plastidele

Plastids, also known as plastides, are a diverse group of double-membrane bound organelles found in the cells of plants and algae. They include chloroplasts, chromoplasts, amyloplasts and other plastids such as leucoplasts. Chloroplasts carry out photosynthesis and contain the photosynthetic machinery; chromoplasts accumulate pigments like carotenoids; amyloplasts and other leucoplasts store starch and other metabolites. Plastids can differentiate into different types according to tissue and developmental cues.

Most plastids contain their own circular DNA and ribosomes, reflecting their origin from ancestral cyanobacteria. The majority of plastid proteins are encoded in the nuclear genome and are imported into plastids via transit peptides through the Toc/Tic protein import machinery. Plastids divide by binary fission in coordination with the host cell cycle.

Plastids originate from proplastids in meristematic cells and can develop into mature chloroplasts, chromoplasts or amyloplasts depending on cellular needs. Some lineages also exhibit plastids derived from secondary endosymbiosis, resulting in additional membranes around the organelle. Non-photosynthetic plastids often lose photosynthetic genes and specialize in other metabolic roles.

Functions of plastids extend beyond photosynthesis. They are involved in the biosynthesis of fatty acids, isoprenoids, amino acids and nucleotides, and in the production of pigments such as chlorophyll and carotenoids. They also participate in starch storage, hormone precursor synthesis, and plastid-to-nucleus signaling that influences nuclear gene expression.

In research and biotechnology, plastid genetics are exploited for transplastomic engineering, which can enable high-level, contained expression of transgenes. Plastid genomes are also valuable in phylogenetics and evolutionary studies due to their conserved structure and maternal inheritance in many species.