Vibriosis is a devastating bacterial disease for the shrimp industry, causing significant economic losses. To combat this problem, scientists have sought to develop shrimp with stable hereditary resistance. A new study has shed light on the mechanisms behind this resistance.
A team of scientists from the Institute of Oceanology of the Chinese Academy of Sciences and the University of Chinese Academy of Sciences, based on resistant and susceptible families of Litopenaeus vannamei obtained through selective breeding, analyzed the mechanisms of resistance to vibriosis in terms of both host and commensal microorganisms.
Approaches in Breeding for Disease Resistance
Selecting and breeding disease-resistant broodstock is an effective and sustainable strategy to control vibriosis. Several families of disease-resistant shrimp have been constructed. Based on these breeding lines, previous studies have focused on identifying genetic variations and differentially expressed genes (DEGs) between resistant and susceptible families to find targets leading to disease resistance.
In previous work, it was suggested that polymorphisms in immune genes such as LvALF and TRAF6 are associated with disease resistance in shrimp. However, the key mechanisms of disease resistance remain unclear despite numerous genetic clues provided.
Epigenetics in Aquaculture
In addition to the genetic basis, epigenetic remodeling also plays a functional role in shaping traits in aquaculture. Epigenetic studies in shrimp are still in their infancy. Environmental factors, including pathogens and artificial selection, can influence epigenetic changes to produce new phenotypes that can be passed on to offspring.
DNA methylation is one of the most studied epigenetic mechanisms, primarily correlated with the negative regulation of gene expression. However, to date, the functional role of methylation and other epigenetic regulators in shaping shrimp aquaculture traits has not been reported.
Gut Microbiota and Disease Resistance
A dense and diverse microbial community inhabits the gut and co-evolves with the host. Gut microbiota is a key regulator in organism physiology, immunity, and health. A primary function of the gut microbiota is to help the host resist pathogen colonization and the overgrowth of indigenous pathobionts, known as the colonization resistance defense mechanism.
Researchers have reported that guts enriched with probiotics in some disease-resistant animal families can effectively inhibit pathogen growth. Therefore, forming a disease-resistant microbial community will profoundly impact improving host resistance to pathogens. However, the composition of the gut microbiome is influenced by multiple factors, and it is unclear whether the host can build a disease-resistant microbial community under artificial selection and what may aid in its formation.
Study on Vibriosis Resistance in L. vannamei
In this study, based on resistant and susceptible families of L. vannamei obtained through artificial selection, researchers analyzed the mechanisms of resistance to vibriosis in terms of both the host and commensal microorganisms. The potential roles of epigenetic regulation and the gut microbiome in Vibrio resistance were identified through methylome, transcriptome, and microbiome sequencing, and methyltransferase inhibitor treatment.
According to the study authors, this study provides the first comprehensive investigation of genome-wide DNA methylation patterns and microbiome variations between resistant and susceptible families.
A Microbial Shield
Researchers managed to create resistant and susceptible Pacific white shrimp (Litopenaeus vannamei) families through four generations of artificial selection. Surprisingly, they discovered that these shrimp had developed resistance to colonization by the Vibrio bacteria.
The key to this resistance lies in the composition of their gut microbiome. Resistant shrimp showed a specific enrichment of a single probiotic species: Shewanella algae. This beneficial bacterium plays a crucial role in reducing Vibrio load.
Epigenetic Memory of Resistance
Even more surprising is the finding that this resistance ability can be hereditary and influenced by epigenetic changes in the shrimp. These changes, which affect how genes are expressed without altering the DNA sequence, appear to be fundamental in developing resistance.
Scientists identified a group of genes specifically activated in resistant shrimp due to reduced DNA methylation. These genes, related to lactate production and iron balance, create a favorable environment for Shewanella algae growth. In turn, the increased lactate benefits shrimp survival against Vibrio infections.
Implications for the Shrimp Industry
This discovery has significant implications for aquaculture. Understanding the mechanisms of resistance to vibriosis will allow the development of more effective strategies to prevent and control this disease. Moreover, selecting shrimp lines with stable genetic resistance can significantly improve the industry’s sustainability and profitability.
In summary, this study reveals a complex defense mechanism against vibriosis in shrimp, based on the interaction between the gut microbiome, shrimp genetics, and epigenetic factors. These findings open new doors for developing healthier and more sustainable farming strategies.
Conclusion
The study results suggest that colonization resistance can be memorized as epigenetic information by the host, playing a crucial role in vibriosis resistance. These findings not only offer new insights into the key mechanisms in forming disease resistance in shrimp but also provide clues for controlling vibriosis in aquaculture and selecting superior shrimp lines with high disease resistance.
The study was funded by the Natural Science Foundation of China, the National Key Research & Development Program of China, the China Agriculture Research system-48, and the Taishan Scholars Program.
Contact
Fuhua Li
CAS and Shandong Province Key Laboratory of Experimental Marine Biology, Center for Ocean Mega-Science, Institute of Oceanology, Chinese Academy of Sciences
Qingdao, China
Email: fhli@qdio.ac.cn
Reference (open access)
Yuan J, Yu Y, Li S, Zhang X, Zhang C, Li R, et al. (2024) Shrimp shapes a resistance trait against vibriosis by memorizing the colonization resistance of intestinal microbiota. PLoS Pathog 20(7): e1012321. https://doi.org/10.1371/journal.ppat.1012321
