The peritoneum of fish expresses a specific gene pattern

The peritoneum is mainly composed of mesothelial cells,fiber cells,and fibers,with many free cells that come from tissue capillaries.Siniperca chuatsi is a valuable fish commodity and important freshwater aquaculture species in China.With the increase in the scale of its breeding,bacterial and viral disease of the S.chuatsi has become increasingly rampant in recent years.This study analyzed the peritoneal gene expression profile using transcriptome technology for the first time.The results showed that 95,711 unigenes were expressed in the peritoneum with an average length of 920.72 bp.In addition to the housekeeping genes,the genes of extracellular matrix protein 1a(ecm1),Angiopoietin-related protein 4-like(angptl4)and cysteine-rich protein 1(crip1)were highly expressed genes in the peritoneum,and they are key factors in peritoneal development and the maintenance of morphology.Meanwhile,many immune genes were also expressed in the peritoneum,including beta-2-microglobulin(b2m),MHC II invariant chain(cd74),prostate stem cell antigen-like protein(psca),claudin(cldn),heat shock protein 90(hsp90),complement component 4(c4),radical S-adenosyl methionine domain-containing protein 2(rsad2),and cathepsin S(ctss).The RT-PCR results showed that different genes exhibited different expression profiles.The transcriptome data indicated that b2m,cldn,hsp90,c4,and rsad2 were highly expressed in the peritoneum.b2m,cd74,psca,c4,and ctss were highly expressed after embryonic hatching,whereas cldn,hsp90,and rsad2 were expressed at early embryonic stages.Quantitative PCR demonstrated that b2m,cd74,cldn,hsp90,c4,and ctss genes were highly expressed after immunostimulation.This study provides significant data for studying the morphological and functional diversity of fish peritoneum and lays a foundation for research on mandarin fish immunity.