Transcriptomics reveals the gene expression dynamics during embryonic development of largemouth bass (Micropterus nigricans) at the endogenous nutrition stage.

Abstract

The early developmental stages of fish exhibit the highest mortality and greatest environmental sensitivity throughout their life cycle. This period encompasses a series of crucial biological events, including morphogenesis, organ differentiation, and nutritional mode transition from fertilized eggs to newly hatched larvae. Although largemouth bass (Micropterus nigricans) is a commercially important fish species in China, the molecular regulatory mechanisms governing its endogenous nutritional stage remain largely unexplored. To elucidate the molecular basis of this critical period, we performed transcriptomic profiling across six consecutive developmental stages (Multicellular, Blastula, Gastrula, Neurula, Organogenesis, and 5 day post hatching larvae). Our results reveal stage-specific transcriptional programs: the multicellular-to-blastula transition is characterized by stage-specific enrichment of by cell cycle and DNA replication pathways, with MCM complex (mcm2-5) upregulation accelerating proliferation; the blastula-to-gastrula transition features activation of bmp4, fgfr2, and lft1 for germ layer induction; the neurula stage exhibits transcriptional bursts and enrichment of neural tube-related pathways; organogenesis involves simultaneous activation of focal adhesion (col1a1b, col4a5, tnc) and Wnt signaling (wnt1, wnt4, wnt3a) pathway; and 5 dph larvae show visual function maturation, with light transduction genes (gnat1, gnat2, gucy2f, pde6b) identified as hub genes. Mfuzz analysis further reveals sustained upregulation of Cluster 14 (igf2r、napin、vamp7、il1b、aco2) indicating functional maturation, while Cluster 29 (mcm10, espl1, cep152, cep44, cep295) confirms declining cell division activity. Collectively, this study provides a transcriptomic resource for understanding largemouth bass embryonic development and offers molecular insights for improving hatchery practices.