MOLT-DEPENDENT TRANSCRIPTOMIC ANALYSIS OF ADULT BARNACLE Amphibalanus amphitrite

Barnacles are major contributors to fouling on submerged surfaces. While their anatomy is well known, a complete understanding of growth and adhesion during cyclic molting is important to develop adhesion mitigation strategies. During growth, barnacles expand their adhesive interface by secreting a proteinaceous material at their leading edge while also developing a new cuticular slip and promoting biomineralization of their rigid shell. Little is known about the molt- and tissue-specific expression of barnacle protein genes, including cement proteins that have been identified in the hardened cement, but could offer valuable insight into the complex multi-step processes of barnacle growth and adhesion.

We analyze the transcriptome of sub-mantle tissue (Figure 1) of the barnacle Amphibalanus amphitrite in pre- and post-molt growth stages using RNA-seq technology and the proteome of barnacle secretions using mass spectrometry. Differential gene expression analysis of the sub-mantle tissue samples reveals a limited number of genes highly expressed in pre-molt samples (Figure 2, red dots) with a range of functions including cuticular development, biominerialization, and proteolytic activity. No significant differences were found in the expression of cement proteins genes at pre- and post-molting stages, but expression levels were highly elevated in sub-mantle tissue compared to the main barnacle body. A novel 114kD cement protein was found and also identified in material secreted onto various surfaces by adult barnacles.

Expression of cement protein genes is mainly confined to the sub-mantle tissue and appears to remain constant in pre- and post-molt barnacles. Our extended transcriptomic analysis of pre- and post-molt identified a number of highly-expressed genes and highlights the complexities of this sessile marine organism throughout its molt cycle as it increases the area over which it exhibits robust adhesion to a substrate.