Faculty of Life Sciences and Biotechnology, Shahid Beheshti University, Tehran, 1983969411, Iran.
Sci Rep. 2024 Aug 20;14(1):19258. doi: 10.1038/s41598-024-70002-8.
Cyanobacteria possess special defense mechanisms to protect themselves against ultraviolet (UV) radiation. This study combines experimental and computational methods to identify the role of protective strategies in Nostoc species against UV-C radiation. To achieve this goal, various species of the genus Nostoc from diverse natural habitats in Iran were exposed to artificial UV-C radiation. The results indicated that UV-C treatment significantly reduced the photosynthetic pigments while simultaneously increasing the activity of antioxidant enzymes. Notably, N. sphaericum ISB97 and Nostoc sp. ISB99, the brown Nostoc species isolated from habitats with high solar radiations, exhibited greater resistance compared to the green-colored species. Additionally, an increase in scytonemin content occurred with a high expression of key genes associated with its synthesis (scyF and scyD) during the later stages of UV-C exposure in these species. The molecular docking of scytonemin with lipopolysaccharides of the cyanobacteria that mainly cover the extracellular matrix revealed the top/side positioning of scytonemin on the glycans of these lipopolysaccharides to form a UV-protective shield. These findings pave the way for exploring the molecular effects of scytonemin in forming the UV protection shield in cyanobacteria, an aspect that has been ambiguous until now.
蓝细菌具有特殊的防御机制来保护自己免受紫外线 (UV) 辐射的伤害。本研究结合实验和计算方法，确定了 Nostoc 属物种针对 UV-C 辐射的保护策略的作用。为了实现这一目标，从伊朗不同自然栖息地采集了各种 Nostoc 属物种，并将其暴露在人工 UV-C 辐射下。结果表明，UV-C 处理显著降低了光合色素的含量，同时增加了抗氧化酶的活性。值得注意的是，与绿色物种相比，从高太阳辐射栖息地分离出的棕色 Nostoc 物种 N. sphaericum ISB97 和 Nostoc sp. ISB99 表现出更强的抗性。此外，在这些物种暴露于 UV-C 的后期阶段，伴随着与 scytonemin 合成相关的关键基因（scyF 和 scyD）的高表达，scytonemin 的含量增加。将 scytonemin 与主要覆盖细胞外基质的蓝细菌的脂多糖进行分子对接表明，scytonemin 以顶/侧的方式定位在这些脂多糖的聚糖上，形成一个 UV 保护屏蔽。这些发现为探索 scytonemin 在蓝细菌中形成 UV 保护屏蔽的分子效应铺平了道路，这在以前一直是不清楚的。
