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The Plant Journal : For Cell and... May 2021Phototropins, the UVA-blue light photoreceptors, endow plants to detect the direction of light and optimize photosynthesis by regulating positioning of chloroplasts and...
Phototropins, the UVA-blue light photoreceptors, endow plants to detect the direction of light and optimize photosynthesis by regulating positioning of chloroplasts and stomatal gas exchange. Little is known about their functions in other developmental responses. A tomato Non-phototropic seedling1 (Nps1) mutant, bearing an Arg495His substitution in the vicinity of LOV2 domain in phototropin1, dominant-negatively blocks phototropin1 responses. The fruits of Nps1 mutant were enriched in carotenoids, particularly lycopene, compared with its parent, Ailsa Craig. On the contrary, CRISPR/CAS9-edited loss of function phototropin1 mutants displayed subdued carotenoids compared with the parent. The enrichment of carotenoids in Nps1 fruits is genetically linked with the mutation and exerted in a dominant-negative fashion. Nps1 also altered volatile profiles with high levels of lycopene-derived 6-methyl 5-hepten2-one. The transcript levels of several MEP and carotenogenesis pathway genes were upregulated in Nps1. Nps1 fruits showed altered hormonal profiles with subdued ethylene emission and reduced respiration. Proteome profiles showed a causal link between higher carotenogenesis and increased levels of protein protection machinery, which may stabilize proteins contributing to MEP and carotenogenesis pathways. The enhancement of carotenoid content by Nps1 in a dominant-negative fashion offers a potential tool for high lycopene-bearing hybrid tomatoes.
Topics: CRISPR-Associated Protein 9; CRISPR-Cas Systems; Carotenoids; Fruit; Gene Editing; Loss of Function Mutation; Solanum lycopersicum; Metabolic Networks and Pathways; Mutation; Phototropins
PubMed: 33608974
DOI: 10.1111/tpj.15206 -
Plant & Cell Physiology Sep 2021The disruption of the sumoylation pathway affects processes controlled by the two phototropins (phots) of Arabidopsis thaliana, phot1 and phot2. Phots, plant UVA/blue...
The disruption of the sumoylation pathway affects processes controlled by the two phototropins (phots) of Arabidopsis thaliana, phot1 and phot2. Phots, plant UVA/blue light photoreceptors, regulate growth responses and fast movements aimed at optimizing photosynthesis, such as phototropism, chloroplast relocations and stomatal opening. Sumoylation is a posttranslational modification, consisting of the addition of a SUMO (SMALL UBIQUITIN-RELATED MODIFIER) protein to a lysine residue in the target protein. In addition to affecting the stability of proteins, it regulates their activity, interactions and subcellular localization. We examined physiological responses controlled by phots, phototropism and chloroplast movements, in sumoylation pathway mutants. Chloroplast accumulation in response to both continuous and pulse light was enhanced in the E3 ligase siz1 mutant, in a manner dependent on phot2. A significant decrease in phot2 protein abundance was observed in this mutant after blue light treatment both in seedlings and mature leaves. Using plant transient expression and yeast two-hybrid assays, we found that phots interacted with SUMO proteins mainly through their N-terminal parts, which contain the photosensory LOV domains. The covalent modification in phots by SUMO was verified using an Arabidopsis sumoylation system reconstituted in bacteria followed by the mass spectrometry analysis. Lys 297 was identified as the main target of SUMO3 in the phot2 molecule. Finally, sumoylation of phot2 was detected in Arabidopsis mature leaves upon light or heat stress treatment.
Topics: Arabidopsis; Arabidopsis Proteins; Chloroplasts; Escherichia coli; Ligases; Lysine; Mutation; Phototropism; Plant Leaves; Plants, Genetically Modified; Protein Serine-Threonine Kinases; Seedlings; Small Ubiquitin-Related Modifier Proteins; Sumoylation
PubMed: 33594440
DOI: 10.1093/pcp/pcab027 -
Scientific Reports Feb 2021The sporangiophores of Phycomyces blakesleeanus have been used as a model system to study sensory transduction, helical growth, and to establish global biophysical...
The sporangiophores of Phycomyces blakesleeanus have been used as a model system to study sensory transduction, helical growth, and to establish global biophysical equations for expansive growth of walled cells. More recently, local statistical biophysical models of the cell wall are being constructed to better understand the molecular underpinnings of helical growth and its behavior during the many growth responses of the sporangiophores to sensory stimuli. Previous experimental and theoretical findings guide the development of these local models. Future development requires an investigation of explicit and implicit assumptions made in the prior research. Here, experiments are conducted to test three assumptions made in prior research, that (a) elongation rate, (b) rotation rate, and (c) helical growth steepness, R, of the sporangiophore remain constant during the phototropic response (bending toward unilateral light) and the avoidance response (bending away from solid barriers). The experimental results reveal that all three assumptions are incorrect for the phototropic response and probably incorrect for the avoidance response but the results are less conclusive. Generally, the experimental results indicate that the elongation and rotation rates increase during these responses, as does R, indicating that the helical growth steepness become flatter. The implications of these findings on prior research, the "fibril reorientation and slippage" hypothesis, global biophysical equations, and local statistical biophysical models are discussed.
Topics: Biological Phenomena; Biophysics; Cell Wall; Gravitropism; Light; Models, Biological; Phototropism; Phycomyces
PubMed: 33574466
DOI: 10.1038/s41598-021-83254-5 -
PloS One 2021In this work, molecular diversity of two hypersaline microbial mats was compared by Whole Genome Shotgun (WGS) sequencing of environmental DNA from the mats. Brava and...
In this work, molecular diversity of two hypersaline microbial mats was compared by Whole Genome Shotgun (WGS) sequencing of environmental DNA from the mats. Brava and Tebenquiche are lakes in the Salar de Atacama, Chile, where microbial communities are growing in extreme conditions, including high salinity, high solar irradiance, and high levels of toxic metals and metaloids. Evaporation creates hypersaline conditions in these lakes and mineral precipitation is a characteristic geomicrobiological feature of these benthic ecosystems. The mat from Brava was more rich and diverse, with a higher number of different taxa and with species more evenly distributed. At the phylum level, Proteobacteria, Cyanobacteria, Chloroflexi, Bacteroidetes and Firmicutes were the most abundant, including ~75% of total sequences. At the genus level, the most abundant sequences were affilitated to anoxygenic phototropic and cyanobacterial genera. In Tebenquiche mats, Proteobacteria and Bacteroidetes covered ~70% of the sequences, and 13% of the sequences were affiliated to Salinibacter genus, thus addressing the lower diversity. Regardless of the differences at the taxonomic level, functionally the two mats were similar. Thus, similar roles could be fulfilled by different organisms. Carbon fixation through the Wood-Ljungdahl pathway was well represented in these datasets, and also in other mats from Andean lakes. In spite of presenting less taxonomic diversity, Tebenquiche mats showed increased abundance and variety of rhodopsin genes. Comparison with other metagenomes allowed identifying xantorhodopsins as hallmark genes not only from Brava and Tebenquiche mats, but also for other mats developing at high altitudes in similar environmental conditions.
Topics: Bacteroidetes; Biodiversity; Carbon Cycle; Chile; Cyanobacteria; Geologic Sediments; Lakes; Microbiota; Phylogeny; Proteobacteria; RNA, Ribosomal, 16S; Rhodopsin; Salinity; Whole Genome Sequencing
PubMed: 33561170
DOI: 10.1371/journal.pone.0246656 -
AoB PLANTS Feb 2021In response to gravistimulation under anisotropic light, tree stems showing an active cambium produce reaction wood that redirects the axis of the trees. Several studies...
In response to gravistimulation under anisotropic light, tree stems showing an active cambium produce reaction wood that redirects the axis of the trees. Several studies have described transcriptomic or proteomic models of reaction wood relative to the opposite wood. However, the mechanisms leading to the formation of reaction wood are difficult to decipher because so many environmental factors can induce various signalling pathways leading to this developmental reprogramming. Using an innovative isotropic device where the phototropic response does not interfere with gravistimulation we characterized the early molecular responses occurring in the stem of poplar after gravistimulation in an isotropic environment, and without deformation of the stem. After 30 min tilting at 35° under anisotropic light, we collected the upper and lower xylems from the inclined stems. Controls were collected from vertical stems. We used a microarray approach to identify differentially expressed transcripts. High-throughput real-time PCR allowed a kinetic experiment at 0, 30, 120 and 180 min after tilting at 35°, with candidate genes. We identified 668 differentially expressed transcripts, from which we selected 153 candidates for additional Fluidigm qPCR assessment. Five candidate co-expression gene clusters have been identified after the kinetic monitoring of the expression of candidate genes. Gene ontology analyses indicate that molecular reprogramming of processes such as 'wood cell expansion', 'cell wall reorganization' and 'programmed cell death' occur as early as 30 min after gravistimulation. Of note is that the change in the expression of different genes involves a fine regulation of gibberellin and brassinosteroid pathways as well as flavonoid and phosphoinositide pathways. Our experimental set-up allowed the identification of genes regulated in early gravitropic response without the bias introduced by phototropic and stem bending responses.
PubMed: 33542802
DOI: 10.1093/aobpla/plaa071 -
Cells Jan 2021Phototropins are plasma membrane-associated photoreceptors of blue light and UV-A/B radiation. The genome encodes two phototropins, and , that mediate phototropism,...
Phototropins are plasma membrane-associated photoreceptors of blue light and UV-A/B radiation. The genome encodes two phototropins, and , that mediate phototropism, chloroplast positioning, and stomatal opening. They are well characterized in terms of photomorphogenetic processes, but so far, little was known about their involvement in photosynthesis, oxidative stress responses, and cell death. By analyzing , single, and double mutants, we demonstrated that both phototropins influence the photochemical and non-photochemical reactions, photosynthetic pigments composition, stomata conductance, and water-use efficiency. After oxidative stress caused by UV-C treatment, and single and double mutants showed a significantly reduced accumulation of HO and more efficient photosynthetic electron transport compared to the wild type. However, all mutants exhibited higher levels of cell death four days after UV-C treatment, as well as deregulated gene expression. Taken together, our results reveal that on the one hand, both phot1 and phot2 contribute to the inhibition of UV-C-induced foliar cell death, but on the other hand, they also contribute to the maintenance of foliar HO levels and optimal intensity of photochemical reactions and non-photochemical quenching after an exposure to UV-C stress. Our data indicate a novel role for phototropins in the condition-dependent optimization of photosynthesis, growth, and water-use efficiency as well as oxidative stress and cell death response after UV-C exposure.
Topics: Antioxidants; Arabidopsis; Arabidopsis Proteins; Biomass; Cell Death; Fluorescence; Gene Expression Profiling; Gene Expression Regulation, Plant; Homeostasis; Hydrogen Peroxide; Mutation; Oxidative Stress; Photosynthesis; Pigments, Biological; Plant Leaves; Plant Stomata; Protein Serine-Threonine Kinases; RNA, Messenger; Transcriptome; Ultraviolet Rays; Water
PubMed: 33498294
DOI: 10.3390/cells10020200 -
Frontiers in Plant Science 2020Ultraviolet (UV) radiation directly affects plants and microorganisms, but also alters the species-specific interactions between them. The distinct bands of UV... (Review)
Review
Ultraviolet (UV) radiation directly affects plants and microorganisms, but also alters the species-specific interactions between them. The distinct bands of UV radiation, UV-A, UV-B, and UV-C have different effects on plants and their associated microorganisms. While UV-A and UV-B mainly affect morphogenesis and phototropism, UV-B and UV-C strongly trigger secondary metabolite production. Short wave (<350 nm) UV radiation negatively affects plant pathogens in direct and indirect ways. Direct effects can be ascribed to DNA damage, protein polymerization, enzyme inactivation and increased cell membrane permeability. UV-C is the most energetic radiation and is thus more effective at lower doses to kill microorganisms, but by consequence also often causes plant damage. Indirect effects can be ascribed to UV-B specific pathways such as the UVR8-dependent upregulated defense responses in plants, UV-B and UV-C upregulated ROS accumulation, and secondary metabolite production such as phenolic compounds. In this review, we summarize the physiological and molecular effects of UV radiation on plants, microorganisms and their interactions. Considerations for the use of UV radiation to control microorganisms, pathogenic as well as non-pathogenic, are listed. Effects can be indirect by increasing specialized metabolites with plant pre-treatment, or by directly affecting microorganisms.
PubMed: 33384704
DOI: 10.3389/fpls.2020.597642 -
Plant Communications Sep 2020Small ubiquitin-like modifier (SUMO) post-translational modification (SUMOylation) plays essential roles in regulating various biological processes; however, its...
Small ubiquitin-like modifier (SUMO) post-translational modification (SUMOylation) plays essential roles in regulating various biological processes; however, its function and regulation in the plant light signaling pathway are largely unknown. SEUSS (SEU) is a transcriptional co-regulator that integrates light and temperature signaling pathways, thereby regulating plant growth and development in . Here, we show that SEU is a substrate of SUMO1, and that substitution of four conserved lysine residues disrupts the SUMOylation of SEU, impairs its function in photo- and thermomorphogenesis, and enhances its interaction with PHYTOCHROME-INTERACTING FACTOR 4 transcription factors. Furthermore, the SUMO E3 ligase SIZ1 interacts with SEU and regulates its SUMOylation. Moreover, SEU directly interacts with phytochrome B photoreceptors, and the SUMOylation and stability of SEU are activated by light. Our study reveals a novel post-translational modification mechanism of SEU in which light regulates plant growth and development through SUMOylation-mediated protein stability.
Topics: Arabidopsis; Arabidopsis Proteins; Basic Helix-Loop-Helix Transcription Factors; Ligases; Phototropism; Reverse Transcriptase Polymerase Chain Reaction; Sumoylation; Two-Hybrid System Techniques
PubMed: 33367258
DOI: 10.1016/j.xplc.2020.100080 -
Plant Communications Sep 2020Light is the most important environmental factor affecting many aspects of plant development. In this study, we report that B-box protein 11 (BBX11) acts as a positive...
Light is the most important environmental factor affecting many aspects of plant development. In this study, we report that B-box protein 11 (BBX11) acts as a positive regulator of red light signaling. BBX11 loss-of-function mutant seedlings display significantly elongated hypocotyls under conditions of both red light and long day, whereas overexpression causes markedly shortened hypocotyls under various light states. BBX11 binds to the promoter to activate its transcription, while both BBX21 and HY5 associate with the promoter of to positively regulate its expression. Taken together, our results reveal positive feedback regulation of photomorphogenesis consisting of BBX11, BBX21, and HY5, thus substantiating a transcriptional regulatory mechanism in the response of plants to light during normal development.
Topics: Arabidopsis; Arabidopsis Proteins; Basic-Leucine Zipper Transcription Factors; Chromatin Immunoprecipitation; Electrophoretic Mobility Shift Assay; Feedback, Physiological; Gene Expression Regulation, Plant; Phototropism; Real-Time Polymerase Chain Reaction; Transcription Factors; Transcription Factors, General
PubMed: 33367254
DOI: 10.1016/j.xplc.2020.100045 -
Science Advances Dec 2020Almost a century ago, Stiles and Crawford reported that the human eye is more sensitive to light entering through the pupil center than through its periphery...
Almost a century ago, Stiles and Crawford reported that the human eye is more sensitive to light entering through the pupil center than through its periphery (Stiles-Crawford effect). This psychophysical phenomenon, later found to correlate with photoreceptor orientation toward the pupil, was dynamically phototropic, adjustable within days to an eccentrically displaced pupil. For decades, this phototropism has been speculated to involve coordinated movements of the rectilinear photoreceptor outer and inner segments. We report here that, unexpectedly, the murine photoreceptor outer segment has a seemingly light-independent orientation, but the inner segment's orientation undergoes light-dependent movement, giving rise to nonrectilinear outer and inner segments in adult mice born and reared in darkness. Light during an early critical period (~P0 to P8), however, largely sets the correct photoreceptor orientation permanently afterward. Unexpectedly, abolishing rod and cone phototransductions did not mimic darkness in early life, suggesting photosignaling extrinsic to rods and cones is involved.
PubMed: 33328242
DOI: 10.1126/sciadv.abe2782