Fu Han-Yi, Wang Ming-Wei
Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan.
Front Plant Sci. 2023 Jun 2;14:1176985. doi: 10.3389/fpls.2023.1176985. eCollection 2023.
Acidothermophilic cyanidiophytes in natural habitats can survive under a wide variety of light regimes, and the exploration and elucidation of their long-term photoacclimation mechanisms promises great potential for further biotechnological applications. Ascorbic acid was previously identified as an important protectant against high light stress in under mixotrophic conditions, yet whether ascorbic acid and its related enzymatic reactive oxygen species (ROS) scavenging system was crucial in photoacclimation for photoautotrophic cyanidiophytes was unclear.
The significance of ascorbic acid and related ROS scavenging and antioxidant regenerating enzymes in photoacclimation in the extremophilic red alga was investigated by measuring the cellular content of ascorbic acid and the activities of ascorbate-related enzymes.
Accumulation of ascorbic acid and activation of the ascorbate-related enzymatic ROS scavenging system characterized the photoacclimation response after cells were transferred from a low light condition at 20 μmol photons m s to various light conditions in the range from 0 to 1000 μmol photons m s. The activity of ascorbate peroxidase (APX) was most remarkably enhanced with increasing light intensities and illumination periods among the enzymatic activities being measured. Light-dependent regulation of the APX activity was associated with transcriptional regulation of the chloroplast-targeted APX gene. The important role of the APX activity in photoacclimation was evidenced by the effect of the APX inhibitors on the photosystem II activity and the chlorophyll a content under the high light condition at 1000 μmol photons m s. Our findings provide a mechanistic explanation for the acclimation of to a wide range of light regimes in natural habitats.
自然栖息地中的嗜酸嗜热蓝藻在多种光照条件下都能存活，对其长期光适应机制的探索和阐明有望为进一步的生物技术应用带来巨大潜力。抗坏血酸先前被确定为混合营养条件下抵御高光胁迫的重要保护剂，但抗坏血酸及其相关的酶促活性氧（ROS）清除系统在光合自养蓝藻的光适应中是否至关重要尚不清楚。
通过测量抗坏血酸的细胞含量和抗坏血酸相关酶的活性，研究了抗坏血酸以及相关的ROS清除和抗氧化剂再生酶在极端嗜热红藻光适应中的重要性。
当细胞从20 μmol光子·m⁻²·s⁻¹的低光照条件转移到0至1000 μmol光子·m⁻²·s⁻¹范围内的各种光照条件后，抗坏血酸的积累和抗坏血酸相关的酶促ROS清除系统的激活表征了光适应反应。在所测量的酶活性中，抗坏血酸过氧化物酶（APX）的活性随着光照强度和光照时间的增加而增强最为显著。APX活性的光依赖性调节与叶绿体靶向APX基因的转录调节相关。在1000 μmol光子·m⁻²·s⁻¹的高光条件下，APX抑制剂对光系统II活性和叶绿素a含量的影响证明了APX活性在光适应中的重要作用。我们的研究结果为[具体藻类名称未给出]在自然栖息地中适应广泛光照条件提供了一种机制解释。
