The Evolutionary Origin of Primary Plastids

This chapter delves into primary endosymbiosis, which gave rise to algal and plant photosynthetic organelles. Primary plastids originated from the integration of a cyanobacterial endosymbiont into a host cell. The process of primary endosymbiosis raises fundamental questions about when, where, who, what, why, and how this intricate relationship evolved. By focusing on the only two known instances of primary plastid origin—those found in the ancestor of Archaeplastida and photosynthetic Paulinella—this chapter aims to provide the reader with a comprehensive understanding of the evolution of primary plastids. We explore the similarities and differences between these two cases, shedding light on the pathways that led to the establishment of photosynthetic capacity in eukaryotes.