Anaeramoebae are a divergent lineage of eukaryotes that shed light on the transition from anaerobic mitochondria to hydrogenosomes

Abstract

Anaeramoebae are a divergent lineage of eukaryotes that shed light on the transition from anaerobic mitochondria to hydrogenosomes Highlights d Deep transcriptomic sequencing of two new anaerobic metamonads d The Anaeramoebae represents a new principal lineage of Metamonada d Anaeramoebae are free-living relatives of the parasitic parabasalids

Reduced mitochondria provide an essential function for the cytosolic methionine cycle

“…PaPyr7077 represents a putative homologue of Tim44, a component of the PAM motor complex (Neupert and Brunner, 2002). The presence of Tim44 has been reported in other Metamonads (Beltrán et al, 2013; Leger et al, 2017; Pyrihová et al, 2018; Rada et al, 2011; Schneider et al, 2011; Stairs et al, 2021) and our phylogenetic reconstruction pinpoints the relationship of PaPyr7077 to Tim44 of Trichomonas vaginalis (Figure S4). Members of the Tim17/22/23 protein family have been identified in all eukaryotes as components of protein translocation complexes in the mitochondrial inner membrane – TIM23 complex facilitates protein import into the matrix, while TIM22 mediates protein insertion into the mitochondrial inner membrane (Chaudhuri et al, 2020; Rassow et al, 1999; Žárský and Doležal, 2016).…”

“…At neutral pH, the N-termini of most proteins were calculated to contain a weak positive net charge close to 1.0 and only in two proteins, mitochondrial membrane carrier 4 (PaPyr9238) and Pex3 (PaPyr5495), the value was above 3.0. Values are similar to those in T. vaginalis hydrogenosomal proteins but lower than those in yeast, human, or Anaeramoeba , where they fall in the range 3.0-4.0 (Garg and Gould, 2016; Garg et al, 2015; Stairs et al, 2021). This suggests that the positive charge of N-termini has low importance for the delivery of proteins into P. pyriformis MRO and that this MRO likely displays weak or no membrane potential.…”

“…and Pex3 (PaPyr5495), the value was above 3.0. Values are similar to those in T. vaginalis hydrogenosomal proteins but lower than those in yeast, human, or Anaeramoeba, where they fall in the range 3.0-4.0 (Garg and Gould, 2016;Garg et al, 2015;Stairs et al, 2021). This suggests that the positive charge of N-termini has low importance for the delivery of proteins into P.…”

“…Leger et al (2017) predicted GCS and SHMT in the MROs of all free-living Fornicates and proposed that glycine degradation correlates with their lifestyle for an unclear reason. Moreover, GCS and SHMT were predicted to be localised in the MRO of other free-living Metamonada, such as Barthelona sp ., Anaeramoeba flamelloides and A. ignava (Stairs et al, 2021; Yazaki et al, 2020) and free-living Archamoebae Mastigamoeba balamuthii and Pelomyxa schiedtii (Nývltová et al, 2015; Záhonová et al, 2022). Our data are consistent with these observations and provide a potential reason for maintaining GCS and SHMT in these organelles – production of folates to supply cytosolic 1C metabolism.…”

“…Several MRO proteins with weak homology to database representatives were present in the LOPIT dataset, and most of them enrich the inventory of membrane proteins responsible for organelle biogenesis. The protein translocation machinery of P. pyriformis appears to be reduced compared to Trichomonas vaginalis and anaeramoebids (Makki et al, 2019; Rada et al, 2011; Stairs et al, 2021), however, most of the core components were detected in the transcriptome or genome (Tom40, Sam50, Tim17, Tim23, Tim14, Cpn10, Cpn60, MPPαβ) (Zubáčová et al, 2013) and in our study, we further identified distant homologues of Tom22 (PaPyr4978), Tim44 (PaPyr7077), an extremely divergent Tim22 protein (PaPyr1418), and DnaK (PaPyr2959). The presence of a tail-anchored (TA) Rho GTPase Miro should be noted with particular interest.…”