Select acetophenones alter flagellar motility in Chlamydomonas

Austin A. Pearce, Shakila K. Evans, Joshua D. Farthing, Victoria. Y. Alfaro, Crystal P. Liles, Todd P. Primm, and Anne R. Gaillard

Department of Biological Sciences, Sam Houston State University, Huntsville, TX 77341, USA, A Member of the Texas State University System

As an alternative to the use of motility mutants in the study of flagellar motility, acetophenones were screened for their ability to alter flagellar motility in order to develop a chemical library of motility inhibitors. Acetophenones were screened for activity against positive phototaxis and negative gravitaxis of Chlamydomonas, processes that require coordinated flagellar motility. Acetophenones were selected for their commercial availability, relatively low toxicity, and reported biological activity. Wild-type (CC-125) Chlamydomonas cells were grown to a density of ~ 5 x 106 cells/ml (mid log phase) and were then incubated with a variety of acetophenones, at concentrations ranging from 250-500 µg/ml (1-4 mM), for 4-6 hours.Following incubation, cells were first tested for their ability to perform positive phototaxis.Several acetophenones blocked phototaxis, although many of these were later determined to be cytotoxic to the cells. Surprisingly, 4-methoxyacetophenone and 4-hydroxyacetophenone induced negative phototaxis in Chlamydomonas, suggesting that these compounds alter control of flagellar dominance. In addition, several derivatives of 4-hydroxyacetophenone also induced negative phototaxis. A gravitaxis screen was also performed following incubation of cells with acetophenones. 4-methoxyacetophenone and 4-hydroxyacetophenone blocked negative gravitaxis of Chlamydomonas cells.In addition, several other acetophenones blocked negative gravitaxis of the cells, including compounds that did not alter phototaxis. Additional assays are currently underway to determine the structure-activity relationships of acetophenones on flagellar motility and cell viability.

e-mail address of presenting author: argaillard@shsu.edu