Expression analyses of C-type lectins (CTLs) in Manila clam under cold stress provide insights for its potential function in cold resistance of Ruditapes philippinarum.

Manila clam Ruditapes philippinarum is an economically and scientifically important marine bivalve species. C-type lectin acts as a pattern-recognition receptor (PPR), plays a crucial role in the innate immunity of invertebrates, and involves in pathogen recognition, and cell-cell interaction. In this study, six different types of C-type lectin genes, CTL-1, CTL-2, CTL-3, CTL-4, CTL-5, and CTL-6, were identified from the R. philippinarum. CTL amino acid sequence was highly conserved compare to other invertebrate CTL sequences. Also, the temporal expressions of CTLs mRNA were detected in R. philippinarum with higher expression level in hepatopancreas and gill, and with lower expression levels in other tissues. The expression pattern of CTL genes in hepatopancreas were investigated under low-temperature stress using real-time quantitative fluorescence PCR (RT-qPCR) and the results showed that the transcription of CTL mRNAs were induced after low-temperature challenge. Overall, the sequence analysis and the expression patterns of CTLs provide clues for understanding the response of the Manila clam to low-temperature stress.