Insights into the Fucoidan and Mannitol Biosynthetic Pathways in the Brown Seaweed Padina Tetrastromatica Based on Draft Genome and Transcriptome Analysis.

Brown seaweeds, such as Padina sp., are reported to have significant potential for industrial applications due to their rich content of bioactive compounds. Despite their importance, they are not widely utilised due to insufficient biomass availability and are largely uncultivable because of their complex reproductive cycle. Hence, omics-based studies can provide a platform for future efficient biotechnological applications. However, genomic and transcriptomic insights into these seaweed species remain largely unexplored. In this study, a complementary genome and transcriptome assembly of the brown seaweed Padina tetrastromatica was generated to elucidate the gene repertoire and transcripts. The draft genome assembly comprised approximately 256.5 Mb across 55,222 transcripts (N50: 6,718 bp) with less than 20% coverage, while the de novo transcriptome assembly yielded 89,735 transcripts, with 86 and 92.5% completeness in Eukaryota and Stramenopiles assembly, respectively, based on Benchmarking Universal Single-Copy Orthologs (BUSCO) analysis. Functional annotation revealed the presence of 15 transcripts encoding enzymes such as fucosyltransferases, sulfotransferases and mannitol-1-phosphate dehydrogenase related to fucoidan and mannitol biosynthesis, providing insights into the molecular framework underlying sulfated polysaccharide production. These findings contribute to understanding macroalgal carbohydrate metabolism and functional genomics and establish a resource that may support future metabolic engineering and synthetic biology efforts aimed at enhancing the production of macroalgal sugars in heterologous systems.