Summary Reverse genetics approaches have revolutionized plant biology and agriculture. Phenomics has the prospect of bridging plant phenotypes with genes, including transgenes, to transform agricultural fields. Genetically encoded fluorescent proteins (FPs) have revolutionized plant biology paradigms in gene expression, protein trafficking and plant physiology. While the first instance of plant canopy imaging of green fluorescent protein (GFP) was performed over 25 years ago, modern phenomics has largely ignored fluorescence as a transgene expression device despite the burgeoning FP colour palette available to plant biologists. Here, we show a new platform for stand‐off imaging of plant canopies expressing a wide variety of FP genes. The platform—the fluorescence‐inducing laser projector (FILP)—uses an ultra‐low‐noise camera to image a scene illuminated by compact diode lasers of various colours, coupled with emission filters to resolve individual FPs, to phenotype transgenic plants expressing FP genes. Each of the 20 FPs screened in plants were imaged at >3 m using FILP in a laboratory‐based laser range. We also show that pairs of co‐expressed fluorescence proteins can be imaged in canopies. The FILP system enabled a rapid synthetic promoter screen: starting from 2000 synthetic promoters transfected into protoplasts to FILP‐imaged agroinfiltrated Nicotiana benthamiana plants in a matter of weeks, which was useful to characterize a water stress‐inducible synthetic promoter. FILP canopy imaging was also accomplished for stably transformed GFP potato and in a split‐GFP assay, which illustrates the flexibility of the instrument for analysing fluorescence signals in plant canopies.

Structural and magnetic property changes of heat treated Nickel (Ni) and 5% Chromium-doped Nickel (5Cr-Ni) nanoparticle (NP) granular films were studied. These films were prepared by allowing the core-shell NPs to deposit on 8 mm × 8 mm silicon substrates using a nanocluster deposition system. The as-prepared Ni core-shell NP granular films showed saturation magnetization (M s ) of ~23.8 emu/g, magnetic remanence (M r ) of ~0.16 emu/g and coercivity (H c ) of ~4.5 Oe. On the other hand, the as-prepared 5Cr-Ni core-shell NP granular films showed M s of ~7.6 emu/g, M r of ~0.2 emu/g and H c of ~8 Oe. Transmission Electron Microscopy measurement shows that, the average particle size of the core-shell Ni and 5Cr-Ni NPs in the as-prepared granular films is around ~20 nm. Heat treatment at 600 °C for 30 min under the constant flow of Argon gas increased the average particle size of both Ni and 5Cr-Ni NPs to 50 nm. The saturation magnetization, magnetic remanence and coercivity also increased under the influence of heat treatment in both the cases. The increase in magnetic properties of the 5Cr-Ni granular film is high compared to the increase in magnetic properties of the Ni NP granular film. The presence of Cr in Ni is reported to be the cause for better enhancement of the magnetic properties in 5Cr-Ni films after heat treatment. The X-ray diffraction confirms the presence of Ni and NiO in the films. Energy-dispersive X-ray spectroscopy measurements confirm the presence of Cr in the 5Cr-Ni samples. The enhancement of magnetic properties was also found to be due to particle growth and aggregation, and it is confirmed by scanning electron microscopy images.

Phytosensors are genetically engineered plant-based sensors that feature synthetic promoters fused to reporter genes to sense and report the presence of specific biotic and abiotic stressors on plants. However, when induced reporter gene output is below detectable limits, owing to relatively weak promoters, the phytosensor may not function as intended. Here, we show modifications to the system to amplify reporter gene signal by using a synthetic transcription factor gene driven by a plant pathogen-inducible synthetic promoter. The output signal was unambiguous green fluorescence when plants were infected by pathogenic bacteria. We produced and characterized a phytosensor with improved sensing to specific bacterial pathogens with targeted detection using spectral wavelengths specific to a fluorescence reporter at 3 m standoff detection. Previous attempts to create phytosensors revealed limitations in using innate plant promoters with low-inducible activity since they are not sufficient to produce a strong detectable fluorescence signal for standoff detection. To address this, we designed a pathogen-specific phytosensor using a synthetic promoter-transcription factor system: the S-Box cis-regulatory element which has low-inducible activity as a synthetic 4xS-Box promoter, and the Q-system transcription factor as an amplifier of reporter gene expression. This promoter-transcription factor system resulted in 6-fold amplification of the fluorescence after infection with a potato pathogen, which was detectable as early as 24 h post-bacterial infection. This novel bacterial pathogen-specific phytosensor potato plant demonstrates that the Q-system may be leveraged as a powerful orthogonal tool to amplify a relatively weak synthetic inducible promoter, enabling standoff detection of a previously undetectable fluorescence signal. Pathogen-specific phytosensors would be an important asset for real-time early detection of plant pathogens prior to the display of disease symptoms on crop plants.

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While the installation of complex genetic circuits in microorganisms is relatively routine, the synthetic biology toolbox is severely limited in plants. Of particular concern is the absence of combinatorial analysis of regulatory elements, the long design-build-test cycles associated with transgenic plant analysis, and a lack of naming standardization for cloning parts. Here, we use previously described plant regulatory elements to design, build, and test 91 transgene cassettes for relative expression strength. Constructs were transiently transfected into Nicotiana benthamiana leaves and expression of a fluorescent reporter was measured from plant canopies, leaves, and protoplasts isolated from transfected plants. As anticipated, a dynamic level of expression was achieved from the library, ranging from near undetectable for the weakest cassette to a ∼200-fold increase for the strongest. Analysis of expression levels in plant canopies, individual leaves, and protoplasts were correlated, indicating that any of the methods could be used to evaluate regulatory elements in plants. Through this effort, a well-curated 37-member part library of plant regulatory elements was characterized, providing the necessary data to standardize construct design for precision metabolic engineering in plants.