Salt perception in a hematophagous insect: Linking peripheral detection to behaviour

PONTES, G; LORENZO, MG; LATORRE-ESTIVALIS, JM; GUTIERREZ, L; BARROZO, RB

Valparaiso

Congreso; V Congress Latino American Society of Chemical Ecology; 2018

Animalsidentify nutrients and avoid toxins with the aid of the taste sense. Salts areunique because depending on concentration produce opposite behaviors. Low-saltconcentration triggers feeding, whereas, high-salt concentration turns anappetitive behavior into aversive. Salts are main components of blood, andcould serve as gustatory cues to blood-sucking insects. Recently, we showed inthe hematophagous kissing bug Rhodniusprolixus, that ingestion is facilitated or prevented depending on saltconcentration of the feeding solution. However, once posed over the selected hostand before feeding, probably Rhodnius do a gustatory evaluation of the hostskin. Consequently, insects decide whether to bite or not. Whether bloodfeeders can evaluate components of the host skin or not is still unknown. In this work, we investigated if Rhodnius detect salts before biting and if this detection could affecttheir feeding decisions. Besides, we analyzed if DEG/ENaC channels or PPKs could play a role in salt sensing. Throughmorphological and electrophysiological approaches, we found gustatory antennal sensillathat house two gustatory receptor neurons tuned to NaCl and KCl. Using bioinformatics tools andphylogenetic analysis we identified two genes, Rproppk28 and Rproppk19,homologous to two Drosophila PPKs relevant in water and saltdetection. Moreover, we showed that these two PPKs are expressed in Rhodniusantennae. Finally, we analyzed the functional role of Rproppk28 and Rproppk19in salt sensing by means of gene silencing through RNA interference. Knockdownedinsects exhibited a significantly reduced levels of these transcripts and wereunable to detect salts.  Our results confirm the importance of the thesetwo PPKs in the salt detection in Rhodnius,and show the relevant role of the gustatory system in a blood-sucking insect.