Monitoring of CO as a plant signaling molecule under heavy metal stress using carbon nanodots

Abstract

Carbon monoxide (CO) is widely acknowledged as a significant environmental pollutant allied to numerous instances of accidental poisoning in humans. However, it also serves a pivotal role as a signaling molecule in plants, exhibiting functions analogous to those of other gaseous signaling molecules, including nitric oxide (NO) and hydrogen sulfide (H2S). In the context of plant physiology, CO is synthesized as an integral component of the defense mechanism against oxidative damage, particularly under abiotic stress conditions such as drought, salinity, and exposure to heavy metals. Current research methodologies have demonstrated a deficiency in effective tools for monitoring CO dynamics in plants during periods of stress under heavy metals accumulation across various developmental stages. Therefore, developing a sensor capable of detecting CO in living plant tissues is essential, facilitating a deeper understanding of its biological functions, underlying mechanisms, and metabolic pathways. In response to this gap, the present study introduces a novel technique for monitoring CO production and its activity in plants using Nitrogen-doped Carbon Quantum Dots (N-CQDs). These nanodots exhibit exceptional biocompatibility, low toxicity, and environmentally sustainable characteristics, rendering them an optimal instrument for CO detection via fluorescence quenching mechanism with a detection limit (LOD) of 0.102 μM. This innovative nanomarker facilitates the detection of trace quantities of CO within plant cells, providing new insights into the stress responses of plants in the presence of heavy metals such as Cu, Zn, Pb, Ru, Cr, Cd, and Hg and the processes involved in seed germination. Additionally, confocal microscopy has validated the interaction between CO and N-CQDs, yielding visual evidence of CO binding within plant cells, further enhancing the understanding of CO's role in plant biology.