A basal body (synonymous with basal granule, kinetosome, and in older cytological literature with blepharoplast) is a protein structure found at the base of a

eukaryotic The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

undulipodium (

cilium The cilium (: cilia; ; in Medieval Latin and in anatomy, ''cilium'') is a short hair-like membrane protrusion from many types of eukaryotic cell. (Cilia are absent in bacteria and archaea.) The cilium has the shape of a slender threadlike pr ...

or flagellum). The basal body was named by Theodor Wilhelm Engelmann in 1880. It is formed from a

centriole In cell biology a centriole is a cylindrical organelle composed mainly of a protein called tubulin. Centrioles are found in most eukaryotic cells, but are not present in conifers ( Pinophyta), flowering plants ( angiosperms) and most fungi, an ...

and several additional protein structures, and is, essentially, a modified centriole. The basal body serves as a nucleation site for the growth of the axoneme microtubules. Centrioles, from which basal bodies are derived, act as anchoring sites for proteins that in turn anchor

microtubule Microtubules are polymers of tubulin that form part of the cytoskeleton and provide structure and shape to eukaryotic cells. Microtubules can be as long as 50 micrometres, as wide as 23 to 27 nanometer, nm and have an inner diameter bet ...

s, and are known as the microtubule organizing center (MTOC). These microtubules provide structure and facilitate movement of vesicles and organelles within many eukaryotic cells.

Assembly, structure

Cilia and basal bodies form during quiescence or the

G1 phase The G1 phase, gap 1 phase, or growth 1 phase, is the first of four phases of the cell cycle that takes place in eukaryotic cell division. In this part of interphase, the cell synthesizes Messenger RNA, mRNA and proteins in preparation for subsequ ...

of the

cell cycle The cell cycle, or cell-division cycle, is the sequential series of events that take place in a cell (biology), cell that causes it to divide into two daughter cells. These events include the growth of the cell, duplication of its DNA (DNA re ...

. Before the cell enters G1 phase, i.e. before the formation of the cilium, the mother centriole serves as a component of the

centrosome In cell biology, the centrosome (Latin centrum 'center' + Greek sōma 'body') (archaically cytocentre) is an organelle that serves as the main microtubule organizing center (MTOC) of the animal cell, as well as a regulator of cell-cycle progre ...

. In cells that are destined to have only one primary cilium, the mother centriole differentiates into the basal body upon entry into G1 or quiescence. Thus, the basal body in such a cell is derived from the centriole. The basal body differs from the mother centriole in at least two aspects. First, basal bodies have basal feet, which are anchored to cytoplasmic microtubules and are necessary for polarized alignment of the cilium. Second, basal bodies have pinwheel-shaped transition fibers that originate from the appendages of mother centriole. In multiciliated cells, however, in many cases basal bodies are not made from centrioles but are generated ''de novo'' from a special protein structure called the deuterosome.

Function

During cell cycle dormancy, basal bodies organize primary cilia and reside at the cell cortex in proximity to plasma membrane. On cell cycle entry, cilia resorb and the basal body migrates to the nucleus where it functions to organize centrosomes. Centrioles, basal bodies, and cilia are important for mitosis, polarity, cell division, protein trafficking, signaling, motility and sensation. Mutations in proteins that localize to basal bodies are associated with several human ciliary diseases, including Bardet–Biedl syndrome, orofaciodigital syndrome, Joubert syndrome, cone-rod dystrophy, Meckel syndrome, and nephronophthisis. Regulation of basal body production and spatial orientation is a function of the nucleotide-binding domain of γ-tubulin. Plants lack centrioles and only lower plants (such as mosses and ferns) with motile sperm have flagella and basal bodies.Philip E. Pack, Ph.D., Cliff's Notes: AP Biology 4th edition.

References

External links

* - "Ultrastructure of the Cell: ciliated epithelium, cilia and basal bodies" {{Authority control Organelles