| 1. |
- Eckert, Diana, et al.
(författare)
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CO2 refixation is higher in leaves of woody species with high mesophyll and stomatal resistances to CO2 diffusion
- 2021
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Ingår i: Tree Physiology. - : Oxford University Press. - 0829-318X .- 1758-4469. ; 41:8, s. 1450-1461
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Tidskriftsartikel (refereegranskat)abstract
- The percentage of respiratory and photorespiratory CO2 refixed in leaves (P-r) represents part of the CO2 used in photosynthesis. The importance of P-r as well as differences between species and functional types are still not well investigated. In this study, we examine how P-r differs between six temperate and boreal woody species: Betula pendula, Quercus robur, Larix decidua, Pinus sylvestris, Picea abies and Vaccinium vitis-idaea. The study covers early and late successional species, deciduous broadleaves, deciduous conifers, evergreen conifers and evergreen broadleaves. We investigated whether some species or functional types had higher refixation percentages than others, whether leaf traits could predict higher P-r and whether these traits and their impact on P-r changed during growing seasons. Photosynthesis CO2 response (A/C-i)-curves, measured early, mid and late season, were used to estimate and compare P-r, mesophyll resistance (r(m)) and stomatal resistance (r(s)) to CO2 diffusion. Additionally, light images and transmission electron microscope images were used to approximate the fraction of intercellular airspace and cell wall thickness. We found that evergreens, especially late successional species, refixed a significantly higher amount of CO2 than the other species throughout the entire growing season. In addition, r(m), r(s) and leaf mass per area, traits that typically are higher in evergreen species, were also significantly, positively correlated with P-r. We suggest that this is due to higher r(m) decreasing diffusion of (photo) respiratory CO2 out of the leaf. Cell wall thickness had a positive effect on P-r and r(m), while the fraction of intercellular airspace had no effect. Both were significantly different between evergreen conifers and other types. Our findings suggest that species with a higher r(m) use a greater fraction of mitochondria-derived CO2, especially when stomatal conductance is low. This should be taken into account when modeling the overall CO2 fertilization effect for terrestrial ecosystems dominated by high r(m) species.
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| 2. |
- Laursen, Tomas, et al.
(författare)
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Characterization of a dynamic metabolon producing the defense compound dhurrin in sorghum
- 2016
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Ingår i: Science. - : American Association for the Advancement of Science. - 0036-8075 .- 1095-9203. ; 354:6314, s. 890-893
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Tidskriftsartikel (refereegranskat)abstract
- Metabolic highways may be orchestrated by the assembly of sequential enzymes into protein complexes, or metabolons, to facilitate efficient channeling of intermediates and to prevent undesired metabolic cross-talk while maintaining metabolic flexibility. Here we report the isolation of the dynamic metabolon that catalyzes the formation of the cyanogenic glucoside dhurrin, a defense compound produced in sorghum plants. The metabolon was reconstituted in liposomes, which demonstrated the importance of membrane surface charge and the presence of the glucosyltransferase for metabolic channeling. We used in planta fluorescence lifetime imaging microscopy and fluorescence correlation spectroscopy to study functional and structural characteristics of the metabolon. Understanding the regulation of biosynthetic metabolons offers opportunities to optimize synthetic biology approaches for efficient production of high-value products in heterologous hosts.
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| 3. |
- Sørensen, Danny Mollerup, et al.
(författare)
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The P5A ATPase Spf1p is stimulated by phosphatidylinositol 4-phosphate and influences cellular sterol homeostasis
- 2019
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Ingår i: Molecular Biology of the Cell. - : American Society for Cell Biology. - 1059-1524 .- 1939-4586. ; 30:9, s. 1069-1084
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Tidskriftsartikel (refereegranskat)abstract
- P5A ATPases are expressed in the endoplasmic reticulum (ER) of all eukaryotic cells, and their disruption results in severe ER stress. However, the function of these ubiquitous membrane proteins, which belong to the P-type ATPase superfamily, is unknown. We purified a functional tagged version of the Saccharomyces cerevisiae P5A ATPase Spf1p and observed that the ATP hydrolytic activity of the protein is stimulated by phosphatidylinositol 4-phosphate (PI4P). Furthermore, SPF1 exhibited negative genetic interactions with SAC1, encoding a PI4P phosphatase, and with OSH1 to OSH6, encoding Osh proteins, which, when energized by a PI4P gradient, drive export of sterols and lipids from the ER. Deletion of SPF1 resulted in increased sensitivity to inhibitors of sterol production, a marked change in the ergosterol/lanosterol ratio, accumulation of sterols in the plasma membrane, and cytosolic accumulation of lipid bodies. We propose that Spf1p maintains cellular sterol homeostasis by influencing the PI4P-induced and Osh-mediated export of sterols from the ER.
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