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

Lateral gene transfer refers to the movement of genetic information from on e genome to another, and the integration of that foreign DNA into its new g enetic 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 proces s 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, he terotrophic flagellates that are closely related to kinetoplastids and eugl enoids. Two distinct classes of diplonemid GAPDH genes were found in diplon emids, however, neither class is closely related to any other euglenozoan G APDH. One diplonemid GAPDH is related to the cytosolic gapC of eukaryotes, although not to either euglenoids or kinetoplastids, and the second is rela ted to cyanobacterial and proteobacterial gap3. The bacterial gap3 gene in diplonemids provides one of the most well-supported examples of lateral gen e transfer from a bacterium to a eukaryote characterised to date, and may i ndicate that diplonemids have acquired a novel biochemical capacity through lateral transfer.