Identification of differentially expressed proteins involved in the early larval development of the Pacific oyster Crassostrea gigas.

The trochophore and D-veliger are two pivotal but distinct developmental stages in bivalve larval development. Complex morphological and physiological processes are involved in the transition between these stages, yet the underlying molecular mechanisms remain largely elusive. In this study, a comparative proteomic analysis was conducted to identify the proteins related to early larval development of the Pacific oyster Crassostrea gigas. Fifty proteins showing different levels of expression were screened. These spots were further analyzed using LC-MS/MS and twenty of them were identified. Together with information from Western blotting and real-time PCR assay of some annotated genes, our results provide insight into novel aspects of cellular processes and protein function in oyster larvae. For example, it was shown that cell division was unexpectedly slowed down in D-veliger larvae, while substantial gene transcription and biochemical activity were revealed. "Quality control" proteins were identified for the first time to be involved in mollusk larval development. Bivalve larval development provides an elegant system for studying cellular processes and tissue morphogenesis. Our data shed light on the molecular mechanisms underlying these complex processes and regulatory networks.