Gene expression analysis of green tide alga Ulva prolifera (Chlorophyta) in China

Ulva prolifera (Ulvophyceae, Chlorophyta) is the causative species of the annual green tides in the Bohai Gulf of Northern China. In order to gain some more insight into the transcriptome of this fast-growing species of algae, we acquired 6,203 high-quality expressed-sequence-tags (ESTs), which were clustered into 4,080 unique sequences (UniSeqs). Functional classification revealed that most of the acquired transcripts were related to metabolic and biosynthetic processes, nucleotide binding, and cell part that might contribute to the organism's rapid growth. Using 39 EST pools, 28 mitochondria genomes, and 18 chloroplast genomes from algae and land plants, we constructed three phylogenetic trees. These trees provided evidence that U. prolifera was in a sister position to Ulva linza, and shared a similar chloroplast origin with Pseudendoclonium akinetum. The findings of this study will improve our knowledge of the transcriptome and taxonomic position of U. prolifera.