eEF-1 is a eukaryotic elongation factor.
Various species of green algae, red algae, chromalveolates, and fungi lack the EF-1α gene but instead possess a related gene called EFL (elongation factor-like). Although its function has not been studied in depth, it appears to be similar to EF-1α.
Only two organisms are known to have both EF-1α and EFL: the fungus Basidiobolus and the diatom Thalassiosira. The evolutionary history of EFL is unclear. It may have arisen one or more times followed by loss of EFL or EF-1α. The presence in three diverse eukaryotic groups (fungi, chromalveolates, and archaeplastida) is supposed to be the result of two or more horizontal gene transfer events.