Exploring the growth hormone and growth hormone receptor gene families in rainbow trout (Oncorhynchus mykiss): A genome-wide perspective

ABSTRACT The growth hormone (GH) and growth hormone receptor (GHR) system is a central regulator of growth and metabolism in vertebrates, with critical implications for aquaculture productivity and functional genomics research. Despite its importance, a comprehensive comparative genome-wide analysis across evolutionarily distant teleosts remains lacking. This study presents the first systematic genome-wide identification and comparative characterization of GH/GHR gene families in two species with significant biological and economic importance: zebrafish ( Danio rerio ), a premier model for developmental biology and functional genomics, and rainbow trout ( Oncorhynchus mykiss ), one of the most economically valuable aquaculture species globally. Our comprehensive analysis identified six conserved orthologs in both species: four somatotropin family genes ( gh1, prl, smtla, smtlb ) and two receptor paralogs ( ghra, ghrb ). In zebrafish, coding sequences (CDS) ranged from 633–1,713 bp with 5–9 exons, whereas in rainbow trout CDS spanned 663–1,932 bp. Notably, gh1 and prl genes exhibited conserved syntenic co-localization on chromosome 3 in zebrafish and chromosome 12 in rainbow trout, suggesting coordinated evolutionary regulation. Protein properties varied from 23.4 kDa (PRL, pI 9.22) to 71.63 kDa (GHRa, pI 4.62), with conserved domain architecture including 4H-Cytokine motifs in hormones and GHBP/FN3 domains in receptors. MEME motif analysis revealed highly preserved functional sequences such as DVLESVRRDYTLLSCFKKDTHKIETFLKLLKCRQSKKRNC across GH family members. Predicted subcellular localizations matched functional roles: hormones targeted to secretory pathways and receptors to membrane compartments. Phylogenetic analysis grouped sequences into distinct monophyletic clades, supporting strong evolutionary conservation across vertebrate lineages. Beyond advancing fundamental understanding of teleost growth biology, this comprehensive genomic framework provides essential resources for applied aquaculture applications, including identification of molecular targets for genetic improvement strategies, selective breeding programs, and optimization of growth performance in farmed fish. Our results establish a foundational genomic resource for future integrative studies of GH and GHR gene function in teleosts, bridging basic evolutionary biology with practical aquaculture biotechnology.