Endoredupplikation

Endoreduplication, also known as endoreplication, is a cellular process in which a cell replicates its DNA without undergoing mitosis, producing polyploid cells with multiple genome copies. This repeated DNA synthesis without cell division results in higher ploidy levels (for example from 2n to 4n, 8n, or more) within a single nucleus or cell.

The phenomenon is widespread in plants, where endoreduplication is common in differentiated tissues such as leaves, fruits, and xeromorphic organs. It is often associated with cell enlargement and increased metabolic capacity, supporting growth and development without increasing cell numbers. In animals, endoreduplication occurs less frequently but is observed in certain cell lineages, including megakaryocytes (which form polyploid nuclei through endomitosis), placental trophoblasts, and some hepatocytes during liver development or regeneration.

Mechanistically, endoreduplication arises when cells re-enter the S phase and duplicate their DNA repeatedly while progression through mitosis is suppressed. In plants, specific regulatory factors, such as cyclin-dependent kinase inhibitors (for example, SIAMESE and related proteins), and other cell cycle regulators, shift the balance from mitotic cycles toward endocycles. Endoreduplication and endomitosis are related but distinct: endoreduplication emphasizes S-phase–driven genome duplication without mitosis, whereas endomitosis involves mitosis without cytokinesis.

Biological significance includes generation of large, metabolically active cells, expanded tissue capacity, and potential adaptive advantages under developmental or environmental stress. Detection and quantification are typically performed by flow cytometry or chromosome counting in targeted tissues.