| 1. |
- Blomqvist, Lisa A., 1978, et al.
(författare)
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Proteomic analysis of highly purified prolamellar bodies reveals their significance in chloroplast development
- 2008
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Ingår i: Photosynthesis Research. - : Springer Science and Business Media LLC. - 0166-8595 .- 1573-5079. ; 96:1, s. 37-50
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Tidskriftsartikel (refereegranskat)abstract
- The prolamellar body (PLB) proteome of dark-grown wheat leaves was characterized. PLBs are formed not only in etioplasts but also in chloroplasts in young developing leaves during the night, yet their function is not fully understood. Highly purified PLBs were prepared from 7-day-old dark-grown leaves and identified by their spectral properties as revealed by low-temperature fluorescence spectroscopy. The PLB preparation had no contamination of extra-plastidal proteins, and only two envelope proteins were found. The PLB proteome was analysed by a combination of 1-D SDS-PAGE and nano-LC FTICR MS. The identification of chlorophyll synthase in the PLB fraction is the first time this enzyme protein was found in extracts of dark-grown plants. This finding is in agreement with its previous localization to PLBs using activity studies. NADPH:protochlorophyllide oxidoreductase A (PORA), which catalyses the reduction of protochlorophyllide to chlorophyllide, dominates the proteome of PLBs. Besides the identification of the PORA protein, the PORB protein was identified for the first time in dark-grown wheat. Altogether 64 unique proteins, representing pigment biosynthesis, photosynthetic light reaction, Calvin cycle proteins, chaperones and protein synthesis, were identified. The in number of proteins' largest group was the one involved in photosynthetic light reactions. This fact strengthens the assumption that the PLB membranes are precursors to the thylakoids and used for the formation of the photosynthetic membranes during greening. The present work is important to enhance our understanding of the significance of PLBs in chloroplast development.
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| 2. |
- Blomqvist, Lisa A., 1978, et al.
(författare)
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Proteomic analysis of the etioplast inner membranes of wheat (Triticum aestivum) by two-dimensional electrophoresis and mass spectrometry
- 2006
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317. ; 128:2, s. 368-381
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Tidskriftsartikel (refereegranskat)abstract
- The proteome of the etioplast inner membranes (EPIM) of dark-grown wheat leaves (Triticum aestivum L.) was mapped as an essential part of studies on plastid differentiation. Proteins were separated by two-dimensional gel electrophoresis and analysed with mass spectrometry (MS). Over 200 protein spots were resolved and visualized by Coomassie blue staining. More than 100 spots were submitted for subsequent mass spectrometry analyses by matrix-assisted laser desorption ionizationtime of flight (MALDI-ToF) MS, electrospray tandem MS (ESI-MS/MS) or liquid chromatographymass spectrometry (LC-MS/MS). There were 46 identified spots, from which at least 21 different proteins were identified. Among these were FtsH proteases and the peptidyl-prolyl cistrans isomerase TLP40, as well as chloroplast coupling factor subunits and extrinsic subunits of photosystem II (PSII). Of special interest is the NADPH:protochlorophyllide oxidoreductase (POR), which is the predominant protein of prolamellar bodies, where it accumulates in a highly stable ternary complex with protochlorophyllide and NADPH. This complex is known to play an important role in the formation and dispersal of prolamellar bodies. Five different isoforms of POR, with different pI values, were identified. We discuss the possibility of these isoforms being differently phosphorylated as part of the regulation of PORpigment complexes. The proteome mapping of EPIM is a crucial step in the understanding of the light-dependent transition of etioplasts to chloroplasts, and provides a basis for functional studies on factors influencing the greening process.
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| 3. |
- Blomqvist, Lisa A., 1978
(författare)
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Steady, ready, go - proteomics of etioplast inner membranes reveals a high readiness for light
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Light is essential for development of photosynthetically active chloroplasts. In the absence of light proplastids develop into etioplasts which are readily transformed into chloroplasts upon illuminat... merion. The etioplast inner membranes (EPIMs) differ significantly from those of chloroplasts regarding composition and structure. EPIMs consist of two laterally separated membrane systems, namely the three-dimensional lattice of tubular membranes, prolamellar bodies (PLBs), and the flat membranes of prothylakoids (PTs) which radiate from the PLBs. PLBs and PTs offer heterogeneity in lipid, pigment and protein composition. This thesis reports on novel proteomic studies of EPIMs and analyses of the light-dependent key enzyme in the chlorophyll biosynthesis, NADPH:protochlorophyllide oxidoreductase (POR). POR, which constitutes at least 90% of the protein content of PLBs, is known to be important for the formation of the PLB membrane structure. Light activates the POR-mediated reduction of protochlorophyllide into chlorophyllide. This event is the starting point for the dispersal of PLBs and thus the whole rebuilding of the plastid inner membranes during etioplast to chloroplast transition. POR is firmly attached to the membrane and transmembrane helix predictions show that POR is a plausible integral transmembrane protein. Proteomic analyses were performed on EPIMs isolated from well-defined sections of dark-grown wheat (Triticum aestivum) leaves. Proteins of EPIMs or subfractionated PLBs and PTs were separated and identified by mass spectrometry analyses. The proteome of PLBs and PTs reveals a far more complex protein composition than previously suggested. In total, 111 proteins were identified in PLBs and PTs. The proteins represent diverse functions such as pigment biosynthesis, photosynthesis and protein degradation. The majority of the identified proteins are directly or indirectly connected to photosynthesis, thus suggesting that PLBs and PTs are well prepared for construction of the photosynthetic apparatus. The spatial separation of certain proteins between PLBs and PTs suggests that photosystem formation is initiated in the PTs. EPIMs contain numerous proteins involved in protection against excess light. Etioplasts are steady in darkness, ready for light and well prepared to go for a fast onset of photosynthesis.
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