Collegial Effects of Salt and Ultraviolet Radiation on Rice-Field Cyanobacterium Nostochopsis lobatus HKAR-21

Abstract Cyanobacteria are a primitive group of photosynthetic oxygen-evolving, Gram-negative prokaryotes. Similar to eukaryotic algae and higher plants, it engages in photosynthesis-dependent oxygen evolution with water as a proton source. Cyanobacteria can be used as a model system to study the mechanisms of signal transduction, photosynthesis, and membrane lipids under abiotic stress, which may also provide an applicable model for higher plants. Salt stress is an abiotic factor that significantly affects plant survival and development. Therefore, improving the salt tolerance of agriculturally important plants is critical. Similar to how rising ultraviolet radiation (UVR) has a negative impact on land and an aquatic ecosystem, climate change has significant interactions with it. Cyanobacteria endure diverse effects from UV radiation, especially UV-B (280–315 nm). These alterations result from the production of free radicals, and PSII is a key target of UVR in photosynthetic organisms. In this experiment, we looked at the variation in photopigments of the cyanobacterium and its photosynthetic performance. The effect of increasing salt concentration on total lipid, carbohydrate composition and PBPs has been assessed. During UV stress, antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) were examined. After that, using 2′,7′-dichlorodihydrofluorescein diacetate (DCFH-DA), ROS was detected in vivo. The induction of lipid peroxidation has been investigated to evaluate the impact of UV radiation on the cyanobacterial membrane in addition to enzymatic defensive systems.