Biology subjects

Sorrells, T. R.

Publications and source records attributed to Sorrells, T. R..

7 recordsLinked to original sources

bioRxiv2026

A molecular and cellular mechanism for bitter taste in the mosquito Aedes aegypti

The yellow fever mosquito, Aedes aegypti, is a vector of Zika, Dengue, Chikungunya and yellow fever, disease-causing viruses impacting millions of people annually across the globe. Female mosquitoes transmit pathogens through serial blood-feeding, while both male and female mosquitoes feed on plant resources. Contact chemosensation (taste) guides these two feeding modes in both positive ways, feeding readily on sugar in nectar or ATP in blood, and negative ways, demonstrating aversion to chemically diverse bitter compounds in blood or sugar meals. Here, we identify a receptor, AaegGr14, that is expressed in neurons in the labellum and cibarium of the mosquito. Activation of Gr14-expressing neurons causes reduced feeding, while Gr14 and Gr14-expressing GRNs are required for aversion to bitter compounds during nectar- but not blood-feeding. This work provides a molecular and cellular on-ramp to understand bitter taste in mosquitoes and establishes that there are feeding context-dependent differences in how taste mechanisms influence blood- and nectar-feeding. Understanding the molecular and cellular basis of bitter taste in mosquitoes during nectar- and blood-feeding will help inform vector control strategies and elucidate shared principles and unique aspects of insect taste systems.

neuroscience↗

bioRxiv2026

Optogenetic Analysis of Behavior in the Mosquito Aedes aegypti

The mosquito Aedes aegypti is an important vector of viral pathogens and serves as a model for other vector species. Pathogens are transmitted when a mosquito bites a host animal, but the neural circuits that control seeking and biting behavior are not known. Here, we detail methods for the manipulation of neural activity in the mosquito using optogenetics, a key technique to determine the causal relationship between neural circuits and behavior. These methods include rearing mosquitoes for optogenetics and three assays that are designed to measure different steps in the sequence of arousal, attraction, proboscis probing, and engorgement on the blood of host animals. These behaviors occur at different spatial scales and in response to different sensory stimuli. Each behavioral assay is outfitted with red (~625 nm) LEDs for optogenetic activation. To detect arousal in response to olfactory stimuli, flight and walking are quantified. To assay attraction or landing, mosquitoes are presented with a heated blood meal in a large arena. Proboscis probing and engorgement are assayed with video resolution that enables measurement of appendages and abdomen size. The protocol describes machine vision models to enable high-resolution temporal quantification of behavior as well as endpoint measurements of feeding. These methods can be used to test the role of any genetically accessible population of neurons in mosquito biting behavior and can be extended to additional behaviors.

neuroscience↗

bioRxiv2023

Cross-modal sensory compensation increases mosquito attraction to humans

Sensory compensation is a process that allows individuals with a loss of one sense, for instance hearing or vision, to adapt to changes in their sensory abilities. Where this phenomenon has been observed, there is enhanced perception by another sense to compensate for deficiency of the lost sense. Such compensation is important for humans and non-human animals that use multisensory integration for effective navigation and the execution of vital tasks. Among these, female mosquitoes are sensory specialists that rely heavily on integrating multiple human-emitted cues in their quest for a suitable host to obtain a blood meal. Here, we identify a previously undescribed mechanism of sensory compensation in female Aedes aegypti mosquitoes. Mutant mosquitoes lacking the odorant receptor co-receptor Orco show specific enhancement in heat-seeking behavior. This s compensation does not require the antenna, which was previously assumed to be the primary mosquito thermosensitive organ. Instead, we found that the tips of the forelegs are required to detect heat, and that the heightened sensitivity in heat detection is mediated by increased neuronal activity in foreleg sensory neurons, which are distant from the head appendage neurons that express Orco. By comparative gene expression analysis in wildtype and Orco mutant legs, we identify Ir140, a foreleg-enriched member of the Ionotropic Receptor (IR) superfamily of sensory receptors, as strongly upregulated in Orco mutant legs. Emphasizing the important role of IRs in thermosensation, we find that mutant mosquitoes lacking the IR co-receptor, Ir25a, lose all responses to heat, and Ir140 mutants show strong deficits in responding to human skin temperatures. We generated an Ir140, Orco double mutant and show that these animals lose the remarkable sensory compensation seen in Orco mutants. This strongly suggests that upregulation of Ir140 in the foreleg is the mechanism of sensory compensation in Orco mutants. Odorant receptor expression is sparse in legs, suggesting an indirect, long-range mechanism of sensory compensation. Our findings reveal a novel compensatory mechanism in which loss of one sensory modality in female Aedes aegypti mosquitoes results in greater sensitivity in another to maintain the overall effectiveness of their host-seeking behavior, further enhancing their status as the most dangerous predator of humans.

neuroscience↗

bioRxiv2021

A persistent behavioral state enables sustained predation of humans by mosquitoes

Predatory animals pursue prey in a noisy sensory landscape, deciding when to continue or abandon their chase. The mosquito Aedes aegypti is a micropredator that first detects humans at a distance through sensory cues such as carbon dioxide. As a mosquito nears its target it senses more proximal cues such as body heat that guides it to a meal of blood. How long the search for blood continues after initial detection of a human is not known. Here we show that a 5-second optogenetic pulse of fictive carbon dioxide induced a persistent behavioral state in female mosquitoes that lasted for more than 10 minutes. This state is highly specific to females searching for a blood meal and was not induced in recently blood-fed females or in males, who do not feed on blood. In males that lack the gene fruitless, which controls persistent social behaviors in other insects, fictive carbon dioxide induced a long-lasting behavior response resembling the predatory state of females. Finally, we show that the persistent state triggered by detection of fictive carbon dioxide enabled females to engorge on a blood meal mimic offered up to 14 minutes after the initial 5-second stimulus. Our results demonstrate that a persistent internal state allows female mosquitoes to integrate multiple human sensory cues over long timescales, an ability that is key to their success as an apex micropredator of humans.

neuroscience↗

bioRxiv2020

The Taste of Blood in Mosquitoes

Blood-feeding mosquitoes survive by feeding on nectar for metabolic energy, but to develop eggs, females require a blood meal. Aedes aegypti females must accurately discriminate between blood and nectar because detection of each meal promotes one of two mutually exclusive feeding programs characterized by distinct sensory appendages, meal sizes, digestive tract targets, and metabolic fates. We investigated the role of the syringe-like blood-feeding appendage, the stylet, and discovered that sexually dimorphic stylet neurons are the first to taste blood. Using pan-neuronal GCaMP calcium imaging, we found that blood is detected by four functionally distinct classes of stylet neurons, each tuned to specific blood components associated with diverse taste qualities. Furthermore, the stylet is specialized to detect blood over nectar. Stylet neurons are insensitive to nectar-specific sugars and responses to glucose, the sugar found in both blood and nectar, depend on the presence of additional blood components. The distinction between blood and nectar is therefore encoded in specialized neurons at the very first level of sensory detection in mosquitoes. This innate ability to recognize blood is the basis of vector-borne disease transmission to millions of people world-wide.

neuroscience↗

bioRxiv2019

New transcriptional circuit evolved by coding sequence changes in a master regulator followed by cis-regulatory changes in its target genes

While changes in both the coding-sequence of transcriptional regulators and in the cis-regulatory sequences recognized by them have been implicated in the evolution of transcriptional circuits, little is known of how they evolve in concert. We describe an evolutionary pathway in fungi where a new transcriptional circuit (a-specific gene repression by Mat2) evolved by coding changes in an ancient master regulator, followed millions of years later by cis-regulatory sequence changes in the genes of its future regulon. We discerned this order of events by analyzing a group of species in which the coding changes in the regulator are present, but the cis-regulatory changes in the target genes are not. In this group we show that the coding changes became necessary for the regulators deeply conserved function and were therefore preserved. We propose that the changes first arose without altering the overall function of the regulator (although changing the details of its mechanism) and were later co-opted to "jump start" the formation of the new circuit.

evolutionary biology↗

bioRxiv2018

Intrinsic cooperativity potentiates parallel cis-regulatory evolution

Convergent evolutionary events in independent lineages provide an opportunity to understand why evolution favors certain outcomes over others. We studied such a case, where a large set of genes--those coding for the ribosomal proteins--gained cis-regulatory sequences for a particular transcription regulator (Mcm1) in independent fungal lineages. We present evidence that these gains occurred because Mcm1 shares a mechanism of transcriptional activation with an ancestral regulator of the ribosomal protein genes, Rap1. Specifically, we show that Mcm1 and Rap1 have the inherent ability to cooperatively activate transcription through contacts with the general transcription factor TFIID. Because the two regulatory proteins share a common interaction partner, the presence of one ancestral cis-regulatory sequence can \"channel\" random mutations into functional sites for the second regulator. At a genomic scale, this type of intrinsic cooperativity can account for a pattern of parallel evolution involving the fixation of hundreds of substitutions.

evolutionary biology↗