In the March 7 issue of the journal Science, molecular evolutionist Jeff Palmer and botanist Charles Delwiche of Indiana University, along with parasitologists Sabine Kohler and David Roos of the University of Pennsylvania and their colleagues report that chloroplast-like plastids recently found in a group of single-celled parasites apparently originated in algal cells that were engulfed by the parasites' ancestors.
The functions of the plastids in the parasites are unknown (they no longer perform photosynthesis) but the fact they remained after being engulfed suggests they play an important role in the cell. And because the cells of humans and other mammalian hosts of the parasites don't have such chloroplast-like plastids, they are likely targets for drug therapies.
It is commonly understood that eukaryotic cells (those of animals, plants, fungi, and protists) acquired some of their most important components, such as the photosynthesizing chloroplast, when they engulfed simpler bacterial cells. The study conducted by Palmer, Roos and six co-authors supports the idea that a more complex cell, in this case an algal cell, can be taken up by, and became an integral part of, another cell. In addition to the implications for new drug treatments, the findings also suggest that the process of cells engulfing other cells may have been more common in molecular evolution than previously suspected.