Identification and functional analysis of Dmrt1 gene and the SoxE gene in the sexual development of sea cucumber, Apostichopus japonicus.

Members of the Doublesex and Mab-3-related transcription factor (Dmrt) gene family handle various vital functions in several biological processes, including sex determination/differentiation and gonad development. Dmrt1 and Sox9 (SoxE in invertebrates) exhibit a very conserved interaction function during testis formation in vertebrates. However, the dynamic expression pattern and functional roles of the Dmrt gene family and SoxE have not yet been identified in any echinoderm species. Herein, five members of the Dmrt gene family (Dmrt1, 2, 3a, 3b and 5) and the ancestor SoxE gene were identified from the genome of Apostichopus japonicus. Expression studies of Dmrt family genes and SoxE in different tissues of adult males and females revealed different expression patterns of each gene. Transcription of Dmrt2, Dmrt3a and Dmrt3b was higher expressed in the tube feet and coelomocytes instead of in gonadal tissues. The expression of Dmrt1 was found to be sustained throughout spermatogenesis. Knocking-down of Dmrt1 by means of RNA interference (RNAi) led to the downregulation of SoxE and upregulation of the ovarian regulator foxl2 in the testes. This indicates that Dmrt1 may be a positive regulator of SoxE and may play a role in the development of the testes in the sea cucumber. The expression level of SoxE was higher in the ovaries than in the testes, and knocking down of SoxE by RNAi reduced SoxE and Dmrt1 expression but conversely increased the expression of foxl2 in the testes. In summary, this study indicates that Dmrt1 and SoxE are indispensable for testicular differentiation, and SoxE might play a functional role during ovary differentiation in the sea cucumber.

The complete mitochondrial genome of Neptunea arthritica cumingii Crosse, (Gastropoda: Buccinidae).

The complete mitochondrial (mt) genome of the Neptune whelk, Neptunea arthritica cumingii, was determined using genome walking techniques in this study. The total length of the mt genome sequence of N. arthritica cumingii was 15 256 bp, including 13 protein-coding genes, 21 transfer RNA genes and 2 ribosomal RNA genes. The overall composition of the mitogenome was estimated to be 30.85% for A, 38.59% for T, 15.15% for C and 15.40% for G, indicating that an A + T (69.44%)-rich feature occurs in the N. arthritica cumingii mitogenome. The phylogenetic relationships of 11 mollusc species were constructed based on the complete mtDNA sequences by the neighbour-joining method using MEGA 5.0 software (MEGA Inc., Englewood, NJ).