# Ras Homolog A (RhoA) Is Involved in the Innate Immune Defense of the Red Swamp Crayfish Procambarus clarkii

## TL;DR

This study identifies the RhoA gene in red swamp crayfish and shows it plays a key role in immune defense, especially in the intestine.

## Contribution

The study characterizes PcRhoA in Procambarus clarkii and demonstrates its regulatory role in innate immunity.

## Key findings

- PcRhoA mRNA is upregulated in the crayfish intestine after immune challenges.
- Knockdown of PcRhoA reduces expression of immune-related genes.
- PcRhoA is phylogenetically close to RhoA in Cherax quadricarinatus.

## Abstract

The RhoA gene was identified in red swamp crayfish, where it functions as a key regulator of the animal’s immune defenses. Following immune challenges, the PcRhoA gene’s activity increases in the intestine, and silencing it impairs immune gene expression. These findings highlight RhoA’s critical role in crayfish immunity and its potential to support healthier breeding practices without the need for antibiotics.

RhoA (Ras homolog A) is a prominent member of the Rho GTPase family, playing a key role in various cellular processes such as cytoskeletal dynamics, cell migration, and immune responses. However, its function in red swamp crayfish remains unclear. In this study, it is proposed that RhoA may regulate the innate immune response in P. clarkii. The gene was fully characterized as PcRhoA in P. clarkii. The results showed that the open reading frame (ORF) of PcRhoA is 663 bp, encoding a 220-amino acid protein with a conserved Rho domain of 174 amino acids. Phylogenetic analysis placed PcRhoA close to Cherax quadricarinatus RhoA. RT-qPCR analysis revealed high expression levels of the PcRhoA gene in the hepatopancreas, muscle, heart, ovary, and stomach, with lower expression in the blood, intestine, gills, and tentacle gland. Furthermore, PcRhoA mRNA transcript was significantly upregulated in the intestine following LPS and Poly I:C challenges. Knockdown of PcRhoA suppressed the expression of downstream genes in the immune signaling pathway. These results indicate that PcRhoA appears to play a pivotal role in regulating the immune response of crayfish.