Basal body

Schematic of the eukaryotic flagellum. 1-axoneme, 2-cell membrane, 3-IFT (Intraflagellar Transport), 4-Basal body, 5-Cross section of flagellum, 6-Triplets of microtubules of basal body.

Longitudinal section through the flagella area in Chlamydomonas reinhardtii. In the cell apex is the basal body that is the anchoring site for a flagellum. Basal bodies originate from and have a substructure similar to that of centrioles, with nine peripheral microtubule triplets (see structure at bottom center of image).

A basal body (synonymous with basal granule, kinetosome, and in older cytological literature with blepharoplast) is an organelle formed from a centriole, and a short cylindrical array of microtubules. It is found at the base of a eukaryotic undulipodium (cilium or flagellum) and 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 microtubules within centrosomes, and are known as the microtubule organizing center (MTOC). These microtubules provide structure and facilitate movement of vesicles and organelles within many eukaryotic cells. The term, basal body is, however, reserved specifically for the base structures of eukaryote cilia and flagella which extend out from the cell.

Basal bodies are derived from centrioles through a largely mysterious process. They are structurally the same, each containing a microtubule triplet 9*3 helicoidal configuration forming a hollow cylinder. The overlying axoneme, however, consists of a 9*2 + 2 structure.

the basal granule is a modified centriole. it is present in the ectoplasm. the tubules arof each triplet are designed as A,B,C from the centre to the periphery. both A,B cross the basal plate and continue as pheripheral doublet above the pellicle in the axoneme. however , the tubule C terminates at the basal plate . thus the triplets of the basal granule are converted into the flagellar or the cillary doublets there are no central microtubules in the basal granule. the basal granule is also ocnnected to the plasma membrane and the neucleus by communication tubules called the rootlets the rootlets can pull the flagellum and alter its orientation .

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.

External links

• Histology image: 21804loa – Histology Learning System at Boston University - "Ultrastructure of the Cell: ciliated epithelium, cilia and basal bodies"