The past 30 years has seen a tremendous increase in our understanding of the light-signaling networks of higher plants. This short review emphasizes the role that Arabidopsis genetics has played in ...deciphering this complex network. Importantly, it outlines how genetic studies led to the identification of photoreceptors and signaling components that are not only relevant in plants, but play key roles in mammals.
As they emerge from the ground, seedlings adopt a photosynthetic lifestyle, which is accompanied by dramatic changes in morphology and global alterations in gene expression that optimizes the plant ...body plan for light capture. Phytochromes are red and far-red photoreceptors that play a major role during photomorphogenesis, a complex developmental program that seedlings initiate when they first encounter light. The earliest phytochrome signaling events after excitation by red light include their rapid translocation from the cytoplasm to subnuclear bodies (photobodies) that contain other proteins involved in photomorphogenesis, including a number of transcription factors and E3 ligases. In the light, phytochromes and negatively acting transcriptional regulators that interact directly with phytochromes are destabilized, whereas positively acting transcriptional regulators are stabilized. Here, we discuss recent advances in our knowledge of the mechanisms linking phytochrome photoactivation in the cytoplasm and transcriptional regulation in the nucleus.
Plants are under relentless challenge by pathogenic bacteria, fungi, and oomycetes, for whom they provide a resource of living space and nutrients. Upon detection of pathogens, plants carry out ...multiple layers of defense response, orchestrated by a tightly organized network of hormones. In this review, we provide an overview of the phytohormones involved in immunity and the ways pathogens manipulate their biosynthesis and signaling pathways. We highlight recent developments, including the discovery of a defense signaling molecule, new insights into hormone biosynthesis, and the increasing importance of signaling hubs at which hormone pathways intersect.
Plants have a complex innate immune system to fight pathogens and pests. Plant hormones communicate and balance the different responses against the diversity of biotic threats. Bürger and Chory review how pathogens manipulate plant hormone production and signaling pathways to remodel and evade host immune responses.
The dynamic and specific transcriptome for high light (HL) stress in plants is poorly understood because heat has confounded previous studies. Here, we perform an in-depth temporal responsive ...transcriptome analysis and identify the core HL-responsive genes. By eliminating the effect of heat, we uncover a set of genes specifically regulated by high-intensity light-driven signaling. We find that 79% of HL-responsive genes restore their expression to baseline within a 14-h recovery period. Our study reveals that plants respond to HL through dynamic regulation of hormones, particularly abscisic acid (ABA), photosynthesis, and phenylpropanoid pathway genes. Blue/UV-A photoreceptors and phytochrome-interacting factor (PIF) genes are also responsive to HL. We further show that ABA biosynthesis-defective mutant nced3nced5, as well as pif4, pif5, pif4,5, and pif1,3,4,5 mutants, are hypersensitive to HL. Our study presents the dynamic and specific high-intensity light-driven transcriptional landscape in plants during HL stress.
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•The specific transcriptome of plants under high-intensity light without heat stress•Different durations of HL stress cause dynamic changes to the transcriptome•Hormone, photosynthetic, and anthocyanin genes are dynamically regulated by HL•nced3nced5 and pif mutants are hypersensitive to high light
Huang et al. present the specific and dynamic transcriptome for high-intensity light (HL) stress in plants. They identify the core HL-responsive genes and uncover that plants respond to HL by dynamically regulating hormones, anthocyanin, photosynthesis, photoreceptors, and PIF genes. They show that ABA and PIFs are required for HL response.
Plant hormones play a major role in plant growth and development. They affect similar processes but, paradoxically, their signaling pathways act nonredundantly. Hormone signals are integrated at the ...gene-network level rather than by cross-talk during signal transduction. In contrast to hormone-hormone integration, recent data suggest that light and plant hormone pathways share common signaling components, which allows photoreceptors to influence the growth program. We propose a role for the plant hormone auxin as an integrator of the activities of multiple plant hormones to control plant growth in response to the environment.
Brassinosteroids, the steroid hormones of plants, are perceived at the plasma membrane by a leucine-rich repeat receptor serine/threonine kinase called BRI1. We report a BRI1-interacting protein, ...BKI1, which is a negative regulator of brassinosteroid signaling. Brassinosteroids cause the rapid dissociation of BKI1-yellow fluorescent protein from the plasma membrane in a process that is dependent on BRI1-kinase. BKI1 is a substrate of BRI1 kinase and limits the interaction of BRI1 with its proposed coreceptor, BAK1, suggesting that BKI1 prevents the activation of BRI1.
Following the acquisition of chloroplasts and mitochondria by eukaryotic cells during endosymbiotic evolution, most of the genes in these organelles were either lost or transferred to the nucleus. ...Encoding organelle-destined proteins in the nucleus allows for host control of the organelle. In return, organelles send signals to the nucleus to coordinate nuclear and organellar activities. In photosynthetic eukaryotes, additional interactions exist between mitochondria and chloroplasts. Here we review recent advances in elucidating the intracellular signalling pathways that coordinate gene expression between organelles and the nucleus, with a focus on photosynthetic plants.
Dancing in the dark: darkness as a signal in plants Seluzicki, Adam; Burko, Yogev; Chory, Joanne
Plant, cell & environment/Plant, cell and environment,
November 2017, Letnik:
40, Številka:
11
Journal Article
Recenzirano
Odprti dostop
Daily cycles of light and dark provide an organizing principle and temporal constraints under which life on Earth evolved. While light is often the focus of plant studies, it is only half the story. ...Plants continuously adjust to their surroundings, taking both dawn and dusk as cues to organize their growth, development and metabolism to appropriate times of day. In this review, we examine the effects of darkness on plant physiology and growth. We describe the similarities and differences between seedlings grown in the dark versus those grown in light–dark cycles, and the evolution of etiolated growth. We discuss the integration of the circadian clock into other processes, looking carefully at the points of contact between clock genes and growth‐promoting gene‐regulatory networks in temporal gating of growth. We also examine daily starch accumulation and degradation, and the possible contribution of dark‐specific metabolic controls in regulating energy and growth. Examining these studies together reveals a complex and continuous balancing act, with many signals, dark included, contributing information and guiding the plant through its life cycle. The extraordinary interconnection between light and dark is manifest during cycles of day and night and during seedling emergence above versus below the soil surface.
Daily cycles of light and darkness provide structure that plants use to temporally organize aspects of their physiology and growth. Plants use distinct modes of growth in continuous dark versus light–dark cycles but these programmes share many components. In this review, we examine progress toward understanding how plants coordinate light‐sensitive and time‐sensitive processes to optimize growth and resource allocation across the day–night cycle, and how darkness changes the function of gene regulatory networks involved in seedling growth, timing and metabolism.
Transcriptional regulation of gene expression is a major mechanism used by plants to confer phenotypic plasticity, and yet compared with other eukaryotes or bacteria, little is known about the design ...principles. We generated an extensive catalog of nascent and steady-state transcripts in Arabidopsis thaliana seedlings using global nuclear run-on sequencing (GRO-seq), 5′GRO-seq, and RNA-seq and reanalyzed published maize data to capture characteristics of plant transcription. De novo annotation of nascent transcripts accurately mapped start sites and unstable transcripts. Examining the promoters of coding and noncoding transcripts identified comparable chromatin signatures, a conserved “TGT” core promoter motif and unreported transcription factor-binding sites. Mapping of engaged RNA polymerases showed a lack of enhancer RNAs, promoter-proximal pausing, and divergent transcription in Arabidopsis seedlings and maize, which are commonly present in yeast and humans. In contrast, Arabidopsis and maize genes accumulate RNA polymerases in proximity of the polyadenylation site, a trend that coincided with longer genes and CpG hypomethylation. Lack of promoter-proximal pausing and a higher correlation of nascent and steady-state transcripts indicate Arabidopsis may regulate transcription predominantly at the level of initiation. Our findings provide insight into plant transcription and eukaryotic gene expression as a whole.
The first exposure to light marks a crucial transition in plant development. This transition relies on the transcription factor HY5 controlling a complex downstream growth program. Despite its ...importance, its function in transcription remains unclear. Previous studies have generated lists of thousands of potential target genes and competing models of HY5 transcription regulation. In this work, we carry out detailed phenotypic and molecular analysis of constitutive activator and repressor HY5 fusion proteins. Using this strategy, we were able to filter out large numbers of genes that are unlikely to be direct targets, allowing us to eliminate several proposed models of HY5's mechanism of action. We demonstrate that the primary activity of HY5 is promoting transcription and that this function relies on other, likely light-regulated, factors. In addition, this approach reveals a molecular feedback loop via the COP1/SPA E3 ubiquitin ligase complex, suggesting a mechanism that maintains low HY5 in the dark, primed for rapid accumulation to reprogram growth upon light exposure. Our strategy is broadly adaptable to the study of transcription factor activity. Lastly, we show that modulating this feedback loop can generate significant phenotypic diversity in both Arabidopsis (
) and tomato (
).
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