De novo transcriptome assembly of the hydrocoral Millepora alcicornis (branching fire coral) from the Caribbean

The hydrocoral Millepora is found in shallow tropical/subtropical regions around the globe and is considered an important reef-building organism. Millepora alcicornis is the most common species in the Atlantic Ocean, and can be found from 0.5 to 50 m deep. It is distributed from the tropical/subtropical eastern western Atlantic Ocean, including Bermuda, Brazil, and on the east in Tenerife of the Canary Islands, the Cape Verde Archipelago and Ascension Island. No genomic information is available for this ecologically important group. Here, we report de novo transcriptome assembly of M. alcicornis sampled from Puerto Rico, Caribbean. We used paired-end sequencing (Illumina HiSeq4000, 2 × 150 bp) and obtained 76,518,693 reads. Transcriptome assembly was performed using Trinity, producing a total of 479,982 transcripts with an average size of 553 bp and a N50 of 749. Data was normalized using RSEM and filtered by a TPM of 3. Open reading frames (ORFs) from the filtered transcripts were obtained by TransDecoder using the hydrozoan Hydra vulgaris protein sequences as reference, generating 16,024 putative ORFs. Blast searches showed that 25.8% (4137) of the ORFs matched H. vulgaris and 24.6% matched other anthozoan cnidarians (i.e. Nematostella vectensis = 1621, Exaiptasia pallida = 1280, Acropora digitifera = 1050). Gene ontology generated by Blast2GO resulted in a total of 7220 ORFs associated with molecular function, 4917 with biological processes, and 2989 with cellular components. A general overview will be presented of the first assembled M. alcicornis transcriptome with emphasis on shared genes among Hydrozoans and Scyphozoans.