| 1. |
- Niittylä, Totte
(författare)
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Sucrose synthases are not involved in starch synthesis in Arabidopsis leaves
- 2022
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Ingår i: Nature Plants. - : Springer Science and Business Media LLC. - 2055-026X .- 2055-0278.
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Tidskriftsartikel (refereegranskat)abstract
- Many plants accumulate transitory starch reserves in their leaves during the day to buffer their carbohydrate supply against fluctuating light conditions, and to provide carbon and energy for survival at night. It is universally accepted that transitory starch is synthesized from ADP-glucose (ADPG) in the chloroplasts. However, the consensus that ADPG is made in the chloroplasts by ADPG pyrophosphorylase has been challenged by a controversial proposal that ADPG is made primarily in the cytosol, probably by sucrose synthase (SUS), and then imported into the chloroplasts. To resolve this long-standing controversy, we critically re-examined the experimental evidence that appears to conflict with the consensus pathway. We show that when precautions are taken to avoid artefactual changes during leaf sampling, Arabidopsis thaliana mutants that lack SUS activity in mesophyll cells (quadruple sus1234) or have no SUS activity (sextuple sus123456) have wild-type levels of ADPG and starch, while ADPG is 20 times lower in the pgm and adg1 mutants that are blocked in the consensus chloroplastic pathway of starch synthesis. We conclude that the ADPG needed for starch synthesis in leaves is synthesized primarily by ADPG pyrophosphorylase in the chloroplasts.Mutant analysis shows that sucrose synthase makes no substantial contribution to transitory starch synthesis in Arabidopsis leaves, resolving a 20-year-old controversy about one of the most important pathways of photosynthetic metabolism.
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| 2. |
- Amunts, Alexey
(författare)
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The revolution evolution
- 2022
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Ingår i: Nature Plants. - : Springer Science and Business Media LLC. - 2055-0278. ; 8:1, s. 14-17
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 3. |
- Feeley, Kenneth J., et al.
(författare)
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Changing forests under climate change
- 2022
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Ingår i: Nature Plants. - : Springer Science and Business Media LLC. - 2055-0278.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 4. |
- Naschberger, Andreas, et al.
(författare)
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Algal photosystem I dimer and high-resolution model of PSI-plastocyanin complex
- 2022
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Ingår i: Nature Plants. - : Springer Science and Business Media LLC. - 2055-0278. ; 8:10, s. 1191-1201
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Tidskriftsartikel (refereegranskat)abstract
- Photosystem I (PSI) enables photo-electron transfer and regulates photosynthesis in the bioenergetic membranes of cyanobacteria and chloroplasts. Being a multi-subunit complex, its macromolecular organization affects the dynamics of photosynthetic membranes. Here we reveal a chloroplast PSI from the green alga Chlamydomonas reinhardtii that is organized as a homodimer, comprising 40 protein subunits with 118 transmembrane helices that provide scaffold for 568 pigments. Cryogenic electron microscopy identified that the absence of PsaH and Lhca2 gives rise to a head-to-head relative orientation of the PSI–light-harvesting complex I monomers in a way that is essentially different from the oligomer formation in cyanobacteria. The light-harvesting protein Lhca9 is the key element for mediating this dimerization. The interface between the monomers is lacking PsaH and thus partially overlaps with the surface area that would bind one of the light-harvesting complex II complexes in state transitions. We also define the most accurate available PSI–light-harvesting complex I model at 2.3 Å resolution, including a flexibly bound electron donor plastocyanin, and assign correct identities and orientations to all the pigments, as well as 621 water molecules that affect energy transfer pathways.
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| 5. |
- Rocchetti, Giulia Albani, et al.
(författare)
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Selecting the best candidates for resurrecting extinct-in-the-wild plants from herbaria
- 2022
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Ingår i: Nature Plants. - : Springer Science and Business Media LLC. - 2055-0278. ; 8:12, s. 1385-1393
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Tidskriftsartikel (refereegranskat)abstract
- Resurrecting extinct species is a fascinating and challenging idea for scientists and the general public. Whereas some theoretical progress has been made for animals, the resurrection of extinct plants (de-extinction sensu lato) is a relatively recently discussed topic. In this context, the term ‘de-extinction’ is used sensu lato to refer to the resurrection of ‘extinct in the wild’ species from seeds or tissues preserved in herbaria, as we acknowledge the current impossibility of knowing a priori whether a herbarium seed is alive and can germinate. In plants, this could be achieved by germinating or in vitro tissue-culturing old diaspores such as seeds or spores available in herbarium specimens. This paper reports the first list of plant de-extinction candidates based on the actual availability of seeds in herbarium specimens of globally extinct plants. We reviewed globally extinct seed plants using online resources and additional literature on national red lists, resulting in a list of 361 extinct taxa. We then proposed a method of prioritizing candidates for seed-plant de-extinction from diaspores found in herbarium specimens and complemented this with a phylogenetic approach to identify species that may maximize evolutionarily distinct features. Finally, combining data on seed storage behaviour and longevity, as well as specimen age in the novel ‘best de-extinction candidate’ score (DEXSCO), we identified 556 herbarium specimens belonging to 161 extinct species with available seeds. We expect that this list of de-extinction candidates and the novel approach to rank them will boost research efforts towards the first-ever plant de-extinction.
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| 6. |
- Yu, Guimei, et al.
(författare)
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Structure of Arabidopsis SOQ1 lumenal region unveils C-terminal domain essential for negative regulation of photoprotective qH
- 2022
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Ingår i: Nature Plants. - : Nature Publishing Group. - 2055-0278. ; 8:7, s. 840-855
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Tidskriftsartikel (refereegranskat)abstract
- Non-photochemical quenching (NPQ) plays an important role for phototrophs in decreasing photo-oxidative damage. qH is a sustained form of NPQ and depends on the plastid lipocalin (LCNP). A thylakoid membrane-anchored protein SUPPRESSOR OF QUENCHING1 (SOQ1) prevents qH formation by inhibiting LCNP. SOQ1 suppresses qH with its lumen-located thioredoxin (Trx)-like and NHL domains. Here we report structural data, genetic modification and biochemical characterization of Arabidopsis SOQ1 lumenal domains. Our results show that the Trx-like and NHL domains are associated together, with the cysteine motif located at their interface. Residue E859, required for SOQ1 function, is pivotal for maintaining the Trx–NHL association. Importantly, the C-terminal region of SOQ1 forms an independent β-stranded domain that has structural homology to the N-terminal domain of bacterial disulfide bond protein D and is essential for negative regulation of qH. Furthermore, SOQ1 is susceptible to cleavage at the loops connecting the neighbouring lumenal domains both in vitro and in vivo, which could be a regulatory process for its suppression function of qH.
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