Archaeal viruses: the dark matter of the virosphere – Biologisk Institut - Københavns Universitet

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Archaeal viruses: the dark matter of the virosphere

Speaker: Dr. Mart Krupovic, Institut Pasteur, Paris

Host: Associate Professor Qunxin She, Section for Functional Genomics

Abstract
The origin of viruses is an outstanding question in Biology. A unique feature of the virus state, which distinguishes viruses from all other types of mobile genetic elements, such as plasmids and transposons, is the ability to form virions. Thus, the origin of viruses is likely to be concomitant with the origin of the major virion proteins. In my talk, I will present evidence from comprehensive sequence and structure analysis of major virion proteins across the virosphere which indicates that these proteins evolved on about 20 independent occasions. In many cases, the origins of the capsid proteins can be traced to diverse ancestral proteins of cellular organisms. However, for ~20% of viral taxa, the information on structural folds and provenance of the capsid proteins is still lacking. Interestingly, many of the viruses in the latter category infect hyperthermophilic archaea. Furthermore, global comparative genomic analyses have indicated that most groups of dsDNA viruses associated with bacteria and eukatyotes are evolutionarily connected within a large modular network, whereas archaeal viruses remain disconnected. Consistently, recent studies have revealed novel, often very simple, structural solution employed by archaeal viruses to protect their genomes and mediate interactions with the hosts in the harsh environmental conditions of their natural habitats. Collectively, these results shed light on the global structural diversity of the viral world and illuminate the origins of certain virus groups but, at the same time, indicate that archaeal viruses form a distinct part of the virosphere which remains largely unexplored.