plastomes

Plastomes are the genomes contained within plastids, a group of organelles in plants and algae that include chloroplasts. The plastid genome is most often a circular, double-stranded DNA molecule and is typically referred to as the chloroplast genome when it resides in chloroplasts. In land plants, plastomes are generally around 120 to 160 kilobases in size and contain a core set of genes involved in photosynthesis and the expression of plastid genes.

Most plastomes exhibit a quadripartite structure consisting of a large single-copy region, a small single-copy region, and two inverted repeats that separate the single-copy regions. This arrangement leads to a relatively conserved gene order across many plant lineages, though some groups have lost the inverted repeats or undergone other rearrangements. Plastid genes encode components of photosystems I and II, the ATP synthase complex, genes for transcription and translation, and a set of ribosomal RNAs and transfer RNAs. Some genes contain introns, and a subset of genes is duplicated in the inverted repeats.

Inheritance of plastomes is predominantly maternal in angiosperms, though there are exceptions with paternal or biparental inheritance reported in some species. Plastid genomes are mostly self-replicating within chloroplasts and exist in multiple copies per cell.

Evolutionarily, plastomes derive from a cyanobacterial endosymbiont and have undergone extensive gene transfer to the nuclear genome. Their relatively conserved structure and gene content, along with regions like matK and rbcL, make plastomes valuable for plant systematics, phylogeny, and DNA barcoding.