Functional Studies Of Lysyl Oxidase Like And Elongator Complex Protein 3 In The Innate Immunity Of Shrimp

Shrimp aquaculture is the pillar industry of aquaculture,but it suffers significant losses due to pathogenic infection of shrimp.Studies on the mechanism of innate immune in shrimp provide a theoretical basis and new ideas for disease prevention and control in shrimp aquaculture,and enrich the theory of innate immunity.Therefore,we conducted a series of studies on the innate immunity of Marsupenaeus japonicus,and obtained the following results:1.LOXL protein recognizes and binds viral envelope proteins and bacterial polysaccharides against pathogen infection via induction of expression of antimicrobial peptidesLysyl oxidases(LOXs)are copper-dependent monoamine oxidases,and they play critical roles in extracellular matrix(ECM)remodeling.The LOX and LOX like(LOXL)proteins also exert a variety of biological functions,such as developmental and growth regulation,tumor suppression,and cellular senescence.However,the functions of LOXLs containing repeated scavenger-receptor cysteine-rich(SRCR)domains in immunity are rarely reported.In this study,we characterized the antiviral and antibacterial functions of a LOXL protein containing tandem SRCR domains in M.japonicus.We found LOXL distribution in multiple tissues,and the mRNA level of LoxL was significantly upregulated in the hemocytes and intestines of shrimp challenged using white spot syndrome virus(WSSV)or bacteria.After the knockdown of LoxL via RNA interference,WSSV replication and bacterial loads were apparently increased,and the survival rate of the shrimp decreased significantly,suggesting that LOXL has a function against pathogen infection in shrimp.Mechanistically,LOXL interacted with the envelope proteins of WSSV or with lipopolysaccharide,peptidoglycan from bacteria in shrimp challenged using WSSV or bacteria;and promoted the expression of a battery of antimicrobial peptides(AMPs)via the induction of Dorsal nuclear translocation against viral and bacterial infection.Moreover,LOXL expression was also positively regulated by Dorsal in the shrimp challenged by pathogens.These results indicate that,by acting as a pattern recognition receptor,LOXL plays vital roles in antiviral and antibacterial innate immunity by enhancing the expression of AMPs in shrimp.2.Elongator complex protein 3 inhibits WSSV duplication as an analogue of interferonstimulated gene in crustaceansElongator complex protein 3,known as ELP3,is essential for the initiation of gene transcription in eukaryotes,acting as the catalytic subunit.ELP3 has,in addition to an acetyltransferase domain,the same domain(Radical S-adenosyl-L-methionine,Radical SAM)with the well-established antiviral factor virus-inhibitory protein(Viperin).Because no Viperin gene was identified in shrimp genome,we reasoned that ELP3 would most likely also have an antiviral function as Viperin.In this study,we characterized the antiviral function of ELP3 protein from M.japonicus.The mRNA level of Elp3 was significantly upregulated in hemocytes and intestines of shrimp challenged by WSSV.After knockdown of Elp3,the level of WSSV envelope protein VP28 was apparently increased at mRNA and protein levels,suggesting that ELP3 has antiviral function in shrimp.We also found that an interferon-like VAGO and transcription factor signal transducer and activator of transcription(STAT)affect ELP3 expression,indicating that Elp3 is most likely an interferon-stimulated gene(ISG).In addition,ELP3 bound to the envelope proteins of WSSV,which might inhibit the viral assembly.All these results indicate that ELP3 plays important roles in antiviral innate immunity in shrimp.