Generation of Eco-Friendly and Disease-Resistant Channel Catfish(Ictalurus punctatus)Harboring the Alligator Cathelicidin Gene via CRISPR/Cas9 Engineering

As a precise and versatile tool for genome manipulation,the clustered regularly interspaced short palindromic repeats(CRISPR)/CRISPR-associated protein 9(Cas9)platform holds promise for modifying fish traits of interest.With the aim of reducing transgene introgression and controlling reproduction,upscaled disease resistance and reproductive intervention in catfish species have been studied to lower the potential environmental risks of the introgression of escapees as transgenic animals.Taking advantage of the CRISPR/Cas9-mediated system,we succeeded in integrating the cathelicidin gene(As-Cath)from an alligator(Alligator sinensis)into the target luteinizing hormone(lh)locus of channel catfish(Ictalurus punctatus)using two delivery systems assisted by double-stranded DNA(dsDNA)and single-stranded oligodeoxynucleotides(ssODNs),respectively.In this study,high knock in(KI)efficiency(22.38%,64/286)but low ontarget events was achieved using the ssODN strategy,whereas adopting a dsDNA as the donor template led to an efficient on-target KI(10.80%,23/213).The on-target KI of As-Cath was instrumental in establishing the lh knockout(LH^(–)_As-Cath^(+))catfish line,which displayed heightened disease resistance and reduced fecundity compared with the wild-type(WT)sibling fish.Furthermore,administration of human chorionic gonadotropin(HCG)and luteinizing hormone-releasing hormone analogue(LHRHa)can restore the reproduction of the transgenic fish line.Overall,we replaced the lh gene with an alligator cathelicidin transgene and then administered hormone therapy to move towards complete reproductive control of diseaseresistant transgenic catfish in an environmentally responsible manner.This strategy not only effectively improves consumer-valued traits but also guards against unwanted introgression,providing a breakthrough in aquaculture genetics to confine fish reproduction and prevent the establishment of transgenic or domestic genotypes in the natural environment.

Functionality of dietary antimicrobial peptides in aquatic animal health:Multiple meta-analyses

Effects of antimicrobial peptides(AMP)added to diets on aquatic animal health and body function are influenced by multiple factors such as animal species,initial body weight,the dosage of AMP and feeding duration.However,there is limited knowledge on the relationship between these factors and the body function of aquatic animals.Here,we aimed to perform multiple meta-analyses to investigate the effects of dietary AMP on growth performance(feed conversion ratio[FCR],specific growth rate[SGR]),enzyme activity(superoxide dismutase activity[SOD],lysozyme activity[LSA]),disease resistance(cumulative survival rate[CSR],the expression of immune-related genes[GENE])and the abundance of gut microbiota(MICRO)from a pool of empirical studies.Additionally,the dose-effect model was applied to determine the optimal AMP dose,initial body weight and feeding duration to maximize body function.To conduct the meta-analyses,we included 34 publications that estimated 705 effect sizes across 21 fish,2 shrimp and 2 shellfish species.The results confirmed that the inclusion of AMP in the diet can significantly improve SGR,SOD,LSA,CSR and GENE and decrease FCR for aquatic animals.Interestingly,our findings implied a slight positive effect of AMP on MICRO albeit with a limited number of studies available on fish gut microbial communities.Although no significant linear or quadratic relationship was predicted by meta-regression,the dose-effect indicated that the optimal AMP doses for FCR,SGR,SOD and LSA were 707.5,750.0,1,050.0 and 937.5 mg/kg,respectively.Taken together,fish with an initial body weight of 30 g could be fed with a dose of 600 to 800 mg/kg for 2 mo when AMP-supplemented diets were applied in aquaculture,which can effectively improve body function and health while lowering aquafeed costs.In addition,more studies should address fish gut microbiota to delimitate the influence of dietary AMP on MICRO in the future.