Project description:Light wavelengths preferentially absorbed by chlorophyll (chl) often display steep absorption gradients. This over-saturates photosynthesis in upper chloroplasts and deprives lower chloroplasts of blue and red light. Reducing chl content could create a more even leaf light distribution and thereby increase leaf light-use efficiency and overall canopy photosynthesis. This was tested on soybean cultivar 'Clark' (WT) and a near-isogenic chl b deficient mutant, Y11y11, grown in controlled environment chambers and in the field. Light attenuation was quantified using a novel approach involving light sheet microscopy. Leaf adaxial and abaxial surfaces were illuminated separately with blue, red, and green wavelengths, and chl fluorescence was detected orthogonally to the illumination plane. Relative fluorescence was significantly greater in deeper layers of the Y11y11 mesophyll than in WT, with the greatest differences in blue, then red, and finally green light when illuminated from the adaxial surface. Modeled relative photosynthesis based on chlorophyll profiles and Beer's Law predicted less steep gradients in mutant relative photosynthesis rates compared to WT. Although photosynthetic light-use efficiency was greater in the field-grown mutant with ~50% lower chl, light-use efficiency was lower in the mutant when grown in chambers where chl was ~80% reduced. This difference is probably due to pleiotropic effects of the mutation that accompany very severe reductions in chlorophyll and may warrant further testing in other low-chl lines.
Project description:The southern green stink bug Nezara viridula and its congener N. antennata are important agricultural pests worldwide. These species show positive phototaxis and their compound eyes have high sensitivity to UV and green lights. The attractiveness of monochromatic UV, green lights and combined UV and green light to stink bugs was investigated under field conditions. The number of stink bugs caught increased with the number of UV LEDs, but very few bugs were caught using green light, irrespective of the number of LEDs. However, the most stink bugs were caught when both colors were combined. These results indicate that monochromatic green light is less attractive to Nezara bugs, but when mixed with UV light, it synergistically enhances the attractiveness of UV light. This finding contributes to the construction of reliable and highly specific light traps to monitor Nezara bugs. The addition of green light hardly affected the attractiveness of the UV light to other insects, such as Anomala beetles, which are often caught in light traps. We conclude that the spectral composition of light that is attractive to nocturnal insects depends on the species, hence it is possible to make ecologically friendly light traps that are target specific.
Project description:Pseudomonas cichorii JBC1 was cultured in LB media till it reached exponential phase and the bacterial cells were collected and resuspended in minimal media and treated under green light and dark condition for 12 hours at 30°C. After treatment, the RNA from each sample was collected and sequenced.
Project description:Masking, measured as a decrease in nocturnal rodent wheel running, is a visual system response to rod/cone and retinal ganglion cell photoreception. Here, the authors show that a few milliseconds of light are sufficient to initiate masking, which continues for many minutes without additional photic stimulation. C57J/B6 mice were tested using flash stimuli previously shown to elicit large circadian rhythm phase shifts. Ten flashes, 2 msec each and equally distributed over 5 min, activate locomotor suppression that endures for an additional 25 to 35 min in the dark and does not differ in magnitude or duration from that elicited by 5-min saturating light pulse. Locomotor activity by mice without access to running wheels is also suppressed by light flashes. The effects of various light flash patterns on mouse locomotor suppression are similar to those previously described for hamster phase shifts. Video analysis of active mice indicates that light flashes initiated at ZT13 rapidly induce an interval of behavioral quiescence that lasts about 10 min at which time the animals assume a typical sleep posture that is maintained for an additional 25 min. Thus, the period coincident with light-induced wheel running suppression appears to consist of two distinct behavioral states, one interval during which locomotor quiescence is initiated and maintained, followed by a second interval characterized by behavioral sleep. Given this sequence effected by light stimulation, we suggest that it be referred to as "photosomnolence," the term reflecting upon both the nature of the stimulus and the associated behavioral change.
Project description:We describe a series of easily accessible, visible-light-sensitive (? > 500 nm) BODIPY (boron-dipyrromethene)-based photoprotecting groups (PPGs) for primary and secondary amines, based on a carbamate linker. The caged compounds are stable under aqueous conditions for 24 h and can be efficiently uncaged in vitro with visible light (? = 530 nm). These properties allow efficient photodeprotection of amines, rendering these novel PPGs potentially suitable for various applications, including the delivery of caged drugs and their remote activation.
Project description:Irradiation of Cp2 TiCl2 with green light leads to electronically excited [Cp2 TiCl2 ]*. This complex constitutes an efficient photoredox catalyst for the reduction of epoxides and for 5-exo cyclizations of suitably unsaturated epoxides. To the best of our knowledge, our system is the first example of a molecular titanium photoredox catalyst.
Project description:Proteins of the green fluorescent protein (GFP) family are well known owing to their unique biochemistry and extensive use as in vivo markers. We discovered that GFPs of diverse origins can act as light-induced electron donors in photochemical reactions with various electron acceptors, including biologically relevant ones. Moreover, via green-to-red GFP photoconversion, this process can be observed in living cells without additional treatment.
Project description:Truncated green fluorescent protein (GFP) with the 11th β-strand removed is potentially interesting for bioconjugation, imaging, and the preparation of semisynthetic proteins with novel spectroscopic or functional properties. Surprisingly, the truncated GFP generated by removing the 11th strand, once refolded, does not reassemble with a synthetic peptide corresponding to strand 11 but does reassemble following light activation. The mechanism of this process has been studied in detail by absorption, fluorescence, and Raman spectroscopy. The chromophore in this refolded truncated GFP is found to be in the trans configuration. Upon exposure to light a photostationary state is formed between the trans and cis conformations of the chromophore, and only truncated GFP with the cis configuration of the chromophore binds the peptide. A kinetic model describing the light-activated reassembly of this split GFP is discussed. This unique light-driven reassembly is potentially useful for controlling protein-protein interactions.
Project description:Cyanobacteriochrome (CBCRs) photoreceptors show various photochemical properties, but their ecophysiological functions remain elusive. Here, we report that the blue/green CBCRs SesA/B/C can serve as physiological sensors of cell density. Because cyanobacterial cells show lower transmittance of blue light than green light, higher cell density gives more green-light-enriched irradiance to cells. The cell-density-dependent suppression of cell aggregation under blue-/green-mixed light and white light conditions support this idea. Such a sensing mechanism may provide information about the cell position in cyanobacterial mats in hot springs, the natural habitat of Thermosynechococcus. This cell-position-dependent SesA/B/C-mediated regulation of cellular sessility (aggregation) might be ecophysiologically essential for the reorganization and growth of phototrophic mats. We also report that the green-light-induced dispersion of cell aggregates requires red-light-driven photosynthesis. Blue/green CBCRs might work as shade detectors in a different niche than red/far-red phytochromes, which may be why CBCRs have evolved in cyanobacteria.
Project description:Although green light is sometimes neglected, it can have several effects on plant growth and development. Green light is probably sensed by cryptochromes (crys), one of the blue light photoreceptor families. The aim of this study is to investigate the possible interaction between green and blue light and the involvement of crys in the green light response of plant photomorphogenesis. We hypothesize that green light effects on morphology only occur when crys are activated by the presence of blue light. Wild-type Moneymaker (MM), cry1a mutant (cry1a), and two CRY2 overexpressing transgenic lines (CRY2-OX3 and CRY2-OX8) of tomato (Solanum lycopersicum) were grown in a climate chamber without or with green light (30 μmol m-2 s-1 ) on backgrounds of sole red, sole blue and red/blue mixture, with all treatments having the same photosynthetic photon flux density of 150 μmol m-2 s-1 . Green light showed no significant effects on biomass accumulation, nor on leaf characteristics such as leaf area, specific leaf area, and chlorophyll content. However, in all genotypes, green light significantly decreased stem length on a sole blue background, whereas green light hardly affected stem length on sole red and red/blue mixture background. MM, cry1a, and CRY2-OX3/8 plants all exhibited similar responses of stem elongation to green light, indicating that cry1a, and probably cry2, is not involved in this green light effect. We conclude that partially replacing blue light by green light reduces elongation and that this is independent of cry1a.