Complete mitochondrial genome of a natural triploid crucian carp mutant, Carassius auratus var. pingxiangnensis, and phylogenetic analysis of different ploidies in crucian carp.

Carassius auratus var. pingxiangnensis is a natural triploid crucian carp mutant. In order to understand its placement and genetic background at the gene level, the characteristics of mitochondrial DNA sequences and phylogenetic relationship were examined. The results showed that the mitochondrial DNA is a circular double-stranded DNA molecule that is 16,576 bp in length with 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes, and a non-coding control region. Mitochondrial genes overlapped by a total of 40 bp in 11 different locations from 1 to 14 bp. The base composition of the C. auratus mitogenome was estimated to be 29.70% A, 26.74% C, 15.35% G, and 28.21% T. The central conserved blocks and the conserved blocks were compared and were similar among C. auratus var. pingxiangnensis and six other cyprinids with different ploidies. The origin of light strand replication was similar to that of other vertebrates; it was 33 bp, but the characteristic sequence motif 5ꞌ-GCCGG-3ꞌ at the base of the stem within tRNA(Cys) was mutated to 5ꞌ-GGCGG- 3ꞌ. Our phylogenetic analysis based on whole mitogenome sequences indicated that C. auratus var. pingxiangnensis was clustered with C. auratus and then sister-grouped with Carassius gibelio. The systemic developmental tree of crucian carp with different chromosome ploidies showed that diploid C. auratus auratus was clustered with triploid C. auratus auratus, sister-grouped with tetraploid C. auratus auratus, and clustered with other diploid, triploid, and tetraploid C. auratus.

Molecular characteristics and expression of calmodulin cDNA from the freshwater pearl mussel, Hyriopsis schlegelii.

Calmodulin (CaM) is a multifunctional intracellular calcium ion receptor protein that participates in a range of cellular processes, including calcium metabolism in mussels. To investigate the role of CaM in freshwater mollusk shell calcium metabolism, the full-length CaM cDNA was isolated from the freshwater pearl mussel, Hyriopsis schlegelii (referred to as hsCaM) using SMART RACE technology. The full-length hsCaM was 855 bp in size, containing a 70-bp 5'-untranslated sequence, a 447-bp open reading frame, a 309-bp 3'-untranslated sequence, and a 26-nucleotide long poly(A) tail. The hsCaM mRNA expression in different mussel tissues was examined using real-time PCR. The hsCaM mRNA was found to be ubiquitously expressed, but far more abundant in the gill, foot, and mantle than in the posterior adductor muscle. Real-time PCR was also used to determine hsCaM mRNA expression levels in mantle tissues of H. schlegelii at different ages. No significant differences between one-, two-, and three-year-old mussels were detected, but expression increased in four-year-old mussels and then decreased in five-year-old mussels. CaM appears to be involved in calcium regulation of the mantle in four-year-old mussels, which may secrete more mother of pearl during pearl culture.