Hubei Key Laboratory of Genetic Regulation and Integrative Biology, School of Life Sciences, Central China Normal University, Wuhan, Hubei, 430079, P. R. China.
Environ Microbiol. 2019 Jul;21(7):2261-2272. doi: 10.1111/1462-2920.14600. Epub 2019 Apr 7.
The subaerial cyanobacterium Nostoc flagelliforme can survive for years in the desiccated state and light exposure may stimulate photosynthetic recovery during rehydration. However, the influence of light quality on photosynthetic recovery and the underlying mechanism remain unresolved. Exposure of field collected N. flagelliforme to light intensity ≥2 μmol photons m s showed that the speed of photosystem II (PSII) recovery was in the following order: red > green > blue ≈ violet light. Decreasing the light intensity showed that weak red light stimulated PSII recovery during rehydration. The chlorophyll fluorescence transient and oxygen evolution activity indicated that the oxygen evolution complex (OEC) was the activated site triggered by weak red light. The damaged D1 protein accumulated in the thylakoid membrane during dehydration and is degraded and resynthesized during dark rehydration. PsbO interaction with the thylakoid membrane was induced by weak red light. Thus, weak red light plays an important role in triggering OEC photoactivation and the formation of functional PSII during rehydration. In its arid habitats, weak red light could stimulate the awakening of dormant N. flagelliforme after absorbing water from nighttime dew or rain to maximize growth during the early daylight hours of the dry season.
气生蓝细菌念珠藻能在干燥状态下存活数年，光照可能会刺激其在复水过程中的光合恢复。然而，光照质量对光合恢复的影响及其潜在机制仍未得到解决。将野外采集的念珠藻暴露在强度≥2 μmol 光子 m s 的光线下，发现光合系统 II（PSII）恢复的速度依次为：红光＞绿光＞蓝光≈紫光。降低光强表明，弱红光在复水过程中刺激 PSII 恢复。叶绿素荧光瞬变和氧气释放活性表明，弱红光触发了类囊体膜上的氧释放复合物（OEC）的激活。脱水过程中在类囊体膜中积累的受损 D1 蛋白在黑暗复水期间降解并重新合成。弱红光诱导 PsbO 与类囊体膜相互作用。因此，弱红光在触发 OEC 光活化和复水过程中功能性 PSII 的形成中起着重要作用。在其干旱栖息地中，弱红光可以在吸收夜间露水或雨水后，刺激休眠的念珠藻苏醒，以在旱季的早期白天最大限度地生长。
