Distribution of Leishmania infantum and Leishmania major differentially expressed genes according to Gene Ontology (GO) function categories. GO categories for L. infantum promastigotes (A), L. infantum amastigotes (B), L. major promastigotes (C) and L. major amastigotes (D). The majority of genes encode unknown biological functions. Unclassified proteins include the hypothetical proteins (proteins with unknown function and not tested experimentally) and proteins with no GO category (unclassified) that have been experimentally characterized (e.g. amastins).