**Plastid Types:**
– Chloroplasts (photosynthesis)
– Chromoplasts (pigment synthesis and storage)
– Leucoplasts (non-pigmented, differentiation)
– Apicoplasts (non-photosynthetic in apicomplexa)
– Examples: Paulinella, Prochlorococcus, Synechococcus
**Plastid Differentiation and Functions:**
– Chloroplasts for photosynthesis
– Synthesis of fatty acids, terpenes
– Storage of starches, fats, proteins
– Derived from proplastids
– Differentiate into chloroplasts, etioplasts, chromoplasts, gerontoplasts, leucoplasts
**Plastid DNA and Nucleoids:**
– Each plastid has a unique plastome
– Variable genome copies per plastid
– Plastome encodes tRNAs, rRNAs, proteins
– Plastid DNA in protein-DNA complexes
– Plastid nucleoids contain plastid DNA copies
– Plastid genome loss evidence in non-photosynthetic plants
**Plastid Inheritance and Evolution:**
– Most plants inherit plastids from one parent
– Angiosperms inherit from female gametes, gymnosperms from male pollen
– Plastids descended from endosymbiotic cyanobacteria
– Primary endosymbiotic event around 1.5 billion years ago
– Complex plastids from secondary endosymbiosis
**Plastid Research and Further Studies:**
– Plastid development cycle
– DNA damage and repair
– Plastid ancestry and genome evolution
– Plastid function and structure
– Ongoing research on plastids and their origins
A plastid, pl. plastids, is a membrane-bound organelle found in the cells of plants, algae, and some other eukaryotic organisms; (from Ancient Greek πλαστός (plastós) 'formed, molded'). They are considered to be intracellular endosymbiotic cyanobacteria.
| Plastid | |
|---|---|
| |
| Plant cells with visible chloroplasts | |
Scientific classification 
| |
| Domain: | Bacteria |
| Phylum: | Cyanobacteria |
| Clade: | Plastid |
Examples of plastids include chloroplasts (used for photosynthesis); chromoplasts (used for synthesis and storage of pigments); leucoplasts (non-pigmented plastids some of which can differentiate); and apicoplasts (non-photosynthetic plastids of apicomplexa derived from secondary endosymbiosis).
A permanent primary endosymbiosis event occurred about 1.5 billion years ago in the Archaeplastida clade—land plants, red algae, green algae—probably with a cyanobiont, a symbiotic cyanobacteria related to the genus Gloeomargarita. Another primary endosymbiosis event occurred later, between 140 to 90 million years ago, in the photosynthetic plastids Paulinella amoeboids of the cyanobacteria genera Prochlorococcus and Synechococcus, or the "PS-clade". Secondary and tertiary endosymbiosis events have also occurred in a wide variety of organisms; and some organisms developed the capacity to sequester ingested plastids—a process known as kleptoplasty.
A. F. W. Schimper was the first to name, describe. and provide a clear definition of plastids, which possess a double-stranded DNA molecule that long has been thought as circular in shape, like that of the circular chromosome of prokaryotic cells—but now, perhaps not; (see "..a linear shape"). Plastids are sites for manufacturing and storing pigments and other important chemical compounds used by the cells of autotrophic eukaryotes. Some contain biological pigments such as used in photosynthesis or which determine a cell's color. Plastids in organisms that have lost their photosynthetic properties are highly useful for manufacturing molecules like the isoprenoids.