The widespread use of antibiotics in aquaculture has led to an urgent issue: the rise of multidrug-resistant bacteria. Addressing this, our study explores a promising solution through the defensive abilities of a newly found type 2 β-defensin, a kind of host defense peptide, which is produced by the defb2 gene in the gilthead seabream (Sparus aurata), a fish important for aquaculture. This β-defensin shares a significant evolutionary heritage with its counterparts in other teleost fish, as evidenced by its conserved genomic structure and characteristic cysteines crucial for its function and stability. Our protein analysis uncovered that defb2 encodes a precursor peptide, which is processed into a mature peptide crucial for combating pathogens.
We’ve found that this gene defb2 predominantly is expressed in organs like the intestine and skin, areas first in line for microbial defense, and interestingly, its levels diminish upon exposure to common aquacultural pathogens, such as Vibrio harveyi and nodavirus. This suggests a highly targeted immune mechanism. Moreover, structural comparisons with other β-defensins revealed subtle differences that suggest a distinct mode of action; while β-defensin 1 might may penetrate pathogen membranes, β-defensin 2 appears to instead block pathogen proteins, preventing their harmful effects without breaking the membrane. Such findings highlight the therapeutic potential of β-defensins beyond traditional antibiotics, providing a sustainable way to combat bacterial resistance in aquaculture. Our investigation reveals the complex evolutionary history and structural details of β-defensins in gilthead seabream, further suggesting them as an innovative and sustainable solution to tackle antibiotic resistance in aquaculture.
References
1. Cuesta, A.; Meseguer, J.; Esteban, M. Á. Molecular and functional characterization of the gilthead seabream β-defensin demonstrate its chemotactic and antimicrobial activity. Molecular Immunology 2011, 48(12), 1432–1438. doi:10.1016/j.molimm.2011.03.022.
2. Das, S.; Pradhan, C.; Pillai, D. β-Defensin: An adroit saviour in teleosts. Fish & Shellfish Immunology 2022, 123, 417–430. doi:10.1016/j.fsi.2022.03.017.
Acknowledgements
Jhon A. Serna-Duque have PhD grants (FPU19/02192). This work has been financed by the project MCIN/ AEI /10.13039/501100011033 (grant number PID2020-113637RB-C21) and is part of the ThinkInAzul programme supported by MCIN with funding from European Union Next Generation EU (PRTR-C17.I1) and by the Comunidad Autónoma de la Región de Murcia-Fundación Séneca (Spain).