Abstract
Different shrimp species are known to possess apparent distinct resistance to different pathogens in aquaculture. However, the molecular mechanism underlying this finding still remains unknown. One kind of important antimicrobial peptides, anti-lipopolysaccharide factors (ALF), exhibit broad-spectrum antimicrobial activities. Here, we reported a newly identified ALF from the shrimp Litopenaeus vannamei and compared the immune function with its counterpart in the shrimp Fenneropenaeus chinensis. The ALF, designated as LvALF8, was specifically expressed in the lymphoid organ of L. vannamei. The expression level of LvALF8 was apparently changed after white spot syndrome virus (WSSV) or Vibrio parahaemolyticus challenges. The synthetic LBD peptide of LvALF8 (LvALF8-LBD) showed strong antibacterial activities against most tested Gram-negative and Gram-positive bacteria. LvALF8-LBD could also inhibit the in vivo propagation of WSSV similar as FcALF8-LBD, the LBD of LvALF8 counterpart in F. chinensis. However, LvALF8-LBD and FcALF8-LBD exhibited apparently different antibacterial activity against V. parahaemolyticus, the main pathogen causing acute hepatopancreatic necrosis disease (AHPND) of affected shrimp. A structural analysis showed that the positive net charge and amphipathicity characteristics of LvALF8-LBD peptide were speculated as two important components for its enhanced antimicrobial activity compared to those of FcALF8-LBD. These new findings may not only provide some evidence to explain the distinct disease resistance among different shrimp species, but also lay out new research ground for the testing and development of LBD-originated antimicrobial peptides to control of shrimp diseases.
Highlights
The LPSbinding domain (LBD) peptide of LvALF8 showed a strong antibacterial effect against all the bacteria tested in this study, including six Gramnegative and three Gram-positive bacteria
The LBD peptide of LvALF8 led to the distinct agglutination with V. parahaemolyticus
In vivo tests confirmed its antibacterial activity to V. parahaemolyticus
Summary
Shrimp products are known to be a significant source of aquatic animal protein [1] and shrimp aquaculture production reached more than 3,000,000 metric tons in 2018, according to the statistics of the Food and Agriculture Organization (FAO) Among the cultured shrimp species, Pacific whiteleg shrimp Litopenaeus vannamei accounts for the main part of the global shrimp production [2]. Since the introduction into China in the 1990s [3], L. vannamei has rapidly replaced its close relative Fenneropenaeus chinensis and become the main cultured shrimp species [1]. One of the main reasons for the replacement is that L. vannamei appears to be more tolerant to the hypersaline environment and pathogens infection than F. chinensis [4,5,6]. Investigation on the molecular mechanism underlying the difference is very limited
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