Transcriptome and protein domain analyses in Aplysia nervous system with evolutionary implications.

The sea hare Aplysia is a powerful model organism for studying the structure and function of the nervous system. Recently, the genomic characterization of Aplysia has been facilitated: A large scale EST sequences was acquired by sequencing cDNA libraries from A. californica and a parallel EST database of the closely related species A. kurodai was reported. These EST databases provide useful tools for both molecular biology and bioinformatics. In our previous report, we demonstrated the utility of the database by screening the candidate genes for the synaptic plasticity and the behavioral sensitization using the microarray containing A. kurodai ESTs. In this addendum, we have expanded our study to show that the protein domain repertoire and the abundance of regulatory genes displayed a linear relationship with the evolution of the complex brains in different lineages. This distinct set of protein domains may play critical roles in evolution of the nervous systems.