Leishmania parasites cause a broad spectrum of clinical disease. Here we report the sequencing of the genomes of two species of Leishmania: Leishmania infantum and Leishmania braziliensis. The comparison of these sequences with the published genome of Leishmania major reveals marked conservation of synteny and identifies only ∼200 genes with a differential distribution between the three species. L. braziliensis, contrary to Leishmania species examined so far, possesses components of a putative RNA-mediated interference pathway, telomere-associated transposable elements and spliced leader–associated SLACS retrotransposons. We show that pseudogene formation and gene loss are the principal forces shaping the different genomes. Genes that are differentially distributed between the species encode proteins implicated in host-pathogen interactions and parasite survival in the macrophage.
Current understanding of the higher order systematics of eukaryotes relies largely on analyses of the small ribosomal subunit RNA (SSU rRNA). Independent testing of these results is still limited. We have combined the sequences of four of the most broadly taxonomically sampled proteins available to create a roughly parallel data set to that of SSU rRNA. The resulting phylogenetic tree shows a number of striking differences from SSU rRNA phylogeny, including strong support for most major groups and several major supergroups.
Most cultivated and characterized eukaryotes can be confidently assigned to one of eight major groups. After a few false starts, we are beginning to resolve relationships among these major groups as well. However, recent developments are radically revising this picture again, particularly (i) the discovery of the likely antiquity and taxonomic diversity of ultrasmall eukaryotes, and (ii) a fundamental rethinking of the position of the root. Together these data suggest major gaps in our understanding simply of what eukaryotes are or, when it comes to the tree, even which end is up.
A class of UDP-glycosyltransferases (UGTs) defined by the presence of a C-terminal consensus sequence is found throughout the plant and animal kingdoms. Whereas mammalian enzymes use UDP-glucuronic acid, the plant enzymes typically use UDP-glucose in the transfer reactions. A diverse array of aglycones can be glucosylated by these UGTs. In plants, the aglycones include plant hormones, secondary metabolites involved in stress and defense responses, and xenobiotics such as herbicides. Glycosylation is known to regulate many properties of the aglycones such as their bioactivity, their solubility, and their transport properties within the cell and throughout the plant. As a means of providing a framework to start to understand the substrate specificities and structure-function relationships of plant UGTs, we have now applied a molecular phylogenetic analysis to the multigene family of 99 UGT sequences in Arabidopsis. We have determined the overall organization and evolutionary relationships among individual members with a surprisingly high degree of confidence. Through constructing a composite phylogenetic tree that also includes all of the additional plant UGTs with known catalytic activities, we can start to predict both the evolutionary history and substrate specificities of new sequences as they are identified. The tree already suggests that while the activities of some subgroups of the UGT family are highly conserved among different plant species, others subgroups shift substrate specificity with relative ease.
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