A Lateral Regulator Diode with Field Plates for Light-Emitting-Diode Lighting

A lateral current regulator diode （CRD） with field plates is proposed and experimentally demonstrated. The proposed CFtD is based on the junction field-effect transistor （JFET） structure. A cathode field plate is adopted to alleviate the channel-length modulation effect and to improve the saturated I-V characteristics. An anode field plate is induced to achieve a high breakdown voltage VB of the CRD. The influence of the key device parameters on the I-V characteristics of the lateral CRD are discussed. Experimental results show that the proposed CRD presents good I-V characteristics with a high VB about 180 V and a low knee voltage （Vk） below 3 V. Furthermore, the proposed CRD has a negative temperature coefficient. The well characteristic of the proposed CRD makes it a cost-effective solution for light-emitting-diode lighting.

Use of Hypocrea jecorina (anamorph Trichoderma reesei) as a model system for Trichoderma biocontrol of Pythium blight identifies new targets for genetic strain improvement

Biocontrol by Trichoderma has been studied mainly with selected isolates of T. harzianum, T. atroviride and T. asperellum, which are members of sections Pachybasium and Trichoderma. In contrast, species from section Longibrachiatum have only rarely been studied. On the other hand, one taxon from this section-Hypocrea jecorina (anamorph: Trichoderma reesei)-has been widely used for the production of cellulolytic and hemicellulolytic enzymes and recombinant proteins. As far as Trichoderma is concerned, molecular genetic methods and tools are most advanced in H. jecorina, and its genome has recently been fully sequenced, thus making this taxon a model organism for the genus. Here we will demonstrate that H. jecorina is able to antagonize plant pathogenic fungi in plate confrontation tests, and can protect tomato and cucumber plants against Pythium ultimum blight. Using this as a model case, we made use of available H. jecorina mutants to investigate (a) whether carbon catabolite repression via the Cre1-regulator protein has an impact on biocontrol, and (b) whether cellulase gene expression is necessary for biocontrol of P. ultimum. In the first case, plate confrontation tests and in planta experiments yielded opposite results, i.e. while a Cre1 mutant was more active in antagonization of fungi on plates, the survival rates of P. ultimum-inoculated cucumber plants was lower than with the H. jecorina wild-type strain. Mutants of H. jecorina, unable to form cellulases, were still able to antagonize fungi on plates and provided similar protection of tomatos against P. ultimum as the wild type, indicating that the pronounced biocontrol ability of H. jecorina against fungi with cellulose-containing cell-walls is not due to its high cellulolytic activity. A strain disrupted in the light-modulator gene envoy (Schmoll et al., ms submitted) exhibited in planta biocontrol activity strongly exceeding that of the wild-type strain, thereby providing a first link between Trichoderma biocontrol and light. In view of the numerous other metabolic and regulatory mutants of H. jecorina available, we suggest that this fungus should increasingly be used in basic studies on the biochemistry and genetics of biocontrol.

Regulated Degradation of HFR1 Desensitizes Light Signaling in Arabidopsis

Arabidopsis seedlings undergo photomorphogenesis in the light and etiolation in the dark. HFR1, a bHLH transcription factor, is required for both phytochrome A (phyA)-mediated far-red and cryptochrome 1 (cry1)-mediated blue light signaling. We report that HFR1 is a short-lived protein in darkness and is degraded through a 26S proteasome-dependent pathway. Light, irrespective of its quality, enhances HFR1 protein accumulation via promoting its stabilization. We demonstrate that HFR1 physically interacts with COP1 and that COP1 exhibits ubiquitin ligase activity toward HFR1 in vitro. In addition, we show that COP1 is required for degradation of HFR1 in vivo. Furthermore, plants overexpressing a C-terminal 161 amino acid fragment of HFR1 (CT161) display enhanced photomorphogenesis, suggesting an autonomous function of CT161 in promoting light signaling. This truncated HFR1 gene product is more stable than the full-length HFR1 protein in darkness, indicating that the COP1-interacting N-terminal portion of HFR1 is essential for COP1-mediated destabilization of HFR1. These results suggest that light enhances HFR1 protein accumulation by abrogating COP1-mediated degradation of HFR1, which is necessary and sufficient for promoting light signaling. Additionally, our results substantiate the E3 ligase activity of COP1 and its critical role in desensitizing light signaling.

Light-Controlled Chemical Reaction Pathways in Disulfide-Based Nonequilibrium Systems

Pathway selection in a complex chemical reaction network(CRN)enables organisms to adapt,evolve,and even learn in response to changing environments.Inspired by this,herein we report an artificial system,where light signal was used to manipulate the reaction pathways in a disulfide-based nonequilibrium CRN.By changing the photon energy and irradiation window,the anion or new radical-mediated pathways were selectively triggered,resulting in a user-defined evolution pathway.Additional photodissipative cycles were achieved by UV(365 nm)irradiation,increasing the total number of reactions from 3 to 7.The emerging pathway selection of the CRN is accurately predictable and controllable even in complex organo-hydrogel materials.We demonstrate up to five-state autonomous sol-gel transitions and the formation of fuel-driven dissipative organo-hydrogel through both chemical and light input.This work represents a new approach to allowing CRNs to communicate with the environment that can be used in the development of materials with lifelike behaviors.

Emerging Perspectives on the Mechanisms, Regulation, and Distribution of Light Color Acclimation in Cyanobacteria

Chromatic acclimation （CA） provides many cyanobacteria with the ability to tailor the properties of their light-harvesting antennae to the spectral distribution of ambient light. CA was originally discovered as a result of its dramatic cellular phenotype in red and green light. However, discoveries over the past decade have revealed that many pairs of light colors, ranging from blue to infrared, can trigger CA responses. The capacity to undergo CA is widespread geographically, occurs in most habitats around the world, and is found within all major cyanobacterial groups. In addition, many other cellular activities have been found to be under CA control, resulting in distinct physiological and morphological states for cells under different light-color conditions. Several types of CA appear to be the result of convergent evolution, where different strategies are used to achieve the final goal of optimizing light-harvesting antenna composition to maximize photon capture. The regulation of CA has been found to occur primarily at the level of RNA abundance. The CA-regulatory pathways uncovered thus far are two-component systems that use phytochrome-class photoreceptors with sensor-kinase domains to control response regulators that function as transcription factors. However, there is also at least one CA- regulatory pathway that operates at the post-transcriptional level. It is becoming increasingly clear that large numbers of cyanobacterial species have the capacity to acclimate to a wide variety of light colors through the use of a range of different CA processes.

Electrospun perovskite nano-network for flexible, near-room temperature, environmentally friendly and ultrastable light regulation

Light regulation devices are essential for signal modulation, information encryption and energy-saving smart windows. Recently, due to their excellent stimuli-responsive properties, lead halide perovskites have shown great potential. However, the high transition temperature, irreversibility of the phase transition and toxicity of heavy metals make perovskite materials unsuitable for devices related to human activity. Herein, for the first time, a flexible perovskite nano-network is proposed and its application as a smart window is demonstrated. The perovskite-sodium alginate(SA) nano-network showed a 31.6 ℃(20% RH) transition temperature and stability over 1200 cycles. The hydrophobic surface and the “eggbox” structure formed by SA make that the lead leakage is only 2.569 ppb, which is much higher than the drinking water standard. This work provides a successful demonstration for energy-efcient buildings and inspires future nontoxic perovskite-based devices through heavy metal control.

THE PIGMENT-PROTEIN COMPLEXES OF HIGHER PLANTS MIGRATION IN THYLAKOID AND THE REGULATION OF LIGHT ENERGY DISTRIBUTION BETWEEN PHOTOSYSTEMS

Appressed and non-appressed lamella membranes of Castor bean leaf chloroplasts were separated by non-ionic detergent Triton-X 100.Appressed membranes showed a high oxygen-evolving activity and low chl a/b ratio. Examining with SDS-PTGE and liquid nitrogen temperature fluorescence measurement showed that they contained only PSII and light-harvesting pigment-protein complexes （LHCP）,and there was no detectable amount of PSI. Freeze-fracture electromicroscopic observation confirmed that this part was really an appressed lamella membrane. Through divalent cation Mg++, the thylakoid membranes were induced to unstack and restack.With the addition of Mg++, the fluorescence intensity was changed instantly. We realized that there existed two processes:One was a rapid process which was accomplished within 30 s. The other was a slow process of which the time duration was about 60 min. This dual effects of Mg++ had not been reported before.We had analyzed the change of F685/F730 and discussed the

Phytochrome Signaling in Green Arabidopsis Seedlings： Impact Assessment of a Mutually Negative phyB-PIF Feedback Loop

The reversibly red （R）/far-red （FR）-Iight-responsive phytochrome （phy） photosensory system initiates both the deetiolation process in dark-germinated seedlings upon first exposure to light, and the shade-avoidance process in fully deetiolated seedlings upon exposure to vegetational shade. The intracellular signaling pathway from the light-activated photoreceptor conformer （Pfr） to the transcriptional network that drives these responses involves direct, physical inter- action of Pfr with a small subfamily of bHLH transcription factors, termed Phy-lnteracting Factors （PIFs）, which induces rapid PIF proteolytic degradation. In addition, there is evidence of further complexity in light-grown seedlings, whereby phyB-PIF interaction reciprocally induces phyB degradation, in a mutually-negative, feedback-loop configuration. Here, to assess the relative contributions of these antagonistic activities to the net phenotypic readout in light-grown seedlings, we have examined the magnitude of the light- and simulated-shade-induced responses of a pentuple phyBpiflpif3pif4pif5 （phyBpifq） mutant and various multiple pif-mutant combinations. The data （1） reaffirm that phyB is the predominant, if not exclusive, photoreceptor imposing the inhibition of hypocotyl elongation in deetiolating seedlings in response to pro- longed continuous R irradiation and （2） show that the PIF quartet （PIF1, PIF3, PIF4, and PIF5） retain and exert a dual capacity to modulate hypocotyl elongation under these conditions, by concomitantly promoting cell elongation through intrinsic transcriptional-regulatory activity, and reducing phyB-inhibitory capacity through feedback-loop-induced phyB degrada- tion. In shade-exposed seedlings, immunoblot analysis shows that the shade-imposed reduction in Pfr levels induces increases in the abundance of PIF3, and mutant analysis indicates that PIF3 acts, in conjunction with PIF4 and PIF5, to promote the known shade-induced acceleration of hypocotyl elongation. Conversely, although the quadruple pifq mutant displays clearly reduced hypocotyl elongation compared to wild-type in response to prolonged shade, immunoblot analysis detects no elevation in phyB levels in the mutant seedlings compared to the wild-type during the majority of the shade-induced growth period, and phyB levels are not robustly correlated with the growth phenotype across the pif-mutant combinations compared. These results suggest that PIF feedback modulation of phyB abundance does not play a dominant role in modulating the magnitude of the PIF-promoted, shade-responsive phenotype under these conditions. In seedlings grown under diurnal light-dark cycles, the data show that FR-pulse-induced removal of Pfr at the beginning of the dark period （End-of-Day-FR （EOD-FR） treatment） results in longer hypocotyls relative to no EOD-FR treatment and that this effect is attenuated in the pif-mutant combinations tested. This result similarly indicates that the PIF quartet members are capable of intrinsically promoting hypocotyl cell elongation in light-grown plants, independently of the effects of PIF feedback modulation of photoactivated-phyB abundance.

Phytochrome Signaling： Time to Tighten up the Loose Ends

Phytochromes are red and far-red light photoreceptors that play fundamental roles in controlling many aspects of plant growth and development in response to light. The past two decades have witnessed the mechanistic elucidation of the action mode of phytochromes, including their regulation by external and endogenous factors and how they exert their function as transcriptional regulators. More importantly, recent advances have substantially deepened our understanding on the integration of the phytochromemediated signal into other cellular and developmental processes, such as elongation of hypocotyls, shoot branching, circadian clock, and flowering time, which ofteninvolves complex intercellular and interorgan signaling. Based on these advances, this review illustrates a blueprint of our current understanding of phytochrome signaling and its crosstalk with other signaling pathways, and also points out still open questions that need to be addressed in the future.

Histone Acetyltransferase AtGCN5/HAG1 Is a Versatile Regulator of Developmental and Inducible Gene Expression in Arabidopsis

Histone acetylation/deacetylation is a dynamic process and plays an important role in gene regulation. Histone acetylation homeostasis is regulated by antagonist actions of histone acetyltransferases （HAT） and deacetylases （HDAC）. Plant genome encodes multiple HATs and HDACs. The Arabidopsis HAT gene AtGCNS/HAGlplays an essential role in many plant development processes, such as meristem function, cell differentiation, leaf and floral organogenesis, and responses to environmental conditions such as light and cold, indicating an important role of this HAT in the regulation of both long-term developmental switches and short-term inducible gene expression. AtGCN5 targets to a large number of promoters and is required for acetylation of several histone H3 lysine residues. Recruitment of AtGCN5 to target promoters is likely to be mediated by direct or indirect interaction with DNA-binding transcription factors and/or by interaction with acetylated histone lysine residues on the targets. Interplay between AtGCN5 and other HATand HDAC is demonstrated to control specific regulatory pathways. Analysis of the role of AtGCN5 in light-inducible gene expression suggests a function of AtGCN5 in preparing chromatin commitment for priming inducible gene activation in plants.

Arabidopsis Thylakoid Formation 1 Is a Critical Regulator for Dynamics of PSII-LHCII Complexes in Leaf Senescence and Excess Light

In higher plants, photosystem II （PSII） is a large pigment-protein supramolecular complex composed of the PSII core complex and the plant-specific peripheral light-harvesting complexes （LHCil）. PSli-LHCII complexes are highly dynamic in their quantity and macro-organization to various environmental conditions. In this study, we reported a critical factor, the Arabidopsis Thylakoid Formation 1 （THF1） protein, which controls PSII-LHCII dynamics during dark- induced senescence and light acclimation. Loss-of-function mutations in THF1 lead to a stay-green phenotype in path- ogen-infected and senescent leaves. Both LHCII and PSll core subunits are retained in dark-induced senescent leaves of thfl, indicative of the presence of PSII-LHCII complexes. Blue native （BN）-polyacrylamide gel electrophoresis （PAGE） and immunoblot analysis showed that, in dark- and high-light-treated thfl leaves, a type of PSII-LHCII megacomplex is selec- tively retained while the stability of PSII-LHCII supercomplexes significantly decreased, suggesting a dual role of THF1 in dynamics of PSII-LHCII complexes. We showed further that THF1 interacts with Lhcb proteins in a pH-dependent manner and that the stay-green phenotype of thfl relies on the presence of LHCII complexes. Taken together, the data suggest that THF1 is required for dynamics of PSII-LHCII supramolecular organization in higher plants.

The Blue Light-Dependent Phosphorylation of the CCE Domain Determines the Photosensitivity of Arabidopsis CRY2

Arabidopsis cryptochrome 2 （CRY2） is a blue light receptor that mediates light inhibition of hypocotyl elongation and long-day promotion of floral initiation, CRY2 is known to undergo blue light-dependent phosphorylation, which is believed to serve regulatory roles in the function of CRY2. We report here on a biochemical and genetics study of CRY2 phosphorylation. Using mass spectrometry analysis, we identified three serine residues in the CCE domain of CRY2 （S588, S599, and S605） that undergo blue light-dependent phosphorylation in Arabidopsis seedlings. A study of serine-substitution mutations in the CCE domain of CRY2 demonstrates that CRY2 contains two types of phosphorylation in the CCE domain, one in the serine cluster that causes electrophoretic mobility upshift and the other outside the serine cluster that does not seem to cause mobility upshift. We showed that mutations in the serine residues within and outside the serine cluster diminished blue light-dependent CRY2 phosphorylation, degradation, and physiological activities. These results support the hypothesis that blue light-dependent phosphorylation of the CCE domain determines the photosensitivity of Arabidopsis CRY2.

Prompt and Easy Activation by Specific Thioredoxins of Calvin Cycle Enzymes of Arabidopsis thaliana Associated in the GAPDH/CP12/PRK Supramolecular Complex

The Calvin cycle enzymes glyceraldehyde-3-phosphate dehydrogenase （GAPDH） and phosphoribulokinase （PRK） can form under oxidizing conditions a supramolecular complex with the regulatory protein CP12. Both GAPDH and PRK activities are inhibited within the complex, but they can be fully restored by reduced thioredoxins （TRXs）. We have investigated the interactions of eight different chloroplast thioredoxin isoforms （TRX f1, m1, m2, m3, m4, y1, y2, x） with GAPDH （A4, B4, and B8 isoforms）, PRK and CP12 （isoform 2）, all from Arabidopsis thaliana. In the complex, both A4-GAPDH and PRK were promptly activated by TRX f1, or more slowly by TRXs ml and m2, but all other TRXs were ineffective. Free PRK was regulated by TRX f1, m1, or m2, while B4- and Bs-GAPDH were absolutely specific for TRX fl. Interestingly, reductive activation of PRK caged in the complex was much faster than reductive activation of free oxidized PRK, and activation of A4-GAPDH in the complex was much faster （and less demanding in terms of reducing potential） than activation of free oxidized B4- or BB-GAPDH. It is proposed that CP12-assembled supramolecular complex may represent a reservoir of inhibited enzymes ready to be released in fully active conformation following reduction and dissociation of the complex by TRXs upon the shift from dark to low light. On the contrary, autonomous redox-modulation of GAPDH （B- containing isoforms） would be more suited to conditions of very active photosynthesis.