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Updated: May 22, 2026
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Studying the Supramolecular Organization of Photosynthetic Membranes within Freeze-fractured Leaf Tissues by Cryo-scanning Electron Microscopy
Published on: June 23, 2016
Evolving a photosynthetic organelle.
Takuro Nakayama1, John M Archibald
1Department of Biochemistry and Molecular Biology, Canadian Institute for Advanced Research, Program in Integrated Microbial Biodiversity, Dalhousie University, 5850 College Street, Halifax, Nova Scotia, Canada.
BMC Biology
|April 26, 2012
Summary
The amoeba Paulinella offers a unique window into organelle evolution, showcasing early stages of endosymbiont transformation into photosynthetic organelles. Its study provides insights into the critical steps of plastid development from cyanobacteria.
Area of Science:
- * Evolutionary Biology
- * Cellular Biology
- * Microbiology
Background:
- * Plastids (chloroplasts) in algae and plants originated from cyanobacteria via endosymbiosis.
- * This event significantly impacted eukaryotic evolution and Earth's climate by enabling photosynthesis.
- * Modern plastids are highly integrated, making early evolutionary steps difficult to study.
Purpose of the Study:
- * To investigate the enigmatic amoeba Paulinella chromatophora as a model for early organellogenesis.
- * To understand how endosymbionts transition into functional organelles.
- * To gain fresh insights into the evolutionary singularity of plastid development.
Main Methods:
- * Analysis of genomic data from Paulinella chromatophora's photosynthetic inclusions (chromatophores).
- * Comparative genomics to trace evolutionary pathways.
- * Studying the unique biological system of Paulinella for insights into endosymbiosis.
Main Results:
- * Paulinella chromatophora possesses photosynthetic chromatophores derived from cyanobacteria.
- * Genomic studies confirm the chromatophore as a bona fide photosynthetic organelle.
- * This organism represents a potential snapshot of early organelle evolution.
Conclusions:
- * Paulinella chromatophora serves as a valuable model for studying the process of endosymbiont-to-organelle transition.
- * Understanding Paulinella's chromatophores can illuminate the evolutionary journey from cyanobacteria to integrated plastids.
- * This research sheds light on a key singularity in the history of life.
Related Concept Videos
01:08The Anatomy of Chloroplasts
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Structure of Chloroplasts
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01:24Eukaryotic Evolution
The endosymbiont theory is the most widely accepted theory of eukaryotic evolution; however, its progression is still somewhat debated. According to the nucleus-first hypothesis, the ancestral prokaryote first evolved a membrane to enclose DNA and form the nucleus. Conversely, the mitochondria-first hypothesis suggests that the nucleus was formed after endosymbiosis of mitochondria.
Contrary to the endosymbiont theory, the eukaryote-first hypothesis proposes that the simpler prokaryotic and...
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01:27Photosystem I
Although structurally similar to photosystem II (PSII), photosystem I (PSI) is has a different electron supplier and electron acceptor.
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...
01:07Anatomy of Chloroplasts
Green algae and plants, including green stems and unripe fruit, harbor chloroplasts—the vital organelles where photosynthesis takes place. In plants, the highest density of chloroplasts is found in the mesophyll cells of leaves.
01:26Origin of Photosynthesis
Photosynthesis represents a fundamental biological process that transformed Earth's atmosphere and paved the way for complex life. Emerging roughly 3.4–3.8 billion years ago, the earliest photosynthetic organisms harnessed light energy to produce organic compounds. These anoxygenic phototrophs used electron donors like hydrogen sulfide (H₂S) or ferrous iron (Fe²⁺), rather than water, and did not release molecular oxygen (O₂) as a byproduct. Various groups, including green sulfur and purple...
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The multi-protein complex photosystem II (PS II) harvests photons and transfers their energy through its bound pigments to its reaction center, and ultimately to photosystem I (PSI) through the electron transport chain. The pigments responsible for caputirng the light energy in photosystems include chlorophyll a, chlorophyll b, and carotenoids.
The pigment molecules are arranged across two photosystem domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
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