Deciphering Plant Signaling Pathway with Semiconducting Single-Walled Carbon Nanotubes

As a consequence of their sessile nature, plants have developed complex signaling mechanisms to cope with the highly dynamic environment that they live in. In response to external stimuli, plants can utilize various signaling pathways for intercellular communication to engage different metabolic and genetic machineries involved in the plant defense system. Among the many signaling molecules recently uncovered, hydrogen peroxide (H2O2) represents one of the most versatile signaling molecule in plants in response to environmental stresses such as mechanical wounding. Here, we develop an optical nanosensor platform using DNA-wrapped semiconducting single-walled carbon nanotubes (SWNT) to monitor the wound-induced H2O2 signaling pathway in plants. This approach enables non-destructive, real-time detection of changes in endogenous H2O2 level in plants at a remote distance with portable and inexpensive electronics. We demonstrate the versatility of this method to investigate the dynamics between H2O2 and electric signalling pathways in different vegetable crops and plant species. The reversibility of the sensor in vivo and its use to monitor insect feeding for agricultural applications are also demonstrated. In addition, we also developed an auto-propagating wave model to explain the propagation dynamics of H2O2 post-wounding. This newly developed tool offers new opportunities to understand plant defense responses as well as to monitor crop health in real time.