The Genome of Naegleria gruberi Illuminates Early Eukaryotic Versatility

Abstract

Genome sequences of diverse free-living protists are essential for understanding eukaryotic evolution and molecular and cell biology. The free-living amoeboflagellate Naegleria gruberi belongs to a varied and ubiquitous protist clade (Heterolobosea) that diverged from other eukaryotic lineages over a billion years ago. Analysis of the 15,727 protein-coding genes encoded by Naegleria's 41 Mb nuclear genome indicates a capacity for both aerobic respiration and anaerobic metabolism with concomitant hydrogen production, with fundamental implications for the evolution of organelle metabolism. The Naegleria genome facilitates substantially broader phylogenomic comparisons of free-living eukaryotes than previously possible, allowing us to identify thousands of genes likely present in the pan-eukaryotic ancestor, with 40% likely eukaryotic inventions. Moreover, we construct a comprehensive catalog of amoeboid-motility genes. The Naegleria genome, analyzed in the context of other protists, reveals a remarkably complex ancestral eukaryote with a rich repertoire of cytoskeletal, sexual, signaling, and metabolic modules.

The Giardia cell cycle progresses independently of the Anaphase Promoting Complex

“…If the latter is true, then the cell cycle in the LECA did not use ubiquitination to regulate cell cycle progression. This must remain an open question for now since its resolution is dependent on how phylogenomic trees of eukaryotic life are rooted (Fritz-Laylin et al, 2010).…”

“…Giardia is a member of the Diplomonads, considered one of the most basal and evolutionary distant eukaryotes (Ciccarelli et al, 2006;FritzLaylin et al, 2010) and thus of considerable interest for the study of basic cell biology. It remains unclear if the Diplomonads are part of a group, including the Parabasalids and the Oxymonads (referred to as the POD group), that diverged directly from the last common eukaryotic ancestor (Fritz-Laylin et al, 2010) or if a group termed the Excavates, diverged first then split into several groups including the POD group (Ciccarelli et al, 2006).…”

Evolution of networks and sequences in eukaryotic cell cycle control

“…The homology between the plant KRP1 and animal p27 is likely indicative of monophyly; it is not clear that the Sic1/Rum1 alignment to KRP1/p27 is any better than would be expected by chance. [106]. Any novel and initially simple circuit will probably have undergone substantial evolution prior to its more elaborate implementation in the LCA of multiple descendant lines.…”

Filamin structure, function and mechanics: are altered filamin-mediated force responses associated with human disease?

“…The FLNs are found in animals, amoeba and at least one excavate, suggesting that FLNs arose early in evolutionary terms in ancestral eukaryotes that utilised an actin-based amoeboid motility mechanism (Fritz-Laylin et al 2010). The human genome contains three FLN genes, filamin A (FLNA), FLNB and FLNC (Stossel et al 2001).…”