De novo transcriptome sequencing of Monodopsis subterranea CCALA 830 and identification of genes involved in the biosynthesis of eicosapentanoic acid and triacylglycerol

Abstract

Monodopsis subterranea, a unicellular yellow-green freshwater microalga, is widely known for its ability to produce high amount of therapeutically beneficial ω-3 polyunsaturated fatty acid eicosapentanoic acid (EPA; C20:5Δ5,8,11,14,17). Currently, no genomic information is available on M. subterranea despite its nutraceutical and commercial applications. Analysis on fatty acid methyl esters from M. subterranea strain CCALA 830 demonstrated accumulation of 28% EPA. In order to obtain better understanding of EPA biosynthesis and to identify genes involved in the process of lipid metabolism and accumulation in this alga, de novo transcriptome sequencing and assembly was performed using Illumina Hiseq 2000 sequencing. A total of 35,954 transcripts were obtained through final transcriptome assembly with an average transcript length of 769.36 bp. BLAST similarity searches for assembled transcripts were performed followed by annotation using Gene ontology and Kyoto Encyclopedia of Genes and Genomes orthology identifiers. Transcripts involved in lipid biosynthesis including various fatty acid desaturases and elongases involved in PUFAs biosynthesis were identified during the study. In addition, sequences for several transcription factors and a number of simple sequence repeats were also ascertained which can be used as powerful genetic markers for further genetic analysis. This study would provide a useful resource for future research on M. subterranea genome.