Functional Study of the BMP Signaling Pathway in Appendage Regeneration of Exopalaemon carinicauda

Appendage autotomy frequently occurs during the cultivation of Exopalaemon carinicauda, which severely impacts its survival and economic benefits. To investigate the molecular mechanism underlying appendage regeneration in E. carinicauda, this study presents a comparative transcriptome analysis on samples from different stages of appendage regeneration in individuals of the same family of E. carinicauda. A total of 6460 differentially expressed genes (DEGs) were identified between the samples collected at 0 h post-autotomy (D0) and those collected at 18 h post-autotomy (D18h). Additionally, 7740 DEGs were identified between D0 and 14 d post-autotomy (D14d), with 3382 DEGs identified between D18h and D14d. Among them, differentially expressed genes such as EcR, RXR, BMP1, and Smad4 are related to muscle growth or molting and may be involved in the regeneration process. qRT-PCR results revealed that EcBMPR2 was expressed at relatively high levels in the gonad and ventral nerve cord tissues and that the highest level of expression was detected in the regenerative basal tissue at 24 h post-autotomy. In situ hybridization results indicated strong signals of this gene in the cells at the wound site at 72 h post-autotomy. Following knockdown of EcBMPR2, the expression levels of both EcBMPR1B and EcSmad1 were significantly downregulated, and long-term interference with the EcBMPR2 gene resulted in a significantly slower appendage regeneration process compared to the control group. When the downstream transcription factor EcSmad1 was knocked down, the two receptor genes EcBMPR2 and EcBMPR1B were downregulated, whereas EcBMP7 was upregulated. After inhibiting the BMP signaling pathway, the degree of cell aggregation at the autotomy site in the experimental group was significantly lower than that in the control group, the wound healing rate was delayed, and the blastema regeneration time was prolonged from 5 d to 7 d. Collectively, these results indicate that the BMP signaling pathway plays a critical role in the early stages of appendage regeneration in E. carinicauda. This study provides important theoretical insights for understanding limb regeneration in crustaceans.