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Plant Physiology May 2020Blue-light-induced chloroplast movements play an important role in maximizing light utilization for photosynthesis in plants. Under a weak light condition, chloroplasts...
Blue-light-induced chloroplast movements play an important role in maximizing light utilization for photosynthesis in plants. Under a weak light condition, chloroplasts accumulate to the cell surface to capture light efficiently (chloroplast accumulation response). Conversely, chloroplasts escape from strong light and move to the side wall to reduce photodamage (chloroplast avoidance response). The blue light receptor phototropin (phot) regulates these chloroplast movements and optimizes leaf photosynthesis by controlling other responses in addition to chloroplast movements. Seed plants such as Arabidopsis () have phot1 and phot2. They redundantly mediate phototropism, stomatal opening, leaf flattening, and the chloroplast accumulation response. However, the chloroplast avoidance response is induced by strong blue light and regulated primarily by phot2. Phots are localized mainly on the plasma membrane. However, a substantial amount of phot2 resides on the chloroplast outer envelope. Therefore, differentially localized phot2 might have different functions. To determine the functions of plasma membrane- and chloroplast envelope-localized phot2, we tethered it to these structures with their respective targeting signals. Plasma membrane-localized phot2 regulated phototropism, leaf flattening, stomatal opening, and chloroplast movements. Chloroplast envelope-localized phot2 failed to mediate phototropism, leaf flattening, and the chloroplast accumulation response but partially regulated the chloroplast avoidance response and stomatal opening. Based on the present and previous findings, we propose that phot2 localized at the interface between the plasma membrane and the chloroplasts is required for the chloroplast avoidance response and possibly for stomatal opening as well.
Topics: Arabidopsis; Arabidopsis Proteins; Cell Membrane; Chloroplasts; Photosynthesis; Phototropins; Phototropism; Plant Leaves; Plants, Genetically Modified
PubMed: 32193212
DOI: 10.1104/pp.20.00059 -
Plant Direct Feb 2020Gene duplication and polyploidization are genetic mechanisms that instantly add genetic material to an organism's genome. Subsequent modification of the duplicated...
Gene duplication and polyploidization are genetic mechanisms that instantly add genetic material to an organism's genome. Subsequent modification of the duplicated material leads to the evolution of neofunctionalization (new genetic functions), subfunctionalization (differential retention of genetic functions), redundancy, or a decay of duplicated genes to pseudogenes. Phytochromes are light receptors that play a large role in plant development. They are encoded by a small gene family that in tomato is comprised of five members: and The most recent gene duplication within this family was in the ancestral gene. Using transcriptome profiling, co-expression network analysis, and physiological and molecular experimentation, we show that tomato and exhibit both common and non-redundant functions Specifically, appears to be the major integrator of light and auxin responses, such as gravitropism and phototropism, while and regulate aspects of photosynthesis antagonistically to each other, suggesting that the genes have subfunctionalized since their duplication.
PubMed: 32128473
DOI: 10.1002/pld3.205 -
FEMS Microbiology Letters Mar 2020Stable, long-term interactions between fungi and algae or cyanobacteria, collectively known as lichens, have repeatedly evolved complex architectures with little... (Review)
Review
Stable, long-term interactions between fungi and algae or cyanobacteria, collectively known as lichens, have repeatedly evolved complex architectures with little resemblance to their component parts. Lacking any central scaffold, the shapes they assume are casts of secreted polymers that cement cells into place, determine the angle of phototropic exposure and regulate water relations. A growing body of evidence suggests that many lichen extracellular polymer matrices harbor unicellular, non-photosynthesizing organisms (UNPOs) not traditionally recognized as lichen symbionts. Understanding organismal input and uptake in this layer is key to interpreting the role UNPOs play in lichen biology. Here, we review both polysaccharide composition determined from whole, pulverized lichens and UNPOs reported from lichens to date. Most reported polysaccharides are thought to be structural cell wall components. The composition of the extracellular matrix is not definitively known. Several lines of evidence suggest some acidic polysaccharides have evaded detection in routine analysis of neutral sugars and may be involved in the extracellular matrix. UNPOs reported from lichens include diverse bacteria and yeasts for which secreted polysaccharides play important biological roles. We conclude by proposing testable hypotheses on the role that symbiont give-and-take in this layer could play in determining or modifying lichen symbiotic outcomes.
Topics: Biofilms; Cyanobacteria; Fungi; Lichens; Phylogeny; Polysaccharides; Symbiosis; Uronic Acids
PubMed: 32037451
DOI: 10.1093/femsle/fnaa023 -
Applied and Environmental Microbiology Apr 2020is an industrial fungal species used for large-scale production of carotenoids. However, light-regulated physiological processes, such as carotenoid biosynthesis and...
is an industrial fungal species used for large-scale production of carotenoids. However, light-regulated physiological processes, such as carotenoid biosynthesis and phototropism, are not fully understood. In this study, we isolated and characterized three photoreceptor genes, , , and , in Bioinformatics analyses of these genes and their protein sequences revealed that the functional domains (PAS/LOV [Per-ARNT-Sim/light-oxygen-voltage] domain and zinc finger structure) of the proteins have significant homology to those of other fungal blue-light regulator proteins expressed by and The photoreceptor proteins were synthesized by heterologous expression in The chromogenic groups consisting of flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN) were detected to accompany BTWC-1 proteins by using high-performance liquid chromatography (HPLC) and fluorescence spectrometry, demonstrating that the proteins may be photosensitive. The absorbance changes of the purified BTWC-1 proteins seen under dark and light conditions indicated that they were light responsive and underwent a characteristic photocycle by light induction. Site-directed mutagenesis of the cysteine residual (Cys) in BTWC-1 did not affect the normal expression of the protein in but did lead to the loss of photocycle response, indicating that Cys represents a flavin-binding domain for photon detection. We then analyzed the functions of BTWC-1 proteins by complementing , , and into the counterpart knockout strains of for each gene. Transformation of the complement into knockout strains restored the positive phototropism, while the addition of complement remedied the deficiency of carotene biosynthesis in the knockout strains under conditions of illumination. These results indicate that and are involved in phototropism and light-inducible carotenogenesis. Thus, genes share a conserved flavin-binding domain and act as photoreceptors for control of different light transduction pathways in Studies have confirmed that light-regulated carotenogenesis is prevalent in filamentous fungi, especially in mucorales. However, few investigations have been done to understand photoinduced synthesis of carotenoids and related mechanisms in , a well-known industrial microbial strains. In the present study, three photoreceptor genes in were cloned, expressed, and characterized by bioinformatics and photoreception analyses, and then functional analyses of these genes were constructed in The results of this study will lead to a better understanding of photoreception and light-regulated carotenoid synthesis and other physiological responses in .
Topics: Amino Acid Sequence; Escherichia coli; Fungal Proteins; Microorganisms, Genetically-Modified; Mucorales; Photoreceptors, Microbial; Sequence Alignment
PubMed: 32033952
DOI: 10.1128/AEM.02962-19 -
Plant, Cell & Environment Jul 2020When exposed to neighbour cues, competitive plants increase stem growth to reduce the degree of current or future shade. The aim of this work is to investigate the...
When exposed to neighbour cues, competitive plants increase stem growth to reduce the degree of current or future shade. The aim of this work is to investigate the impact of weather conditions on the magnitude of shade avoidance responses in Arabidopsis thaliana. We first generated a growth rate database under controlled conditions and elaborated a model that predicts daytime hypocotyl growth as a function of the activity of the main photosensory receptors (phytochromes A and B, cryptochromes 1 and 2) in combination with light and temperature inputs. We then incorporated the action of thermal amplitude to account for its effect on selected genotypes, which correlates with the dynamics of the growth-promoting transcription factor PHYTOCHROME-INTERACTING FACTOR 4. The model predicted growth rate in the field with reasonable accuracy. Thus, we used the model in combination with a worldwide data set of current and future whether conditions. The analysis predicted enhanced shade avoidance responses as a result of higher temperatures due to the geographical location or global warming. Irradiance and thermal amplitude had no effects. These trends were also observed for our local growth rate measurements. We conclude that, if water and nutrients do not become limiting, warm environments enhance the shade avoidance response.
Topics: Arabidopsis; Arabidopsis Proteins; Basic Helix-Loop-Helix Transcription Factors; Hypocotyl; Light; Models, Biological; Phototropism; Temperature
PubMed: 31925796
DOI: 10.1111/pce.13720 -
Frontiers in Microbiology 2019We performed an incubation experiment of seawater confined in plastic bottles with samples collected at three depths (15, 60, and 90 m) after retrieval from a single...
We performed an incubation experiment of seawater confined in plastic bottles with samples collected at three depths (15, 60, and 90 m) after retrieval from a single offshore location in the Mediterranean Sea, from a late summer stratified water column. Two samples representative of each depth were collected and stored in opaque bottles after two periods of 7 h. We took advantage of the "bottle effect" to investigate changes in the natural microbial communities (abundant and rare). We recovered 94 metagenome-assembled genomes (MAGs) and 1089 metagenomic viral contigs and examined their abundance using metagenomic recruitment. We detected a significant fast growth of copiotrophic bacteria such as or throughout the entire water column with different dynamics that we assign to "clonal," "polyclonal," or "multispecies" depending on the recruitment pattern. Results also showed a marked ecotype succession in the phototropic picocyanobacteria that were able to grow at all the depths in the absence of light, highlighting the importance of their mixotrophic potential. In addition, "wall-chain-reaction" hypothesis based on the study of phage-host dynamics showed the higher impact of viral predation on archaea in deeper waters, evidencing their prominent role during incubations. Our results provide a step forward in understanding the mechanisms underlying dynamic patterns and ecology of the marine microbiome and the importance of processing the samples immediately after collection to avoid changes in the community structure.
PubMed: 31921085
DOI: 10.3389/fmicb.2019.02926 -
Journal of Experimental Botany Mar 2020Phototropism represents a simple physiological mechanism-differential growth across the growing organ of a plant-to respond to gradients of light and maximize...
Phototropism represents a simple physiological mechanism-differential growth across the growing organ of a plant-to respond to gradients of light and maximize photosynthetic light capture (in aerial tissues) and water/nutrient acquisition (in roots). The phototropin blue light receptors, phot1 and phot2, have been identified as the essential sensors for phototropism. Additionally, several downstream signal/response components have been identified, including the phot-interacting proteins NON-PHOTOTROPIC HYPOCOTYL 3 (NPH3) and PHYTOCHROME SUBSTRATE 4 (PKS4). While the structural and photochemical properties of the phots are quite well understood, much less is known about how the phots signal through downstream regulators. Recent advances have, however, provided some intriguing clues. It appears that inactive receptor phot1 is found dispersed in a monomeric form at the plasma membrane in darkness. Upon light absorption dimerizes and clusters in sterol-rich microdomains where it is signal active. Additional studies showed that the phot-regulated phosphorylation status of both NPH3 and PKS4 is linked to phototropic responsiveness. While PKS4 can function as both a positive (in low light) and a negative (in high light) regulator of phototropism, NPH3 appears to function solely as a key positive regulator. Ultimately, it is the subcellular localization of NPH3 that appears crucial, an aspect regulated by its phosphorylation status. While phot1 activation promotes dephosphorylation of NPH3 and its movement from the plasma membrane to cytoplasmic foci, phot2 appears to modulate relocalization back to the plasma membrane. Together these findings are beginning to illuminate the complex biochemical and cellular events, involved in adaptively modifying phototropic responsiveness under a wide varying range of light conditions.
Topics: Arabidopsis Proteins; Membrane Microdomains; Phosphorylation; Phototropism; Protein Serine-Threonine Kinases
PubMed: 31907539
DOI: 10.1093/jxb/eraa005 -
Frontiers in Plant Science 2019Traveling to nearby extraterrestrial objects having a reduced gravity level (partial gravity) compared to Earth's gravity is becoming a realistic objective for space...
Traveling to nearby extraterrestrial objects having a reduced gravity level (partial gravity) compared to Earth's gravity is becoming a realistic objective for space agencies. The use of plants as part of life support systems will require a better understanding of the interactions among plant growth responses including tropisms, under partial gravity conditions. Here, we present results from our latest space experiments on the ISS, in which seeds of were germinated, and seedlings grew for six days under different gravity levels, namely micro-, several intermediate partial- levels, and 1, and were subjected to irradiation with blue light for the last 48 h. RNA was extracted from 20 samples for subsequent RNAseq analysis. Transcriptomic analysis was performed using the HISAT2-Stringtie-DESeq pipeline. Differentially expressed genes were further characterized for global responses using the GEDI tool, gene networks and for Gene Ontology (GO) enrichment. Differential gene expression analysis revealed only one differentially expressed gene (AT4G21560, VPS28-1 a vacuolar protein) across all gravity conditions using FDR correction (q < 0.05). However, the same 14 genes appeared differentially expressed when comparing either micro-, low- level (< 0.1) or the Moon -level with 1 control conditions. Apart from these 14-shared genes, the number of differentially expressed genes was similar in microgravity and the Moon -level and increased in the intermediate -level (< 0.1), but it was then progressively reduced as the difference with the Earth gravity became smaller. The GO groups were differentially affected at each -level: light and photosynthesis GO under microgravity, genes belonged to general stress, chemical and hormone responses under low-, and a response related to cell wall and membrane structure and function under the Moon -level. Transcriptional analyses of plants under blue light stimulation suggests that root blue-light phototropism may be enough to reduce the gravitational stress response caused by the lack of gravitropism in microgravity. Competition among tropisms induces an intense perturbation at the micro- level, which shows an extensive stress response that is progressively attenuated. Our results show a major effect on cell wall/membrane remodeling (detected at the interval from the Moon to Mars gravity), which can be potentially related to graviresistance mechanisms.
PubMed: 31850027
DOI: 10.3389/fpls.2019.01529 -
The Plant Journal : For Cell and... Apr 2020Jasmonates are key regulators of the balance between defence and growth in plants. However, the molecular mechanisms by which activation of defence reduces growth are...
Jasmonates are key regulators of the balance between defence and growth in plants. However, the molecular mechanisms by which activation of defence reduces growth are not yet fully understood. Here, we analyze the role of MYC transcription factors (TFs) and jasmonic acid (JA) in photomorphogenic growth. We found that multiple myc mutants share light-associated phenotypes with mutants of the phytochrome B photoreceptor, such as delayed seed germination in the dark and long hypocotyl growth. Overexpression of MYC2 in a phyB background partially suppressed its long hypocotyl phenotype. Transcriptomic analysis of multiple myc mutants confirmed that MYCs are required for full expression of red (R) light-regulated genes, including the master regulator HY5. ChIP-seq analyses revealed that MYC2 and MYC3 bind directly to the promoter of HY5 and that HY5 gene expression and protein levels are compromised in multiple myc mutants. Altogether, our results pinpoint MYCs as photomorphogenic TFs that control phytochrome responses by activating HY5 expression. This has important implications in understanding the trade-off between growth and defence as the same TFs that activate defence responses are photomorphogenic growth regulators.
Topics: Arabidopsis; Arabidopsis Proteins; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; Basic-Leucine Zipper Transcription Factors; Cyclopentanes; Gene Expression Regulation, Plant; Genes, myc; Oxylipins; Phototropism; Plant Growth Regulators; Signal Transduction
PubMed: 31755159
DOI: 10.1111/tpj.14618 -
American Journal of Botany Nov 2019Plants synthesize information from multiple environmental stimuli when determining their direction of growth. Gravity, being ubiquitous on Earth, plays a major role in...
PREMISE
Plants synthesize information from multiple environmental stimuli when determining their direction of growth. Gravity, being ubiquitous on Earth, plays a major role in determining the direction of growth and overall architecture of the plant. Here, we utilized the microgravity environment on board the International Space Station (ISS) to identify genes involved influencing growth and development of phototropically stimulated seedlings of Arabidopsis thaliana.
METHODS
Seedlings were grown on the ISS, and RNA was extracted from 7 samples (pools of 10-15 plants) grown in microgravity (μg) or Earth gravity conditions (1-g). Transcriptomic analyses via RNA sequencing (RNA-seq) of differential gene expression was performed using the HISAT2-Stringtie-DESeq2 RNASeq pipeline. Differentially expressed genes were further characterized by using Pathway Analysis and enrichment for Gene Ontology classifications.
RESULTS
For 296 genes that were found significantly differentially expressed between plants in microgravity compared to 1-g controls, Pathway Analysis identified eight molecular pathways that were significantly affected by reduced gravity conditions. Specifically, light-associated pathways (e.g., photosynthesis-antenna proteins, photosynthesis, porphyrin, and chlorophyll metabolism) were significantly downregulated in microgravity.
CONCLUSIONS
Gene expression in A. thaliana seedlings grown in microgravity was significantly altered compared to that of the 1-g control. Understanding how plants grow in conditions of microgravity not only aids in our understanding of how plants grow and respond to the environment but will also help to efficiently grow plants during long-range space missions.
Topics: Arabidopsis; Arabidopsis Proteins; Seedlings; Space Flight; Weightlessness
PubMed: 31709515
DOI: 10.1002/ajb2.1384