Beta tubulins are found dimerized with alpha tubulins for which there are also four isoforms in Drosophila. In all cases an alpha tubulin - beta tubulin heterodimer is the functional form of tubulin in the cell.
Adult expression is confined to specific somatic cells in the gonads .
These microtubule arrays are associated with growing myofibriles in embryonic body wall and gut muscle. Microtubule assembly precedes sarcomere formation, and microtubules are later intermingled among growing sarcomere elements. Muscle-associated microtubules are transient and are disassembled after completion of myogenesis. Microtubule assembly in the myogenic cells begins in stage 12. Nevertheless, organization and structure of the sarcomeres in the flightless mutants can not be distinguished from wild type.