The Cloning of the PtDNMT1 Gene of Portunus trituberculatus and Its Expression Analysis in Low Salinity Adaptation

Abstract:

Methyltransferase (DNMT1) is an important gene that maintains the methylation state of the genome. This study uses the SMART-RACE technique to clone the DNMT1 gene of Portunus trituberculatus (PtDNMT1). The cDNA sequence of PtDNMT1 gene is 5919 bp, including the open reading frame of 4832 bp, and 1610 amino acids are encoded. The predicted molecular weight is 148.15 kDa, and the theoretical isoelectric point is 4.68. The structure prediction found that there are two special PtDNMT1 domain structures: the zf-CXXC zinc finger domain and the methyltransferase familial Dcm structure domain. The analysis of the evolutionary tree showed that PtDNMT1 gene and insects DNMT gather into one. PtDNMT1 was expressed in the hepatopancreas, gill, ovary, muscle, stomach, heart, and blood. The highest expression was found in the hepatopancreas, followed by the ovaries and gills. Then we get a further research about the PtDNMT1 gene expression during low salinity stress in gill, l hepatopancreas and muscle tissue. In gill tissue, we found that PtDNMT1 gene expression peaked (5 folds) after 6 h, and continued to 12 h (6 folds), then declined gradually, but was still significantly higher than the control group (3 folds). The expression of PtDNMT1 in the hepatopancreas was similar to the gills, however the peak time was later than in gill tissue (24 h), and the peak was higher than in the gills (8 folds). After low salinity stress, the expression of the PtDNMT1 gene in muscle was firstly reduced, then (24 h) increased to a peak (2.2 times), and the expression was raised to 72 h. This study is the first to clone the PtDNMT1 gene. According to its distribution characteristics and occurrence in various organizations, expression changes under salinity stress. We speculate that low salinity adaptations in DNA methylation in P. trituberculatus played an important role.