Massive invasion of organellar DNA drives nuclear genome evolution in Toxoplasma

This study reveals how DNA located in cellular compartments called organelles can be transferred to the nucleus of the cell and inserted into the nuclear genome of the apicomplexan parasite Toxoplasma. Insertions alter the DNA sequence and may lead to significant changes in how genes function. Unexpectedly, we found that the human protist pathogen Toxoplasma gondii and closely related species have the largest observed organellar genome fragment content (>11,000 insertions comprising over 1 Mb of DNA) inserted into their nuclear genome sequence despite their compact 65-Mb nuclear genome. Insertions are occurring at a rate that makes them a significant mutational force that deserves further investigation when examining causes of adaptation and virulence of these parasites.