| 1. |
- Cocco, Emma, et al.
(författare)
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The Influence of Blue and Red Light on Seed Development and Dormancy in Nicotiana tabacum L.
- 2022
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Ingår i: Seeds. - : MDPI. - 2674-1024. ; 1:3, s. 152-163
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Tidskriftsartikel (refereegranskat)abstract
- The correct development of seeds is a pivotal requirement for species preservation. This process depends on the balance between sensing the environmental stimuli/stressors and hormone-mediated transduction, which results in physiological responses. The red and blue regions of the electromagnetic spectrum are known to influence seed dormancy and germination. Here, we report on the effects induced by the blue (peak at 430 nm) and red (peak at 650 nm) regions of the electromagnetic spectrum on seeds from photo- and skotomorphogenetic capsules developed under white, blue, or red light. Regardless of exposure, seeds from skotomorphogenetic capsules showed an almost absent dormancy in association with altered germination kinetics. Conversely, in seeds from photomorphogenetic capsules, the exposure to the blue region induced skotomorphogenetic-like effects, while the exposure to the whole visible range (350–750 nm), as well as to only the red region, showed a dose-related trend. The observed differences appeared to be dependent on the wavelengths in the red and to be based on transduction mechanisms taking place in fruits. While the molecular bases of this differential effect need to be clarified, the results hint at the role played by different light wavelengths and intensities in seed development and germination. These findings may be relevant for applications in crop production and species safeguarding.
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| 2. |
- Fantuzzi, Andrea, et al.
(författare)
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Bicarbonate activation of the monomeric photosystem II-PsbS/Psb27 complex
- 2023
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Ingår i: Plant Physiology. - : Oxford University Press. - 0032-0889 .- 1532-2548. ; 192:4, s. 2656-2671
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Tidskriftsartikel (refereegranskat)abstract
- In thylakoid membranes, photosystem II (PSII) monomers from the stromal lamellae contain the subunits PsbS and Psb27 (PSIIm-S/27), while PSII monomers (PSIIm) from granal regions lack these subunits. Here, we have isolated and characterized these 2 types of PSII complexes in tobacco (Nicotiana tabacum). PSIIm-S/27 showed enhanced fluorescence, the near absence of oxygen evolution, and limited and slow electron transfer from QA to QB compared to the near-normal activities in the granal PSIIm. However, when bicarbonate was added to PSIIm-S/27, water splitting and QA to QB electron transfer rates were comparable to those in granal PSIIm. The findings suggest that the binding of PsbS and/or Psb27 inhibits forward electron transfer and lowers the binding affinity for bicarbonate. This can be rationalized in terms of the recently discovered photoprotection role played by bicarbonate binding via the redox tuning of the QA/QA•- couple, which controls the charge recombination route, and this limits chlorophyll triplet-mediated 1O2 formation. These findings suggest that PSIIm-S/27 is an intermediate in the assembly of PSII in which PsbS and/or Psb27 restrict PSII activity while in transit using a bicarbonate-mediated switch and protective mechanism.
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| 3. |
- Farci, Domenica, et al.
(författare)
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The cryo-EM structure of the S-layer deinoxanthin-binding complex of Deinococcus radiodurans informs properties of its environmental interactions
- 2022
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Ingår i: Journal of Biological Chemistry. - : American Society for Biochemistry and Molecular Biology. - 0021-9258 .- 1083-351X. ; 298:6
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Tidskriftsartikel (refereegranskat)abstract
- The radiation-resistant bacterium Deinococcus radiodurans is known as the world's toughest bacterium. The S-layer of D. radiodurans, consisting of several proteins on the surface of the cellular envelope and intimately associated with the outer membrane, has therefore been useful as a model for structural and functional studies. Its main proteinaceous unit, the S-layer deinoxanthin-binding complex (SDBC), is a hetero-oligomeric assembly known to contribute to the resistance against environmental stress and have porin functional features; however, its precise structure is unknown. Here, we resolved the structure of the SDBC at ∼2.5 Å resolution by cryo-EM and assigned the sequence of its main subunit, the protein DR_2577. This structure is characterized by a pore region, a massive β-barrel organization, a stalk region consisting of a trimeric coiled coil, and a collar region at the base of the stalk. We show that each monomer binds three Cu ions and one Fe ion and retains one deinoxanthin molecule and two phosphoglycolipids, all exclusive to D. radiodurans. Finally, electrophysiological characterization of the SDBC shows that it exhibits transport properties with several amino acids. Taken together, these results highlight the SDBC as a robust structure displaying both protection and sieving functions that facilitates exchanges with the environment.
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| 4. |
- Farci, Domenica, et al.
(författare)
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The structured organization of Deinococcus radiodurans' cell envelope
- 2022
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Science. - 0027-8424 .- 1091-6490. ; 119:45
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Tidskriftsartikel (refereegranskat)abstract
- Surface layers (S-layers) are highly ordered coats of proteins localized on the cell surface of many bacterial species. In these structures, one or more proteins form elementary units that self-assemble into a crystalline monolayer tiling the entire cell surface. Here, the cell envelope of the radiation-resistant bacterium Deinococcus radiodurans was studied by cryo-electron microscopy, finding the crystalline regularity of the S-layer extended into the layers below (outer membrane, periplasm, and inner membrane). The cell envelope appears to be highly packed and resulting from a three-dimensional crystalline distribution of protein complexes organized in close continuity yet allowing a certain degree of free space. The presented results suggest how S-layers, at least in some species, are mesoscale assemblies behaving as structural and functional scaffolds essential for the entire cell envelope.
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| 5. |
- Haniewicz, Patrycja, et al.
(författare)
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Isolation of monomeric photosystem II that retains the subunit PsbS.
- 2013
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Ingår i: Photosynthesis Research. - : Springer. - 0166-8595 .- 1573-5079. ; 118:3, s. 199-207
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Tidskriftsartikel (refereegranskat)abstract
- Photosystem II has been purified from a transplastomic strain of Nicotiana tabacum according to two different protocols. Using the procedure described in Piano et al. (Photosynth Res 106:221-226, 2010) it was possible to isolate highly active PSII composed of monomers and dimers but depleted in their PsbS protein content. A "milder" procedure than the protocol reported by Fey et al. (Biochim Biophys Acta 1777:1501-1509, 2008) led to almost exclusively monomeric PSII complexes which in part still bind the PsbS protein. This finding might support a role for PSII monomers in higher plants.
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