In silico characterization and expression analysis of eight C-type lectins in obscure puffer Takifugu obscurus

Abstract

C-type lectins (CTLs) are a group of carbohydrate-binding proteins that play crucial roles in innate immune defense against invading pathogens. CTLs have been extensively studied in lower vertebrates, such as fish, for their roles in eliminating pathogens; however, their homologs in pufferfish are not well known. In the present study, eight CTLs from obscure puffer Takifugu obscurus (designated as ToCTL3–10 according to the order they were discovered) were obtained. All predicted ToCTL proteins contained a single carbohydrate recognition domain (CRD). ToCTL7 also contained one calcium-binding epidermal growth factor (EGF)-like domain (EGF_CA) and a transmembrane region. ToCTL9 also contained an SCP domain, an EGF domain, and an EGF-like domain. Bioinformatics analysis revealed that ToCTL3–10 mainly clustered with the corresponding CTL homologs of other pufferfish species. Tissue distribution analysis detected ToCTL3–10 in all tissues examined, including kidneys, liver, gills, spleen, intestines, and heart. Moreover, the expressions of ToCTL3–10 were significantly induced in the kidneys of obscure puffer following challenges with three Gram-negative bacterial pathogens, namely, Vibrio harveyi, Aeromonas hydrophila, and Edwardsiella tarda, and a synthetic analog of double-stranded RNA poly(I:C). The expression patterns of ToCTL3–10 in response to different immune stimulants were different. Our results indicated that the eight ToCTLs obtained herein might be involved in host defense against bacterial and poly(I:C) infections in T. obscurus.