# Transcriptomics and Neuropeptidomics of the Cockroach Rhyparobia maderae to Characterize the Neuropeptide Landscape of the Cockroach’s Circadian Clock

## TL;DR

This study identifies and characterizes neuropeptides in the circadian clock of the cockroach Rhyparobia maderae using transcriptomics and mass spectrometry.

## Contribution

The study provides the first comprehensive neuropeptidomic profile of the cockroach’s circadian clock, revealing 192 mature neuropeptides.

## Key findings

- Transcriptome analysis identified 68 neuropeptide-related genes in Rhyparobia maderae.
- Mass spectrometry revealed 192 mature neuropeptides, including 155 newly identified ones.
- The AME contains 166 bioactive neuropeptides potentially involved in circadian regulation.

## Abstract

The circadian clock
of Rhyparobia maderae is the accessory
medulla (AME) in the optic lobes of the brain.
Controlled by compound ocular photoreceptors, the cockroach clock
orchestrates circadian rhythms in physiology and behavior synchronized
with environmental light–dark cycles. Approximately 240 neurons,
rich in partially colocalized neuropeptides, innervate the AME. Since
the identity and function of most of these neuropeptides are unknown
in the cockroach, the transcriptome of the Madeira cockroach was prepared,
revealing 68 neuropeptides, neuropeptide-like and protein hormone
genes. To identify the neuropeptidome, a combination of analyses of
brain/retrocerebral complex extracts by Q-Exactive Orbitrap mass spectrometry
(MS) and direct tissue profiling of different parts of the nervous
system by matrix-assisted laser desorption/ionization time-of-flight
(MALDI-TOF) MS was used. The resulting data set revealed 192 mature
neuropeptides, with 155 identified for the first time and 57 precursor
peptides. The AME neuropeptidomic profile revealed 166 mature neuropeptides
with potential bioactive circadian clock functions. The precision
of our MS data was validated by immunostaining, as illustrated by
an example of immunoreactive patterns for proctolin in AME neurons.
This peptidergic data set serves as the foundation for future research
on neuropeptide-based functional studies that regulate the timing
of disparate neuronal circuits.