Transcriptomic analysis of differentially expressed genes in the larval settlement and metamorphosis of peanut worm Sipunculus nudus

Abstract

Larval development, especially settlement and metamorphosis, has a vital influence on commercial culture during the life cycle of marine invertebrates. Sipunculus nudus, a peanut worm, is an important economic aquaculture species. However, information about the mechanism of its larval settlement and metamorphosis is still limited. Transcriptomic analysis was performed to determine the DEGs between the pelagospheric larva and creeping larva of S. nudus. A total of 96,455 unique unigenes were obtained and 46,355 were annotated. Transcriptome analysis revealed 19,352 DEGs, including 9,923 that were upregulated and 9,429 downregulated after settlement and metamorphosis. KEGG pathway enrichment analyses revealed that these DEGs were mainly involved in the Notch signaling pathway, TNF signaling pathway, protein digestion and absorption, thyroid hormone signaling pathway, and ECM–receptor interaction, and so on. Furthermore, the changes in genes related to cytoskeleton and cell adhesion indicated that protein degradation and apoptosis during metamorphosis mediate the loss of larval cilia and ECM remodeling functions in S. nudus metamorphosis. Changes in genes related to signal transduction and nervous system suggested the cessation of larval swimming, which is involved in settlement and metamorphosis. Changes in genes related to ingestion and digestion indicated that dietary shift occurred with metamorphic transition. Changes in some genes related to stress response and immunity indicated that conditioning induced the immune response of peanut worm. The results improve understanding of the physiological traits controlling S. nudus metamorphosis and provide a solid basis for further study.

Keywords

• Sipunculus nudus
• transcriptomic
• settlement and metamorphosis
• larval