Global expression profiling reveals shared and distinct transcript signatures in arrested act2(-) and CDPK4(-) Plasmodium berghei gametocytes.

Gametocytogenesis and gametogenesis in malaria parasites are complex processes of cell differentiation and development likely involving many gene products. Gametocytes develop in the blood of the vertebrate host but mature gametocytes are not activated until taken up by the mosquito vector. Several distinct mutants have been described that block gametogenesis but the detailed molecular causes for the mutant phenotypes are not understood. To investigate whether a block in gametogenesis also results in a changed transcriptional profile we studied two gene deletions mutants; act2(-) lacking stage-specific actin II and CDPK4(-) lacking calcium-dependent protein kinase 4. Whole genome microarray analysis was performed from RNA of mature gametocytes to compare the transcriptomes of the mutants with wild-type Plasmodium berghei. The microarray analysis identified ∼12% of all genes being differentially expressed in either or both mutants compared to normal gametocytes, as defined by at least two-fold change in transcript abundance. A large proportion of the differentially expressed genes overlapped in the two mutants, consistent with a related outcome of gametocyte arrest. Distinct profiles in each mutant were also observed. Among the down-regulated genes were thioredoxin 2 and members of the merozoite surface protein 7 family. Generation and characterization of a msp7(-)/mspr1(-)/mspr2(-) triple mutant and re-analysis of trx2(-) parasites revealed no impairment of life cycle progression. Together, our analysis provides a resource for molecular signatures of Plasmodium berghei gametogenesis and exemplifies the potential of expression profiling of distinct genetically arrested parasites.