Ontogeny Of Immune Organs And Expression Characterization Of Socs1 Gene In Chinese Sturgeon(Acipenser Sinensis)

Chinese sturgeon,Acipenser sinensis,is the flagship species of the Yangtze River.Extensive studies have shown that the natural resources of wild Chinese sturgeon decreased rapidly since the closure of Gezhouba Dam.Chinese sturgeon is on the verge of extinction and was listed as a Category Ⅰ nationally protected species in China since 1988.And in 2010,this species is considered by the International Union for the Conservation of Nature(IUCN)as critically endangered.Artificial breeding is the foundation of the Chinese sturgeon off-site protection.The immune organs of sturgeon mainly include head kidney,thymus and spleen,and the main lymphomyeloid tissues are the meningel myeloid tissue,skin mucosa tissue,gill tissue the pericardial tissue and lymphoid masses of the intestine,especially in the spiral valve.The highly diversiform and well developed lymphoid tissues of sturgeons may serve as basis of efficient immune mechanisms.In this paper,the ontogeny of immune organs and expression characterization of suppressor of cytokine signalling 1(socs1)were studied on farmed F2 generation Chinese sturgeon(A.sinensis).These results will further deepen the understanding of the immune system of Chinese sturgeon.In theory,it enriches the basic biological data of sturgeon immune system research,and in practice provides theoretical guidance for the healthy breeding and disease prevention of Chinese sturgeon.Ontogeny of immune organs in Chinese sturgeon: The anatomy,continuous paraffin section and transmission electron microscopy(TEM)were used to observe the morphology,early development and ultrastructure of the head-kidney,thymus and spleen organs of larvae and juveniles Chinese sturgeon from 1 to 300 days of age.Themain results are as follows:1.The anatomical results showed that the head-kidney of Chinese sturgeon is located in the front of the ventral septum of the heart.It is the most front expanding part of the renal tube and covered with the basal layer.This tissue is diffuse in the early stage and developed into parenchyma in the later stage,showing a symmetrical distribution.The thymus of Chinese sturgeon is located on dorsal of the second gill arches,one pair and symmetry distributing.This organ is a smooth,soft,opalescent,translucent,lamellar and parenchymal tissue.The spleen of Chinese sturgeon is dull red and located near the stomach and the bending place of gut.Its surface is smooth and covered with the basement layer,and the main part is composed of the strip structure at the front and the butterfly structure at the back.2.The continuous paraffin section and microscopic observation results showed that the primordial appearance of Chinese sturgeon immune organs was in the order of head kidney,thymus and spleen,and the appearance of small lymphocytes was thymus,head kidney and spleen.The head kidney primordium can be seen at 3 dph,15 dph begins to lymphatic,39 dph renal tubules degenerate,and 150 dph develops into complete lymphoid hematopoietic tissue.Thymus primordium is visible at 7 dph,small lymphocytes can be observed at 12 dph,connective tissue and capillaries enter the thymus tissue at 20 dph,and the thymus at 26 dph is divided into cortical and medullary areas.The spleen primordium was visible at 9 dph,small lymphocytes were observed at33 dph,and red and white pulp regions appeared at 92 dph.The lymphocyte bridges were observed between the head kidney and thymus in larval stage.At 180 dph,Hassall’s corpuscles were observed in the thymus,and Melanocyte or Melano-macrophage centres(MMCs)were found in the head kidney,thymus and spleen.In conclusion,the immune organs of Chinese sturgeon have the characteristics of early primordial differentiated,slow developmental rate and long developmental cycle.3.The observation results of TEM showed that the head-kidney,thymus and spleen of Chinese sturgeon are all lymphoid organs connected by reticular cells.The most abundant cell types and the most complex tissue structure are found in the headkidney,which is mainly composed of granular cells and red cells.The spleen is the second complex tissue,in which red cells are mainly distributed,and more leukocytes can be seen in the white pulp.The thymic tissue is relatively simple,and the reticulocyte scaffold is mainly filled with lymphocytes.The results of TEM were consistent with those of continuous paraffin sections.Expression characterization of socs1 gene in Chinese Sturgeon: Suppressors of cytokine signaling(SOCS)are important suppressors of cytokine signal transduction and play an important role in the immune system.As an important member of this family,SOCS1 is involved in the differentiation,maturation and functional regulation of T lymphocytes,and plays a negative role in JAK/STAT signaling pathway.The RT-PCR was applied to clone the coding sequence of socs1.The predicted protein sequence and phylogenetic relationships were analyzed by bioinformatics methods.qRT-PCR was used to analyze the expression characterization of Chinese sturgeon.The main results are as follows:1.It was found that the length of socs1 was 639 bp,encoding 212 amino acids.Compared with the SOCS1 of other species,socs1 has a highly conserved central SH2 domain,a relatively conservative C-terminal SOCS box domain and a low complexity N-terminal region.Phylogenetic analysis showed that the SOCS1 amino acid sequence of Chinese sturgeon were clustered together with fish,and also showed highest similarity(96.23%)with the Acipenser ruthenus.The amphibians,reptiles,birds and mammals were clustered into another branch.2.The results of expression pattern analysis showed that socs1 gene of Chinese sturgeon was expressed in 8 tissues including liver,spleen,thymus,head kidney,middle kidney,gill,intestine and skin,among which the highest expression was in gill,the second in thymus,the lower in intestine and head kidney,and other tissues expression levels are similar.After poly(I:C)and Aeromonas hydrophila infection,the expression of socs1 in spleen primary cells of Chinese Sturgeon increased significantly.The socs1 expression level in the head-kidney,thymus and spleen tissues of juvenile Chinese sturgeon at different developmental stages first increased and then decreased.These indicated that socs1 may play an important role in maintaining the normal physiological state of the body and responding to pathogenic infections.