A proteomic investigation of sporophyte and gametophyte in the red seaweed Asparagopsis

The red seaweed, Asparagopsis taxiformis, is a promising ruminant feed-additive with significant anti-methanogenic properties, which could provide a global solution to climate-change. Emerging genomics in this species has provided a strong foundation for in-depth molecular investigations, including proteomics. Here, we investigated the A. taxiformis (L6) proteome of sporophyte and gametophyte (male and female), using soluble and insoluble extraction methods followed by mass spectrometry. A combined total of 741 and 2007 unique non-redundant proteins were identified using genome-derived and transcriptome-derived databases, respectively. Genome-derived proteins were used for further analysis including a relatively large proportion of proteins that were annotated as ion binding proteins (i.e. iron, zinc, manganese, potassium and copper), which may play a role in heavy metal bioremediation. In addition, we identified 44 photosynthesis-related proteins (e.g. phycobilisomes, photosystem I, photosystem II and ATPase) and 58 stress-related proteins (e.g. heat shock proteins and vanadium-dependent haloperoxidases). Forty proteins were predicted to be secreted, supporting a role for them in extracellular activities such as mucilage development and defence. Two Gal-2,6-Sulfurylases II proteins are likely necessary for carrageenan biosynthesis, as well as development of reproductive-associated structures. These findings provide a comprehensive overview of expressed proteins in A. taxiformis (L6) at two different life stages, highlighting the potential of proteomic approaches and warrant further studies for understanding protein functions.