Inhibition of sulfur assimilation by S-benzyl-L-cysteine: Impacts on growth, photosynthesis, and leaf proteome of maize plants.

Sulfur is an essential nutrient for various physiological processes, including protein synthesis and enzyme activation. We aimed to evaluate how S-benzyl-L-cysteine (SBC), an inhibitor of the sulfur assimilation pathway, affects maize plants' growth, photosynthesis, and leaf proteomic profile. Thus, maize plants were grown for 14 days in vermiculite supplemented with SBC. Photosynthesis was assessed using light and CO2 response curves and chlorophyll a fluorescence. Leaf proteome analysis was conducted to evaluate photosynthetic protein biosynthesis, and ROS content was quantified to assess oxidative stress. Applying SBC resulted in a significant decrease in the growth of maize plants. The gas exchange analysis revealed that maize plants exhibited a diminished rate of CO2 assimilation attributable to both stomatal and non-stomatal limitations. Furthermore, SBC suppressed the activity of important elements involved in the photosynthetic electron transport chain (including photosystems I and II, cytochrome b6f, and ATP synthase) and enzymes responsible for the Calvin cycle, some of which have sulfur-containing prosthetic groups. Consequently, the diminished electron flow rate resulted in a substantial increase in the levels of ROS within the leaves. Our research highlights the crucial role of SBC in disrupting maize photosynthesis by limiting L-cysteine and assimilated sulfur availability, which are essential for the synthesis of protein and prosthetic groups and photosynthetic processes, emphasizing the potential of OAS-TL as a new herbicide site of action.