Biomarkers for determining the stress response in black tiger shrimp Penaeus monodon

Abstract

Mn-SOD gene and AK were amplified from haemocyte of P.monodon. Four novel variants of Mn-SOD were found whereas only one form of AK was observed. Tissue distribution and polymorphisms of Mn-SOD and AK of P.monodon were determined. The results indicated that the same level of Mn-SOD was clearly found in gill, heart, haemocyte, hepatopancreas, muscle and digestive tract while the highest level of AK was found in gill, followed by heart, haemocyte, hepatopamcreas, muscle, and digestive tract, respectively. A number of stress responsive genes in P.monodon, including Mn-SOD, AK, HSP70, HSP90, DAD-I, and IPx were under investigation on their responses to oxidative stress causing by vibrio infection, osmotic stress inducing by salinity changes, and handing stress stimulating by disturbing water and exposing to air. Transcriptional levels of Mn-SOD in both haemocytes and gills of P.monodon, were raised by the effect of oxidative, osmotic, and handling stress. The levels of HSP70 and HSP90 genes were reduced during oxidative, osmotic, and handling stress. These results are in contrast with the results reported in other studies. However, more study is needed to clarify the contradictory result. The level of AK gene expression in gill reduced during osmotic stress while up regulation of AK gene is observed in the haemocytes of handling stressed shrimps. The expression of DAD-I genes detected in gill of P.monodon was not induced by osmotic stress but repressed by oxidative and handling stresses. TPx gene was not induced by osmotic stress. The expression levels of TPx were decreased in haemocyte shrimps exposed to oxidative and handling stresses while it is raised in the gill of oxidative stressed shrimps. In conclusion. Mn-SOD, AK, and TPx can be further applied as biomarkers for determination of stresses in P.monodon.