroside signatures were heavily enriched in the purified virus fraction strongly suggesting that these sphingolipids are an inherent component of the virion membranes and essential for viral replication cycle. We revealed these unique lipid signatures in natural coccolithophores from the north Atlantic and therefore propose they can act as novel biomarkers of viral infection in the marine environment. This is the first characterization of sphingolipids as infochemicals that mediate virus-host interactions in marine phytoplankton.