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Open Access Highly Accessed Research article

The transcriptome of Leishmania major in the axenic promastigote stage: transcript annotation and relative expression levels by RNA-seq

Alberto Rastrojo1, Fernando Carrasco-Ramiro1, Diana Martín1, Antonio Crespillo1, Rosa M Reguera2, Begoña Aguado1* and Jose M Requena1*

Author Affiliations

1 Centro de Biología Molecular “Severo Ochoa” (CSIC-UAM), Universidad Autónoma de Madrid, 28049 Madrid, Spain

2 Departamento de Ciencias Biomédicas, Universidad de León, 24071 León, Spain

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BMC Genomics 2013, 14:223  doi:10.1186/1471-2164-14-223

Published: 4 April 2013

Abstract

Background

Although the genome sequence of the protozoan parasite Leishmania major was determined several years ago, the knowledge of its transcriptome was incomplete, both regarding the real number of genes and their primary structure.

Results

Here, we describe the first comprehensive transcriptome analysis of a parasite from the genus Leishmania. Using high-throughput RNA sequencing (RNA-seq), a total of 10285 transcripts were identified, of which 1884 were considered novel, as they did not match previously annotated genes. In addition, our data indicate that current annotations should be modified for many of the genes. The detailed analysis of the transcript processing sites revealed extensive heterogeneity in the spliced leader (SL) and polyadenylation addition sites. As a result, around 50% of the genes presented multiple transcripts differing in the length of the UTRs, sometimes in the order of hundreds of nucleotides. This transcript heterogeneity could provide an additional source for regulation as the different sizes of UTRs could modify RNA stability and/or influence the efficiency of RNA translation. In addition, for the first time for the Leishmania major promastigote stage, we are providing relative expression transcript levels.

Conclusions

This study provides a concise view of the global transcriptome of the L. major promastigote stage, providing the basis for future comparative analysis with other development stages or other Leishmania species.

Keywords:
Gene Expression; RNA-seq; Transcript annotation; mRNAs; Leishmania; Trypanosomatids