RESUMO
We have performed a genomic characterization of a kinetoplastid protist living within the amoebozoan Neoparamoeba pemaquidensis. The genome of this "Ichthyobodo-related organism" was found to be unexpectedly large, with at least 11 chromosomes between 1.0 and 3.5 Mbp and a total genome size of at least 25 Mbp.
Assuntos
Amebozoários/genética , Kinetoplastida/genética , Amebozoários/microbiologia , DNA de Cinetoplasto/genética , Genoma , Cariótipo , Kinetoplastida/microbiologia , Dados de Sequência Molecular , Filogenia , Análise de Sequência de DNA , SimbioseRESUMO
For a vast majority of living organisms, haem is an essential compound that is synthesised through a conserved biosynthetic pathway. However, certain organisms are haem auxotrophs and need to obtain this molecule from exogenous sources. Kinetoplastid flagellates represent an interesting group of species, as some of them lost the complete pathway while others possess only the last three biosynthetic steps. We decided to supplement a current view on the phylogeny of these important pathogens with the expected state of haem synthesis in representative species. We propose a scenario in which the ancestor of all trypanosomatids was completely deficient of the synthesis of haem. In trypanosomatids other than members of the genus Trypanosoma, the pathway was partially rescued by genes encoding enzymes for the last three steps, supposedly obtained by horizontal transfer from a gamma-proteobacterium. This event preceded the diversification of the non-Trypanosoma trypanosomatids. Later, some flagellates acquired a beta-proteobacterial endosymbiont which supplied them with haem precursors. On the other hand, the medically important trypanosomes have remained fully deficient of haem synthesis and obtain this compound from the host.
Assuntos
Evolução Biológica , Heme/biossíntese , Kinetoplastida/metabolismo , Kinetoplastida/microbiologia , Gammaproteobacteria/fisiologia , Kinetoplastida/classificação , Kinetoplastida/genética , Filogenia , Proteínas de Protozoários/genética , Proteínas de Protozoários/metabolismo , SimbioseRESUMO
A double-stranded RNA (ds RNA) with an approximate size of 4.7 kb was found in 6 Phytomonas isolates specifically associated with plant pathogenicity in coconut trees ("Hartrot" disease) and oil palm ("Marchitez sorpressiva" disease). This ds RNA was not detected in 10 non-pathogenic Phytomonas isolates from different lactiferous plants or in the insect trypanosomatids Crithidia and Herpetomonas. Analysis by electron microscopy of a sucrose gradient fraction containing this ds RNA revealed virus-like particles.
