Revealing Mytilus galloprovincialis transcriptomic profiles during ontogeny

Area of Science:

• Marine Biology
• Developmental Biology
• Genomics

Background:

• Bivalve reproduction, particularly larval development, is crucial for species success but requires more research.
• Mediterranean mussels (Mytilus galloprovincialis) are globally significant, with their reproductive strategy potentially linked to their success.

Purpose of the Study:

• To investigate the transcriptomic profile during the ontogeny of Mytilus galloprovincialis.
• To analyze gene expression patterns across various developmental stages, from oocytes to juveniles.

Main Methods:

• Transcriptome sequencing (454 sequencing) of mussel hemocytes, adult tissues, and larvae.
• Development and utilization of a custom DNA microarray for gene expression analysis.
• Analysis of gene expression in unfertilized oocytes, veliger, pediveliger, settled larvae, and juvenile stages.

Main Results:

• Distinct transcriptomic profiles were observed across developmental stages, clustering by ontogeny.
• Oocytes possess a unique transcriptome, while settled larvae and juveniles exhibit similar gene expression patterns.
• Metamorphosis involves a specific set of differentially expressed genes related to differentiation and biosynthesis, with a notable down-regulation of immune response genes, including antimicrobial peptides.

Conclusions:

• Maternal RNA diminishes during larval development, and gene expression stabilizes post-settlement.
• The down-regulation of immune genes during metamorphosis suggests a developmental trade-off, prioritizing growth over defense.
• Oocytes with higher expression of genes like myticins are vital for successful offspring development, with low levels correlating to developmental failure before metamorphosis.