Nuss, A. | Search bioRxiv

bioRxiv2025

A cytochrome P450 G subfamily member, CYP4G35, is highly expressed in antennae and modulates olfactory response in Aedes aegypti mosquitoes.

The cytochrome P450 enzymes of the CYP4G subfamily are some of the most enigmatic insect P450s. The dipterans with sequenced genomes have two CYP4G paralogs. In Drosophila melanogaster, CYP4G1 is highly expressed in the oenocytes and catalyzes the last enzymatic step in the biosynthesis of cuticular hydrocarbons. In contrast, CYP4G15 is expressed in the brain glial cells, but its function is unknown. The Aedes aegypti genome encodes two CYP4Gs: CYP4G36 (ortholog of DmCYP4G1) and CYP4G35 (ortholog of DmCYP4G15). Here, we show that CYP4G35 is highly expressed in mosquito antennae, and the RNAi knockdown of CYP4G35 results in delayed host-seeking. Ae. aegypti CYP4G knockout lines confirmed delayed host-seeking behavior in CYP4G35 knockout females. Proteomics analysis of CYP4G35 KO females also corroborates the physiological findings and shows upregulation of proteins related to olfaction and other CYP4Gs to compensate for the lack of CYP4G35. Immunohistochemistry and in situ hybridization were used to localize CYP4G35 and demonstrated its expression in the sensilla lymph of the antennae and the tip of the proboscis. CYP4G35 and CYP4G36 fusion proteins with cytochrome P450 reductase demonstrated that, unlike CYP4G36, CYP4G35 lacks an oxidative decarbonylase function. Together, our data support a novel function of CYP4G35 in modulating olfactory response.

molecular biology↗

bioRxiv2019

The alarmone (p)ppGpp is part of the heat shock response of Bacillus subtilis

Here, B. subtilis was used as a model organism to investigate how cells respond and adapt to proteotoxic stress conditions. Our experiments suggested that the stringent response, caused by raised levels of the (p)ppGpp alarmone, plays a role during thermotolerance development and the heat shock response. Accordingly, our experiments revealed a rapid increase of cellular (p)ppGpp levels upon heat shock as well as salt- and oxidative stress. Strains lacking (p)ppGpp exhibited increased stress sensitivity, while raised (p)ppGpp levels conferred increased stress tolerance to heat- and oxidative stress. During thermotolerance development, stress response genes were highly up-regulated together with a concurrent transcriptional down-regulation of the rRNA, which was influenced by the second messenger (p)ppGpp and the transcription factor Spx. Remarkably, we observed that (p)ppGpp appeared to control the cellular translational capacity and that during heat stress the raised cellular levels of the alarmone were able to curb the rate of protein synthesis. Furthermore, (p)ppGpp controls the heat-induced expression of Hpf and thus the formation of translationally inactive 100S disomes. These results indicate that B. subtilis cells respond to heat-mediated protein unfolding and aggregation, not only by raising the cellular repair capacity, but also by decreasing translation involving (p)ppGpp mediated stringent response to concurrently reduce the protein load for the cellular protein quality control system.\n\nAuthor SummaryHere we demonstrate that the bacterial stringent response, which is known to slow down translation upon sensing nutrient starvation, is also intricately involved in the stress response of B. subtilis cells. The second messengers (p)ppGpp act as pleiotropic regulators during the adaptation to heat stress. (p)ppGpp slows down translation and is also involved in the transcriptional down-regulation of the translation machinery, together with the transcriptional stress regulator Spx. The stress-induced elevation of cellular (p)ppGpp levels confers increased stress tolerance and facilitates an improved protein homeostasis by reducing the load on the protein quality control system.

microbiology↗