Shotgun DNA microarrays and stage-specific gene expression in Plasmodium falciparum malaria

Malaria infects over 200 million individuals and kills 2 million young chil dren every year. Understanding the biology of malarial parasites will be fa cilitated by DNA microarray technology, which can track global changes in g ene expression under different physiological conditions. However, genomes o f Plasmodium sp. (and many other important pathogenic organisms) remain to be fully sequenced so, currently, it is not possible to construct gene-spec ific microarrays representing complete malarial genomes. In this study, 364 8 random inserts from a Plasmodium falciparum mung bean nuclease genomic li brary were used to construct a shotgun DNA microarray. Through differential hybridization and sequencing of relevant clones, large differences in gene expression were identified between the blood stage trophozoite form of the malarial parasite and the sexual stage gametocyte form. The present study lengthens our list of stage-specific transcripts in malaria by at least an order of magnitude above all previous studies combined. The results offer a n unprecedented number of leads for developing transmission blocking agents and for developing vaccines directed at blood stage antigens. A significan t fraction of the stage-selective transcripts had no sequence homologues in the current genome data bases, thereby underscoring the importance of the shotgun approach. The malarial shotgun microarray will be useful for unrave lling additional important aspects of malaria biology and the general appro ach may be applied to any organism, regardless of how much of its genome is sequenced.