The cyanobacterial phytochrome Cph2 inhibits phototaxis towards blue light

Abstract

Summary We analysed the effects of inactivation of the phytochrome genes cph1 and cph2 on the phototactic migration of the cyanobacterium Synechocystis sp. PCC 6803 under different light qualities. Motility towards white, green, red and far red light was not altered in several independently raised cph1, cph2 and cph1/cph2 double mutants. Blue light (λ = 400–500 nm) did not induce motility in wild‐type and cph1 mutant cells, whereas cph2 and cph1/cph2 double mutants moved towards the blue light. Inhibition of the photosynthetic electron transport by DCMU influenced the motility of cph2 mutants under blue light, but not under white, red and far red light. RNA blot hybridizations did not indicate an altered transcript accumulation of the pilin‐encoding pilA1 gene under blue light. We propose that the Cph2 protein is part of a light‐stimulated signal transduction chain inhibiting the movement of Synechocystis sp. PCC 6803 cells towards blue light.

Ethylene Regulates the Physiology of the Cyanobacterium Synechocystis sp. PCC 6803 via an Ethylene Receptor

“…S3B). In air, positive phototaxis was observed in response to red and green light, but consistent with prior studies, no phototaxis occurred in response to blue or UV-A light at the fluence rates used (Wilde et al, 2002;Song et al, 2011). Application of ethylene enhanced movement toward red and green light and caused cells to move toward blue light.…”

“…SynEtr1DTM2 Synechocystis showed a large enhancement in the distance moved toward white light (Fig. 2, A (Wilde et al, 2002). This suggests that both Cyanobacteria Phytochrome2 and SynEtr1 inhibit movement toward blue light.…”

“…SynEtr1 is one of several phytochrome-like proteins identified in Synechocystis; some of these proteins, including SynEtr1, are involved in the regulation of phototaxis (Kaneko et al, 1996;Hughes et al, 1997;Yeh et al, 1997;Park et al, 2000;Wilde et al, 2002;Narikawa et al, 2011;Song et al, 2011 (Ikeuchi and Tabata, 2001;Trautmann et al, 2012), failed to move in response to directional white light in the absence or presence of ethylene, indicating that ethylene affects taxis rather than growth (data not shown). The effect of ethylene on light sensitivity also was examined by performing phototaxis assays in air and 1 mL L 21 ethylene at fluence rates ranging from 3.5 to 30 mmol m 22 s 21 white light.…”

Structure of the Cyanobacterial Phytochrome 2 Photosensor Implies a Tryptophan Switch for Phytochrome Signaling

“…c-di-GMP is known to be a universal regulator for pili-based motility in eubacteria (18) with domains of the GGDEF and EAL type being responsible for its synthesis and degradation (19). SynCph2 inhibits phototaxis, when cyanobacterial cells are exposed to blue but not to white or red light (20,21). Accordingly, the complex architecture of SynCph2 (Fig.…”

A molecular understanding of complementary chromatic adaptation

“…Lagarias and colleagues have demonstrated that plant phytochrome synthesized in yeast can undergo autophosphorylation, although this protein appears to have serine/threonine kinase rather than histidine kinase activity (Yeh and Lagarias 1998). Other phytochromelike proteins in bacteria appear to control growth under certain light conditions (Wilde et al 1997), carotenoid synthesis (Davis et al 1999) and phototactic move-ment Wilde et al 2002). Defining the signal transduction processes that are triggered by phytochrome-like photoreceptors in prokaryotes is providing us with new insights into mechanisms involved in light-regulated gene expression and the evolution of phytochrome structure and function in plants.…”