Molecular characterization of a p38 MAPK from Litopenaeus vannamei and its expression during the molt cycle and following pathogen infection.

The p38 mitogen-activated protein kinase (MAPK), a serine/threonine-specific protein kinase, has been reported to be involved in innate immunity, development and muscle differentiation. To explore the function of p38 in shrimp, partial cDNA sequence of p38 in Litopenaeus vannamei (designated as Lv-p38) was characterized and the expression of Lv-p38 in hepatopancreas of the shrimp after being infected with Vibrio parahaemolyticus and in muscle of the shrimp at different molt stages was detected by quantitative RT-PCR in this study. The results showed that the open reading frame of Lv-p38 was 1098 bp and encoded a protein of 365 amino acids. The protein of Lv-p38 which showed close phylogenetic relationship to Marsupenaeus japonicus p38 had a conserved TGY motif and serine/threonine protein kinase (S_TKc) domain. The expression of Lv-p38 was detected in all tested tissues, especially in the hepatopancreas and muscle. The expression of Lv-p38 in the hepatopancreas was different from that of the control at the 24th hour after the injection of V. parahaemolyticus and in the muscle significantly increased at stage C but decreased at other stages during molt, illustrating that Lv-p38 could be involved in pathogen infection and the molt cycle of shrimp. In conclusion, we identified Lv-p38 and studied its role in pathogen infection and molting, which might facilitate our understanding of the function of p38 in innate immunity and growth during molt of shrimp.