Editors' ChoiceTactic Responses

Shedding Light on Phototaxis

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Science's STKE  07 Mar 2000:
Vol. 2000, Issue 22, pp. tw6
DOI: 10.1126/stke.2000.22.tw6

Under starvation conditions, the single-cell slime mold Dictyostelium discoideum aggregates into a multicellular mass referred to as a slug. Aggregation occurs as a chemotactic response to cAMP wave signals initiated at the center of accretion. Although these cAMP waves coordinate chemotaxis, it is unclear how light produces phototaxis. Miura and Siegert demonstrated that light directly induces the release of cAMP from severed slug tips in culture and that this is followed by migration of unicellular slime mold cells toward the slug tip aggregate. As expected, this chemotactic response was specifically dependent on the presence of cAMP, as cAMP receptor-deficient slime molds were incapable of light-dependent chemotaxis. In addition, light increased the frequency of cAMP wave signaling in Dictyostelium aggregates. Therefore, light is directly capable of stimulating cAMP pulses in cell-to-cell signaling. Phototaxis and light perception are mediated in the multicellular slug by the anterior tip, which initiates the propagation of cAMP waves toward the posterior region of the slug. Thus, Miura and Siegert provide evidence that light directs cAMP signaling as well as slug locomotion.

Miura, K., and Siegert, F. (2000) Light affects cAMP signaling and cell movement activity in Dictyostelium discoideum. Proc. Natl. Acad. Sci. USA 97: 2111-2116. [Abstract] [Full Text]

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