Genome-wide identification of the LLTP superfamily in three cuttlefish species and expression profiling in Sepiella japonica.

The large lipid transfer protein (LLTP) superfamily, characterized by a conserved LPD_N domain, plays important roles not only in lipid transport but also in diverse physiological processes, including animal development, reproduction, and immunity. However, comprehensive characterization of the LLTP gene family in cuttlefish remains limited. In this study, a total of 15 LLTP genes were identified in three cuttlefish species, Sepiella japonica, Sepia officinalis, and S. esculenta, using bioinformatic approaches. Phylogenetic analysis revealed that these genes clustered into three distinct families: VTG, Apo, and MTP. Analyses of motif patterns and gene structures revealed distinct yet conserved features among LLTP families. Chromosomal localization and synteny analyses revealed conserved organization with species-specific variations among LLTP genes. Tissue expression profiling of LLTP genes in S. japonica revealed distinct expression patterns among the three families, with VTG genes showing ovary-biased expression, whereas Apo and MTP genes exhibited broader tissue distribution patterns. Our findings advance the understanding of LLTP evolutionary diversification in cuttlefish and provide insights into their potential roles in lipid transport and other physiological processes.