Photophobotaxis in the filamentous cyanobacterium Phormidium lacuna: Mechanisms and implications for photosynthesis ‐based light direction sensing

How do filaments ofPhormidium lacuna find the lighted area? Each filament moves in random direction. If a filament crosses the light –dark border, it returns and stays in the light. AbstractCyanobacteriumPhormidium lacuna filaments move from dark to illuminated areas by twitching motility. Time-lapse recordings demonstrated that this photophobotaxis response was based on random movements with movement reversion at the light –dark border. The filaments in the illuminated area form a biofilm attached to the surface. The wild-type and thepixJ andcphA mutants were investigated for photophobotaxis at diverse wavelengths and intensities. CphA is a cyanobacterial phytochrome; PixJ is a biliprotein with a methyl-accepting chemotaxis domain and is regarded as a phototaxis photoreceptor in other species. ThecphA mutant exhibited reduced biofilm surface binding. ThepixJ mutant was characterized as a negative photophobotaxis regulator and not as a light direction sensor. 3-(3,4-dichlorophenyl)1,1-dimethylurea (DCMU) blocks electron transfer in PS II. At concentrations of 100 and 1000  μM DCMU, photophobotaxis was inhibited to a greater extent than motility, suggesting that PSII has a role in photophobotaxis. We argue that the intracellular concentrations of regular photoreceptors, including CphA or PixJ, are too small for a filament to sense rapid light intensity changes in v ery weak light. Three arguments, specific inhibition by DCMU, broad spectral sensitivity, and sensitivity ...

Source: Photochemistry and Photobiology - January 26, 2024 Category: Science Authors: Elina Schwabenland, Carolina Janine Jelen, Nora Weber, Tilman Lamparter Tags: RESEARCH ARTICLE Source Type: research