Light Regulation\nof Insect Behavior by Azobenzene-modified\nFlonicamid as Novel Molecular Tools

Photopharmacology, an emerging interdisciplinary field,\nenables\nprecise modulation of target biological activity by employing light-controllable\nphotoswitchable molecules. The research on nicotinamidase (Naam),\na recently identified target molecule for pesticides, remains relatively\nunderexplored. Therefore, based on the structure of its inhibitor\nFlonicamid, we designed and synthesized a series of photopharmacological\nligands (FAB<sub>S</sub>) by incorporating a light-controllable azobenzene\nswitch, further investigating their effects on insect behavior and\nactivity. Compound <b>FAB03</b> exhibited an LC<sub>50</sub> value of 32.8 μM before light exposure and 154 μM after\nlight exposure against <i>Aedes albopictus</i>, indicating\na 4.7-fold difference in activity. Compound <b>FAB05</b> exhibited\nan LC<sub>50</sub> value of 0.691 μM before light exposure and\n2.85 μM after light exposure against nymphs (1 day old) of <i>Aphis craccivora</i>, indicating a 4.1-fold difference in activity.\nAdditionally, this series of photopharmacological ligands has successfully\nachieved light-mediated modulation of locomotor behavior in both <i>Drosophila melanogaster</i> and <i>A. albopictus</i> larvae. Fluorescence staining experiments with <i>A. albopictus</i> larvae were conducted to explore potential modes of action of the\ndrug. Calcium content analysis showed that Flonicamid at 20 μg/mL\nsignificantly caused an inward Ca<sup>2+</sup> flux in the ovarian\nof <i>Spodoptera frugiperda</i> (SF9), and the trans-configurations\nof the photopharmacological ligands <b>FAB03</b> and <b>FAB05</b> also led to a certain increase in the concentration of intracellular\nCa<sup>2+</sup>. AlphaFold2 was employed to predict the three-dimensional\nstructure of Naam, and potential binding modes were elucidated through\nmolecular docking studies.