[4S04e] 19. Marine Biotechology - Part 3

5:50 PM - 6:10 PM JST(8:50 AM - 9:10 AM UTC)

[4Marine-14] From Natures's Blueprint to Biomanufacturing: Harnessing Diatom Carotenoid Pathways

○Xiaobo Li¹, Tianjun Cao¹, Yanyou Jiang¹ (1. Westlake University (China))

Keywords:

Carotenoid,Fucoxanthin,Algae,Diatom

Fucoxanthin is the most abundant marine carotenoid, with high market value due to its demonstrated bioactivities as an antioxidant and its potential for human health applications. Beyond its economic value, fucoxanthin plays an essential ecological role as a photosynthetic pigment: together with chlorophylls, it comprises the fucoxanthin-chlorophyll proteins (FCPs) that enable diatoms, brown algae, and haptophytes to capture the blue-green light prevailing in marine habitats. Despite its importance, the biosynthetic pathway of fucoxanthin had remained elusive for decades. Using the model diatom Phaeodactylum tricornutum, we dissected the terminal steps of fucoxanthin biosynthesis. Mutants of two candidate genes appeared green and were deficient in fucoxanthin accumulation. Novel intermediates were detected and structurally elucidated using mass spectrometry and NMR, and in vitro enzyme assays proved that the two proteins catalyze epoxidation and alkyne hydration—the two last steps of the pathway (published collaboratively: Bai et al. 2022 PNAS; Cao et al. 2023 Plant Cell). Phylogenetic analyses suggest these genes arose via gene duplication and functional diversification, and are broadly conserved among fucoxanthin-accumulating algae. Because chlorophyll c and fucoxanthin are highly correlated in abundance within the FCP complexes, we also explored chlorophyll c biosynthesis, leading to the identification of the long-sought-after chlorophyll c synthase (Jiang et al. 2023 Science). Following the elucidation of these pathways, we have launched metabolic engineering trials in tomato fruit and yeast to produce fucoxanthin, with the aim of supporting its nutritional fortification and scalable industrial manufacturing.