# Transcriptome Analysis Reveals the Requirement of the TGFβ Pathway in Ascidian Tail Regression

## TL;DR

This study identifies the TGFβ signaling pathway's role in tail regression during metamorphosis in the ascidian Styela clava.

## Contribution

The study reveals the TGFβ pathway's involvement in ascidian tail regression and identifies downstream genes critical for metamorphosis.

## Key findings

- The TGFβ signaling pathway is involved in tail regression in Styela clava.
- Four gene functional categories were identified as downstream targets of the TGFβ pathway.
- Cross-species analysis showed conservation and divergence in gene regulation between Ciona robusta and Styela clava.

## Abstract

Metamorphosis is a common developmental process in invertebrate development. It is essential for the degeneration of larval organs, formation of adult organs, and adaptation transformation of the living environment. However, the underlying molecular regulatory mechanism remains to be elucidated. In this study, we used tail regression of ascidian Styela clava as a model to understand the gene regulation pathway and molecular mechanism in organ metamorphosis. The TGFβ signaling pathway was screened and demonstrated to be involved in tail regression based on RNA sequencing on the different larval stages and verification with inhibitor treatment experiments. We further investigated the downstream gene network of the TGFβ signaling pathway through comparative transcriptome data analysis on the TGFβ pathway inhibition samples. Together with qRT-PCR verification, we identified four critical gene functional categories, including ion transporters/water channel, extracellular matrix structural constituent, extracellular matrix organization, and cell polarity establishment. Furthermore, a cross-species comparative analysis between Ciona robusta and S. clava was performed to understand the conservation and divergence of gene regulation in ascidians. Overall, our work identifies a crucial gene regulation pathway in ascidian tail regression and provides several potential downstream targets for understanding the molecular mechanism of larval metamorphosis.