Jessica Webb1, Min Zhao1, Nicholas Paul1, David Heyne1, Scott F. Cummins1
1UniSC Seaweed Research Group, University of the Sunshine Coast, Queensland, Australia
Managing light intensity in Asparagopsis taxiformis aquaculture is crucial for enhancing production of biomass and halogenated natural products, specifically bromoform. However, a comprehensive understanding of the genes involved in bromoform biosynthesis is required to explore the interplay between light, growth and bromoform production to direct culture management. Bromoform is synthesised by vanadium bromoperoxidases (vBPOs) but the influence of specific vBPOs on bromoform concentration in A. taxiformis is unclear. Here, we investigated the impact of light intensity on the filamentous sporophyte-stage of A. taxiformis to determine the relationship between gene expression and bromoform production. A. taxiformis (Lineage 6, Sunshine Coast, Australia) was cultured under five different light intensities for 14 days, in which the highest treatment of 173 µmol photons m−2 s−1 promoted both the highest growth rate (6.8% daily growth) and highest bromoform concentration (14.3 mg/g dry weight). We observed differential expression in genes relating to growth, energy metabolism and oxidative stress response, including photosynthesis-associated genes and other peroxidases. Three vBPO genes were characterised through comparative sequence and phylogenetic analyses, but no upregulation in expression was detected when comparing the highest light to the lowest light treatment. Although high light levels produced faster growing seaweed, with increased bromoform content, there was no clear relationship between a high bromoform concentration and expression of the vBPO genes. We discuss these results in the context of broader gene regulation of the vBPOs, as determined by q-PCR, and the potential involvement of other bromoform biosynthesis-associated genes in A. taxiformis.