title: Detection of a troponin I-like protein in non-striated muscle of the tardigrades (water bears).
abstract: Tardigrades, also known as water bears, have somatic muscle fibers that are responsible for movement of their body and legs. These muscle fibers contain thin and thick filaments in a non-striated pattern. However, the regulatory mechanism of muscle contraction in tardigrades is unknown. In the absence of extensive molecular and genomic information, we detected a protein of 31 kDa in whole lysates of tardigrades that cross-reacted with the antibody raised against nematode troponin I (TnI). TnI is a component of the troponin complex that regulates actin-myosin interaction in a Ca(2+)-dependent and actin-linked manner. This TnI-like protein was co-extracted with actin in a buffer containing ATP and EGTA, which is known to induce relaxation of a troponin-regulated contractile system. The TnI-like protein was specifically expressed in the somatic muscle fibers in adult animals and partially co-localized with actin filaments in a non-striated manner. Interestingly, the pharyngeal muscle did not express this protein. These observations suggest that the non-striated somatic muscle of tardigrades has an actin-linked and troponin-regulated system for muscle contraction.
authors.affiliation: Department of Biology; Faculty of Science; Chiba University; Chiba, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Obinata
authors.forename: Kanako
authors.initials: K
authors.lastname: Ono
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Ono