Effects Of Exposure In Air On Immune Index And Gene Expression In Ruditapes Philippinarum

Ruditapes philippinarum is one of the important breeding mudflat shellfishes distributed along the coast of China. R. philippinarum are cultured intertidally and may be exposed to stressful environmental conditions for several hours each day. These conditions may include hours of air exposure and temperature changes. In this study, the immune indexes were measured in clams sufferred exposure in air and then emersion into water. And the differentially expressed genes of R. philippinarum after the stress of exposure in air were screeneed using RNA-seq technique. The main research results are as follows:1. The effect of air exposure at different temperature(5℃、15℃、25℃) on the survival r ates in R. philippinarumThe survival rates increased with the rising temperature and time of exposure in air in clam. Less than 10% clams were dead during exposure in air at three temperature groups, which showed that the clams could be transported air exposure within 48 h. Lower temperature should be considered when transported them air exposure for a longer time. These results showed that R. philippinarum have a strong ability to resistant air exposure for the reason of the tightly closed shells.2. The effect of air exposure at different temperature(5℃、15℃、25℃) on the immune indexes in R. philippinarumThe levels of MDA and NO in visceral mass and gill of clams were raised during air exposure, which indicated that there were a large of malondialdehyde through lipid peroxidation reaction along with air exposure, and the clams could produce large amount of NO to protect themselves. The activities of AKP, ACP, SOD and CAT did not show significant changes during air exposure, but rised when the clams reculutred in sea water, which suggested that there would be compensatory reaction after suffering air exposure and temperature change. And this would be a good direction of health aquaculture in clams. The visceral mass responsed quickly and played more important role than gill during air exposure and reculture in sea water in clams.3. Gene expression analysis during air exposure.Illumina paired-end(PE) RNA-Sequencing was performed to identify the differentially expressed genes upon exposure stress. The reads were de novo assembled into 241381 transcripts(>200bp) by using a combined assembly strategy, the average length was 769 and N50 was 1277 bp. 156644 unigenes were assembled, with the average lengh of 649 bp and N50 of 1046 bp. 30.76% unigenes got BLASTX hits. Compared to the control, a total of 1765 unigenes with significantly differential expression levels were identified in the visceral mass, among them, 1171 were up-regulated and 571 were down-regulated. 1765 unigenes showed differential expression levels in gill with control, 832 were up-regulated and 933 were down-regulated. These results showed that the metabolic activity in visceral mass were promoted, and the respiratory activity were depressed in gill during air exposure in R. philippinarum.These results will facilitate further studies of cloning genes and molecular mechanisms of stress tolerance of air exposure in R. philippinarum.