Light intensity and reactive oxygen species are centrally involved in photoregulatory responses during complementary chromatic adaptation in Fremyella diplosiphon

Abstract

Light, including properties such as light quality and light quantity or intensity, and light-associated factors, including light-dependent, oxidative stress-associated accumulation of reactive oxygen species (ROS), are involved in the photoregulation of cellular morphogenesis in the freshwater cyanobacterium Fremyella diplosiphon. Although it has been long noted that differences in light quality can impact cellular morphology and filament lengths of F. diplosiphon, our recent findings indicate that light intensity and light-associated regulation of ROS levels are correlated with changes in morphology as well. Red light (RL) induces accumulation of ROS, as does an increase in light intensity, both of which are associated with a shift toward a more spherical cell shape. As the impacts of increased light intensity on pigmentation, cellular ROS levels and morphology are reversible when cells are shifted from high RL intensity to a lower intensity, our cumulative results suggest a causative impact of light-intensity mediated increases in ROS levels on cellular morphology.