Expression and silencing of Selenoprotein M (SelM) from the white shrimp Litopenaeus vannamei: Effect on peroxidase activity and hydrogen peroxide concentration in gills and hepatopancreas

Selenoprotein M (SelM), is a selenocysteine containing protein with redox activity involved in the antioxidant response. In the white shrimp Litopenaeus vannamei, SelM expression in gills is induced transiently during viral infection by the White Spot Syndrome Virus (WSSV). We report that SelM expression was detected in healthy shrimp L. vannamei in gills, muscle, hepatopancreas and pleopods, with more abundance in the hepatopancreas and gills. SelM transcripts were silenced by intramuscular injection with double-stranded RNAs (dsRNAs). In gills and hepatopancreas, all shrimp injected with long dsRNAs had lower SelM transcripts levels compared with controls. Peroxidase activity and hydrogen peroxide concentration were measured to detect effects on antioxidants. Peroxidase activity decreased upon silencing of SelM in gills, but no significant effect was detected in hepatopancreas. In contrast, total cell hydrogen peroxide concentration did not change in gills and hepatopancreas of silenced shrimp. Non-heme peroxidases are new players in the oxidative stress system that need to be addressed in detail, as well as selenium as a critical micronutrient for the antioxidant and innate immune systems in crustaceans.