Diplonemid glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and prokaryote-to-eukaryote lateral gene transfer.

Lateral gene transfer refers to the movement of genetic information from one genome to another, and the integration of that foreign DNA into its new genetic environment. There are currently only a few well-supported cases of prokaryote-to-eukaryote transfer known that do not involve mitochondria or plastids, but it is not clear whether this reflects a lack of such transfer events, or poor sampling of diverse eukaryotes. One gene where this process is apparently active is glyceraldehyde-3-phosphate dehydrogenase (GAPDH), where lateral transfer has been implicated in the origin of euglenoid and kinetoplastid genes. We have characterised GAPDH genes from diplonemids, heterotrophic flagellates that are closely related to kinetoplastids and euglenoids. Two distinct classes of diplonemid GAPDH genes were found in diplonemids, however, neither class is closely related to any other euglenozoan GAPDH. One diplonemid GAPDH is related to the cytosolic gapC of eukaryotes, although not to either euglenoids or kinetoplastids, and the second is related to cyanobacterial and proteobacterial gap3. The bacterial gap3 gene in diplonemids provides one of the most well-supported examples of lateral gene transfer from a bacterium to a eukaryote characterised to date, and may indicate that diplonemids have acquired a novel biochemical capacity through lateral transfer.