A process that is carried out at the cellular level which results in the formation of ER (endoplasmic reticulum) body. ER body is a compartment found in plant cells that is derived from the ER. The structures have a characteristic shape and size (10 mm long and 0.5 mm wide) and are surrounded with ribosomes. They have been found in Arabidopsis thaliana and related Brassicaceae species.
ER body organisation