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Catalytic Scavenging of Plant Reactive Oxygen Species <em>In Vivo</em> by Anionic Cerium Oxide Nanoparticles

Reactive oxygen species (ROS) accumulation is a hallmark of plant abiotic stress response. ROS play&#160;a dual role in plants by acting as signaling ...

University of California

Transgenic components in genetically modified organisms consist not only of the transgenic genes, but also the transgenic protein. However, compared with transgenic DNA, less attention has been paid to the detection of expressed protein, especially those degraded from genetically modified soybean after food processing. In this study, the full length 5-enolpyruvyl-shikimate-3-phosphate synthase (CP4-EPSPS, 47.6 kD) protein was probed with the SC-16 (S19-R33) and the DC-16 (D219-K233) polyclonal antibodies in immunoblots. Both antibodies were able to detect the full length CP4-EPSPS and its residues in soy powder made from Roundup-Ready soybeans after heating and microwaving treatments which also reduced the molecular weight of the protein to 45.8 and 38.7 kD, respectively. Taken together the immunoblot results suggest that the middle region of the CP4-EPSPS protein possessed better stability than its N-terminal during thermal processing. This deduction was further validated by autoclave treatment, where a 37.4 kD residue of the protein was recognized by DC-16. A similar result was obtained in processed smoked sausage containing Roundup Ready soybean protein isolate (as an extender). The additional use of a further polyclonal antibody CK-17 (C372-K388), showed that compared with only the one signal for CP4-EPSPS detected by the SC-16 and CK-17 antibodies, the DC-16 middle region antibody detected four signals for CP4-EPSPS from five market sourced soy protein concentrates. Taken together, the study suggested that the middle region of CP4-EPSPS was more useful than the N- and C-terminal for tracing transgenic CP4-EPSPS protein and its remnants in highly processed soy-related products.

Targeting the middle region of CP4-EPSPS protein for its traceability in highly processed soy-related products.

Plant abiotic stress leads to accumulation of reactive oxygen species (ROS) and a consequent decrease in photosynthetic performance. We demonstrate that a plant nanobionics approach of localizing negatively charged, sub-11 nm, spherical cerium oxide nanoparticles (nanoceria) inside chloroplasts in vivo augments ROS scavenging and photosynthesis of Arabidopsis thaliana plants under excess light (2000 μmol m s, 1.5 h), heat (35 °C, 2.5 h), and dark chilling (4 °C, 5 days). Poly(acrylic acid) nanoceria (PNC) with a hydrodynamic diameter (10.3 nm)-lower than the maximum plant cell wall porosity-and negative ζ-potential (-16.9 mV) exhibit significantly higher colocalization (46%) with chloroplasts in leaf mesophyll cells than aminated nanoceria (ANC) (27%) of similar size (12.6 nm) but positive charge (9.7 mV). Nanoceria are transported into chloroplasts via nonendocytic pathways, influenced by the electrochemical gradient of the plasma membrane potential. PNC with a low Ce/Ce ratio (35.0%) reduce leaf ROS levels by 52%, including hydrogen peroxide, superoxide anion, and hydroxyl radicals. For the latter ROS, there is no known plant enzyme scavenger. Plants embedded with these PNC that were exposed to abiotic stress exhibit an increase up to 19% in quantum yield of photosystem II, 67% in carbon assimilation rates, and 61% in Rubisco carboxylation rates relative to plants without nanoparticles. In contrast, PNC with high Ce/Ce ratio (60.8%) increase overall leaf ROS levels and do not protect photosynthesis from oxidative damage during abiotic stress. This study demonstrates that anionic, spherical, sub-11 nm PNC with low Ce/Ce ratio can act as a tool to study the impact of oxidative stress on plant photosynthesis and to protect plants from abiotic stress.

Anionic Cerium Oxide Nanoparticles Protect Plant Photosynthesis from Abiotic Stress by Scavenging Reactive Oxygen Species.

Plant nanobiotechnology is an interdisciplinary field at the interface of nanotechnology and plant biology that aims to utilize nanomaterials as tools to study, augment or impart novel plant functions. The delivery of nanoparticles to plants in vivo is a key initial step to investigate plant nanoparticle interactions and the impact of nanoparticles on plant function. Quantum dots are smaller than plant cell wall pores, have versatile surface chemistry, bright fluorescence and do not photobleach, making them ideal for the study of nanoparticle uptake, transport, and distribution in plants by widely available confocal microscopy tools. Herein, we describe three different methods for quantum dot delivery into leaves of living plants: leaf lamina infiltration, whole shoot vacuum infiltration, and root to leaf translocation. These methods can be potentially extended to other nanoparticles, including nanosensors and drug delivery nanoparticles. © 2017 by John Wiley & Sons, Inc.

In Vivo Delivery of Nanoparticles into Plant Leaves.

Tea plants grow in acidic soil, but to date, their intrinsic mechanisms of acidic stress tolerance have not been elucidated. Here, we assessed the tea plant response to growth on NH nutrient media having different pH and iron levels. When grown in standard NH nutrient solution (iron insufficient, 0.35 mg L Fe ), tea roots exhibited significantly lower nitrogen accumulation, plasma membrane H -ATPase activity, and protein levels; net H efflux was lower at pH 4.0 and 5.0 than at pH 6.0. Addition of 30 mg L Fe (iron sufficient, mimicking normal soil Fe concentrations) to the NH nutrient solution led to more efficient iron plaque formation on roots and increased root plasma membrane H -ATPase levels and activities at pH 4.0 and 5.0, compared to the pH 6.0 condition. Furthermore, plants grown at pH 4.0 and 5.0, with sufficient iron, exhibited significantly higher nitrogen accumulation than those grown at pH 6.0. Together, these results support the hypothesis that efficient iron plaque formation, on tea roots, is important for acidic stress tolerance. Furthermore, our findings establish that efficient iron plaque formation is linked to increased levels and activities of the tea root plasma membrane H -ATPase, under low pH conditions.

Efficient iron plaque formation on tea (Camellia sinensis) roots contributes to acidic stress tolerance.

Glucose is a major product of photosynthesis and a key energy source for cellular respiration in organisms. Herein, we enable in vivo optical glucose sensing in wild-type plants using a quantum dot (QD) ratiometric approach. The optical probe is formed by a pair of QDs: thioglycolic acid-capped QDs which remain invariable to glucose (acting as an internal fluorescent reference control) and boronic acid (BA)-conjugated QDs (BA-QD) that quench their fluorescence in response to glucose. The fluorescence response of the QD probe is within the visible light window where photosynthetic tissues have a relatively low background. It is highly selective against other common sugars found in plants and can be used to quantify glucose levels above 500 μM in planta within the physiological range. We demonstrate that the QD fluorescent probe reports glucose from single chloroplast to algae cells ( Chara zeylanica) and plant leaf tissues ( Arabidopsis thaliana) in vivo via confocal microscopy and to a standoff Raspberry Pi camera setup. QD-based probes exhibit bright fluorescence, no photobleaching, tunable emission peak, and a size under plant cell wall porosity offering great potential for selective in vivo monitoring of glucose in photosynthetic organisms in situ.

Honghong Wu

Department of Botany and Plant Sciences

University of California

Catalytic Scavenging of Plant Reactive Oxygen Species In Vivo by Anionic Cerium Oxide Nanoparticles

Honghong Wu

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Botany and Plant Sciences

University of California

Catalytic Scavenging of Plant Reactive Oxygen Species In Vivo by Anionic Cerium Oxide Nanoparticles

Department of Botany and Plant Sciences