Transcriptome Reveals Molecular Mechanisms of Neuroendocrine Regulation of Allometric Growth in the Red Swamp Crayfish Procambarus clarkii

Abstract

Allometric growth is a typical characteristic of crustaceans, which mainly occurs among individuals, life stages, tissues, and between sexes. The red swamp crayfish Procambarus clarkii is an economically important crustacean species in the world. To date, the molecular regulatory mechanisms of neuroendocrine system in the allometric growth of P. clarkii remain unclear. In this study, P. clarkii exhibiting significant allometric growth among individuals were sampled from three full-sibling families. The brain, eyestalk, nerve cord, and Y-organ were dissected for transcriptome analysis. Key functional genes were identified by random forest and DESeq2 methods. The gene pathways were enriched utilizing Kyoto Encyclopedia Genes and Genomes (KEGG) analysis. Gene topological analysis was established through weighted gene co-expression network analysis (WGCNA), and hub genes were screened by protein-protein interaction (PPI) networks. Transcriptomic analysis results were validated via qRT-PCR. RNA-Seq identified 31 differentially expressed genes (DEGs) (7 up- and 24 downregulated); 301 DEGs (23 up- and 278 downregulated); 1308 DEGs (474 up- and 834 downregulated); and 64 DEGs (52 up- and 12 downregulated) in the brain, eyestalk, Y-organ, and nerve cord, respectively. Crucial functional genes such as CHIA in the brain and perlucin-like in the eyestalk were notably identified. WGCNA revealed two hub modules, while PPI networks identified neuroendocrine regulators module which hub genes mainly including CP1876-like and cuticle protein AM1199-like, and structural components module which hub genes mainly including CUB& CCP Domain-Containing Protein, ARRDC, and E3 Ubiquitin protein ligase MCYCBP2-like. Correspondingly, the significant gene pathways such as amino sugar and nucleotide sugar metabolism (pcla00520) and insect hormone biosynthesis (pcla00981) were enriched. The results revealed the complex interactions and regulatory relationships of hub genes within hub modules to coordinate molting and growth. The results of RNA-Seq analysis were validated by the consistency of gene expression in qRT-PCR. In present study, key functional genes in the neuroendocrine system regulating allometric growth among individuals were identified, and significant pathways mainly include hormone synthesis were screened, thus constructing a neuroendocrine molecular regulatory network for the allometric growth of P. clarkii. Building on these investigations, a comprehensive mechanism whereby neuroendocrine regulators interact with structural components to coordinate molting and growth was proposed. The result would provide valuable insights into the molecular regulatory mechanisms of allometric growth, highlighting the interplay between the neuroendocrine system and relevant tissues.

Keywords: Procambarus clarkii; Allometric growth; Molecular regulation; Neuroendocrine system; Transcriptome.