Global Metagenomics Reveals Plastid Diversity and Unexplored Algal Lineages
This project uses cultivation-independent metagenomic approaches to investigate the diversity and evolutionary origins of photosynthetic organelles (plastids) across eukaryotes. Plastids arose through endosymbiosis events involving cyanobacterial (primary endosymbiosis) or algal (secondary and higher-order endosymbiosis) partners with eukaryotic hosts. While primary plastids in Archaeplastida are well-characterized, the origins and distribution of secondary plastids remain debated. Current understanding of plastid evolution relies primarily on genomes from cultured isolates, which represent only a fraction of existing diversity since many lineages and environments remain undersampled. We screened 26,257 publicly available metagenomes from the Integrated Microbial Genomes and Microbiomes (IMG/M) database to identify and assemble plastid sequences. Through metagenomic binning and assembly, we generated a comprehensive dataset of plastid metagenome-assembled genomes (ptMAGs) and expanded the available Cyanobacteriota MAG collection from 31,152 metagenomes. The final dataset includes 1,027 plastid sequences, of which 300 represent novel lineages from previously unsequenced plastids and uncultured microeukaryotes.