Preliminary Study On The Structure Of The Digestive System And The Partial FABPs Family Gene Cloning And Expression Of Collichthys Lucidus

The digestive system is where fish digest and absorb nutrients and a vital immune organ.Once the barrier effect of the intestinal mucosa is damaged,it can cause hemorrhage in the organism,leading fish to death.Long-chain fatty acids regulate the health of the intestinal tract of fish.However,they cannot be directly broken down and used by cells.They are broken down into triglycerides,which are then used by the circulatory system to supply energy to the body and participate in its metabolic regulation.The participation of long-chain fatty acids in the reaction requires the assistance of related proteins,such as fatty acid transport proteins,fatty acid translocases,and fatty acid-binding proteins.In this paper,We have observed the digestive system’s morphology and the intestine’s histological structure in Collichthys lucidus.We identified,analyzed,and cloned for the expression of some members of the FABP gene family.The specific results are as follows.(1)By Anatomical observation of the morphology of the digestive system and by tissue slice to observe the structural features of the anterior,middle,and posterior intestine.The study showed that the digestive system of C.lucidus consisted of a short and thick esophagus,a finger-like pyloric caecum connected with the anterior intestine,and a short intestine.All of which were consistent with the characteristics of the digestive system of carnivorous fish.The plicamucosa height,muscle thickness,and crypt depth in the anterior intestine of C.lucidus were more significant than those in the posterior intestine,and there were significant differences(P<0.05).The number of goblet cells in the posterior intestine was significantly different(P<0.05)and more numerous than in the anterior intestine.This study can provide basic information for the subsequent in-depth study on the feeding,digestion and absorption,and immune regulation of C.lucidus.(2)We analyzed the composition of FABP gene family members in C.lucidus and studied the expression of FABP gene family members in various tissues of C.lucidus by bioinformatics.The results showed that 15 members of the FABP gene family were identified,with the length of the coding sequence(CDS)ranging from 378 bp to 432 bp,the number of amino acids ranging from 125 aa to 143 aa,and the structure consisting of 10 β-pleated sheets and two α-helix.Evolutionary analysis showed that the C.lucidus FABP gene is most closely related to Larimichthys crocea,a member of the family Sciaenidae,and most distantly related to the freshwater fish Astyanax mexicanus,distinguishing it from the mammalian Homo sapiens,Rattus norvegicus,and Mus musculus.Analysis of collinearity identified duplication fragments on only 6 of the 24 chromosomes of C.lucidus and identified six pairs of fragment duplication genes.Tissue-specific expression analysis showed that all genes were expressed in all tissues of C.lucidus,except for the fabp11 b gene,which is expressed in some tissues.The identification and analysis of the FABP gene family in C.lucidus can provide a biological basis for studying intestinal health,digestion,and metabolism of triglycerides in C.lucidus.(3)We cloned and obtained the c DNA sequence containing the open reading frame of fabp1,fabp7 a,and fabp11 b genes,using bioinformatics methods to analyze the structure and evolutionary relationships of the encoded proteins.Real-time PCR studied the expression of the genes in different tissues.The results showed that the c DNA sequence of the fabp1 gene was 475 bp,the c DNA sequence of the fabp7 a gene was 690 bp,and the c DNA sequence of the fabp11 b gene was 647 bp.The fabp1,fabp7 a,and fabp11 b genes encoded protein PI was less than 7,which was an acidic protein;and the stability coefficient was less than 40,which was a stable protein;all of them contained Lipocalin/cytosolic fatty-acid binding domain.The fabp1,fabp7 a,and fabp11 b genes of C.lucidus were more closely homologous with L.crocea and Nibea albiflora.The fabp1,fabp7 a,and fabp11 b genes were expressed in all tissues except for the fabp11 b gene,which didn’t detect in the middle kidney,spleen,and heart tissues,and the expression was significantly different in each tissue(P<0.05).This study provides a primary reference for further study on the biological properties of FABP gene family members and the role of fabp1,fabp7 a,and fabp11 b genes in lipid metabolism in C.lucidus.