author={Geoffrey Ian McFadden},
  journal={Journal of Phycology},
  • G. McFadden
  • Published 1 December 2001
  • Biology
  • Journal of Phycology
The theory of endosymbiosis describes the origin of plastids from cyanobacterial‐like prokaryotes living within eukaryotic host cells. The endosymbionts are much reduced, but morphological, biochemical, and molecular studies provide clear evidence of a prokaryotic ancestry for plastids. There appears to have been a single (primary) endosymbiosis that produced plastids with two bounding membranes, such as those in green algae, plants, red algae, and glaucophytes. A subsequent round of… 

The origin and establishment of the plastid in algae and plants.

Recent genomic and phylogenomic approaches have significantly clarified plastid genome evolution, the movement of endosymbiont genes to the "host" nuclear genome (endosYmbiotic gene transfer), and plastsid spread throughout the eukaryotic tree of life.

Photosynthetic eukaryotes unite: endosymbiosis connects the dots.

Algal diversity is examined and endosymbiosis is shown to be a major force in algal evolution, with long-standing issues such as the chromalveolate hypothesis and the extent of endOSymbiotic gene transfer clarified.

Diversity and Evolution of Plastids and Their Genomes

This chapter provides an overview of the structural, functional and molecular diversity of plastids in the context of current views on the evolutionary relationships among the eukaryotic hosts in which they reside.

A Genomic and Phylogenetic Perspective on Endosymbiosis and Algal Origin

Algal plastid diversity is examined using phylogenetic and genomic methods and endosymbiosis is shown to be a major force in algal evolution, particularly on the evolution of targeting signals that facilitate the import of nuclear-encoded photosynthetic proteins into the plastids.

The endosymbiotic origin, diversification and fate of plastids

  • P. Keeling
  • Biology
    Philosophical Transactions of the Royal Society B: Biological Sciences
  • 2010
The many twists and turns of plastid evolution each represent major evolutionary transitions, and each offers a glimpse into how genomes evolve and how cells integrate through gene transfers and protein trafficking.

The number, speed, and impact of plastid endosymbioses in eukaryotic evolution.

  • P. Keeling
  • Biology
    Annual review of plant biology
  • 2013
Questions are examined about the number of endosymbiotic events needed to explain plastid diversity, whether the genetic contribution of the endOSymbionts to the host genome goes far beyond plastids-targeted genes, and whether organelle origins are best viewed as a singular transition involving one symbiont or as a gradual transition involving a long line of transient food/symbiont.


The ideas that became the direct inspiration for formulation of the ”chromalveolate” hypothesis are also now questionable and are discussed in the light of the most recent phylogenetic, cytological, and genomic data.

Cyanobacterial Genes Transmitted to the Nucleus Before Divergence of Red Algae in the Chromista

The results indicate that the Chromista might have originated from the ancient secondary endosymbiosis before the divergence of extant red algae.



The origin of plastids and their spread via secondary symbiosis

A review of the phylogenetic evidence from plastid genes indicates that the three major lineages of primary plastids are probably monophyletic, and a secondary origin of plastIDS is unequivocal for cryptomonads and chlorarachniophytes, and is suggested for the nonphotosynthetic parasites of phylum Apicomplexa.

Tracing the Thread of Plastid Diversity through the Tapestry of Life

The eukaryotic crown group Alveolata has a particularly complex history of plastid acquisition, and may or may not be descended from a single endosymbiotic event.

Protozoa as Hosts for Endosymbioses and the Conversion of Symbionts into Organelles1,2

The ways by which (present-day) chloroplasts and mitochondria may have been derived from early endosymbionts are discussed: a single ancestral cyanobacterium, in the first case, and asingle ancestral purple-nonsulfur bacterium,In this paper, numerous foraminifera appear to have characteristics making them very favorable as hosts for certain algae.

A Plastid of Probable Green Algal Origin in Apicomplexan Parasites

Observations indicate that the Apicomplexa acquired a plastid by secondary endosymbiosis, probably from a green alga.

Cryptomonad algae are evolutionary chimaeras of two phylogenetically distinct unicellular eukaryotes

It is shown here that Cryptomonas Φ contains two phylogenetically separate, nuclear-type small-subunit rRNA genes, both of which are transcriptionally active and infer the evolutionary ancestry of the host and symbiont components of Cryptomona Φ.

Principles of Protein and Lipid Targeting in Secondary Symbiogenesis: Euglenoid, Dinoflagellate, and Sporozoan Plastid Origins and the Eukaryote Family Tree 1 , 2

It is argued that dinoflagellate and sporozoan plastids are directly related and that the common ancestor of dinof lagellates and Sporozoa was photosynthetic, and a novel theory for the function of periplastid vesicles in membrane biogenesis of chlorarachneans and chromists is proposed.

Membrane heredity and early chloroplast evolution.

Protein Import: the Hitchhikers Guide into Chloroplasts

Plastids originated from an endosymbiotic event between an early eukaryotic host cell and an ancestor of today's cyanobacteria, and contain an N-terminal cleavable transit sequence that is necessary for translocation.

Evidence that an amoeba acquired a chloroplast by retaining part of an engulfed eukaryotic alga.

The authors cloned and sequenced nuclear-type rRNA genes from chlorarachniophytes and found two highly divergent genes and in situ hybridization shows that one gene is expressed by the amoebal (host) nucleus and the other is expression by the putative endosymbiont nucleus, suggesting that the latter is indeed a foreign genome.

Evidence for nucleomorph to host nucleus gene transfer: light-harvesting complex proteins from cryptomonads and chlorarachniophytes.

In each organism these genes reside in the secondary host nuclei, but phylogenetic evidence, and analysis of the targeting mechanisms, suggest the genes were initially in the respective nucleomorphs (symbiont nuclei).