The salinity effect on giant grouper innate immunity, Na+-K+-2Cl-cotransporter (NKCC2) and betanodavirus replication
Date Issued
2014
Date
2014
Author(s)
Chen, Tz-Shiang
Abstract
Giant grouper (Epinephelus lanceolatus) is an economically important fish species for marine aquaculture in Taiwan, but has been attacked by nervous necrosis virus (NNV) for years. In our previous study, high expression level of Na+-K+-2Cl- cotransporter 2 (NKCC2) was found in the survivor grouper larvae. In this study, the full length cDNA of NKCC2 was cloned, and its highest expression level was detected in the intestine, and low level expression was found in the brain. NKCC2 is a membrane channel protein for NaCl adsorption, and we found that its expression level in 30 ppt-acclimated grouper was higher than that in 15 ppt-acclimated fish. The adsorption of salt in intestine in marine fish is suggested to aid the passive adsorption of water for water homeostasis. To date, the information about the impact of salinity on the pathogen-induced mortality is still limited. Therefore, we compared the expression levels of NKCC2 gene, NNV RNA2 and some innate immunity genes, and the accumulated mortality of groupers reared in 30 and 15 ppt sea water after NNV infection. The cumulated mortality of NNV-challenged groupers reared in 30 ppt sea water was higher than that reared in 15 ppt sea water. When the salinity decreased from 30 ppt to 15 ppt after NNV infection, the cumulated mortality declined from 90% to 80%. On the contrary, as the salinity increased from 15 ppt to 30 ppt post NNV challenge, the cumulated mortality increased from 79% to 91%. During 5 days post infection (dpi), the expression patterns of NKCC2, Mx, TLR-3, MDA-5 and C3 genes were all increased at the first and then smoothly decreased, but the expression level of IL-1β continuously increased at the 5th day in head kidney and spleen. At 1 dpi, Mx gene expression in the fish of 30-ppt group was higher than that in 15 ppt-group; however, NNV RNA2 expression level in 30 ppt-group was lower than that in 15 ppt-group at the following 3rd and 5th days. In the same period of time, the leucocytes count in 30 ppt-group was higher than that of 15 ppt-group. In the fish which died within one day and collected at the 10 dpi, the expression level of NNV RNA2 in 30 ppt-group was lower than that in 15 ppt-group, but the expression level of IL-1β in 30 ppt-group was significantly higher than that of 15 ppt-group. In the survival fish sampled at the 14 dpi, the gene expression levels of NNV RNA2 and IL- 1β were much lower than that in the live and dead fish during acute infection. It is still unclear why higher salinity induced higher expression levels of some innate immune genes, but the inflammation maker gene IL-1β continuously increased at the 5th dpi might be one of the important factors result in higher mortality of the fish reared in 30 ppt salinity.
Subjects
石斑魚
β-野田病毒
鹽度
鈉鉀氯共轉運蛋白2
免疫基因
SDGs
Type
thesis
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