Abstract
The triangle sail mussel Hyriopsis cumingii (Lea) is the most important mussel species used for commercial freshwater pearl production in China. Mussel color is an important indicator of pearl quality. To identify genes involved in the nacre coloring, we conducted RNA-seq and obtained 541,268 sequences (298 bp average size) and 440,034 sequences (293 bp average size) in secreting purple and white nacre libraries (P- and W-libraries), respectively. The 981,302 Expressed Sequence Tags (ESTs) were assembled into 47,812 contigs and 289,386 singletons. In BLASTP searches of the deduced protein, 22,495 were proteins with functional annotations. Thirty-three genes involved in pearl or shell formation were identified. Digital expression analysis identified a total of 358 differentially expressed genes, and 137 genes in the P-library and 221 genes in the W-library showed significantly higher expression. Furthermore, a set of SSR motifs and SNPs between the two samples was identified from the ESTs, which provided the markers for genetic linkage, QTL analysis and future breeding. These EST sequences provided valuable information to further understand the molecular mechanisms involved in the formation, color determination and evolution of the pearl or shell.
Highlights
Pearl and nacre, or mother of pearl, have long been appreciated for their beauty, but have only been scientifically studied for the past 150 years [1]
Ethics Statement The handling of mussels was conducted in accordance with the guidelines on the care and use of animals for scientific purposes set by the Institutional Animal Care and Use Committee (IACUC) of Shanghai Ocean University, Shanghai, China
Small open reading frames might encode translated and biologically active peptides [35], so we included the short sequence in this study
Summary
Mother of pearl, have long been appreciated for their beauty, but have only been scientifically studied for the past 150 years [1]. As a result of this research, nacre is not just of interest for its aesthetic qualities, and as a material of exceptional performance when compared to the properties of its component parts [2]. For those engaged in fabricating biomimetic products, it has become a challenge to replicate the structure of the iconic biomineral [3]. The molluscan shell forming secretome is rapidly evolving This is pronounced in the genes encoding secreted proteins, many of which are likely to contribute directly to shell formation [8]. By directly comparing the transcriptomes of nacre forming cells in a bivalve and a gastropod, dramatic differences in the gene sets used to biofabricate the nacreous layer of the shell were identified [9]
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