Transcriptomics and gut microbiome analysis of the edible herb Bidens pilosa as a functional feed additive to promote growth and metabolism in tilapia (Oreochromis spp.)

Abstract

Background To reduce the use of antibiotics and chemicals in aquaculture, an edible herb - B. pilosa - has been selected as multifunctional feed additives to address this issue. Although there has been considerable research into the effects of B. pilosa on poultry, the wider effects, particularly on the growth and gut microbiota in fish, remain largely unexplored. We aim to investigate the interactive effects between the host on growth and the gut microbiota using transcriptomics and gut microbiota in B. pilosa-fed tilapia. Results In this study, we added 0.5% and 1% B. pilosa to the diet and observed that the growth performance of tilapia was significantly increased after 8 weeks of feeding. Comparative transcriptome analysis was performed on RNA sequence profiles obtained from liver and muscle tissues. Functional enrichment analysis showed that B. pilosa regulates several pathways and genes including amino acid metabolism, lipid metabolism, carbohydrate metabolism, endocrine system, signal transduction and metabolism of other amino acids. The expression of selected growth-associated genes was validated by qRT-PCR. The qRT-PCR result indicated that B. pilosa may enhance growth performance by activating the expression of liver igf1 and muscle igf1rb genes and inhibiting the expression of the muscle negative regulator myostatin b (mstnb). Enhancement of endocrine Igf1/Igf1rb signaling and suppression of Mstn signaling both induced the expression of myogenic regulatory factors (MRFs), myod1, myogenin and mrf4, to promote muscle growth in tilapia. The predicted function of the gut microbiota showed several significantly different pathways that overlapped with the KEGG enrichment results of differentially expressed genes in the liver transcriptomes. This suggests that gut microbiota may be able to influence liver metabolism through the gut-liver axis in B. pilosa-fed tilapia. Conclusions In conclusion, dietary B. pilosa can regulate endocrine igf1 signaling and myostatin signaling to activate expression of MRFs to promoter muscle growth, and alter the composition of gut bacteria, which can then affect liver amino acid metabolism, carbohydrate metabolism, the endocrine system, lipid metabolism, metabolism of other amino acids, and signal transduction of the host, ultimately enhancing growth performance. Our results suggest that B. pilosa has the potential to be a functional additive that can be an alternative to reduce antibiotics as growth promoter in aquaculture organisms.