UC Santa Cruz

Mosquito-borne diseases are the deadliest of all vector-bornediseases. Malaria alone accounted for 249 million cases and 608,000 deaths in 2022, while Dengue is estimated to put half the world’s population at risk for contracting the virus. Vector control by the use of insecticides significantly reduces the risk of contracting these diseases, but harms other animals and humans in the process. Many of these insecticides are also used for other insects in agriculture. Because of this, resistance is on the rise for these nonspecific insecticides. Now more than ever, a mosquito-specific toxin is needed to prevent the spread of these deadly diseases without harming other organisms. A natural product NP-34, produced by SNC-034 (Streptomyces malachitospinus), was found to selectively kill mosquito cells vs. Drosophila and Spodoptera cells. Further animal studies proved NP-34 was active against both adult mosquitos and larvae. Characterization of NP-34 showed a boronated polyketide macrolide from the aplasmomycin family. Sequencing and genome mining led to the discovery of the biosynthetic gene cluster (BGC) of NP-34, a trans-AT-PKS. By constructing a bacterial artificial chromosome with the NP-34 BGC, NP-34 was heterologously expressed in Streptomyces albus J1074. Knockout of the downstream acyltransferase by homologous recombination led to the discovery that the acyltransferase controls the last step of NP-34 production. Because NP-34 has multiple analogs, this step is responsible for creating the different analogs by incorporating different acyl-groups. Knockout of the last thiosetrase (TE) led to no production of NP-34, indicating the TE could be responsible for releasing the polyketide chain off the phosphopantetheine arm and the dimerization and cyclization of the molecule. Loss of production of NP-34 after knock out of the transcriptional regulator, LuxR, could indicate LuxR is a transcriptional activator. Feeding studies with CoA mimic SNAC, indicated the possibility that new analogs of NP-34 could be produced. With this in mind, NP-34 could be further manipulated and tested to create a more selective and effective mosquitocide for the prevention of mosquito-borne diseases.