Name: Christopher Brown

Email: cbrown@marine.rutgers.edu

Author: Christopher M. Brown, Patricia M. Woodruff, Kay D. Bidle

Author affiliation: Rutgers Institute of Marine and Coastal Science

Abstract title: Virus-Induced Programmed Cell Death in Aureococcus anophagefferens

Absstract:

Aureococcus anophagefferens (Pelagophyceae) is the harmful alga responsible for brown-tide in eastern US coastal areas. We are examining a putative link between infection by phycodnavirus AaV and programmed cell death (PCD) in the demise of populations of A. anophagefferens. PCD is a coordinated cellular self-destruction that occurs in response to various stresses, including nutrient limitation, age, and oxidative stress. Infection of A. anophagefferens by AaV at multiplicities of infection (m.o.i.) of up to 20 leads to a complete lysis of cultures within 24 hours, concomitant with a burst of approximately 170 viruses per cell and a sharp increase in virus concentration. Higher multiplicities of infection (>25) lead to similar declines in cell numbers. However, yields of new viruses during these high m.o.i. infections are severely dampened or even abolished, suggestive of a PCD-driven lytic pathway that is independent of virus production. The fully sequenced genome of A. anophagefferens reveals an orthologue of a cysteine protease, or caspase (metacaspase) sequence as well as putative autophagy-related (ATG) sequences. The detection of age-related upregulation of caspase-lke activity suggests that autocatalytic pathways are indeed active in this unicellular phytoplankton. We are currently monitoring cultures during infection to determine whether lysis of cultures is accompanied by hallmarks of PCD such as caspase-like activity and enhanced presentation of phosphatidyl serine (PS) to the outside of cell membranes.