Control by Ammonium Ion of the Change from Step-Up to Step-Down Photophobically Responding Cells in the Flagellate Alga Euglena gracilis |
| |
Authors: | Matsunaga Shigeru; Takahashi Tetsuo; Watanabe Masakatsu; Sugai Michizo; Hori Terumitsu |
| |
Institution: | 1 Institute of Biological Sciences, University of Tsukuba Tsukuba, Ibaraki, 305-8572 Japan
2 Japan Advanced Institute of Science and Technology Tatsunokuchi, Ishikawa, 923-1292 Japan
3 National Institute for Basic Biology Okazaki, Aichi, 444-8585 Japan
4 Department of Biology, Faculty of Science, Toyama University Toyama, Toyama, 930-8555 Japan |
| |
Abstract: | The regulation between step-down and step-up photophobic responses,resulting in photoaccumulation of the cells in an actinic lighttrap or cells' avoidance from an excessive illumination, iscrucially important for the survival of phototrophic organismssuch as Euglena gracilis. As for the factors involved in thisregulation in Euglena gracilis, we for the first time reporthere that ammonium ion specifically enhances step-down photophobicresponse, together with the effects of L-methionine-DL-sulfoximine(L-MSO), an inhibitor of ammonium assimilation, to specificallyenhance step-up photophobic response. The apparent positivecorrelation between the degree of greening and the step-downphotophobic response did not seem to reflect real causal relationshipin view of the results with effects of gabaculine, an inhibitorof -aminolaevulinic acid ( -ALA) formation. The transmissionof stigma and step-down appearance did not show any correlationeither, in contrast to a previous assumption by other authors.Cycloheximide (CHX), an inhibitor of eukaryotic protein synthesis,suppressed step-down appearance and enhanced step-up appearance,probably suggesting an involvement of some (newly synthesized)protein(s) specifically in the step-down photosignal detectionand/or signal transduction process(es). (Received August 18, 1998; Accepted December 3, 1998) |
| |
Keywords: | |
本文献已被 Oxford 等数据库收录! |
|