Engineering and understanding chloroplast function with nanomaterials
We are demonstrating that that engineered nanomaterials enhance chloroplast photosynthesis, act as gene delivery tools, and turn chloroplasts into biomanufacturing devices. For example, semiconducting single walled carbon nanotubes (SWNT) enhance photosynthesis by capturing solar energy in wavelengths that are weakly absorbed by chloroplasts. Cerium oxide nanoparticles (nanoceria) act as potent antioxidants protecting plant photosynthesis from reactive oxygen species accumulation (ROS). We are also utilizing nanomaterials to deliver plasmid DNA and augment chloroplast function in plants and algae. This nanoengineering approach may lead to crops with improved stress tolerance and plants/algae that act as biomanufacturing platforms on demand.
Nanoparticle Interactions with photosyntetic organisms
Near infrared images of single walled carbon nanotube (SWCNT) photoluminescence showing SWCNT spontaneous assembly within an extracted chloroplast
Impact of nanomaterial chemical and physical properties on their interactions with plant/algae biosurfaces and biomolecules
The mechanisms of uptake, transport, and distribution of nanoparticles in plants and algae are poorly understood. Our research has highlighted that the surface properties of nanoparticles determine their transport through chloroplast lipid bilayers. Highly cationic or anionic nanoparticles are able to penetrate the chloroplast envelope but not those with more neutral charge or coated in lipids. Positively charged nanomaterials preferentially localize inside leaf cells and chloroplasts in planta whereas anionic nanomaterials translocate into the plant vascular system. We are discovering how nanomaterial properties such as size, surface chemistry, and aspect ratios, shape their interaction with plant lipid membranes, cell walls, proteins, lipids and other biomolecules. We aim to leverage this knowledge to enable novel targeted and controlled chemical and biomolecule delivery tools for studying plant/algae biology and lead to a more sustainable and precise agriculture.
Major abiotic and biotic stresses and resource deficiencies are associated with signalling molecules that communicate and regulate plant responses including ROS (for example, H2O2), Ca2+, NO and ABA among others. Nanomaterial-mediated delivery of genetically encoded sensors enables research on signalling mechanisms of plant health that inform the design and engineering of smart plant sensors. Optical nanosensors and wearable nanotechnology-based sensors interfaced with plants allow the translation of plant chemical signals into optical and radio waves, and electric signals, which can be monitored by electronic devices. Machines with the capacity to decode spatiotemporal patterns of plant chemical signals will allow smart nanobiotechnology-based sensors to actuate agricultural devices for optimizing the plant environment. These nanobiotechnology approaches have applications ranging from research and development of technologies in the laboratory, chemical phenotyping in specialized facilities to monitoring and automation in crops for urban farming and precision agriculture.
Nanobiotechnology approaches for enabling plant communication with electronic devices
Signaling molecules play a central role in controlling metabolism, stress resistance, growth and development in plants. We are developing nanosensors to image and quantify with precision the location and concentration of signaling molecules in plants. Our research has shown that carbon nanotube-based sensors enable the detection of nitric oxide and hydrogen peroxide in extracted chloroplasts and leaves of living plants. We have used this approach to develop plants that report their health or stress levels in real time to electronic devices. Optical nanomaterials offer a robust platform for detection of plant signaling molecules in vivo. They do not photobleach and can take down the detection limit to the single-molecule level. Our objective is to develop nanoparticle-based sensors for monitoring subcellular spatial and temporal changes in plant signaling molecules in real-time. This will allow us to understand the role of signaling molecules in the regulation of plant physiological mechanisms. Our nanosensors approach is leading to plants that act as environmental and crop health monitoring devices.
Model of nanoceria improvement of salt tolerance by enabling higher leaf mesophyll K+ retention. (A) Polyacrylic acid coated nanoceria (PNC) are delivered to Arabidopsis leaf mesophyll cells through stomatal pores. (B) Nanoceria scavenging of hydroxyl radicals and its precursor hydrogen peroxide influences mesophyll K+ transport under salt stress. (C) PNC infiltrated Arabidopsis plants have higher salt tolerance (100 mM NaCl, two weeks) than controls without nanoparticles. As, air space; Ep, epidermal cell; G, guard cell.
Nanotechnology as a tool to study and engineer plant/algae tolerance to stress
Environmental stress leads to accumulation of reactive oxygen species (ROS) and consequent decrease in photosynthetic performance. We are demonstrating that interfacing negatively charged spherical cerium oxide nanoparticles (nanoceria) with chloroplasts in vivo augments ROS scavenging and photosynthesis of Arabidopsis thaliana plants under excess light, heat, and dark chilling. Nanoceria are transported into chloroplasts via non-endocytic pathways, influenced by the electrochemical gradient of the plasma membrane potential. Nanoceria augment plant ROS scavenging including superoxide anion and hydroxyl radicals, for the latter ROS there is no known plant enzyme scavenger. Plants with embedded nanoceria that are exposed to abiotic stress have enhanced quantum yield of photosystem II, carbon assimilation rates, and Rubisco carboxylation rates relative to plants without nanoparticles.