Constitutive expression and tissue-specific variations of antimicrobial peptide genes in healthy adult Oreochromis niloticus

Background

Antimicrobial peptides (AMPs) are molecules of the innate immune defense mechanism, which play a vital role in maintaining the healthy state of organisms thriving in varied and diverse habitats.

Methods and results

The present study investigated the expression profile of ten AMP genes, such as β-defensin, hepcidin, histone H2A-derived AMP, piscidin-1 to -5, thymosin β1, and thymosin β4, in tissues like gill, blood, skin, muscle, stomach, intestine, pancreas, gonad, brain, heart, and liver of healthy adult Oreochromis niloticus. Quantitative PCR analysis affirmed the constitutive expression of all AMP genes, albeit at varying levels across tissues. The constitutive expression pattern of β-defensin, hepcidin, and histone H2A-derived AMP in mucosal and systemic tissues indicates its active involvement in the innate immune responses. The expression profile of piscidin isoforms also reinstates the functional diversity within the piscidin AMP family and the transcriptomic profiling of thymosin isoforms suggests its involvement in various physiological functions.

Conclusions

The findings suggest tissue-specific roles for AMPs in the innate immune defense system of Oreochromis niloticus. The expression of thymosin β in non-immune related tissues highlights its involvement in broader physiological processes. These results contribute to the understanding of AMP expression patterns and their functional disposition in the fish tissues. Further studies are needed to elucidate the functional significance of tissue-specific AMP expression and its role in fish health and disease resistance.