Transcriptome analysis provides insights into the skeletal malformation induced by dietary phospholipids deficiency in largemouth bass (Micropterus salmoides) larvae

Largemouth bass is one of the most important freshwater aquaculture species in China. However, the mechanisms underlying the development of skeleton in the fish are unclear. High-throughput RNA-Seq was used to analyze the transcriptome of largemouth bass skeleton between high-phospholipids and low-phospholipids groups. Thirty individuals each from 3 high-phospholipids families and 3 low-phospholipids families were used to reduce inaccuracies. The results indicated that 255 up-regulated and 329 down-regulated genes were identified in the differentially expressed genes (DEGs). GO and KEGG enrichment analyses revealed the DEGs were involved in the MAPK signaling pathway, phosphatidylinositol signaling system, glycosphingolipid biosynthesis-lacto and neolacto series and fatty acid degradation. Twist2 and Daam1, genes related to osteoblast development, were up-regulated in high-phospholipids group. BGLAP, gene associated with the skeletal development and osteohormatology, was also up-regulated in high-phospholipids group. PCOLCE b, a gene related to the development of gristle, was up-regulated in high-phospholipids group. Higher expression of SCPP1 and SCPP7 in high-phospholipids group was associated with tooth and bone development. The trend changes in the above genes all indicate that the lack of phospholipids may affect the skeletal development through the above genes, increasing malformations. In summary, these results provide valuable information about the reduction of deformity rates in largemouth bass and contribute to our understanding of the molecular mechanisms and regulative pathways regulating skeletal growth in teleosts. Overall design: The largemouth bass larvae were collected from the feeding trail of (Wang et al. 2022). Briefly, after 12 days' feeding trial, larvae fed the diet without phospholipid inclusion resulted in skeletal malformation at high proportion. The visual deformity rate was decreased with the increase of dietary phospholipids in a dose dependent manner, and only sporadic malformed fish was observed in the larvae fed the diet with 8% phospholipids inclusion. Therefore, three replicates of 30 deformity larvae per tank fed the diet without phospholipids supplementation were pooled after being measured for the body weight and body length for transcriptome analysis and gene expression analysis, and named as SP_L. Equivalent normal larvae per tank fed the diet with 8% phospholipids supplementation were sampled and named as SP_H.