Cloning and expression analysis of mitogen-activated protein kinase (MAPK) p38 in pearl oyster Pinctada fucata martensii

The mitogen-activated protein kinase (MAPK) signaling pathway is crucial in cellular response to extracellular stimuli. This pathway utilizes serine/threonine-protein kinases that transmit extracellular signals through a phosphorylation cascade to cells. Rapid-amplification of cDNA ends (RACE) was utilized for cloning and quantitative PCR (qPCR) used for expression profiling of p38 MAPK in this study. Our findings reveal that the Pinctada fucata martensii (PmMAPK p38) has a full-length cDNA of 1 516 bp, an open reading frame (ORF) of 1 071 bp, and has an estimated molecular mass of 40.88 ku which is encoded 356 amino acids. Domain prediction analysis indicates that PmMAPK p38 has the typical MAPK family S_TKc domain and sequence alignment, tree construction, and MatGAT calculation demonstrate its high similarity and conservation to MAPK genes in other species. Our qPCR results show that PmMAPK p38 is extensively expressed in various P. fucata martensii tissues, with the highest levels in hepatopancreas, followed by mantle, and the lowest levels in adductor muscle. Stimulation with LPS resulted in relative expression peaking at 2 h, decreasing to the least at 12 h. The greatest expression was roughly 5 times higher than the lowest. After stimulation with Vibrio harveyi, relative expression peaked at 2 h, decreased to the lowest at 8 h, with the highest expression approximately 4 times greater than the lowest. Our findings suggest that PmMAPK p38 may be a crucial component of the immune response in P. fucata martensii, and this study provides essential data for further investigation on the immune defense system of shellfish.