Integration of bioaccumulations, chemical forms and gene expression responses to understand the transformation and detoxification of inorganic arsenic, cadmium and lead in the brown seaweed Sargassum fusiforme.

This study investigated the accumulation and detoxification mechanisms of inorganic arsenic (iAs), cadmium (Cd), and lead (Pb) in Sargassum fusiforme through controlled laboratory exposure experiments combined with chemical speciation analysis and comparative transcriptomics. Our results revealed that S. fusiforme exhibited similar accumulation capacities for arsenite [As(III)] and arsenate [As(V)], with the less toxic As(V) being the predominant species in both treatment groups. The algae demonstrated higher accumulation capacity for Pb compared to Cd. Chemical speciation analysis indicated that S. fusiforme primarily detoxified Cd through organic ligand binding, while Pb was predominantly immobilized as insoluble compounds. Transcriptomic analysis revealed metal-specific detoxification pathways: As(III) exposure significantly enriched pathways related to free radical scavenging, including phenylpropanoid biosynthesis, stilbenoid/diarylheptanoid/gingerol biosynthesis, and flavonoid biosynthesis; As(V) treatment notably affected oxidative phosphorylation among five significantly enriched pathways; Cd exposure triggered complex responses involving 23 significantly enriched pathways; Pb treatment primarily influenced ribosomal biogenesis and translation among four enriched pathways. These findings demonstrated distinct detoxification mechanisms in S. fusiforme for each of the four studied toxic elements.