89(P-46) Bioorganic studies on nyctinasty in legumes using fluorescence-labeled probe compounds : direct observation of target cell for leaf-opening substance

Most legumes close their leaves in the evening, as if to sleep, and open them in the morning. This is called nyctinasty, and we have identified several bioactive substances that regulate this leaf movement. Investigation of the site where bioactive substances are perceived at the cellular level is an essential step towards the isolation and identification of the receptor molecule. A fluorescence-labeled probe compounds is most suitable for the study of this problem, so we designed and synthesized fluorescence-labeled probe compounds and revealed target cell of bioactive substances. Based on the results of structure-activity relationships of potassium isolespedezate, we designed and synthesized fluorescence-labeled probe compounds(14-18). These probes compounds showed specific leaf-opening activity against the leaf of C. mimosides. We used probe 15 for fluorescence study of the interaction between the leaf-opening substance and the plant motor cell, which plays a central role in the plant leaf movement. The staining pattern for the fluorescence of probe compound 15 was observed on the surface of motor cell(Fig 3). These results suggest that specific binding site for 15 would exist on the plasma membrane of the motor cell. We also observed other plant as well as the leaf of C. mimosides, but no stain was observed in the other plant. These result suggested that fluorescence-labeled probe compounds bound motor cell of C. mimosoides specifically, and each plant have specific binding site for the leaf-opening substance on the plasma membrane of the motor cell.