SummaryTrypanosome parasites control their virulence and spread by using quorum sensing (QS) to generate transmissible “stumpy forms” in their host bloodstream. However, the QS signal “stumpy induction factor” (SIF) and its reception mechanism are unknown. Although trypanosomes lack G protein-coupled receptor signaling, we have identified a surface GPR89-family protein that regulates stumpy formation. TbGPR89 is expressed on bloodstream “slender form” trypanosomes, which receive the SIF signal, and when ectopically expressed, TbGPR89 drives stumpy formation in a SIF-pathway-dependent process. Structural modeling of TbGPR89 predicts unexpected similarity to oligopeptide transporters (POT), and when expressed in bacteria, TbGPR89 transports oligopeptides. Conversely, expression of an E. coli POT in trypanosomes drives parasite differentiation, and oligopeptides promote stumpy formation in vitro. Furthermore, the expression of secreted trypanosome oligopeptidases generates a paracrine signal that accelerates stumpy formation in vivo. Peptidase-generated oligopeptide QS signals being received through TbGPR89 provides a mechanism for both trypanosome SIF production and reception.

SummaryThe biological membranes of Trypanosoma brucei contain a complex array of phospholipids that are synthesized de novo from precursors obtained either directly from the host, or as catabolised endocytosed lipids. This paper describes the use of nanoflow electrospray tandem mass spectrometry and high resolution mass spectrometry in both positive and negative ion modes, allowing the identification of ~500 individual molecular phospholipids species from total lipid extracts of cultured bloodstream and procyclic form T. brucei. Various molecular species of all of the major subclasses of glycerophospholipids were identified including phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol as well as phosphatidic acid, phosphatidylglycerol and cardolipin, and the sphingolipids sphingomyelin, inositol phosphoceramide and ethanolamine phosphoceramide. The lipidomic data obtained in this study will aid future biochemical phenotyping of either genetically or chemically manipulated commonly used bloodstream and procyclic strains of Trypanosoma brucei. Hopefully this will allow a greater understanding of the bizarre world of lipids in this important human pathogen.

The reason why Leishmania parasites are susceptible to organic antimonial drugs, the standard chemotherapeutic agents for over 50 years, apparently lies in the fact that the mammalian stage of the parasite reduces the pentavalent form of the administered drug to a trivalent form that causes parasite death. We have identified and characterized a parasite-specific enzyme that can catalyse the reduction of pentavalent antimonials and may therefore be central to the anti-parasite activity of the drug. The unusual protein, a trimer of two-domain monomers in which each domain has some similarity to the Omega class glutathione S-transferases, is a thiol-dependent reductase (designated TDR1) that converts pentavalent antimonials into trivalent antimonials using glutathione as the reductant. The higher abundance of the enzyme in the mammalian stage of the parasite could explain why this parasite form is more susceptible to the drug.

Row crop production on highly erodible soils of the Piedmont in the southeastern USA is often limited by surface sealing, excessive surface water runoff, soil erosion, and low crop yields. The effects of four tillage practices on corn (Zea mays L.) growth and soil properties on two crust‐prone soils were evaluated. Tillage treatments at two Piedmont locations, Oxford and Reidsville, NC, were no‐till (NT), in‐row subsoiling (IRS) (1987 only), chisel plow (CP), and moldboard plow‐disk (MP). Residue cover was 1% for MP and ranged from 75 to 87% for NT and 38 to 27% for CP. The interaction between tillage, soil properties, and plant performance was complex. Mean bulk density of the Ap horizon at Reidsville for the 2‐yr period was 1.56 Mg m−3 for NT, compared with 1.48 Mg m−3 for CP and 1.46 Mg m−3 for MP. Cone index was not affected by tillage but was greatest in the trafficked interrow, 3.50 MPa, compared with 1.91 and 1.09 MPa in the row and nontrafficked interrow, respectively. Mean corn grain yield for the four year‐locations was least, 1.23 Mg ha−1, for MP, compared with 2.97 Mg ha−1 for NT and 2.44 Mg ha−1 for CP; mean yield for IRS in 1987 was 3.69 Mg ha−1. Tillage practices leaving crop residues on the soil surface, such as NT, CP, and IRS, can reduce or eliminate surface crusting, increase infiltration, and reduce surface runoff and soil loss while increasing crop yield.

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