Glutathione S-transferase theta 1 (GSTT1) modulates inflammation in Manila clam (Ruditapes philippinarum) during...

Inflammatory responses are essential for Manila clams (Ruditapes philippinarum) to resist Perkinsus olseni infection; however, the underlying regulatory mechanisms remain poorly understood. Glutathione S-transferase theta 1 (GSTT1) is known to modulate inflammatory processes in many organisms, yet its role during P. olseni infection in Manila clams has not been elucidated. In this study, we combined transcriptomic analysis with functional assays to investigate the involvement of RpGSTT1 in P. olseni-induced inflammation. Comparative transcriptomic profiling of clams with high and low P. olseni burdens identified 3332 differentially expressed genes, among which RpGSTT1 was the most significantly enriched gene in the drug metabolism-cytochrome P450 pathway, exhibiting approximately four-fold upregulation. RpGSTT1 encodes a 231-amino-acid protein containing a conserved GST-N domain and shares 80.57% and 75.83% sequence similarity with GSTT1 homologs from Mercenaria mercenaria and Dreissena polymorpha, respectively. Following infection, RpGSTT1 expression was significantly upregulated in gill tissues, and immunofluorescence analysis localized RpGSTT1 predominantly to the cytoplasm of gill cells. Functional analyses demonstrated that RpGSTT1 knockdown markedly increased the expression of pro-inflammatory cytokines and exacerbated gill tissue damage, whereas RpGSTT1 overexpression significantly attenuated inflammatory responses. Moreover, RpGSTT1 overexpression negatively regulated P. olseni-induced inflammation responses, indicating that GSTT1 exerts a conserved anti-inflammatory function in bivalves, likely through modulation of pro-inflammatory cytokine expression. Collectively, these findings provide new insights into the immune regulatory mechanisms of Manila clams during parasitic infection and highlight RpGSTT1 as a key modulator of host inflammatory responses.