Δ9 desaturase from Trypanosoma cruzi : Key enzyme in the parasite metabolism. Cloning and overexpression

Lipid and fatty acid metabolism in trypanosomatids

Trypanosomiases and leishmaniases are neglected tropical diseases that have been spreading to previously non-affected areas in recent years. Identification of new chemotherapeutics is needed as there are no vaccines and the currently available treatment options are highly toxic and often ineffective. The causative agents for these diseases are the protozoan parasites of the Trypanosomatidae family, and they alternate between invertebrate and vertebrate hosts during their life cycles. Hence, these parasites must be able to adapt to different environments and compete with their hosts for several essential compounds, such as amino acids, vitamins, ions, carbohydrates, and lipids. Among these nutrients, lipids and fatty acids (FAs) are essential for parasite survival. Trypanosomatids require massive amounts of FAs, and they can either synthesize FAs de novo or scavenge them from the host. Moreover, FAs are the major energy source during specific life cycle stages of T. brucei, T. cruzi, and Leishmania. Therefore, considering the distinctive features of FAs metabolism in trypanosomatids, these pathways could be exploited for the development of novel antiparasitic drugs. In this review, we highlight specific aspects of lipid and FA metabolism in the protozoan parasites T. brucei, T. cruzi, and Leishmania spp., as well as the pathways that have been explored for the development of new chemotherapies.

Monoglucosyldiacylglycerol participates in phosphate stress adaptation in Synechococcus sp. PCC 7942

Cyanobacterial monoglucosyldiacylglycerol (MGlcDG) not only serves as a precursor for monogalactosyldiacylglycerol (MGDG) synthesis, but also participates in stress acclimation. Two genes (mgdA and mgdE) related to MGDG synthesis of Synechococcus sp. PCC 7942 were identified. The mgdE-suppressed mutant (AE) accumulated MGlcDG (4.2%) and showed better growth and photosynthetic activities compared with WT and other mutants (mgdA/mgdE-overexpressed and mgdA-suppressed strains), which suggested that MGlcDG was involved in phosphate stress adaptation for Synechococcus sp. PCC 7942. A notable increase in contents of 18:1 fatty acid (FA) of MGDG (127%), DGDG (68%), and SQDG (105%) in AE were found under phosphate starvation. However, the expression of △9 desaturase (desC) was not higher in AE than that in WT during phosphate-starved period. These results suggested that MGlcDG might be involved in the process of FA desaturation, which contributed to membrane fluidity and cell basic metabolism for stress acclimation in cyanobacteria. In complementary experiments of E. coli, although the expression of mgdA and desC in the mgdA and desC coexpressed strain (OEAC) reduced by 22% and 35% compared with that of the strains only overexpressing mgdA (OEA) or desC (OEC), the content of unsaturated FA in OEAC was the highest. This further implied that the accumulation of MGlcDG could prompt FA desaturation in E. coli. Therefore, we propose that an overproduction of MGlcDG is responsible for FA desaturation and participates in phosphate stress adaptation in cyanobacteria.

Comparative transcriptome analysis of Eimeria necatrix third-generation merozoites and gametocytes reveals genes involved in sexual differentiation and gametocyte development

Eimeria necatrix is one of the most pathogenic parasites causing high mortality in chicken older than 8 weeks. Eimeria spp. possess a coccidian lifecycle including both sexual and asexual stages. Sexual differentiation and development occupies a central place in the life cycle of the Eimeria parasite. However, our knowledge of the sexual differentiation and gametocyte development of Eimeria is very limited. Here using RNA sequencing, we conducted a comparative transcriptome analysis between third-generation merozoites (MZ-3) and gametocytes (GAM) of E. necatrix to identify genes with functions related to sexual differentiation and gametocyte development. Approximately 4267 genes were differentially expressed between MZ-3 and GAM. Compared with MZ-3, 2789 genes were upregulated and 1478 genes were downregulated in GAM. Approximately 329 genes in MZ-3 and 1289 genes in GAM were further analyzed in the evaluation of stage-specific genes. Gene Ontology (GO) classification and KEGG analysis revealed that 953 upregulated gametocyte genes were annotated with 170 GO assignments, and 405 upregulated genes were associated with 231 signaling pathways. We also predicted a further 83 upregulated gametocyte genes, of which 53 were involved in the biosynthesis of the oocyst wall, and 30 were involved in microgametocyte development. This information offers insights into the mechanisms governing the sexual development of E. necatrix and may potentially allow the identification of targets for blocking parasite transmission.