Biochemical Characterization of a Novel Redox-Regulated Metacaspase in a Marine Diatom

Programmed cell death (PCD) in marine microalgae was suggested to be one of the mechanisms that facilitates bloom demise, yet its molecular components phytoplankton are unknown. Phytoplankton completely lacking any canonical PCD, such as caspases, but possess metacaspases. Metacaspases were shown regulate PCD plants and some protists, their roles algae other organisms still elusive. Here, we identified biochemically characterized a type III metacaspase from model diatom Phaeodactylum tricornutum , termed PtMCA-IIIc. Through expression recombinant PtMCA-IIIc E. coli revealed exhibits calcium-dependent protease activity, including auto-processing cleavage after arginine. Similar activity detected P. extracts. overexpressing cells exhibited higher while CRISPR/Cas9-mediated knockout had decreased compared WT cells. Site-directed mutagenesis cysteines predicted form disulfide bond suggesting enhancement under oxidizing conditions. One those oxidized, redox proteomics, specifically response lethal concentrations hydrogen peroxide derived aldehyde. Phylogenetic analysis this cysteine-pair is unique widespread among The characterization associated protein diatoms provides insights into evolutionary origins ecological significance algal dynamics.