Photosensory transduction in unicellular eukaryoteBlepharisma

✍ Scribed by Matsuoka, Tatsuomi ;Kotsuki, Hiyoshizo

• Book ID: 102334352
• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 172 KB
• Volume: 289
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/jez.1028

✦ Synopsis

Abstract

In the ciliated protozoan Blepharisma, step‐up photophobic response is mediated by a novel type of photosensory complex of pink‐colored pigment “blepharismins” and 200‐kDa membrane protein contained in the pigment granules located just beneath the plasma membrane. We found that the fluorescence intensity of isolated blepharismins decreased prominently with a decrease of H^+^ concentration in the surrounding medium. In the present study, therefore, we utilized the endogenous pigment blepharismins as the pH indicator. Light stimulation evoked a sudden decrease in fluorescence intensity in a photosensitive anterior portion of the cell, suggesting that a drop in H^+^ concentration occurred in the anterior region. The result indicates that the photosignal is transduced into cytoplasmic signaling of H^+^ translocation across the outer membrane surrounding the pigment granules, so that cytosolic H^+^ concentration in the vicinity of plasma membrane might be increased. J. Exp. Zool. 289:467–471, 2001. © 2001 Wiley‐Liss, Inc.