Viruses control algae behavior with stolen protein, study finds

Channelrodopsins are an essential tool used by neuroscience and optogenetics.

Viruses (antennae) are seen attacking algae. (photo credit: COURTESY TECHNION)
Viruses (antennae) are seen attacking algae.
(photo credit: COURTESY TECHNION)
For the first time, scientists from the Technion-Israel Institute of Technology have found that marine giant viruses could be stealing proteins from algae and reinfecting them with it as a means to control their movements and behavior.
The study itself focuses on rhodopsins, a type of protein used by single-cell organisms to both harvest and detect light. One of these rhodopsins, known as channelrodopsins (ChRs), was first found as green algal proteins, and were believed to have originated as part of a giant marine virus that infects algae.
ChRs works by directly translating light into ion fluxes on cell membranes. They are often used by neuroscientists as part of optogenetics to both simulate and inhibit neurons through light. The field of optogenetics itself has essentially revolutionized the neuroscience research, and is widely considered to be the most effective means to activate specific cells and study their impact on the overall body.
But when Technion's Prof. Oded Béjà and postdoctoral researcher Dr. Andrey Rozenberg began studying ChRs further through a metagenomic analysis of the seawater, they ended up discovering a previously unknown family of ChRs. And these findings, published in the academic journal Current Biology, shows that widespread scientific consensus on the origin of ChRs may have been mistaken.
“Our quest led us to the conclusion that the origin of these channelrhodopsins is not in the virus but in the algae that they infect, and we estimate that at some point in the evolutionary process, a giant alga-infecting virus 'stole' a channelrhodopsin gene for its own benefit,” Béjà said in a statement. 
While it remains unclear why exactly viruses carry ChR genes, it is most likely that they use it essentially control their hosts.
“We hypothesize that the viruses can manipulate the host’s swimming behavior, thus controlling its light responses and directing it to locations where irradiation conditions are favorable for the virus.”