The ventral peptidergic system of the adult ascidian Ciona robusta (Ciona intestinalis Type A) insights from a transgenic animal model

Tomohiro Osugi,Honoo Satake,Yasunori Sasakura

doi:10.1038/s41598-020-58884-w

Tomohiro Osugi, Honoo Satake + Show 1 more

Open Access

https://doi.org/10.1038/s41598-020-58884-w

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Abstract

Ascidians are the sister group of vertebrates and occupy a critical position in explorations of the evolution of the endocrine and nervous systems of chordates. Here, we describe the complete ventral peptidergic system in adult transgenic Ciona robusta (Ciona intestinalis Type A) which expresses the Kaede reporter gene driven by the prohormone convertase 2 (PC2) gene promoter. Numerous PC2 promoter-driven fluorescent (Kaede-positive) non-neural cells were distributed in the blood sinus located at the anterior end of the pharynx, suggesting the acquisition of a peptidergic circulatory system in Ciona. Kaede-positive ciliated columnar cells, rounded cells, and tall ciliated cells were observed in the alimentary organs, including the endostyle, pharynx, esophagus, stomach, and intestine, suggesting that digestive functions are regulated by multiple peptidergic systems. In the heart, Kaede-positive neurons were located in the ring-shaped plexus at both ends of the myocardium. Nerve fiber–like tracts ran along the raphe and appeared to be connected with the plexuses. Such unique structures suggest a role for the peptidergic system in cardiac function. Collectively, the present anatomic analysis revealed the major framework of the ventral peptidergic system of adult Ciona, which could facilitate investigations of peptidergic regulation of the pharynx, endostyle, alimentary tissues, and heart.

Highlights

The phylogenetic position of tunicates as the sister group of vertebrates sheds light on their significance in investigations of the anatomic, molecular, and functional evolution of the chordate nervous and endocrine systems[1,2,3]
To investigate the peptidergic systems in peripheral organs, we previously used transgenic Ciona that expresses the Kaede reporter gene driven by the prohormone convertase 2 (PC2) gene promoter
Transgenic Ciona harboring the Kaede reporter gene construct driven by the PC2 promoter can be used to investigate the morphological features of peptidergic systems

Summary

Introduction

The phylogenetic position of tunicates as the sister group of vertebrates sheds light on their significance in investigations of the anatomic, molecular, and functional evolution of the chordate nervous and endocrine systems[1,2,3]. The endostyle, pharynx, heart, esophagus, stomach, and intestine are located in the ventral region, suggesting that the ventral peptidergic system is essential for the regulation of visceral functions in Ciona. The present study examined the distribution of PC2 promoter-driven Kaede-positive cells in the peripheral organs, including the blood sinus, endostyle, pharynx, heart, stomach, and intestine, located in the ventral part of transgenic adult Ciona.

Results

Conclusion