Transcriptome characrerization of Trichoplax adhaerens (Phylum Placozoa)

Deep transcriptome analysis of of Trichoplax was performed using 454 pyrosequencing and Sanger sequencing. To prevent contamination from food sources, we constructed 3’-& 5’- biased libraries from several individuals starved for one day before RNA isolation. The libraries were designed in a way that one endogenous transcript corresponds to a single tag. Therefore, occurrence of sequencing tags correlates to the expression level of relevant gene products in the animal. First, we found that one group of the most abundant transcripts is related to putative secretory signal peptide molecules and digestive enzymes, the fact that more likely illustrates the feeding adaptations of Trichoplax. Second, we identified a number of novel transcripts including those involved in cell-cell communications, differentiation as well as non-coding RNAs. Finally, our analysis illustrates a substantial degree of gene loss and gain in the lineages of basal Metazoan.