Photoregulation of morphological structure and its physiological relevance in the cyanobacterium Arthrospira (Spirulina) platensis

Abstract

The spiral structure of the cyanobacterium Arthrospira (Spirulina) platensis (Nordst.) Gomont was previously found to be altered by solar ultraviolet radiation (UVR, 280-400 nm). However, how photosynthetic active radiation (PAR, 400-700 nm) and UVR interact in regulating this morphological change remains unknown. Here, we show that the spiral structure of A. platensis (D-0083) was compressed under PAR alone at 30 degrees C, but that at 20 degrees C, the spirals compressed only when exposed to PAR with added UVR, and that UVR alone (the PAR was filtered out) did not tighten the spiral structure, although its presence accelerated morphological regulation by PAR. Their helix pitch decreased linearly as the cells received increased PAR doses, and was reversible when they were transferred back to low PAR levels. SDS-PAGE analysis showed that a 52.0 kDa periplasmic protein was more abundant in tighter filaments, which may have been responsible for the spiral compression. This spiral change together with the increased abundance of the protein made the cells more resistant to high PAR as well as UVR, resulting in a higher photochemical yield.

Independence and interdependence of the photoregulation of pigmentation and development inFremyella diplosiphon

“…13 These results together with recent results obtained from studies of F. diplosiphon suggest that photoregulation of cyanobacterial cellular and filament morphologies are linked with organismal adaptation to environmentally important light variations. We thus anticipate that continued studies in the photoregulation of pigmentation and morphology in cyanobacterial systems will lead to additional insights into the physiologically relevant photoadaptations that occur in these systems.…”

Photosynthetic and biochemical characterization of pigments and UV-absorbing compounds in Phormidium tenue due to UV-B radiation

“…There are several targets for the potentially toxic ROS including pigments, lipids, DNA, and proteins; moreover, damage to photosynthetic apparatus is also partially mediated by ROS (He and Häder 2002). Morphology, cell differentiation, survival, growth, pigmentation, motility and orientation, nitrogen metabolism, phycobiliprotein composition, protein profile, DNA, and CO 2 uptake have been reported to be affected by UVR (Ma and Gao 2009;Lesser 2008). …”

“…UV radiation can cause a broad spectrum of genetic and cytotoxic effects in aquatic organisms. However, these responses are partly offset by various protection strategies such as morphological adaptations (Ma and Gao 2009), avoidance, screening, photochemical quenching, and repair (Roy 2000). One of the important concerns with ozone depletion is the potential contribution to global greenhouse gas warming by reducing the sink capacity for atmospheric carbon dioxide through UV inhibition of marine primary production (Takahashi et al 1997).…”

Reactive oxygen species are involved in the morphology-determining mechanism of Fremyella diplosiphon cells during complementary chromatic adaptation

“…morphological change was found to improve photosynthetic efficiency in Arthrospira platensis (Ma & Gao, 2009;Rastogi et al, 2010). Thus, our results are in accordance with Bennett & Bogorad (1973) and here we propose that selective lysis of cells by oxidative stress results in fragmentation of the filaments under RL.…”