Identification and characterisation of a cryptic Golgi complex in Naegleria gruberi

Although the Golgi complex has a conserved morphology of flattened stacked cisternae in most eukaryotes, it has lost the stacked organisation in several lineages, raising the question of what range of morphologies is possible for the Golgi. In order to understand this diversity, it is necessary to characterise the Golgi in many different lineages. Here, we identify the Golgi complex in Naegleria, one of the first descriptions of an unstacked Golgi organelle in a non-parasitic eukaryote, other than fungi. We provide a comprehensive list of Golgi-associated membrane trafficking genes encoded in two species of Naegleria and show that nearly all are expressed in mouse-passaged N. fowleri cells. We then study distribution of the Golgi marker (Ng)CopB by fluorescence in Naegleria gruberi, identifying membranous structures that are disrupted by Brefeldin A treatment, consistent with Golgi localisation. Confocal and immunoelectron microscopy reveals that NgCOPB localises to tubular membranous structures. Our data identify the Golgi organelle for the first time in this major eukaryotic lineage, and provide the rare example of a tubular morphology, representing an important sampling point for the comparative understanding of Golgi organellar diversity. This article has an associated First Person interview with the first author of the paper.