Comparative analysis of K+-channels from two Chlorella species: information on their role in endosymbiosis and on the origin of viral K+-channels

• Applicant: Professor Dr. Gerhard Thiel
• Subject Area: Plant Biochemistry and Biophysics ; Plant Physiology
• Term: from 2008 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 71861630

• Final Report Year: 2011

Final Report Abstract

Many viruses including HIV and influenza A code for proteins with channel properties. These channels have auxiliary functions in infection and replication of these viruses. The viral proteins share generally no structural similarity with channels from pro- and eukaryotes. The exceptions are the large dsDNA viruses, which infect algae. They code for K+ channels with all the structural hallmarks of pro- and eukaryotic potassium channels. The results of the present project show that these viruses are not only the source of channels; surprisingly they also code for functional orthologs of K+ transporters and Ca2+ ATPases known from pro- and eukaryotes. The complete genomic sequencing of the hosts of one of the viruses reveals the presence of six putative genes for K+ channels in the alga Chlorella NC64A (now called Chlorella variabilis). A bioinformatics comparison of viral and host channels shows that they are clearly separated on different branches of a phylogenetic tree. These data support the view that the viral genes were not acquired by molecular piracy from the host. The same conclusion can be drawn for the K+ transporter genes. The long evolutionary separation between the Chlorella viruses and the Ectocarpus virus EsV-1, which all code for very similar K+ channels, stresses that the respective viral genes must have a very old evolutionary history. Collectively the data support a recent idea in evolutionary biology, which considers viruses as important elements in evolution. They are probably not only important as a shuttle for lateral gene transfer but also as a source of genes. The K+ channels in prokaryotes and eukaryotes could be among these genes.

Publications

• (2010) A functional Calcium transporting ATPase encoded by Chlorella viruses. J. Gen. Virol. 91:2620-2629
  Bonza, M.C., Martin, H., Kang, M., Lewis, G., Greiner, T., Giacometti, S., Van Etten, J.L., De Michelis, M.I., Thiel. G., Moroni A.
  
• (2011). lon channel activity of HIV-1 Vpu is dispensable for counteraction of CD317. Virology 416:75-85
  Bolduan, S., Votteler, J., Lodermeyer, V., Greiner, T., Koppensteiner, H., Schindler, M., Thiel, G., Schubert, U.