De novo transcriptome assembly and functional annotation supports potential biotechnological applications for the non-model thraustochytrid Ulkenia visurgensis Lng2.

Thraustochytrids are heterotrophic marine protists known for their ability to produce valuable lipids such as docosahexaenoic acid (DHA). However, like many non-model organisms, they present challenges for transcriptomic studies due to the limited reliable reference genomes and compatibility with curated protein databases, complicating the respective assembly and annotation. This study presents a de novo transcriptome assembly and functional annotation for the recently isolated thraustochytrid strain Ulkenia visurgensis Lng2 using solely free access software and code available in public domain repositories. The assembled transcriptome presented 45,867 unique gene models, with a total of 66,623 transcripts and a contig N50 of 3162. Functional annotations highlighted high amounts of transcripts related to the biosynthesis of relevant lipidic molecules, as well as stress-adaptive features including catalytic and xenobiotic degrading activity. Likewise, 2381 transcripts were linked to enzymes with potential biotechnological applications. Notably, several transcripts corresponding to uncommon enzymatic activities in thraustochytrids, including laccases, cellulases, and chitinases, were identified. Additionally, evidence for a potential lactamase activity was found, marking the first report of such activity in thraustochytrids. Overall, this study offers a simple free-access procedural strategy for a de novo transcriptome assembly and functional annotation in non-model organisms. These results provide valuable insights into the biotechnological potential of thraustochytrids, while also expanding the limited transcriptomic data available for these protists. Notably, it represents the first transcriptomic analysis of the Ulkenia genus.