Transcriptome Analysis of Shell Color-Related Genes in the Clam Meretrix meretrix

Abstract

Color polymorphism has received much attention due to its strong implications for speciation and adaptation. In contrast to body color, little is currently known about the molecular mechanism of shell color formation. This study represents the first analysis of the relationship between whole-scale gene expression and shell color variations in the marine bivalve mollusks via comparative transcriptome analyses. Three clam Meretrix meretrix strains with different and monotonous shell color patterns, which were developed by our 10-year artificial selection, combined with clams with nearly white shell color were used in the analyses. The results supported the idea that there was a relationship between gene expression and shell pigmentation in the clam M. meretrix, and complex signal transduction were involved. It was proposed that Notch signaling pathway played a crucial role in shell pigmentation in a gene-dosage dependent pattern and also potentially involved in the shell color patterning. Calcium signaling process may equally be implicated in shell color formation via activation of Notch pathway. Other differentially expressed genes (e.g., Myl, Mitf) potentially implicated in shell color pigmentation were also noticed. This study provides information on the expression profiles of clams with different shell color morphs and sheds light on color formation mechanism of shell.

The Whole-Genome and Transcriptome of the Manila Clam (Ruditapes philippinarum)

“…To date, genomic and transcriptomic analysis of many other bivalve species focusing on the identification of candidate genes related to immunological defense (Ertl et al 2016; Moreira et al 2012; Nam et al 2016; Rao et al 2015), response to benzo (a) pyrene toxicity (Liu et al 2014b), shell color (Yue et al 2015), reproduction (Li et al 2016; Patnaik et al 2016; Teaniniuraitemoana et al 2014), and environmental stress (Milan et al 2011) in order to understand the biological mechanisms involved in the above factors. Recently, transcriptome analysis of R. philippinarum using 454 pyrosequencing technology revealed putative members of immunological defense genes involved in complement cascades, apoptosis, and the toll like signaling pathways (Moreira et al 2012).…”

Identification of a laccase gene involved in shell periostracal tanning of the clam Meretrix petechialis

“…M. petechialis has a typical periostracum outside the calcified shell; the colour of this periostracum determines the colour of the shell (Yue et al 2015). Periostracum synthesis starts at the early stages of development, and the periostracum grows continuously over the entire life of the bivalve.…”

“…After a basic local alignment search tool (BLAST) analysis of the expressed sequence tag (EST) sequences from the cDNA library of Meretrix petechialis that we had previously constructed (Yue et al 2015), one EST sequence (~400 bp) showed the highest similarity to the laccase gene. The full-length laccase cDNA of M. petechialis (MpLac) was then obtained by using the rapid amplification of cDNA ends (RACE).…”

“…Clams with maroon shell colour (strain WM) (Yue et al 2015) were acclimated in the laboratory for a week and then randomly divided into 3 groups, i.e. the dsLac-injected group, dsEGFP-injected group (negative control) and PBS-injected group (blank control).…”

“…The Asiatic hard clam Meretrix petechialis is mainly distributed in the coastal areas of South and Southeast Asia and is an important commercial marine bivalve species (Tang et al 2006). M. petechialis has a typical periostracum outside the calcified shell (Yue et al 2015); thus, this species is an excellent model for investigation of shell periostracal tanning. In the present study, we identified a laccase-like gene from M. petechialis (MpLac) and investigated whether laccase is also involved in the tanning of the clam periostracum.…”