| 1. |
- Fan, Kaijian, et al.
(författare)
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The pentatricopeptide repeat protein EMP603 is required for the splicing of mitochondrial Nad1 intron 2 and seed development in maize
- 2021
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Ingår i: Journal of Experimental Botany. - : Oxford University Press (OUP). - 0022-0957 .- 1460-2431. ; 72:20, s. 6933-6948
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Tidskriftsartikel (refereegranskat)abstract
- Intron splicing is an essential event in post-transcriptional RNA processing in plant mitochondria, which requires the participation of diverse nuclear-encoded splicing factors. However, it is presently unclear how these proteins cooperatively take part in the splicing of specific introns. In this study, we characterized a nuclear-encoded mitochondrial P-type pentatricopeptide repeat (PPR) protein named EMP603. This protein is essential for splicing of intron 2 in the Nad1 gene and interacts with the mitochondria-localized DEAD-box RNA helicase PMH2-5140, the RAD52-like proteins ODB1-0814 and ODB1-5061, and the CRM domain-containing protein Zm-mCSF1. Further study revealed that the N-terminal region of EMP603 interacts with the DEAD-box of PMH2-5140, the CRM domain of Zm-mCSF1, and OBD1-5061, but not with OBD1-0814, whereas the PPR domain of EMP603 can interact with ODB1-0814, ODB1-5061, and PMH2-5140, but not with Zm-mCSF1. Defects in EMP603 severely disrupt the assembly and activity of mitochondrial complex I, leading to impaired mitochondrial function, and delayed seed development. The interactions revealed between EMP603 and PMH2-5140, ODB1-0814, ODB1-5061, and Zm-mCSF1 indicate a possible involvement of a dynamic 'spliceosome-like' complex in intron splicing, and may accelerate the elucidation of the intron splicing mechanism in plant mitochondria.
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| 2. |
- Hao, Meng-Shu, et al.
(författare)
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The Ca2+-Regulation of the Mitochondrial External NADPH Dehydrogenase in Plants Is Controlled by Cytosolic pH
- 2015
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:9
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Tidskriftsartikel (refereegranskat)abstract
- NADPH is a key reductant carrier that maintains internal redox and antioxidant status, and that links biosynthetic, catabolic and signalling pathways. Plants have a mitochondrial external NADPH oxidation pathway, which depends on Ca2+ and pH in vitro, but concentrations of Ca2+ needed are not known. We have determined the K-0.5(Ca2+) of the external NADPH dehydrogenase from Solanum tuberosum mitochondria and membranes of E. coli expressing Arabidopsis thaliana NDB1 over the physiological pH range using O-2 and decylubiquinone as electron acceptors. The K-0.5(Ca2+) of NADPH oxidation was generally higher than for NADH oxidation, and unlike the latter, it depended on pH. At pH 7.5, K-0.5(Ca2+) for NADPH oxidation was high (approximate to 100 mu M), yet 20-fold lower K-0.5(Ca2+) values were determined at pH 6.8. Lower K-0.5(Ca2+) values were observed with decylubiquinone than with O-2 as terminal electron acceptor. NADPH oxidation responded to changes in Ca2+ concentrations more rapidly than NADH oxidation did. Thus, cytosolic acidification is an important activator of external NADPH oxidation, by decreasing the Ca2+-requirements for NDB1. The results are discussed in relation to the present knowledge on how whole cell NADPH redox homeostasis is affected in plants modified for the NDB1 gene.
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| 3. |
- Ren, Zhenjing, et al.
(författare)
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Tetratricopeptide-containing SMALL KERNEL 11 is essential for the assembly of cytochrome c oxidase in maize mitochondria
- 2023
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 192:1, s. 170-187
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Tidskriftsartikel (refereegranskat)abstract
- Assembly of the functional complexes of the mitochondrial respiratory chain requires sophisticated and efficient regulatory mechanisms. In plants, the subunit composition and assembly factors involved in the biogenesis of cytochrome c oxidase (complex IV) are substantially less defined than in mammals and yeast. In this study, we cloned maize (Zea mays) Small kernel 11 (Smk11) via map-based cloning. Smk11 encodes a mitochondria-localized tetratricopeptide repeat protein. Disruption of Smk11 severely affected the assembly and activity of mitochondrial complex IV, leading to delayed plant growth and seed development. Protein interactions studies revealed that SMK11 might interact with four putative complex IV assembly factors, Inner membrane peptidase 1A (ZmIMP1A), MYB domain protein 3R3 (ZmMYB3R-3), cytochrome c oxidase 23 (ZmCOX23), and mitochondrial ferredoxin 1 (ZmMFDX1), among which ZmMFDX1 might interact with subunits ZmCOX6a and ZmCOX-X1; ZmMYB3R-3 might also interact with ZmCOX6a. The mutation of SMK11 perturbed the normal assembly of these subunits, leading to the inactivation of complex IV. The results of this study revealed that SMK11 serves as an accessory assembly factor required for the normal assembly of subunits into complex IV, which will accelerate the elucidation of the assembly of complex IV in plant mitochondria.
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| 4. |
- Yao, Yunjun, et al.
(författare)
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Assessment and simulation of global terrestrial latent heat flux by synthesis of CMIP5 climate models and surface eddy covariance observations
- 2016
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Ingår i: Agricultural and Forest Meteorology. - : Elsevier BV. - 0168-1923. ; 223, s. 151-167
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Tidskriftsartikel (refereegranskat)abstract
- The latent heat flux (LE) between the terrestrial biosphere and atmosphere is a major driver of the global hydrological cycle. In this study, we evaluated LE simulations by 45 general circulation models (GCMs) in the Coupled Model Intercomparison Project Phase 5 (CMIP5) by a comparison with eddy covariance (EC) observations from 240 globally distributed sites from 2000 to 2009. In addition, we improved global terrestrial LE estimates for different land cover types by synthesis of seven best CMIP5 models and EC observations based on a Bayesian model averaging (BMA) method. The comparison results showed substantial differences in monthly LE among all GCMs. The model CESM1-CAM5 has the best performance with the highest predictive skill and a Taylor skill score (S) from 0.51-0.75 for different land cover types. The cross-validation results illustrate that the BMA method has improved the accuracy of the CMIP5 GCM's LE simulation with a decrease in the averaged root-mean-square error (RMSE) by more than 3 W/m2 when compared to the simple model averaging (SMA) method and individual GCMs. We found an increasing trend in the BMA-based global terrestrial LE (slope of 0.018 W/m2 yr-1, p <0.05) during the period 1970-2005. This variation may be attributed directly to the inter-annual variations in air temperature (Ta), surface incident solar radiation (Rs) and precipitation (P). However, our study highlights a large difference from previous studies in a continuous increasing trend after 1998, which may be caused by the combined effects of the variations of Rs, Ta, and P on LE for different models on these time scales. This study provides corrected-modeling evidence for an accelerated global water cycle with climate change.
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| 5. |
- Liu, Yunjun, et al.
(författare)
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A Redox-Mediated Modulation of Stem Bolting in Transgenic Nicotiana sylvestris Differentially Expressing the External Mitochondrial NADPH Dehydrogenase.
- 2009
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 1532-2548. ; 150, s. 1248-1259
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Tidskriftsartikel (refereegranskat)abstract
- Cytosolic NADPH can be directly oxidized by a calcium-dependent NADPH dehydrogenase, NDB1, present in the plant mitochondrial electron transport chain. However, little is known regarding the impact of modified cytosolic NADPH reduction levels on growth and metabolism. Nicotiana sylvestris plants overexpressing potato NDB1 displayed early bolting whereas sense-suppression of the same gene led to delayed bolting, with consequential changes in flowering time. The phenotype was dependent on light irradiance, but not linked to any change in biomass accumulation. Whereas the leaf NADPH/NADP(+)-ratio was unaffected, the stem NADPH/NADP(+)-ratio was altered following the genetic modification and strongly correlated to the bolting phenotype. Metabolic profiling of the stem displayed that the NADP(H) change affected relatively few, albeit central, metabolites, including 2-oxoglutarate, glutamate, ascorbate, sugars and hexose phosphates. Consistent with the phenotype, the modified NDB1 level also affected expression of putative floral meristem identity genes of the SQUAMOSA and LEAFY types. Further evidence for involvement of the NADPH redox in stem development was seen in the distinct decrease in the stem apex NADPH/NADP(+)-ratio during bolting. Additionally, the potato NDB1 protein was specifically detected in mitochondria, and a survey of its abundance in major organs revealed that the highest levels are present in green stems. The results thus strongly suggest that NDB1 in the mitochondrial electron transport chain can, by modifying cell redox levels, specifically affect developmental processes.
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| 6. |
- Liu, Yunjun, et al.
(författare)
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The mitochondrial external NADPH dehydrogenase modulates the leaf NADPH/NADP+ ratio in transgenic Nicotiana sylvestris
- 2008
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Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 1471-9053 .- 0032-0781. ; 49:1, s. 251-263
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Tidskriftsartikel (refereegranskat)abstract
- Plant mitochondria contain alternative external NAD(P)H dehydrogenases, which oxidise cytosolic NADH or NADPH and reduce ubiquinone without inherent linkage to proton pumping and ATP production. In potato, St-NDB1 is an external Ca2+-dependent NADPH dehydrogenase. The physiological function of this enzyme was investigated in homozygous Nicotiana sylvestris lines overexpressing St-ndb1 and co-suppressing St-ndb1 and an N. sylvestris ndb1. In leaf mitochondria isolated from the overexpressor lines, higher activity of alternative oxidase (AOX) was detected. However, the AOX induction was substantially weaker than in the complex I deficient CMSII mutant, previously shown to contain elevated amounts of NAD(P)H dehydrogenases and AOX. An aox1b and an aox2 gene were up-regulated in CMSII, but only aox1b showed a response, albeit smaller, in the transgenic lines, indicating differences in AOX activation between the genotypes. As in CMSII, the increase of AOX in the overexpressing lines was not due to a general oxidative stress. The lines overexpressing St-ndb1 had consistently lowered leaf NADPH/NADP+ ratios in the light and variably decreased levels in darkness, but unchanged NADH/NAD+ ratios. CMSII instead had similar NADPH/NADP+ and lower NADH/NAD+ ratios than wildtype. These results demonstrate that St-NDB1 is able to modulate the cellular balance of NADPH and NADP+ at least in the day and that reduction of NADP(H) and NAD(H) is independently controlled. Similar growth rates, chloroplast malate dehydrogenase activation and xanthophyll ratios indicate that the change in reduction does not communicate to the chloroplast, and that the cell tolerates significant changes in NADP(H) reduction without deleterious effects.
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