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.