Histologic Features Of Some Organs And Preliminary Study On Gene Expressions Of Large Yellow Croaker(larimichthys Crocea)cultured In Low Salinity Water

In this paper,the features of some organs of large yellow croaker?Larimichthys crocea?cultured in low salinity water were studied by histology method,while genes differentially expressed between large yellow croaker reared in low salinity water and in normal sea water were studied by RNA-seq analysis.Additionally,some significantly differentially expressed genes were verified by real-time qPCR.The results are as follows:?1?There was obvious changes between low salinity and control group in gill,liver,kidney and gonad.In low salinity group,epithelial cell of gill lamella became hyperplasia,part of them intumesced apparently and some even shed and became necrosis.The mucous cells became larger and the number increased,the chlorine cells showed the same conditions.The renal corpuscle expanded.The liver cell swelled,then became out of shape and occurred large number of vacuole and part of their nucleus deviated from the cell center.The oocyte of the phase 2 and phase 3 appeared more frequently than the phase 4,the oocyte of the phase 3 showed irregular polygons.The fat droplets were small and dense;what's more,the yolks localized on the inner edge of cell membrane and were less than those in control group.?2?The transcriptome sequencing result shows that the low salinity has great influence to breathing,cell morphology and immunity.In this study,the total number of low salinity transcriptome reads is 40585004,the total number of control transcriptome reads is 33475402,then wipe off the redundancy and splicing.We get 45877 isoforms in low salinity group,45416isoforms for the control group,and 50738 isoforms above all the samples.Among this there are712 isoforms which have significant differences of expression and 482 isoforms have highly significantly differences,355 isoforms increased and 357 isoforms decreased.We classify these transcriptions to three categories:biological processes,molecular function and cellular components?cellular component?,and then divided into 145 small classes.The hemoglobin complex,kinetochore microtubules,cytoplasmic microtubules of types of cells,the oxygen transporter activity,kinetochore binding,oxygen binding,microtubule plus-end binding,phospholipase activity of molecular function,and the oxygen transport of biological processes have highly significant difference?FDR 0.01 or less?,chemokine activity of molecular functional have significant differences?FDR 0.05 or less?.There are 690 isoforms can be positioned in KEGG database,and respectively set in 215 pathways.The significantly enriched pathways are 6,including the most significant difference of linoleic acid metabolism,arachidonic acid metabolism,others are alpha-Linolenic acid metabolism,vascular smooth muscle contraction,ether lipid metabolism and platelet activation.Among them,the platelet activation contains most differentially expressed isoforms 17,take up 2.46%of all.The linoleic acid metabolism,arachidonic acid metabolism,alpha-Linolenic acid metabolism,vascular smooth muscle contraction have extremely significant difference?FDR 0.01 or less?.Finally we find out four isoforms is closely related to the low salinity for subsequent fluorescence quantitative PCR.?3?The content of hemoglobin in low salinity groups was 105.13±4.95 g/L,increased by36.4%compared to the 77.05±3.95 g/L in control group,which had highly significant difference?P<0.01?.At the same time,the content of red blood cells in low salinity was 2.94±0.43×10⁶ mm^-3 compared to the control group of 1.06±0.19×10⁶ mm^-3 increased about 1.77folds,and also had significant differences?P<0.01?.?4?Fluorescence quantitative PCR results are consistent with the transcriptome,which prove the reliability of the transcriptome results.The RQ of comp14534_c0_seq1,comp34613_c1_seq1,comp36660_c1_seq25,comp36845_c1_seq17 in the low salinity groups were 4.53±0.25,7.02±0.29,6.78±0.27,3.21±0.23.And the RQ of control are 1.06±0.09,1.21±0.14,1.29±0.18,1.01±0.12.They had highly significant difference?P<0.01?.Among them,the hemoglobin compound raised 4.3 folds,oxygen binding raised 5.8 folds,cytoplasmic microtubules raised 5.3 folds and phospholipase activity raised 3.2 folds.