Dependency on de novo protein synthesis and proteomic changes during metamorphosis of the marine bryozoan Bugula neritina

When larvae were incubated with transcription and translation inhibitors, metamorphosis initiated through the first phase but did not complete. We found a significant down-regulation of 60 protein spots and the percentage of phosphoprotein spots decreased from 15% in the larval stage to12% during early metamorphosis. Two proteins--the mitochondrial processing peptidase beta subunit and severin--were abundantly expressed and phosphorylated in the larval stage, but down-regulated during metamorphosis. MPPbeta and severin were also down-regulated on the gene expression level.The initial morphogenetic changes that led to attachment of B. neritina did not depend on de novo protein synthesis, but the subsequent gradual morphogenesis did. This is the first time that the mitochondrial processing peptidase beta subunit or severin have been shown to be down-regulated on both gene and protein expression levels during the metamorphosis of B. neritina. Future studies employing immunohistochemistry to reveal the expression locality of these two proteins during metamorphosis should provide further evidence of the involvement of these two proteins in the morphogenetic rearrangement of B. neritina.To explain the rapid metamorphosis of many marine invertebrates, a 'need for speed' hypothesis has been suggested due to strong predation pressures and the relative defenselessness of transitioning larvae [1]. To cope, the larvae of many marine invertebrates enable rapid metamorphosis by the pre-formation of some juvenile structures [1,2]. Metamorphosis of the cosmopolitan marine bryozoan Bugula neritina--a species that causes biofouling problems worldwide [3-5] and also yields the antitumor compound bryostatin [6]--completes very rapidly and the morphological changes associated with metamorphosis have been described well [7,8]. However, the presumptive juvenile tissues in the larvae of B. neritina are largely undifferentiated when they commit to metamorphosis [8]. In this case, we suggest