Plastid

Having only one plastid severely limits gene transfer as the lysis of the single plastid would likely result in cell death.

Plastid interconversion Plastid differentiation is not permanent, in fact many interconversions are possible.

The plastid is responsible for haem biosynthesis, which requires plastid encoded tRNA-Glu (from the gene trnE) as a precursor molecule.

Whether a proplastid develops into a chloroplast some other kind of plastid is mostly controlled by the nucleus and is largely influenced by the kind of cell it resides in. Many plastid interconversions are possible.

A plastid is required to continue expressing the gene for tRNA-fmet so long as the mitochondrion is translating proteins.

A remnant of the outer plastid dividing ring remains floating between the two daughter chloroplasts, and a remnant of the dynamin ring remains attached to one of the daughter chloroplasts.

As a result, many plastid and mitochondrial processes are driven by nuclear encoded gene products.

Biparental chloroplast inheritance—where plastid genes are inherited from both parent plants—occurs in very low levels in some flowering plants.

Chloroplasts are a special type of a plant cell organelle called a plastid, though the two terms are sometimes used interchangeably.

Consistent with this hypothesis, organisms with multiple plastids show an 80-fold increase in plastid to nucleus gene transfer compared to organisms with single plastids.

Curiously the mitochondrion and the plastid of the diatom remain functional.

Disturbance was common in the early stages of endosymbiosis, however, once the host cell gained control of organelle division, eukaryotes could evolve to have only one plastid per cell.

Gitte Petersen, Ole Seberg, Sarah Thorsøe, Tina Jørgensen & Brian Mathew: A phylogeny of the genus Crocus (Iridaceae) based on sequence data from five plastid regions.

Late into the constriction phase, dynamin proteins assemble around the outer plastid-dividing ring, helping provide force to squeeze the chloroplast.

Meanwhile, the Z-ring and the inner plastid-dividing ring break down.

The endosymbiotic acquisition of a eukaryote cell is represented in the cryptophytes; where the remnant nucleus of the red algal symbiont (the nucleomorph ) is present between the two inner and two outer plastid membranes.

The gene for tRNA- formylmethionine (tRNA-fmet) is also encoded in the plastid genome and is required for translation initiation in both plastids and mitochondria.

The outer plastid-dividing ring is found wrapped around the outer chloroplast membrane.

There are two main hypotheses to explain this occurrence: The essential tRNA hypothesis: There have been no documented functional plastid to nucleus gene transfers of genes encoding RNA products (tRNAs and rRNAs).

The single most convincing evidence of the descent of organelles from bacteria is the position of mitochondria and plastid DNA sequences in phylogenetic trees of bacteria.