Plant Photomorphogenesis Research Articles

Plants and Small Molecules: An Up-and-Coming Synergy.

The emergence of Arabidopsis thaliana as a model system has led to a rapid and wide improvement in molecular genetics techniques for studying gene function and regulation. However, there are still several drawbacks that cannot be easily solved with molecular genetic approaches, such as the study of unfriendly species, which are of increasing agronomic interest but are not easily transformed, thus are not prone to many molecular techniques. Chemical genetics represents a methodology able to fill this gap. Chemical genetics lies between chemistry and biology and relies on small molecules to phenocopy genetic mutations addressing specific targets. Advances in recent decades have greatly improved both target specificity and activity, expanding the application of this approach to any biological process. As for classical genetics, chemical genetics also proceeds with a forward or reverse approach depending on the nature of the study. In this review, we addressed this topic in the study of plant photomorphogenesis, stress responses and epigenetic processes. We have dealt with some cases of repurposing compounds whose activity has been previously proven in human cells and, conversely, studies where plants have been a tool for the characterization of small molecules. In addition, we delved into the chemical synthesis and improvement of some of the compounds described.

High-performance Gd3Al4GaO12:Cr3+ phosphors for next-generation far-red LEDs

Far-red (FR) photosensitive pigment (PFR) is important for plant photomorphogenesis. Phosphor-converted (pc) LED is the next-generation FR light device. How to obtain FR-emitting phosphors with a good external quantum efficiency (EQE), suitable photoluminescence and high thermal stability is still a challenge. Herein, by optimizing the sintering technology and chemical design, we develop an excellent FR phosphor, Gd3Al4GaO12:Cr3+. The phosphor has an emission peak at 734 nm and a band width of 70 nm, matched well with the PFR absorption band. By adjusting the flux of H3BO3 and Cr3+ concentration, the EQE reaches 47.2%, and the thermal stability maintains 96.8% at 423 K. Because of its excellent optical properties, the power-conversion efficiency of the FR pc-LED reaches 24.0% driven at 100 mA, demonstrating the high performance and promising applications in the next-generation FR light source.

Silencing of Pepper CaFtsH1 or CaFtsH8 Genes Alters Normal Leaf Development.

Filamentation temperature-sensitive H (FtsH) is a proteolytic enzyme that plays an important role in plant photomorphogenesis and stress resistance. However, information regarding the FtsH family genes in pepper is limited. In our research, through genome-wide identification, 18 members of the pepper FtsH family (including five FtsHi members) were identified and renamed based on phylogenetic analysis. CaFtsH1 and CaFtsH8 were found to be essential for pepper chloroplast development and photosynthesis because FtsH5 and FtsH2 were lost in Solanaceae diploids. We found that the CaFtsH1 and CaFtsH8 proteins were located in the chloroplasts and specifically expressed in pepper green tissues. Meanwhile, CaFtsH1 and CaFtsH8-silenced plants created by virus-induced gene silencing exhibited albino leaf phenotypes. In addition, CaFtsH1-silenced plants were observed to contain very few dysplastic chloroplasts and lost the capacity for photoautotrophic growth. Transcriptome analysis revealed that the expression of chloroplast-related genes such as those coding the photosynthesis-antenna protein and structural proteins was downregulated in CaFtsH1-silenced plants, resulting in the inability to form normal chloroplasts. This study improves our understanding of pepper chloroplast formation and photosynthesis through the identification and functional study of CaFtsH genes.

Cu2+ and Cr3+ doped borate glasses and glass-ceramics as light conversion materials for plant photosynthesis

We present a kind of Cu2+/Cr3+ doped borate luminescence glasses and glass-ceramics for potential indoor plant cultivation applications. These materials were prepared using a melt-quenching route and their luminescent and structural properties were investigated. The Cu2+ in the as-obtained materials can generate blue emission under ultraviolet (UV) excitations. The Cr3+ ions doped glasses and glass-ceramics display two intense broadband absorptions located in the UV and green light regions, also exhibit the sharp-line 2E2→4A2 emission and the broadband 4T2→4A2 luminescence. These emissions originating from Cu2+ and Cr3+ have blue (peaking at ∼480 nm) and far-red-emitting components (∼690–780 nm), which play a promising role in regulating the photomorphogenesis of plants. For certain base glass compositions, the crystals ZrO2 were spontaneously precipitated during the melt quenching process and the glass-ceramics were obtained accordingly. The relative emission intensity, position of emission bands, and fluorescence decay kinetics of Cu/Cr doped borate glasses and glass-ceramics can be effectively modulated via a compositional design engineering and the variation of excitation wavelength. The excellent photoluminescence features make these glasses and glass-ceramics very promising for applications in plant growth light-emitting diodes (LEDs).

Response of photomorphogenesis and photosynthetic properties of sweet pepper seedlings exposed to mixed red and blue light.

Various light spectra, especially red (RL) and blue light (BL), have great effects on physiological processes and growth of plants. Previously, we revealed that the plant photomorphogenesis and photosynthesis of sweet pepper was significantly altered under BL or mixed RL and BL. The present study aimed to elucidate how mixed RL and BL influences plant photosynthesis during photomorphogenesis. We examined the growth, plant morphology, photosynthetic response of sweet pepper seedlings under monochromatic RL, BL, different ratios of mixed RL and BL (9R1B, 6R1B, 3R1B, 1R1B, 1R3B) with the same photosynthetic photon flux density of 300 μmol·m-2·s-1. White light (WL) were used as a control. The findings showed that the elongation of hypocotyl and first internode as well as leaf expansion were all stimulated by RL, while significantly restrained by BL compared with WL. Conversely, the leaf development, biomass accumulation and photosynthetic properties were inhibited by RL but promoted by BL. Additionally, compared with WL and other treatments, 3R1B could significantly improve the net photosynthetic rate, gas exchange, photosynthetic electron transport capacity, photochemical efficiency, shoot and root biomass accumulation. Furthermore, seedlings grew robustly and exhibited the greatest value of seedling index when exposed to this treatment. Overall, these results suggested that pepper seedlings grown under 3R1B performed better, possibly due to the more balanced light spectrum. It was more conducive to improve the plant photomorphogenesis and photosynthesis of sweet pepper, and a higher biomass accumulation and energy utilization efficiency could be achieved simultaneously under this mixed light spectrum.

Genome-Wide Characterization of B-Box Gene Family in Salvia miltiorrhiza.

B-box (BBX) is a type of zinc finger transcription factor that contains a B-box domain. BBX transcription factors play important roles in plant photomorphogenesis, signal transduction, as well as abiotic and biological stress responses. However, the BBX gene family of Salvia miltiorrhiza has not been systematically investigated to date. For this study, based on the genomic data of Salvia miltiorrhiza, 27 SmBBXs genes were identified and clustered into five evolutionary branches according to phylogenetic analysis. The promoter analysis suggested that SmBBXs may be involved in the regulation of the light responses, hormones, stress signals, and tissue-specific development. Based on the transcriptome data, the expression patterns of SmBBXs under different abiotic stresses and plant hormones were analyzed. The results revealed that the expressions of the SmBBXs genes varied under different conditions and may play essential roles in growth and development. The transient expression analysis implied that SmBBX1, SmBBX4, SmBBX9, SmBBX20, and SmBBX27 were in the nucleus. A transcriptional activation assay showed SmBBX1, SmBBX4, SmBBX20, and SmBBX24 had transactivation activities, while SmBBX27 had none. These results provided a basis for further research on the role of SmBBXs in the development of Salvia miltiorrhiza.

Regulation of Plant Photoresponses by Protein Kinase Activity of Phytochrome A.

Extensive research has been conducted for decades to elucidate the molecular and regulatory mechanisms for phytochrome-mediated light signaling in plants. As a result, tens of downstream signaling components that physically interact with phytochromes are identified, among which negative transcription factors for photomorphogenesis, PHYTOCHROME-INTERACTING FACTORs (PIFs), are well known to be regulated by phytochromes. In addition, phytochromes are also shown to inactivate an important E3 ligase complex consisting of CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) and SUPPRESSORs OF phyA-105 (SPAs). This inactivation induces the accumulation of positive transcription factors for plant photomorphogenesis, such as ELONGATED HYPOCOTYL 5 (HY5). Although many downstream components of phytochrome signaling have been studied thus far, it is not fully elucidated which intrinsic activity of phytochromes is necessary for the regulation of these components. It should be noted that phytochromes are autophosphorylating protein kinases. Recently, the protein kinase activity of phytochrome A (phyA) has shown to be important for its function in plant light signaling using Avena sativa phyA mutants with reduced or increased kinase activity. In this review, we highlight the function of phyA as a protein kinase to explain the regulation of plant photoresponses by phyA.

Gene regulatory network models for modules of molecular mechanism of the control of the photo-morphogenesis in plants

Plants are dynamic systems able to continuously adapt to changing environmental conditions, showing a remarkable phenotypic plasticity as from transition from germination to vegetative growth then to reproductive development. In this review, effect of light, molecular mechanisms photo-morphogenesis and gene regulatory networks were reviewed. This review provides insight into regulatory mechanisms for phytochrome-mediated light signaling pathway; and the roles of phytochromes and their downstream signaling components, molecular mechanisms light-perceiving photoreceptors and other positive and negative regulators of light signaling as well as interactions between these components during plant growth and development. Light is one of the most important factors regulating plant growth and development (photo-morphogenesis). Photomorphogenesis and skotomorphogenesis are two key events that control plant development, from seed germination to flowering and senescence. A group of wavelength-specific photoreceptors, E3 ubiquitin ligases, and various transcription factors work together to regulate these two critical processes. Phytochromes are the main photoreceptors in plants for perceiving red/far-red light and transducing the light signals to downstream factors that regulate the gene expression network for photomorphogenic development.

Dissecting the functions of COP1 in the UVR8 pathway with a COP1 variant in Arabidopsis.

COP1 is a critical repressor of plant photomorphogenesis in darkness. However, COP1 plays distinct roles in the photoreceptor UVR8 pathway in Arabidopsis thaliana. COP1 interacts with UV-B-activated UVR8 monomers and promotes their retention and accumulation in the nucleus. Moreover, COP1 has UV-B signaling function, which involves the binding of its WD40 domain to UVR8 and HY5 via conserved VP motifs of these proteins. UV-B-activated UVR8 interacts with COP1 via both the core domain and the VP motif, leading to the displacement of HY5 from COP1 and HY5 stabilization. However, whether the UV-B signaling function of COP1 is solely dependent on its VP motif binding capacity and whether UV-B regulates COP1 subcellular localization remain unclear. Based on published structures of COP1 WD40 domain, we generated a single amino acid substitution COP1 variant, COP1C509S , which cannot bind to VP motifs but retains the ability to interact with the UVR8 core domain. UV-B only marginally increased nuclear YFP-COP1 levels but promoted YFP-COP1 accumulation significantly in the cytosol, but not with YFP-COP1C509S . Thus, the full UVR8-COP1 interaction is important for COP1 accumulation in cytosol. Notably, UV-B signaling including activation of HY5 transcription was obviously retained in the Arabidopsis lines expressing YFP-COP1C509S , which cannot bind VP motifs. We conclude that the full binding of UVR8 to COP1 leads to the predominant accumulation of COP1 in the cytosol and COP1 has additional UV-B signaling function besides VP binding-mediated protein destabilization.

OsCSN1 regulates the growth of rice seedlings through the GA signaling pathway in blue light

Blue light can regulate the photomorphogenesis of plants through blue light receptors to influence seedling growth and development. The COP9 signaling complex (CSN), a vital regulator of photomorphogenesis, is a highly conserved protein complex. CSN1 is the largest and most critical subunit in the CSN with a complex N-terminal function that supports most of the functions of CSN1 and is mainly involved in plant growth and development processes. The CSN is also required in the blue light-mediated photomorphogenesis response of seedlings. In this study, the OsCSN1 subunit of Oryza sativa subsp. japonica (rice) was edited and screened, and OsCSN1 deletion mutant, OsCSN1 weak expression mutant and OsCSN1 overexpression mutant were constructed. The mechanism of OsCSN1 and its N-terminal effects on rice seedling growth and development under blue light conditions were investigated. The addition of exogenous hormone gibberellin (GA3) and gibberellin synthesis inhibitor paclobutrazol (PAC) caused aboveground phenotypic and protein (such as CUL4 and SLR1) changes. Blue light regulates the degradation of SLR1 through OsCSN1, which regulates the growth and development of rice seedling height, the first incomplete leaf, and the coleoptile. It is hypothesized that rice affects CRY-COP1 interactions after sensing blue light signals through the cryptochrome, and the nuclear localization of COP1 is regulated by the CSN complex. OsCSN1 is a negative regulator in response to blue light. The core structural domain of action that inhibits the growth of the aboveground part of rice seedlings is located at the N-terminal of OsCSN1. OsCSN1 regulates the nuclear localization of COP1 through the COP9 signaling complex and degrades SLR1 through CUL4-based E3 ligase. Ultimately, it affects the synthesis of the endogenous hormone GA, thereby inhibiting the aboveground growth and development of rice seedlings.

Phytochrome A mediated modulation of photosynthesis, development and yield in rice (Oryza sativa L.) in fluctuating light environment

Phytochromes are sensory photoreceptors associated with the photomorphogenesis of plants. Rice has 3 phytochromes (phy); phyA, phyB and phyC. To understand the role of phyA under low light (LL) and normal light (NL) environments in plant growth, photosynthesis, biomass and yield, rice phytochrome A mutant (phyA) along with its wild-type (WT) genotype Akitakomachi were grown in field conditions. To induce LL (∼338 μmole photons m−2 s−1) both WT and phyA were shaded by the agro-shade net that reduced light intensity by ∼75%. The NL intensity (∼1355 μmole photons m−2 s−1) served as the experimental control. The plant height decreased by 8%−10% in phyA mutants both in NL and LL. Other developmental parameters, leaf area index, specific leaf weight, and spikelet fertility declined in the mutants in NL and to a larger extent in the LL. phyA had a lower electron transport rate (ETR), which increased its non-photochemical quenching (NPQ). The photosynthetic rate (PN), stomatal conductance(gs), transpiration rate (E), apparent quantum yield (AQE), maximum carboxylation efficiency (Vcmax) and mesophyll conductance (gm) significantly decreased in phyA than WT in LL. Furthermore, the expression of rice phytochrome-interacting factor-like protein (OsPIL1) was relatively downregulated in phyA under LL, resulting in a reduced total chlorophyll (Chl) and Chl b content and an increased Chl a/b ratio. Additionally, a relatively lower upregulation of Fv/Fm and expression of the isoforms of chlorophyll-a/b-proteins in phyA under LL suggests its inferior light-harvesting capacity compared to WT plants. Reduced PN resulted in a lowered overall carbon budget in phyA that hampered grain yield by 55% more than WT under LL. Our findings demonstrated the critical role of phytochrome A in orchestrating a series of shade-acclimation responses to salvage LL-induced stress and optimize the harvest index in rice.

The blue light receptor CRY1 interacts with FIP37 to promote N6 -methyladenosine RNA modification and photomorphogenesis in Arabidopsis.

Light is a particularly important environmental cue that regulates a variety of diverse plant developmental processes, such as photomorphogenesis. Blue light promotes photomorphogenesis mainly through the activation of the photoreceptor cryptochrome 1 (CRY1). However, the mechanism underlying the CRY1-mediated regulation of growth is not fully understood. Here, we found that blue light induced N6 -methyladenosine (m6 A) RNA modification during photomorphogenesis partially via CRY1. Cryptochrome 1 mediates blue light-induced expression of FKBP12-interacting protein 37 (FIP37), which is a component of m6 A writer. Moreover, we showed that CRY1 physically interacted with FIP37 invitro and invivo, and mediated blue light activation of FIP37 binding to RNA. Furthermore, CRY1 and FIP37 modulated m6 A on photomorphogenesis-related genes PIF3, PIF4, and PIF5, thereby accelerating the decay of their transcripts. Genetically, FIP37 repressed hypocotyl elongation under blue light, and fip37 mutation could partially rescue the short-hypocotyl phenotype of CRY1-overexpressing plants. Together, our results provide a new insight into CRY1 signal in modulating m6 A methylation and stability of PIFs, and establish an essential molecular link between m6 A modification and determination of photomorphogenesis in plants.

The sweet potato B-box transcription factor gene IbBBX28 negatively regulates drought tolerance in transgenic Arabidopsis.

B-box (BBX) which are a class of zinc finger transcription factors, play an important role in regulating of photoperiod, photomorphogenesis, and biotic and abiotic stresses in plants. However, there are few studies on the involvement of BBX transcription factors in response to abiotic stresses in sweet potato. In this paper, we cloned the DNA and promoter sequences of IbBBX28. There was one B-box conserved domain in IbBBX28, and the expression of IbBBX28 was induced under drought stress. Under drought stress, compared to wild type Arabidopsis, the protective enzyme activities (SOD, POD, and CAT) were all decreased in IbBBX28-overexpression Arabidopsis but increased in the mutant line bbx28, while the MDA content was increased in the IbBBX28-overexpression Arabidopsis and decreased in the bbx28. Moreover, the expression levels of the resistance-related genes showed the same trend as the protective enzyme activities. These results showed that IbBBX28 negatively regulates drought tolerance in transgenic Arabidopsis. Additionally, the yeast two-hybrid and BiFC assays verified that IbBBX28 interacted with IbHOX11 and IbZMAT2. The above results provide important clues for further studies on the role of IbBBX28 in regulating the stress response in sweet potato.

Влияние спектрального состава света на некоторые биохимические и морфологические показатели листьев регенерантов представителей рода Hydrangea L. в культуре in vitro

Hydrangea macrophylla (Thunb.) Ser. is one of the most popular ornamental crops used in landscaping. The growing area of H. macrophylla is expanding due to climate warming. Light plays an important role in plant ontogenesis, determining photosynthetic pigments and photomorphogenesis. n the photomorphogenesis of plants, an important role is assigned to the light of the red and blue bands of the spectrum. In the photomorphogenesis of plants, the light of the red and blue bands of the spectrum plays the greatest role. In our studies, a combination of red (70%) and blue (30%) spectra was used in the treatment of explants of the Bodensee H. macrophylla in vitro conditions. At the end of the illumination, the plants were subjected to low-temperature stress for 24 hours at t +2 ° C. The following physiological indicators were noted: the number of stomata, leaf thickness, epidermis thickness. Also we determined morphological parameters: the content of phenolic carboxylic acids: chlorogenic, caffeic, ferulic; abscisic acid and the amount of flavonoids. Morphological parameters were determined: the content of phenolic carboxylic acids: chlorogenic, caffeic, ferulic; abscisic acid and the amount of flavonoids. Additional illumination with red and blue light showed the best results in the process of plant development and adaptation to the effects of low positive temperatures. Keywords: HYDRANGEA MACROPHYLLA, BLUE AND RED LIGHT SPECTRUM OF LIGHT, ADDITIONAL ILLUMINATION, PHYSIOLOGICAL INDICATORS, ADAPTIVE POTENTIAL

Characterization of Cry2 genes (CRY2a and CRY2b) of B. napus and comparative analysis of BnCRY1 and BnCRY2a in regulating seedling photomorphogenesis.

Cryptochrome 2 (CRY2) perceives blue/UV-A light and regulates photomorphogenesis in plants. However, besides Arabidopsis, CRY2 has been functionally characterized only in native species of japonica rice and tomato. In the present study, the BnCRY2a, generating a relatively longer cDNA and harboring an intron in its 5'UTR, has been characterized in detail. Western blot analysis revealed that BnCRY2a is light labile and degraded rapidly by 26S proteasome when seedlings are irradiated with blue light. For functional analysis, BnCRY2a was over-expressed in Brassica juncea, a related species more amenable to transformation. The BnCRY2a over-expression (BnCRY2aOE) transgenics developed short hypocotyl and expanded cotyledons, accumulated more anthocyanin in light-grown seedlings, and displayed early flowering on maturity. Early flowering in BnCRY2aOE transgenics was coupled with the up-regulation of many flowering-related genes such as FT. The present study also highlights the differential light sensitivity of cry1 and cry2 in controlling hypocotyl elongation growth in Brassica. BnCRY2aOE seedlings developed much shorter hypocotyl under the low-intensity of blue light, while BnCRY1OE seedling hypocotyls were shorter under the high-intensity blue light, compared to untransformed seedlings.

BBX24 Interacts with DELLA to Regulate UV-B-Induced Photomorphogenesis in Arabidopsis thaliana.

UV-B radiation, sensed by the photoreceptor UVR8, induces signal transduction for plant photomorphogenesis. UV-B radiation affects the concentration of the endogenous plant hormone gibberellin (GA), which in turn triggers DELLA protein degradation through the 26S proteasome pathway. DELLA is a negative regulator in GA signaling, partially relieving the inhibition of hypocotyl growth induced by UV-B in Arabidopsis thaliana. However, GAs do usually not work independently but integrate in complex networks linking to other plant hormones and responses to external environmental signals. Until now, our understanding of the regulatory network underlying GA-involved UV-B photomorphogenesis had remained elusive. In the present research, we investigate the crosstalk between the GA and UV-B signaling pathways in UV-B-induced photomorphogenesis of Arabidopsis thaliana. Compared with wild type Landsberg erecta (Ler), the abundance of HY5, CHS, FLS, and UF3GT were found to be down-regulated in rga-24 and gai-t6 mutants under UV-B radiation, indicating that DELLA is a positive regulator in UV-B-induced photomorphogenesis. Our results indicate that BBX24 interacts with RGA (one of the functional DELLA family members). Furthermore, we also found that RGA interacts with HY5 (the master regulator in plant photomorphogenesis). Collectively, our findings suggest that the HY5–BBX24–DELLA module serves as an important signal regulating network, in which GA is involved in UV-B signaling to regulate hypocotyl inhibition.

How much do radiative transfer models influence red:far-red simulation and subsequent modelling of plant photomorphogenesis?

Abstract Red:far-red ratio (R:FR) plays an important role in the architectural dynamics of vegetation. The integration of its effects into the crop model and/or into modelling work on plant dynamics over years requires new methods for describing R:FR spatial and temporal variability. This study assesses the sensitivity of simulating plant morphogenesis to the methods of R:FR modelling. The approach consisted in using a generic individual-based legume model coupled with radiative transfer models allowing the computation of R:FR values. Three methods of computation of R:FR were evaluated based on reference radiative transfer model CANESTRA and on turbid-medium model RIRI. The effects of R:FR simulated by the three methods on the simulation of plant morphogenesis were evaluated for the petiole and internodes of two contrasted plant architectures (alfalfa and white clover) at different stages of plant development and density. Plant morphogenesis expressed by the simulated petiole and internode length was sensitive to R:FR values provided by the models, especially at an early stage of development. Contrasted plant architectures exhibit different ranges of sensitivity to R:FR computed by the different models. However, this sensitivity follows a similar pattern between the two types of plant architecture, also for other conditions such as density or stage of development. This study highlights that the choice of radiative transfer model is of main importance for modelling plant morphogenetical responses, in particular at an early stage of plant development. The role of coupling of the FSP and radiative transfer models to address photomorphogenetic issues in order to consider plant-to-plant interactions is discussed.

CHANGES IN LIGHT RADIATION AND MICROCLIMATIC CONDITIONS ALTER THE POMEGRANATE CUTTINGS PHOTOMORPHOGENESIS TREATED WITH AQUEOUS EXTRACT OF Cyperus rotundus

Technological advances in agriculture make it possible to manage the light spectrum radiation in a protected environment and generate improvements in plant photomorphogenesis, which can be a promising strategy for the supply of seedlings of pomegranate qualities. It aimed to evaluate whether the microclimatic environmental changes, due to the management of light spectrum radiation, modify the photomorphogenesis and water consumption by pomegranate cuttings treated with aqueous C. rotundus (nutsedge) extract, as well as determine the most important variables to explain such effects. A completely randomized design, in a 4x4 factorial scheme, and with three replications. Four light spectrum radiation (white, blue, red, and extreme red lights) and four nutsedge extract concentrations (0, 25, 50, and 100%) were applied. Throughout the experimental period, the environments were monitored to establish the illuminance, average air temperature, relative air humidity, average soil temperature and evapotranspiration water consumption by the cuttings. The numbers of shoots were recorded weekly, numbers of roots and shoots were calculated 60 days after cutting planting. All microclimatic variables were influenced by light conditions. Shoots were observed on the cuttings under white and blue lights with application of 0, 25, 50, and 100% of nutsedge extract concentrations. Variations in light spectrum radiation promote environmental microclimate changes and influence photomorphogenesis and water consumption by pomegranate cuttings treated with aqueous extract of nutsedge. All variables studied were considered as important to explain the influence of environmental microclimate changes, due to light spectrum variation, on photomorphogenesis and water evapotranspiration and consumption by pomegranate cuttings.

Phytochrome-Dependent Regulation of ZFP6 and ZFPH Impacts Photomorphogenesis in Arabidopsis thaliana.

Phytochromes (phy) are key regulators of photomorphogenesis in plants. Among the different phys characterized in higher plants (i.e., phyA to phyE), phyA and phyB primarily regulate phenotypic responses in plants under far-red (FR) and red (R) conditions, respectively. Recent findings suggest that some zinc finger proteins (ZFPs) are involved in plant light-modulated morphogenesis. However, the interaction(s) between phyA, phyB and ZFP homologs potentially involved in photomorphogenesis, as well as their phenotypic and molecular effects in Arabidopsis seedlings exposed to R and FR light remain to be elucidated fully. Prior analyses with phytochrome chromophore deficient lines indicated that ZFP6 expression is misregulated compared to levels in Col-0 wild type (WT). Here, we used plants with phytochrome chromophore or apoprotein (specifically phyA and phyB) deficiencies, lines with mutations in ZFP6 and ZFP6 HOMOLOG (ZFPH) genes, and plants overexpressing ZFP6 to examine regulatory interactions between phytochromes, ZFP6, and ZFPH. Our results indicate that phytochromes are required for downregulation of ZFP6 and ZFPH and suggest a role for light-regulated control of ZFP levels in phytochrome-dependent photomorphogenesis. Conversely, PHYB is downregulated in zfp6 mutants under R light. Analyses of a zfp6zfph double mutant confirmed disruption in photomorphogenic phenotypes, including the regulation of hypocotyl elongation in seedlings grown under FR light. In addition, PIF3 and PIF4 levels are transcriptionally regulated by ZFP6 and ZFPH in a gibberellic acid-dependent manner. ZFP6 overexpression resulted in opposite phenotypic responses to those observed in the zfp6 and zfph mutants grown in FR and R light, as well as a reduction in the rosette size of mature ZFP6 OX plants relative to WT under white light. Based on these observations, we provide insight into how phy and ZFPs interact to regulate specific aspects of light-dependent processes in Arabidopsis.

Upregulation of GLRs expression by light in Arabidopsis leaves

BackgroundGlutamate receptor-like (GLR) channels are plant homologs of iGluRs, animal ionotropic glutamate receptors which participate in neurotransmission. GLRs mediate plant adaptive processes and photomorphogenesis. Despite their contribution to light-dependent processes, signaling mechanisms that modulate GLR response to light remain unknown. Here we show that leaf expression of 7 out of 20 Arabidopsis GLRs is significantly up-regulated by monochromatic irradiation.ResultsOur data indicates that both red and blue light stimulate the expression of selected AtGLRs. Using a photosynthesis inhibitor and different irradiation regimes, we demonstrated that retrograde signaling from photosystem II is unlikely to be involved in light-dependent GLR up-regulation. Analysis of transcriptional patterns in mutants of key photoreceptors allowed us to observe that both phytochromes and cryptochromes are likely to be involved in the control of light-dependent up-regulation of AtGLR expression, with phytochromes playing a clearly dominating role in this process.ConclusionsIn mature Arabidopsis leaves, phytochromes, assisted by cryptochromes, mediate light-driven transcriptional up-regulation of several genes encoding GLR proteins. Since GLRs are known to be involved in a wide range of plant developmental processes our results provide mechanistic insight into how light may influence plant growth and development.