Leishmania major strain:Ryan Transcriptome or Gene expression. Leishmania major strain:Ryan

The life-cycle of the Leishmania parasite in the sand fly vector involves differentiation into several distinctive forms, each thought to represent an adaptation to specific microenvironments in the midgut of the fly. Using RNA-seq, we provide the first high resolution analysis of the transcriptome dynamics of four distinct stages of L. major as they develop in a natural vector, Phlebotomus duboscqi. The early transformation from tissue amastigotes to procyclic promastigotes in the blood-fed midgut was accompanied by the greatest number of differentially expressed genes, including the down regulation of amastins, and upregulation of multiple cell surface proteins, sugar and amino acid transporters, and genes related to glucose metabolism and cell cycle progression. The global changes accompanying the post-blood meal differentiation of procyclic promastigotes to the nectomonad and metacyclic stages were less extensive, though each displayed a unique signature. The transcriptome of nectomonads, which has not been studied previously, revealed changes consistent with cell cycle arrest and the upregualtion of genes associated with starvation and stress, including autophagic pathways of protein recycling. Maturation to the infective, metacyclic stage was accompanied by changes suggesting pre-adaptation to the intracellular environment of the mammalian host, demonstrated by the amastigote-like profiles of surface proteins and metabolism related genes. Finally, a direct comparison between sand fly- and culture-derived metacyclics revealed a reassuring similarity between the two forms, with the in vivo forms distinguished mainly by a stronger upregulation of transcripts associated with nutrient stress.