A Chimeric Peptide for Shielding Plant Photosynthetic Systems against Excess Light Stress via Chloroplast-Targeted...

The ability to quench reactive oxygen species (ROS) overproduced in plant chloroplasts under light stress conditions is essential for securing plant photosynthetic performance and agricultural yield. Although genetic engineering can enhance plant stress resistance, its widespread application faces limitations due to challenges in successful transformation across plant species and public acceptance concerns. This study proposes a nontransgenic chemical approach using a designed chimeric peptide that scavenges ROS within plant chloroplasts for managing light stress. The chimeric peptide was strategically designed by combining cell-penetrating and chloroplast-targeting sequences, each with antioxidant ability against destructive ROS such as hydroxyl radical (•OH) and singlet oxygen (¹O₂). Our analyses involving various cell-penetrating peptides and a chloroplast-targeting peptide revealed that the •OH-scavenging ability predominantly relied on side chain oxidation in tryptophan residues, while the ¹O₂-quenching capacity was attributed to the oxidation of cysteine and methionine side chains. We further demonstrated that the chimeric peptide could traverse the cell wall and membranes to reach chloroplasts, where it scavenged •OH and ¹O₂ and alleviated light-stress-induced chlorophyll degradation in leaves. Foliar spraying of the peptide successfully protected photosynthetic activity in leaves exposed to excessive light, highlighting its potential for practical agricultural applications. This work can offer a promising approach for managing abiotic stress without genetic modifications and provide valuable insights into the design of effective peptide-based ROS quenchers specifically targeting plant chloroplasts.