Toward understanding molecular mechanisms of barnacle larval settlement: a comparative transcriptomic approach

The striped barnacle, Balanus amphitrite, is a globally distributed bio-fouler, and also a model species for intertidal ecology and larval settlement studies. However, the lack of genetic information has hindered the understanding of the comprehensive molecular mechanisms in the larval attachment and metamorphosis of this species. In this study, we report the result of a 454 pyrosequencing based transcriptomic profiling of pelagic larval stages and sessile adult stage. Altogether, a 226M bp pyrosequencing data contained 215,308 reads from the larval pool and 415,537 reads from the adult pool. After de novo assembly, 630,845 contigs were generated while 77,785 remained as singlets. We annotated 31,720 of the 92,322 predicted open reading frames, which matched hits in the NCBI NR database. We also used DEGseq software pack to analyze the differently expressed genes and identified 7,954 genes putatively differently expressed between the larva and the adult. Several differentially expressed genes were selected and further characterized with quantitative real-time PCR and in situ hybridization. The gene expression profiling indicate 1) the vitellogenin uniquely expressed in late nauplius stage probably play an energy source for non-feeding cyprid larva; 2) the mannose receptors may be involved in chemical and/or mechanical sensing; 3) the 20 kDa-cement protein homologues expressed in cyprid cement grand function as larval cement during cyprid attachment; 4) the receptor tyrosine kinases expressed higher in cyprid stage may be involved in metamorphosis signal perception. Based on our barnacle transcriptome, further progress of study on molecular mechanisms of larval settlement is expected.