ABSTRACTMalaria remains one of the most deadly diseases in the world, killing nearly a million people each year. Malariais hard to control because the immunogenicity of malaria pathogens is very poor, which has made it hard togenerate anti-malaria vaccines. The fast spread of insecticide-resistance in mosquito populations and drug-resistance of Plasmodium parasites further serves to increase the rate of malaria transmission. Therefore,there is critical need for the development of novel approaches for malaria control. Since malaria transmissiondepends on Plasmodium infected mosquitoes, inhibiting parasite infection in mosquitoes represents a noveland practical way to break malaria transmission. At present, most transmission-blocking studies focus onparasite gametocytes in blood with limited success because gametocytes are strongly resistant to drugs.However, very few efforts have been taken to use compounds against mosquito proteins to block malariatransmission. We recently identified the FREP1 gene in wild An. gambiae from malaria endemic areas inKenya through association studies. Molecular and biochemical analyses revealed that the FREP1 proteinmediates the invasion of multiple species of Plasmodium parasites in mosquito midguts through directinteraction with parasites. Based on these findings, we have developed a new high throughput platform toscreen a library of natural fungal extracts targeting FREP1, which enabled our team to identify a bioactivecompound named P-orlandin that significantly inhibits P. falciparum infection in mosquitoes. Based on thesepreliminary studies, we hypothesize that small compounds interfere with malaria-mosquito interaction willinhibit malaria transmission. Since multi-pathways involve Plasmodium invasion in mosquitoes, the overarchinggoal of this application is developing a novel and effective approach for using multiple fungal natural productsto block malaria transmission by targeting multiple mosquito proteins that mediate parasites invasion inmosquitoes. We will use our successful collaborative studies as a springboard for identifying additional targetsthat mediate parasite transmission, as well as small molecules that disrupt the process of malaria transmission.Not only will the compounds we find serve as potential leads for field applications, but they will also serve asessential chemical probes to dissect the molecular biology of the novel pathways we uncover. In this study, wewill identify additional candidate genes through genomic-block assistant-associated studies and verify theirfunctional relationship with P. falciparum infection in mosquitoes. The candidate gene products that promotePlasmodium infection in mosquitoes will be chosen as targets to screen for small molecule compounds thatblock malaria transmission. This work will provide bioactive compounds that are leads for development ofdrugs or spray reagents to block malaria transmission. In addition, this work provides the malaria communitieswith new mechanistic insight into Plasmodium transmission to mosquitoes at a molecular level.