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Plant Physiology Aug 2020Shade-avoiding plants, including Arabidopsis (), display a number of growth responses, such as elongation of stem-like structures and repositioning of leaves, elicited...
Shade-avoiding plants, including Arabidopsis (), display a number of growth responses, such as elongation of stem-like structures and repositioning of leaves, elicited by shade cues, including a reduction in the blue and red portions of the solar spectrum and a low-red to far-red ratio. Shade also promotes phototropism of de-etiolated seedlings through repression of phytochrome B, presumably to enhance capture of unfiltered sunlight. Here we show that both low blue light and a low-red to far-red light ratio are required to rapidly enhance phototropism in Arabidopsis seedlings. However, prolonged low blue light treatments are sufficient to promote phototropism through reduced cryptochrome1 (cry1) activation. The enhanced phototropic response of mutants in the lab and in response to natural canopies depends on (). In favorable light conditions, cry1 limits the expression of , while in low blue light, PIF4 expression increases, which contributes to phototropic enhancement. The analysis of quantitative DII-Venus, an auxin signaling reporter, indicates that low blue light leads to enhanced auxin signaling in the hypocotyl and, upon phototropic stimulation, a steeper auxin signaling gradient across the hypocotyl. We conclude that phototropic enhancement by canopy shade results from the combined activities of phytochrome B and cry1 that converge on PIF regulation.
Topics: Arabidopsis; Arabidopsis Proteins; Cryptochromes; Gene Expression Regulation, Plant; Hypocotyl; Indoleacetic Acids; Phototropism
PubMed: 32554507
DOI: 10.1104/pp.20.00243 -
Nature Communications Oct 2021Polarity underlies all directional growth responses in plants including growth towards the light (phototropism). The plasma-membrane associated protein, NON-PHOTOTROPIC...
Polarity underlies all directional growth responses in plants including growth towards the light (phototropism). The plasma-membrane associated protein, NON-PHOTOTROPIC HYPOCOTYL 3 (NPH3) is a key determinant of phototropic growth which is regulated by phototropin (phot) AGC kinases. Here we demonstrate that NPH3 is directly phosphorylated by phot1 within a conserved C-terminal consensus sequence (RxS) that is necessary to promote phototropism and petiole positioning in Arabidopsis. RxS phosphorylation also triggers 14-3-3 binding combined with changes in NPH3 phosphorylation and localisation status. Mutants of NPH3 that are unable to bind or constitutively bind 14-3-3 s show compromised functionality consistent with a model where phototropic curvature is established by signalling outputs arising from a gradient of NPH3 RxS phosphorylation across the stem. Our findings therefore establish that NPH3/RPT2-Like (NRL) proteins are phosphorylation targets for plant AGC kinases. Moreover, RxS phosphorylation is conserved in other members of the NRL family, suggesting a common mechanism of regulating plant growth to the prevailing light environment.
Topics: 14-3-3 Proteins; Amino Acid Motifs; Arabidopsis; Arabidopsis Proteins; Consensus Sequence; Gene Expression Regulation, Plant; Hypocotyl; Light; Phosphorylation; Phototropism; Protein Binding; Protein Serine-Threonine Kinases
PubMed: 34675214
DOI: 10.1038/s41467-021-26333-5 -
Journal of the American Chemical Society Jan 2019Bacteriorhodopsin represents the simplest, and possibly most abundant, phototropic system requiring only a retinal-bound transmembrane protein to convert photons of...
Bacteriorhodopsin represents the simplest, and possibly most abundant, phototropic system requiring only a retinal-bound transmembrane protein to convert photons of light to an energy-generating proton gradient. The creation and interrogation of a microbial rhodopsin mimic, based on an orthogonal protein system, would illuminate the design elements required to generate new photoactive proteins with novel function. We describe a microbial rhodopsin mimic, created using a small soluble protein as a template, that specifically photoisomerizes all- trans to 13- cis retinal followed by thermal relaxation to the all- trans isomer, mimicking the bacteriorhodopsin photocycle, in a single crystal. The key element for selective isomerization is a tuned steric interaction between the chromophore and protein, similar to that seen in the microbial rhodopsins. It is further demonstrated that a single mutation converts the system to a protein photoswitch without chromophore photoisomerization or conformational change.
Topics: Bacteriorhodopsins; Biomimetics; Light; Models, Molecular; Movement; Protein Conformation; Stereoisomerism; Temperature
PubMed: 30580520
DOI: 10.1021/jacs.8b12493 -
Plant Physiology Nov 2021One conserved feature among angiosperms is the development of flat thin leaves. This developmental pattern optimizes light capture and gas exchange. The blue light (BL)...
One conserved feature among angiosperms is the development of flat thin leaves. This developmental pattern optimizes light capture and gas exchange. The blue light (BL) receptors phototropins are required for leaf flattening, with the null phot1phot2 mutant showing curled leaves in Arabidopsis (Arabidopsis thaliana). However, key aspects of their function in leaf development remain unknown. Here, we performed a detailed spatiotemporal characterization of phototropin function in Arabidopsis leaves. We found that phototropins perceive light direction in the blade, and, similar to their role in hypocotyls, they control the spatial pattern of auxin signaling, possibly modulating auxin transport, to ultimately regulate cell expansion. Phototropin signaling components in the leaf partially differ from hypocotyls. Moreover, the light response on the upper and lower sides of the leaf blade suggests a partially distinct requirement of phototropin signaling components on each side. In particular, NON PHOTOTROPIC HYPOCOTYL 3 showed an adaxial-specific function. In addition, we show a prominent role of PHYTOCHROME KINASE SUBSTRATE 3 in leaf flattening. Among auxin transporters, PIN-FORMED 3,4,7 and AUXIN RESISTANT 1 (AUX1)/LIKE AUXIN RESISTANT 1 (LAX1) are required for the response while ABCB19 has a regulatory role. Overall, our results show that directional BL perception by phototropins is a key aspect of leaf development, integrating endogenous and exogenous signals.
Topics: Arabidopsis; Indoleacetic Acids; Light; Phototropins; Phytochrome; Plant Leaves; Signal Transduction
PubMed: 34618121
DOI: 10.1093/plphys/kiab410 -
Frontiers in Plant Science 2018Phototropins (phot1 and phot2) are blue-light receptors that control cotyledon flattening and positioning under strong light; however, their functional redundancy...
Phototropins (phot1 and phot2) are blue-light receptors that control cotyledon flattening and positioning under strong light; however, their functional redundancy restricts our understanding of the specific roles of phot2. To identify the factors responsible for phot2-dependent cotyledon flattening and growth, we screened for light-insensitive mutants among mutagenized mutants in . The double mutant (), which is defective in cotyledon flattening and positioning but not the phototropic response was selected. This mutant phenotype could be alleviated by constitutively expressing (), indicating that was allelic to . The mutants ( and ) are defective in cotyledon flattening, which is similar to that of the mutants. Moreover, the amounts of MAX2 transcripts are inhibited in leaves of mutant. However, the additional disruption of gene in or did not affect their phenotype, including MAX2-mediated inhibition of hypocotyl elongation. By contrast, phototropins-mediated hypocotyl phototropism was not regulated by MAX2. Together, these results suggest that cotyledon flattening was mediated by both phototropins and MAX2 signaling, but the relationship between two pathways need further study.
PubMed: 30386362
DOI: 10.3389/fpls.2018.01507 -
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 -
Plant Signaling & Behavior 2015Shoot phototropism enables plants to position their photosynthetic organs in favorable light conditions and thus benefits growth and metabolism in land plants. To...
Shoot phototropism enables plants to position their photosynthetic organs in favorable light conditions and thus benefits growth and metabolism in land plants. To understand the evolution of this response, we established an experimental system to study phototropism in gametophores of the moss Physcomitrella patens. The phototropic response of gametophores occurs slowly; a clear response takes place more than 24 hours after the onset of unilateral light irradiation, likely due to the slow growth rate of gametophores. We also found that red and far-red light can induce phototropism, with blue light being less effective. These results suggest that plants used a broad range of light wavelengths as phototropic signals during the early evolution of land plants.
Topics: Biological Evolution; Bryopsida; Germ Cells, Plant; Light; Phototropism; Plant Shoots
PubMed: 25848889
DOI: 10.1080/15592324.2015.1010900 -
Nature Communications Jun 2018Phototropins are light-activated protein kinases, which contribute to photosynthesis optimization both through enhancement of photon absorption when light is limiting...
Phototropins are light-activated protein kinases, which contribute to photosynthesis optimization both through enhancement of photon absorption when light is limiting and avoidance responses in high light. This duality is in part endowed by the presence of phototropins with different photosensitivity (phot1 and phot2). Here we show that phot1, which senses low light to promote positive phototropism (growth towards the light), also limits the response in high light. This response depends in part on phot1-mediated phosphorylation of Phytochrome Kinase Substrate 4 (PKS4). This light-regulated phosphorylation switch changes PKS4 from a phototropism enhancer in low light to a factor limiting the process in high light. In such conditions phot1 and PKS4 phosphorylation prevent phototropic responses to shallow light gradients and limit phototropism in a natural high light environment. Hence, by modifying PKS4 activity in high light the phot1-PKS4 regulon enables appropriate physiological adaptations over a range of light intensities.
Topics: Adaptation, Physiological; Arabidopsis; Arabidopsis Proteins; Dose-Response Relationship, Radiation; Gene Expression Regulation, Plant; Intracellular Signaling Peptides and Proteins; Light; Phosphoproteins; Phosphorylation; Phototropism; Plants, Genetically Modified; Protein Serine-Threonine Kinases
PubMed: 29921904
DOI: 10.1038/s41467-018-04752-1 -
The Plant Cell Jun 2016Roots normally grow in darkness, but they may be exposed to light. After perceiving light, roots bend to escape from light (root light avoidance) and reduce their...
Roots normally grow in darkness, but they may be exposed to light. After perceiving light, roots bend to escape from light (root light avoidance) and reduce their growth. How root light avoidance responses are regulated is not well understood. Here, we show that illumination induces the accumulation of flavonols in Arabidopsis thaliana roots. During root illumination, flavonols rapidly accumulate at the side closer to light in the transition zone. This accumulation promotes asymmetrical cell elongation and causes differential growth between the two sides, leading to root bending. Furthermore, roots illuminated for a long period of time accumulate high levels of flavonols. This high flavonol content decreases both auxin signaling and PLETHORA gradient as well as superoxide radical content, resulting in reduction of cell proliferation. In addition, cytokinin and hydrogen peroxide, which promote root differentiation, induce flavonol accumulation in the root transition zone. As an outcome of prolonged light exposure and flavonol accumulation, root growth is reduced and a different root developmental zonation is established. Finally, we observed that these differentiation-related pathways are required for root light avoidance. We propose that flavonols function as positional signals, integrating hormonal and reactive oxygen species pathways to regulate root growth direction and rate in response to light.
Topics: Arabidopsis; Arabidopsis Proteins; Cell Differentiation; Flavonols; Gene Expression Regulation, Plant; Light; Phototropism; Plant Growth Regulators; Plant Roots; Signal Transduction
PubMed: 26628743
DOI: 10.1105/tpc.15.00857 -
Structure (London, England : 1993) May 2016COP1 proteins are E3 ubiquitin ligases that regulate phototropism in plants and target transcription factors for degradation in mammals. The substrate-binding region of...
COP1 proteins are E3 ubiquitin ligases that regulate phototropism in plants and target transcription factors for degradation in mammals. The substrate-binding region of COP1 resides within a WD40-repeat domain that also binds to Trib proteins, which are adaptors for C/EBPα degradation. Here we report structures of the human COP1 WD40 domain in isolation, and complexes of the human and Arabidopsis thaliana COP1 WD40 domains with the binding motif of Trib1. The human and Arabidopsis WD40 domains are seven-bladed β propellers with an inserted loop on the bottom face of the first blade. The Trib1 peptide binds in an extended conformation to a highly conserved surface on the top face of the β propeller, indicating a general mode for recognition of peptide motifs by COP1. Together, these studies identify the structural basis and key interactions for motif recognition by COP1, and hint at how Trib1 autoinhibition is overcome to target C/EBPα for degradation.
Topics: Arabidopsis; Arabidopsis Proteins; Binding Sites; Humans; Intracellular Signaling Peptides and Proteins; Molecular Docking Simulation; Peptide Fragments; Protein Binding; Protein Serine-Threonine Kinases; Substrate Specificity; Ubiquitin-Protein Ligases; WD40 Repeats
PubMed: 27041596
DOI: 10.1016/j.str.2016.03.002