Transcriptomics supports local sensory regulation in the antenna of the kissing-bug Rhodnius prolixus

Background Rhodnius prolixus has become a model for revealing the molecular bases of insect sensory biology due to the publication of its genome and its well-characterized behavioural repertoire. Gene expression modulation underlies behaviour-triggering processes at peripheral and central levels. Still, the regulation of sensory-related gene transcription in sensory organs is poorly understood. Here we study the genetic bases of plasticity in antennal sensory function, using R. prolixus as an insect model. Results Antennal expression of neuromodulatory genes such as those coding for neuropeptides, neurohormones and their receptors was characterized in fifth instar larvae and female and male adults by means of RNA-Sequencing (RNA-Seq). New nuclear receptor and takeout gene sequences were identified for this species, as well as those of enzymes involved in the biosynthesis and processing of neuropeptides and biogenic amines. Conclusions We report a broad repertoire of neuromodulatory and neuroendocrine-related genes expressed in the antennae of R. prolixus and suggest that they may serve as the local basis for modulation of sensory neuron physiology. Diverse neuropeptide precursor genes showed consistent expression in the antennae of all stages studied. Future studies should characterize the role of these modulatory components acting over antennal sensory processes to assess the relative contribution of peripheral and central regulatory systems on the plastic expression of insect behaviour.


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For instance, mature kissing-bugs seek host cues promptly, but they do not express proper host-seeking       Table S1). Both AKH isoforms share the signal 141 peptide and the active conserved peptide, but differ in the C-terminal region. Whereas the previously 142 reported isoform encodes the core peptide and a single spacer peptide, the isoform presented here 143 encodes the core peptide and two non-conserved spacer peptides. The gene models of eclosion hormone 144 (EH); ion transport peptide (ITP) isoform A; NVP-like; orcokinin-B; and orcokinin-C remained incomplete 145 because it was impossible to fix them due to problems in the genome assembly, e.g. some fragments were 146 located in the opposite strand or were absent from the genome assembly (Supplementary Table S1). Most of the biogenic amine-related GPCR gene models were edited (Supplementary Table S2). However, 149 many of these genes models are still incomplete. In the case of Family A neuropeptide receptor genes, a   . Using sequences from Drosophila as queries, we were able to identify a total of 9 enzyme 174 genes that seem to correspond to R. prolixus orthologues (Supplementary Table S4). The processing of 175 neuropeptides involves the following enzymes: 1) signal peptidase (SP), which cleaves the signal peptides 176 from their N-terminals; 2) three members of the furin subfamily (dFUR1, dFUR2a and dFUR2b), which are      (Table S7). The antennal expression of allatotropin 222 (AT); OK and IDLSRF-like peptide seems to increase after imaginal moult (Fig. 1a). The expression reported 223 for OK; Dh31; CAPA; AKH and ITP is the sum of their different isoforms or splicing variants.  and Table S7). The antennal expression reported for ACP/CZ related peptide, Capability (CAPA) and CZ 233 receptors, as well as for Pyrokinin receptor 2 was the sum of their different isoforms.

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In Database 3). CT/DH receptor 3, which according to our phylogenetic analysis seems to be exclusive of 238 heteropterans, showed the highest expression for this family. In fact, its expression showed a significant 239 increase in the antennae of adults (FDR=0.0978 and FDR=0.041 for female and male, respectively) when 240 compared to those from larvae ( Fig. 1b and Table S7). A similar expression pattern was observed for CT/DH 241 receptor 1 gene (isoforms B and C included) and for the corticotropin releasing factor like diuretic hormone 242 (CRF/DH) receptor 2 (isoforms A and B included) (Fig. 1b). Regarding opsin expression, transcripts of UV 243 opsin and long wave sensitive opsin 1 (LWS1) were detected in all three libraries (Fig. 1b). The neuropeptide-like precursor 1 (NPLP1) putative receptor (tyrosine kinase-type) and the potential 246 neuroparsin (guanylyl cyclase receptor) seem to be expressed in the antennae of R. prolixus (Fig. 1b).  Table S7). The peptidyl-amidating monooxigenase, signal peptidase and furin-like protease 1 genes showed 251 the highest expression (Fig. 1c).

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All genes encoding for enzymes involved in the biosynthetic pathway of biogenic amines were detected in 260 the antennae of R. prolixus (Fig. 2b). The gene that encodes for Tyrosine 3-monoxigenase, which 261 synthesizes DOPA from L-tyrosine, was the most highly expressed of this enzyme group (Fig. 2b).

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In recent years, modulatory action by different neuropeptides have been shown for both antennal and

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2008) which could relate to the high antennal expression observed for 5-HT receptors in R. prolixus, (Fig.   346   2a). The dopamine ecdysone receptor, which binds dopamine and ecdysone, showed a high expression on 347 adult antennae, especially in those from males (Fig. 2a). Interestingly, this receptor modulates sex

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The Hnf4 gene, which induces the expression of enzymes that drive lipid mobilization and β-oxidation as a 368 response to starvation in D. melanogaster (Palanker et al., 2009), also showed high expression in antennae.  (Fig. 4), however, functional studies need to be performed to be able to confirm 385 these roles in the antennae of kissing-bugs. Two to genes presented significant differences between larval 386 and adult antennal transcriptomes (to11 and to3, with an up and downregulation, respectively) and to2 is 387 significantly down-regulated when male antennae are compared to those of larvae (Supplementary Table   388 S7