| Apostichopus japonicus (Selenka) is a typical kind of temperate zone species. It undergoes aestivation in high-temperature environments with serious tissue regression, metabolic rate depression and defence regulation. In this dissertation, the transcriptome analysis, the regulatory mechanism of tissue regression and the transcriptional variation of epigenetic modifiers, antioxidant enzymes and ion motive ATPase were studied in aestivating A. japonicus. The main results were as follows:1. Intestine regression of aestivating A. japonicus was associated with apoptosis. A. japonicus was induced into aestivation at temperature 25°C, and the intestine histology, intestine histochemistry and apoptosis associated genes expression were measured. H&E staining and TUNEL in situ analysis revealed the apoptosis of intestinal cells during aestivation visually. It indicated that aestivation led the intestine of A. japonicus into cells deletion by apoptosis soon after the sea water temperature rose and out of apoptotic events in 20 days. Transcriptional quantification of three genes associated with apoptotic regulation BAX, CTSD and ACIN1 was carried out. Comparing the mRNA level of these genes between active and aestivated sea cucumbers, variations of these genes during aestivation showed that:at 0d, only the expression of BAX got significant increase; at 5d and 10d, all the BAX, ACIN1 and CTSD got notably transcriptional increase; at 20d and 40d, all three objective genes expression reverted to the control level except the CTSD got significantly decrease at 40d.2. Gene expression was notably regulated during aestivation of A. japonicus and several groups of dominantly expressed genes were transcriptionally suppressed. High-throughput 454 cDNA sequencing by Roche 454 (GS FLX Titanium System) was performed on A. japonicus and a comprehensive evaluation of transcriptional variation during aestivation was revealed. Totally 279,933 high-quality ESTs were obtained and assembled into 87,059 Unigenes (56,416 Contigs and 30,643 Singlets). Assembled sequences were annotated with gene names (7,786 Unigenes) and gene ontology terms (3,755 Unigenes). Gene ontology analysis showed that suppression of gene expression occurred in several groups of dominantly expressed genes which associated with binding and catalytic activities, biological regulation and metabolic processes and extracellular region part. Site polymorphism of Unigenes was analysised and numerous sites of SSR and SNP were obtained.3. Transcriptional variation of epigenetic modifiers indicated that gene suppression during aestivation of A. japonicus was associated with epigenetic regulation. Eight genes which played important roles in epigenetic modification were obtained from transcriptome database. The sea cucumbers were induced to aestivation at temperature 25°C, and the intestines were analyzed for epigenetic modification associated genes expression. Comparing the mRNA level of identified epigenetic modifiers between active and aestivated sea cucumbers, variations of these genes expression during aestivation were revealed. The DNA methylation, chromatin remodelling, histone deacetylation and histone methylation associated modifiers got significantly transcriptional increase during aestivation. Consistent result was found in the investigation of aestivated sea cucumber in Aug.4. Transcriptional variation of antioxidant enzymes was found in respiratory tree of A. japonicus during aestivation. Five genes which played important roles in antioxidant defence of A. japonicus were analyzed in transcription level. In thermal induced aestivated sea cucumbers, the expression of Cu/Zn-SOD and PRDX5 got increase and the expression of CAT and PHGPx got decrease, meanwhile the PRDX6 was basically got little expressional change. Consistent variation was found in the investigation of aestivated sea cucumber in Aug.5. Ion motive ATPase in intestine A. japonicus got constant transcription during aestivation. Four genes associated with ion motive ATPase were obtained and analyzed in transcription level. In field sampled and thermal induced aestivated sea cucumbers, the Na+/K+ ATPase, SERCA and V-ATPase, B expressed stably except the V-ATPase, A got significant decrease.
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