Department of Chemistry, University of California, Berkeley, CA 94720.
Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
Proc Natl Acad Sci U S A. 2024 Oct 15;121(42):e2411620121. doi: 10.1073/pnas.2411620121. Epub 2024 Oct 8.
Zeaxanthin (Zea) is a key component in the energy-dependent, rapidly reversible, nonphotochemical quenching process (qE) that regulates photosynthetic light harvesting. Previous transient absorption (TA) studies suggested that Zea can participate in direct quenching via chlorophyll (Chl) to Zea energy transfer. However, the contamination of intrinsic exciton-exciton annihilation (EEA) makes the assignment of TA signal ambiguous. In this study, we present EEA-free TA data using thylakoid membranes, including the wild type and three NPQ mutants (, , and ) generated by CRISPR/Cas9 mutagenesis. The results show a strong correlation between excitation energy transfer from excited Chl Q to Zea S and the xanthophyll cycle during qE activation. Notably, a Lut S signal is absent in the thylakoids which lack zeaxanthin. Additionally, the fifth-order response analysis shows a reduction in the exciton diffusion length (L) from 62 ± 6 nm to 43 ± 3 nm under high light illumination, consistent with the reduced range of exciton motion being a key aspect of plants' response to excess light.
玉米黄质（Zea）是能量依赖性、快速可逆、非光化学猝灭过程（qE）的关键组成部分，可调节光合作用的光捕获。先前的瞬态吸收（TA）研究表明，玉米黄质可以通过叶绿素（Chl）到玉米黄质能量转移参与直接猝灭。然而，内禀激子-激子湮灭（EEA）的污染使得 TA 信号的分配不明确。在这项研究中，我们使用类囊体膜呈现了无 EEA 的 TA 数据，包括通过 CRISPR/Cas9 诱变生成的野生型和三种 NPQ 突变体（、和）。结果表明，在 qE 激活过程中，从激发的 Chl Q 到 Zea S 的激发能量转移与叶黄素循环之间存在很强的相关性。值得注意的是，在缺乏玉米黄质的 类囊体中不存在 Lut S 信号。此外，五阶响应分析显示，在高光照射下，激子扩散长度（L）从 62±6nm 降低到 43±3nm，这与激子运动范围的减小是植物对过量光响应的关键方面一致。
