Reductive Evolution of the Mitochondrial Processing Peptidases of the Unicellular Parasites Trichomonas vaginalis and Giardia intestinalis

Mitochondrial processing peptidases are heterodimeric enzymes (α/βMPP) that play an essential role in mitochondrial biogenesis by recognizing and cleaving the targeting presequences of nuclear-encoded mitochondrial proteins. The two subunits are paralogues that probably evolved by duplication of a gene for a monomeric metallopeptidase from the endosymbiotic ancestor of mitochondria. Here, we characterize the MPP-like proteins from two important human parasites that contain highly reduced versions of mitochondria, the mitosomes of Giardia intestinalis and the hydrogenosomes of Trichomonas vaginalis. Our biochemical characterization of recombinant proteins showed that, contrary to a recent report, the Trichomonas processing peptidase functions efficiently as an α/β heterodimer. By contrast, and so far uniquely among eukaryotes, the Giardia processing peptidase functions as a monomer comprising a single βMPP-like catalytic subunit. The structure and surface charge distribution of the Giardia processing peptidase predicted from a 3-D protein model appear to have co-evolved with the properties of Giardia mitosomal targeting sequences, which, unlike classic mitochondrial targeting signals, are typically short and impoverished in positively charged residues. The majority of hydrogenosomal presequences resemble those of mitosomes, but longer, positively charged mitochondrial-type presequences were also identified, consistent with the retention of the Trichomonas αMPP-like subunit. Our computational and experimental/functional analyses reveal that the divergent processing peptidases of Giardia mitosomes and Trichomonas hydrogenosomes evolved from the same ancestral heterodimeric α/βMPP metallopeptidase as did the classic mitochondrial enzyme. The unique monomeric structure of the Giardia enzyme, and the co-evolving properties of the Giardia enzyme and substrate, provide a compelling example of the power of reductive evolution to shape parasite biology

Genetic variability of the neogregarine apicystis bombi, an etiological agent of an emergent bumblebee disease

The worldwide spread of diseases is considered a major threat to biodiversity and a possible driver of the decline of pollinator populations, particularly when novel species or strains of parasites emerge. Previous studies have suggested that populations of introduced European honeybee (Apis mellifera) and bumblebee species (Bombus terrestris and Bombus ruderatus) in Argentina share the neogregarine parasite Apicystis bombi with the native bumblebee (Bombus dahlbomii). In this study we investigated whether A. bombi is acting as an emergent parasite in the non-native populations. Specifically, we asked whether A. bombi, recently identified in Argentina, was introduced by European, non-native bees. Using ITS1 and ITS2 to assess the parasite's intraspecific genetic variation in bees from Argentina and Europe, we found a largely unstructured parasite population, with only 15% of the genetic variation being explained by geographic location. The most abundant haplotype in Argentina (found in all 9 specimens of non-native species) was identical to the most abundant haplotype in Europe (found in 6 out of 8 specimens). Similarly, there was no evidence of structuring by host species, with this factor explaining only 17% of the genetic variation. Interestingly, parasites in native Bombus ephippiatus from Mexico were genetically distant from the Argentine and European samples, suggesting that sufficient variability does exist in the ITS region to identify continent-level genetic structure in the parasite. Thus, the data suggest that A. bombi from Argentina and Europe share a common, relatively recent origin. Although our data did not provide information on the direction of transfer, the absence of genetic structure across space and host species suggests that A. bombi may be acting as an emergent infectious disease across bee taxa and continents

Biología de nidificación e insectos enemigos asociados a la abeja exótica Megachile (Eutricharaea) concinna (Hymenoptera: Megachilidae) en Argentina

The nesting biology of the exotic bee Megachile (Eutricharaea) concinna Smith, 1879 and its negative interactions with other insects were studied. Trap nests made of wood were located in an urban environment in Buenos Aires province, Argentina, and surveyed during 26 months. The lifecycle and the structure of the nest of M. concinna are described. We also report six interactions between this bee and native and exotic parasitoids and cleptoparasites. The species Baryscapus megachilidis is recorded here for the first time in Argentina.Se estudió la biología de nidificación y las interacciones negativas con otros insectos de la abeja exótica Megachile (Eutricharaea) concinna Smith, 1879. Para este estudio se utilizaron trampas nidos construidas con madera colocadas en un ambiente urbano en la provincia de Buenos Aires, Argentina los cuales fueron seguidos durante 26 meses. Se describe el ciclo de vida y la estructura de los nidos de M. conncina. Registramos la presencia de seis interacciones entre esta abeja y parasitoides y cleptoparásitos exóticos y nativos. Se cita además por primera vez la presencia de Baryscapus megachilidis en Argentina.Fil: Alvarez, Leopoldo Jesús. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Entomología; ArgentinaFil: Lucia, Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Entomología; ArgentinaFil: Aquino, Daniel Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Entomología; ArgentinaFil: Ramello, Pablo José. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Entomología; ArgentinaFil: Abrahamovich, Alberto Horacio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Entomología; Argentin