| 1. |
- Amstutz, Cynthia L., et al.
(författare)
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An atypical short-chain dehydrogenase–reductase functions in the relaxation of photoprotective qH in Arabidopsis
- 2020
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Ingår i: Nature Plants. - : Nature Publishing Group. - 2055-026X .- 2055-0278. ; 6, s. 154-166
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Tidskriftsartikel (refereegranskat)abstract
- Photosynthetic organisms experience wide fluctuations in light intensity and regulate light harvesting accordingly to prevent damage from excess energy. The antenna quenching component qH is a sustained form of energy dissipation that protects the photosynthetic apparatus under stress conditions. This photoprotective mechanism requires the plastid lipocalin LCNP and is prevented by SUPPRESSOR OF QUENCHING1 (SOQ1) under non-stress conditions. However, the molecular mechanism of qH relaxation has yet to be resolved. Here, we isolated and characterized RELAXATION OF QH1 (ROQH1), an atypical short-chain dehydrogenase–reductase that functions as a qH-relaxation factor in Arabidopsis. The ROQH1 gene belongs to the GreenCut2 inventory specific to photosynthetic organisms, and the ROQH1 protein localizes to the chloroplast stroma lamellae membrane. After a cold and high-light treatment, qH does not relax in roqh1 mutants and qH does not occur in leaves overexpressing ROQH1. When the soq1 and roqh1 mutations are combined, qH can neither be prevented nor relaxed and soq1 roqh1 displays constitutive qH and light-limited growth. We propose that LCNP and ROQH1 perform dosage-dependent, antagonistic functions to protect the photosynthetic apparatus and maintain light-harvesting efficiency in plants.
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| 2. |
- Chen, Ming, et al.
(författare)
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Distinct structural modulation of photosystem I and lipid environment stabilizes its tetrameric assembly
- 2020
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Ingår i: Nature Plants. - : Springer Science and Business Media LLC. - 2055-026X .- 2055-0278. ; 6:3, s. 314-
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Tidskriftsartikel (refereegranskat)abstract
- Photosystem I (PSI) is able to form different oligomeric states across various species. To reveal the structural basis for PSI dimerization and tetramerization, we structurally investigated PSI from the cyanobacterium Anabaena. This revealed a disrupted trimerization domain due to lack of the terminal residues of PsaL in the lumen, which resulted in PSI dimers with loose connections between monomers and weaker energy-coupled chlorophylls than in the trimer. At the dimer surface, specific phospholipids, cofactors and interactions in combination facilitated recruitment of another dimer to form a tetramer. Taken together, the relaxed luminal connections and lipid specificity at the dimer interface account for membrane curvature. PSI tetramer assembly appears to increase the surface area of the thylakoid membrane, which would contribute to PSI crowding. Photosystem I from the cyanobacterium Anabaena has a disrupted trimerization domain resulting in dimers with loose connections between monomers. Phospholipids and cofactors at the dimer surface facilitate further dimerization to form a tetramer.
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| 3. |
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| 4. |
- Franklin, Oskar, et al.
(författare)
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Organizing principles for vegetation dynamics
- 2020
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Ingår i: Nature plants. - : Springer Science and Business Media LLC. - 2055-026X .- 2055-0278. ; 6:5, s. 444-453
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Tidskriftsartikel (refereegranskat)abstract
- Plants and vegetation play a critical-but largely unpredictable-role in global environmental changes due to the multitude of contributing processes at widely different spatial and temporal scales. In this Perspective, we explore approaches to master this complexity and improve our ability to predict vegetation dynamics by explicitly taking account of principles that constrain plant and ecosystem behaviour: natural selection, self-organization and entropy maximization. These ideas are increasingly being used in vegetation models, but we argue that their full potential has yet to be realized. We demonstrate the power of natural selection-based optimality principles to predict photosynthetic and carbon allocation responses to multiple environmental drivers, as well as how individual plasticity leads to the predictable self-organization of forest canopies. We show how models of natural selection acting on a few key traits can generate realistic plant communities and how entropy maximization can identify the most probable outcomes of community dynamics in space- and time-varying environments. Finally, we present a roadmap indicating how these principles could be combined in a new generation of models with stronger theoretical foundations and an improved capacity to predict complex vegetation responses to environmental change. Integrating natural selection and other organizing principles into next-generation vegetation models could render them more theoretically sound and useful for earth system applications and modelling climate impacts.
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| 5. |
- Müller, Niels A., et al.
(författare)
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A single gene underlies the dynamic evolution of poplar sex determination.
- 2020
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Ingår i: Nature Plants. - : Springer Nature. - 2055-0278 .- 2055-026X. ; 6:6, s. 630-637
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Tidskriftsartikel (refereegranskat)abstract
- Although hundreds of plant lineages have independently evolved dioecy (that is, separation of the sexes), the underlying genetic basis remains largely elusive. Here we show that diverse poplar species carry partial duplicates of the ARABIDOPSIS RESPONSE REGULATOR 17 (ARR17) orthologue in the male-specific region of the Y chromosome. These duplicates give rise to small RNAs apparently causing male-specific DNA methylation and silencing of the ARR17 gene. CRISPR–Cas9-induced mutations demonstrate that ARR17 functions as a sex switch, triggering female development when on and male development when off. Despite repeated turnover events, including a transition from the XY system to a ZW system, the sex-specific regulation of ARR17 is conserved across the poplar genus and probably beyond. Our data reveal how a single-gene-based mechanism of dioecy can enable highly dynamic sex-linked regions and contribute to maintaining recombination and integrity of sex chromosomes.
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| 6. |
- Perez-Boerema, Annemarie, et al.
(författare)
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Structure of a minimal photosystem I from the green alga Dunaliella salina
- 2020
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Ingår i: Nature plants. - : Springer Science and Business Media LLC. - 2055-026X .- 2055-0278. ; 6:3, s. 321-327
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Tidskriftsartikel (refereegranskat)abstract
- Solar energy harnessed by oxygenic photosynthesis supports most of the life forms on Earth. In eukaryotes, photosynthesis occurs in chloroplasts and is achieved by membrane-embedded macromolecular complexes that contain core and peripheral antennae with multiple pigments. The structure of photosystem I (PSI) comprises the core and light-harvesting (LHCI) complexes, which together form PSI-LHCI. Here we determined the structure of PSI-LHCI from the salt-tolerant green alga Dunaliella salina using X-ray crystallography and electron cryo-microscopy. Our results reveal a previously undescribed configuration of the PSI core. It is composed of only 7 subunits, compared with 14-16 subunits in plants and the alga Chlamydomonas reinhardtii, and forms the smallest known PSI. The LHCI is poorly conserved at the sequence level and binds to pigments that form new energy pathways, and the interactions between the individual Lhca1-4 proteins are weakened. Overall, the data indicate the PSI of D. salina represents a different type of the molecular organization that provides important information for reconstructing the plasticity and evolution of PSI. The photosystem I light-harvesting complex from the salt-tolerant green alga Dunaliella salina has a core configuration composed of only seven subunits. This unusual molecular organization could inform the reconstruction of photosystem evolution.
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| 7. |
- Radhakrishnan, Guru V., et al.
(författare)
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An ancestral signalling pathway is conserved in intracellular symbioses-forming plant lineages
- 2020
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Ingår i: NATURE PLANTS. - : NATURE PUBLISHING GROUP. - 2055-026X .- 2055-0278. ; 6:3, s. 280-289
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Tidskriftsartikel (refereegranskat)abstract
- Plants are the foundation of terrestrial ecosystems, and their colonization of land was probably facilitated by mutualistic associations with arbuscular mycorrhizal fungi. Following this founding event, plant diversification has led to the emergence of a tremendous diversity of mutualistic symbioses with microorganisms, ranging from extracellular associations to the most intimate intracellular associations, where fungal or bacterial symbionts are hosted inside plant cells. Here, through analysis of 271 transcriptomes and 116 plant genomes spanning the entire land-plant diversity, we demonstrate that a common symbiosis signalling pathway co-evolved with intracellular endosymbioses, from the ancestral arbuscular mycorrhiza to the more recent ericoid and orchid mycorrhizae in angiosperms and ericoid-like associations of bryophytes. By contrast, species forming exclusively extracellular symbioses, such as ectomycorrhizae, and those forming associations with cyanobacteria, have lost this signalling pathway. This work unifies intracellular symbioses, revealing conservation in their evolution across 450 million yr of plant diversification. An extensive phylogenomics study based on hundreds of genomes and transcriptomes provides a new interpretation of the evolution of different types of symbiotic associations in land plants, and reveals a conserved ancestral symbiosis pathway.
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| 8. |
- Simura, Jan, et al.
(författare)
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Auxin export from proximal fruits drives arrest in temporally competent inflorescences
- 2020
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Ingår i: Nature Plants. - : Springer Science and Business Media LLC. - 2055-026X .- 2055-0278. ; 6, s. 699-707
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Tidskriftsartikel (refereegranskat)abstract
- The authors investigate the mechanisms behind floral arrest in Arabidopsis. Despite what was previously believed, they show that it is not a global process but a locally regulated mechanism, driven by the export of auxin from fertile fruits.A well-defined set of regulatory pathways control entry into the reproductive phase in flowering plants, but little is known about the mechanistic control of the end-of-flowering despite this being a critical process for optimization of fruit and seed production. Complete fruit removal, or lack of fertile fruit-set, prevents timely inflorescence arrest in Arabidopsis, leading to a previous proposal that a cumulative fruit/seed-derived signal causes simultaneous 'global proliferative arrest'. Recent studies have suggested that inflorescence arrest involves gene expression changes in the inflorescence meristem that are, at least in part, controlled by the FRUITFULL-APETALA2 pathway; however, there is limited understanding of how this process is coordinated at the whole-plant level. Here, we provide a framework for the communication previously inferred in the global proliferative arrest model. We show that the end-of-flowering in Arabidopsis is not 'global' and does not occur synchronously between branches, but rather that the arrest of each inflorescence is a local process, driven by auxin export from fruit proximal to the inflorescence apex. Furthermore, we show that inflorescences are competent for arrest only once they reach a certain developmental age. Understanding the regulation of inflorescence arrest will be of major importance to extending and maximizing crop yields.
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| 9. |
- Zhu, Mingyuan, et al.
(författare)
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Robust organ size requires robust timing of initiation orchestrated by focused auxin and cytokinin signalling
- 2020
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Ingår i: Nature Plants. - : Springer Science and Business Media LLC. - 2055-0278. ; 6, s. 686-698
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Tidskriftsartikel (refereegranskat)abstract
- The shape of plant organs shows low variability. Sepals of the same age look the same. Here the authors identify one transcription factor (DRMY1) crucial for sepal size reproducibility, and its effect on initiation timing and growth of the organ. Organ size and shape are precisely regulated to ensure proper function. The four sepals in each Arabidopsis thaliana flower must maintain the same size throughout their growth to continuously enclose and protect the developing bud. Here we show that DEVELOPMENT RELATED MYB-LIKE 1 (DRMY1) is required for both timing of organ initiation and proper growth, leading to robust sepal size in Arabidopsis. Within each drmy1 flower, the initiation of some sepals is variably delayed. Late-initiating sepals in drmy1 mutants remain smaller throughout development, resulting in variability in sepal size. DRMY1 focuses the spatiotemporal signalling patterns of the plant hormones auxin and cytokinin, which jointly control the timing of sepal initiation. Our findings demonstrate that timing of organ initiation, together with growth and maturation, contribute to robust organ size.
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