Insights into the STARD family in arthropods: Genome-wide identification, evolutionary analysis and expression...

Steroidogenic acute regulatory domain (STARD) protein family plays a crucial role in cholesterol and carotenoids transport; however, little is known about their evolution history, gene structure and potential ligands in arthropods. This study comprehensively investigated the STARD family in crustaceans, focusing on phylogenetic relationships, evolutionary dynamics, ligand preferences, and expression patterns in the Chinese mitten crab Eriocheir sinensis. In total, 196 STARD genes were identified across 34 representative arthropods, and the STARD1/3 alternative was exhibited in most arthropods. STARDs were grouped into six clades, each exhibiting distinct affinities for eight carotenoids. STARDs were evolutionarily conserved, they were under purifying selection with a preference for similar codons. In E. sinensis, six STARD genes were identified with distinct tissue-specific expression patterns. Moreover, the mRNA levels of STARD3 and STARD11 in the hepatopancreas were significantly upregulated upon high-pH exposure, likely reflecting an adaptive mechanism to enhance carotenoid utilization, thereby mitigating oxidative damage from high-pH stress and maintaining hepatopancreatic homeostasis. Overall, these results provide valuable insights into the evolutionary dynamics, ligand preferences and functional diversification of STARD family in arthropods, which highlights the future research direction of this gene family in arthropods.