Biogenesis and homeostasis of chloroplasts and other plastids
TL;DR: The genetic system of this organelle and its coordination with the nucleocytosolic system, the import and routing of nucleus-encoded proteins, as well as organellar division all contribute to the biogenesis and homeostasis of plastids.
Abstract: Chloroplasts are the ancestral members of the plastid organelle family. Their identity, division and biogenesis require the import of nucleus-encoded proteins and tight coordination between the organellar genetic system and the nucleocytosolic system. The ubiquitin–proteasome system also links plastid homeostasis and biogenesis to organismal development. Chloroplasts are the organelles that define plants, and they are responsible for photosynthesis as well as numerous other functions. They are the ancestral members of a family of organelles known as plastids. Plastids are remarkably dynamic, existing in strikingly different forms that interconvert in response to developmental or environmental cues. The genetic system of this organelle and its coordination with the nucleocytosolic system, the import and routing of nucleus-encoded proteins, as well as organellar division all contribute to the biogenesis and homeostasis of plastids. They are controlled by the ubiquitin–proteasome system, which is part of a network of regulatory mechanisms that integrate plastid development into broader programmes of cellular and organismal development.
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TL;DR: New findings on the processes by which organelle communication is initiated, transmitted, and perceived are discussed, not only to regulate chloroplastic processes but also to intersect with cellular signaling and alter physiological responses.
Abstract: The chloroplast can act as an environmental sensor, communicating with the cell during biogenesis and operation to change the expression of thousands of proteins This process, termed retrograde signaling, regulates expression in response to developmental cues and stresses that affect photosynthesis and yield Recent advances have identified many signals and pathways-including carotenoid derivatives, isoprenes, phosphoadenosines, tetrapyrroles, and heme, together with reactive oxygen species and proteins-that build a communication network to regulate gene expression, RNA turnover, and splicing However, retrograde signaling pathways have been viewed largely as a means of bilateral communication between organelles and nuclei, ignoring their potential to interact with hormone signaling and the cell as a whole to regulate plant form and function Here, we discuss new findings on the processes by which organelle communication is initiated, transmitted, and perceived, not only to regulate chloroplastic processes but also to intersect with cellular signaling and alter physiological responses
411 citations
TL;DR: This review provides a comprehensive overview of the impact of various types of plastids on carotenoid biosynthesis and accumulation, and discusses recent advances in the understanding of the regulatory control ofCarotenogenesis and metabolic engineering ofcarotenoids in light ofplastid types in plants.
388 citations
Cites background from "Biogenesis and homeostasis of chlor..."
...Nevertheless, amyloplast readjustments regularly occur in special plant organs or tissues (Jarvis and Lopez-Juez, 2013)....
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...Amyloplasts store starch granules, which are important to plants in energy storage and gravitropism (Jarvis and Lopez-Juez, 2013)....
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...Plastids are found ubiquitously in plants and exist in various types, such as proplastids, amyloplasts, etioplasts, chloroplasts, and chromoplasts (Lopez-Juez and Pyke, 2004; Jarvis and Lopez-Juez, 2013)....
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TL;DR: Although operating at a low constitutive level in all plant cells, autophagy is upregulated during senescence and various environmental challenges and is essential for proper nutrient allocation, which places it at the nexus of robust crop performance, especially under suboptimal conditions.
Abstract: Plants have evolved sophisticated mechanisms to recycle intracellular constituents, which are essential for developmental and metabolic transitions; for efficient nutrient reuse; and for the proper disposal of proteins, protein complexes, and even entire organelles that become obsolete or dysfunctional. One major route is autophagy, which employs specialized vesicles to encapsulate and deliver cytoplasmic material to the vacuole for breakdown. In the past decade, the mechanics of autophagy and the scores of components involved in autophagic vesicle assembly have been documented. Now emerging is the importance of dedicated receptors that help recruit appropriate cargo, which in many cases exploit ubiquitylation as a signal. Although operating at a low constitutive level in all plant cells, autophagy is upregulated during senescence and various environmental challenges and is essential for proper nutrient allocation. Its importance to plant metabolism and energy balance in particular places autophagy at the...
337 citations
Cites background from "Biogenesis and homeostasis of chlor..."
...As the definitive photoautotrophic organelle, chloroplasts harbor the photosynthetic machinery and perform other essential metabolic functions (75)....
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TL;DR: The protein ubiquitin is a covalent modifier of proteins, including itself, and within the ubiquitination machinery “half” of the Ubiquitin system are redundant, partially redundant, and unique components affecting diverse developmental and environmental responses in plants.
Abstract: The protein ubiquitin is a covalent modifier of proteins, including itself. The ubiquitin system encompasses the enzymes required for catalysing attachment of ubiquitin to substrates as well as proteins that bind to ubiquitinated proteins leading them to their final fate. Also included are activities that remove ubiquitin independent of, or in concert with, proteolysis of the substrate, either by the proteasome or proteases in the vacuole. In addition to ubiquitin encoded by a family of fusion proteins, there are proteins with ubiquitin-like domains, likely forming ubiquitin's β-grasp fold, but incapable of covalent modification. However, they serve as protein-protein interaction platforms within the ubiquitin system. Multi-gene families encode all of these types of activities. Within the ubiquitination machinery “half” of the ubiquitin system are redundant, partially redundant, and unique components affecting diverse developmental and environmental responses in plants. Notably, multiple aspects of biotic...
256 citations
Cites background from "Biogenesis and homeostasis of chlor..."
...This turnover of TOC is proposed to facilitate developmental transitions, when different TOC complexes are utilized such as during greening and senescence (Ling et al., 2012; Jarvis and Lopez-Juez, 2013)....
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TL;DR: The current status of studies on transcription factors and phytohormones that regulate carotenoid biosynthesis, catabolism, and storage capacity in plastids, as well as the responses of carOTenoid metabolism to environmental cues in tomato fruits are summarized.
250 citations
References
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TL;DR: Genome sequences reveal that a deluge of DNA from organelle DNA has constantly been bombarding the nucleus since the origin of organelles, abolished organelle autonomy and increased nuclear complexity.
Abstract: Genome sequences reveal that a deluge of DNA from organelles has constantly been bombarding the nucleus since the origin of organelles. Recent experiments have shown that DNA is transferred from organelles to the nucleus at frequencies that were previously unimaginable. Endosymbiotic gene transfer is a ubiquitous, continuing and natural process that pervades nuclear DNA dynamics. This relentless influx of organelle DNA has abolished organelle autonomy and increased nuclear complexity.
1,324 citations
TL;DR: This work proposes a model in which multiple indicators of aberrant plastid function in Arabidopsis are integrated upstream of GUN1 within plastids, which leads to ABI4-mediated repression of nuclear-encoded genes.
Abstract: Plastid-to-nucleus retrograde signaling coordinates nuclear gene expression with chloroplast function and is essential for the photoautotrophic life-style of plants. Three retrograde signals have been described, but little is known of their signaling pathways. We show here that GUN1, a chloroplast-localized pentatricopeptide-repeat protein, and ABI4, an Apetala 2 (AP2)-type transcription factor, are common to all three pathways. ABI4 binds the promoter of a retrograde-regulated gene through a conserved motif found in close proximity to a light-regulatory element. We propose a model in which multiple indicators of aberrant plastid function in Arabidopsis are integrated upstream of GUN1 within plastids, which leads to ABI4-mediated repression of nuclear-encoded genes.
924 citations
TL;DR: Genomic studies have further revealed that light induces massive reprogramming of the plant transcriptome, and that the early light-responsive genes are enriched in transcription factors, and these combined approaches provide new insights into light-regulated transcriptional networks.
Abstract: Plants have evolved complex and sophisticated transcriptional networks that mediate developmental changes in response to light. These light-regulated processes include seedling photomorphogenesis, seed germination and the shade-avoidance and photoperiod responses. Understanding the components and hierarchical structure of the transcriptional networks that are activated during these processes has long been of great interest to plant scientists. Traditional genetic and molecular approaches have proved powerful in identifying key regulatory factors and their positions within these networks. Recent genomic studies have further revealed that light induces massive reprogramming of the plant transcriptome, and that the early light-responsive genes are enriched in transcription factors. These combined approaches provide new insights into light-regulated transcriptional networks.
912 citations
TL;DR: Several recent papers are discussed that cover the evolutionary history and molecular mode of action of Pentatricopeptide repeat proteins, and propose hypotheses for their physiological roles that could explain why PPR proteins are so numerous in terrestrial plants.
772 citations
TL;DR: A dynamic transcriptome is revealed, with transcripts for primary cell wall and basic cellular metabolism at the leaf base transitioning to transcripts for secondary cell wall biosynthesis and C4 photosynthetic development toward the tip.
Abstract: We have analyzed the maize leaf transcriptome using Illumina sequencing. We mapped more than 120 million reads to define gene structure and alternative splicing events and to quantify transcript abundance along a leaf developmental gradient and in mature bundle sheath and mesophyll cells. We detected differential mRNA processing events for most maize genes. We found that 64% and 21% of genes were differentially expressed along the developmental gradient and between bundle sheath and mesophyll cells, respectively. We implemented Gbrowse, an electronic fluorescent pictograph browser, and created a two-cell biochemical pathway viewer to visualize datasets. Cluster analysis of the data revealed a dynamic transcriptome, with transcripts for primary cell wall and basic cellular metabolism at the leaf base transitioning to transcripts for secondary cell wall biosynthesis and C(4) photosynthetic development toward the tip. This dataset will serve as the foundation for a systems biology approach to the understanding of photosynthetic development.
684 citations