Salt perception in a hematophagous insect: Linking peripheral detection to behavior.

PONTES, GINA; GUTIERREZ, LAURA; LATORRE-ESTIVALIS, J; MARCELO G. LORENZO; BARROZO, ROMINA B.

Congreso; Congreso Latino Americano de Ecologia química; 2018

Animals identify nutrients and avoid toxins with the aid of the taste sense. Salts are unique because depending on concentration produce opposite behaviors. Low-salt concentration triggers feeding, whereas, high-salt concentration turns an appetitive behavior into aversive. Salts are main components of blood, and could serve as gustatory cues to blood-sucking insects. Recently, we showed in the hematophagous kissing bug Rhodnius prolixus, that ingestion is facilitated or prevented depending on salt concentration of the feeding solution. However, once posed over the selected host and before feeding, probably Rhodnius do a gustatory evaluation of the host skin. Consequently, insects decide whether to bite or not. Whether blood feeders 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 affect their feeding decisions. Besides, we analyzed if DEG/ENaC channels or PPKs could play a role in salt sensing. Through morphological and electrophysiological approaches, we found gustatory antennal sensilla that house two gustatory receptor neurons tuned to NaCl and KCl. Using bioinformatics tools and phylogenetic analysis we identified two genes, Rproppk28 and Rproppk19, homologous to two Drosophila PPKs relevant in water and salt detection. Moreover, we showed that these two PPKs are expressed in Rhodnius antennae. Finally, we analyzed the functional role of Rproppk28 and Rproppk19 in salt sensing by means of gene silencing through RNA interference. Knockdowned insects exhibited a significantly reduced levels of these transcripts and were unable to detect salts. Our results confirm the importance of the these two PPKs in the salt detection in Rhodnius, and show the relevant role of the gustatory system in a blood-sucking insect.