Wu Guangxi, Ma Lin, Sayre Richard T, Lee Choon-Hwan
Department of Molecular Biology, Pusan National University, Busan, South Korea.
Pebble Labs, Los Alamos, NM, United States.
Front Plant Sci. 2020 May 15;11:505. doi: 10.3389/fpls.2020.00505. eCollection 2020.
One of the major constraints limiting biomass production in autotrophs is the low thermodynamic efficiency of photosynthesis, ranging from 1 to 4%. Given the absorption spectrum of photosynthetic pigments and the spectral distribution of sunlight, photosynthetic efficiencies as high as 11% are possible. It is well-recognized that the greatest thermodynamic inefficiencies in photosynthesis are associated with light absorption and conversion of excited states into chemical energy. This is due to the fact that photosynthesis light saturates at one quarter full sunlight intensity in plants resulting in the dissipation of excess energy as heat, fluorescence and through the production of damaging reactive oxygen species. Recently, it has been demonstrated that it is possible to adjust the size of the light harvesting antenna over a broad range of optical cross sections through targeted reductions in chlorophyll content, selectively resulting in reductions of the peripheral light harvesting antenna size, especially in the content of Lhcb3 and Lhcb6. We have examined the impact of alterations in light harvesting antenna size on the amplitude of photoprotective activity and the evolutionary fitness or seed production in Camelina grown at super-saturating and sub-saturating light intensities to gain an understanding of the driving forces that lead to the selection for light harvesting antenna sizes best fit for a range of light intensities. We demonstrate that plants having light harvesting antenna sizes engineered for the greatest photosynthetic efficiency also have the greatest capacity to mitigate high light stress through non-photochemical quenching and reduction of reactive oxygen associated damage. Under sub-saturating growth light intensities, we demonstrate that the optimal light harvesting antenna size for photosynthesis and seed production is larger than that for plants grown at super-saturating light intensities and is more similar to the antenna size of wild-type plants. These results suggest that the light harvesting antenna size of plants is designed to maximize fitness under low light conditions such as occurs in shaded environments and in light competition with other plants.
限制自养生物生物量生产的主要制约因素之一是光合作用的热力学效率较低，仅为1%至4%。鉴于光合色素的吸收光谱和太阳光的光谱分布，光合效率高达11%是有可能的。人们普遍认识到，光合作用中最大的热力学低效率与光吸收以及激发态向化学能的转化有关。这是因为植物光合作用在四分之一全日照强度下就会达到光饱和，导致多余的能量以热量、荧光的形式耗散，并通过产生具有破坏性的活性氧物质而耗散。最近，已经证明通过有针对性地降低叶绿素含量，可以在很宽的光学横截面积范围内调节光捕获天线的大小，从而选择性地减小外周光捕获天线的大小，特别是Lhcb3和Lhcb6的含量。我们研究了光捕获天线大小的改变对在超饱和和亚饱和光强下生长的荠蓝中光保护活性的幅度以及进化适应性或种子产量的影响，以了解导致选择最适合一系列光强的光捕获天线大小的驱动力。我们证明，为实现最大光合效率而设计光捕获天线大小的植物，也具有通过非光化学猝灭和减少活性氧相关损伤来减轻高光胁迫的最大能力。在亚饱和生长光强下，我们证明光合作用和种子生产的最佳光捕获天线大小大于在超饱和光强下生长的植物，并且更类似于野生型植物的天线大小。这些结果表明，植物的光捕获天线大小旨在在低光条件下（如在阴凉环境中和与其他植物的光竞争中）实现适应性最大化。
