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Chotewutmontri P, Barkan A. Multilevel effects of light on ribosome dynamics in chloroplasts program genome-wide and psbA-specific changes in translation. PLoS Genet 2018; 14:e1007555. [PMID: 30080854 PMCID: PMC6095610 DOI: 10.1371/journal.pgen.1007555] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 08/16/2018] [Accepted: 07/11/2018] [Indexed: 11/22/2022] Open
Abstract
Plants and algae adapt to fluctuating light conditions to optimize photosynthesis, minimize photodamage, and prioritize energy investments. Changes in the translation of chloroplast mRNAs are known to contribute to these adaptations, but the scope and magnitude of these responses are unclear. To clarify the phenomenology, we used ribosome profiling to analyze chloroplast translation in maize seedlings following dark-to-light and light-to-dark shifts. The results resolved several layers of regulation. (i) The psbA mRNA exhibits a dramatic gain of ribosomes within minutes after shifting plants to the light and reverts to low ribosome occupancy within one hour in the dark, correlating with the need to replace damaged PsbA in Photosystem II. (ii) Ribosome occupancy on all other chloroplast mRNAs remains similar to that at midday even after 12 hours in the dark. (iii) Analysis of ribosome dynamics in the presence of lincomycin revealed a global decrease in the translation elongation rate shortly after shifting plants to the dark. The pausing of chloroplast ribosomes at specific sites changed very little during these light-shift regimes. A similar but less comprehensive analysis in Arabidopsis gave similar results excepting a trend toward reduced ribosome occupancy at the end of the night. Our results show that all chloroplast mRNAs except psbA maintain similar ribosome occupancy following short-term light shifts, but are nonetheless translated at higher rates in the light due to a plastome-wide increase in elongation rate. A light-induced recruitment of ribosomes to psbA mRNA is superimposed on this global response, producing a rapid and massive increase in PsbA synthesis. These findings highlight the unique translational response of psbA in mature chloroplasts, clarify which steps in psbA translation are light-regulated in the context of Photosystem II repair, and provide a foundation on which to explore mechanisms underlying the psbA-specific and global effects of light on chloroplast translation.
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Affiliation(s)
| | - Alice Barkan
- Institute of Molecular Biology, University of Oregon, Eugene, OR, United States of America
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2
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Murata N, Nishiyama Y. ATP is a driving force in the repair of photosystem II during photoinhibition. PLANT, CELL & ENVIRONMENT 2018; 41:285-299. [PMID: 29210214 DOI: 10.1111/pce.13108] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 11/21/2017] [Accepted: 11/22/2017] [Indexed: 05/15/2023]
Abstract
Repair of photosystem II (PSII) during photoinhibition involves replacement of photodamaged D1 protein by newly synthesized D1 protein. In this review, we summarize evidence for the indispensability of ATP in the degradation and synthesis of D1 during the repair of PSII. Synthesis of one molecule of the D1 protein consumes more than 1,300 molecules of ATP equivalents. The degradation of photodamaged D1 by FtsH protease also consumes approximately 240 molecules of ATP. In addition, ATP is required for several other aspects of the repair of PSII, such as transcription of psbA genes. These requirements for ATP during the repair of PSII have been demonstrated by experiments showing that the synthesis of D1 and the repair of PSII are interrupted by inhibitors of ATP synthase and uncouplers of ATP synthesis, as well as by mutation of components of ATP synthase. We discuss the contribution of cyclic electron transport around photosystem I to the repair of PSII. Furthermore, we introduce new terms relevant to the regulation of the PSII repair, namely, "ATP-dependent regulation" and "redox-dependent regulation," and we discuss the possible contribution of the ATP-dependent regulation of PSII repair under environmental stress.
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Affiliation(s)
- Norio Murata
- National Institute for Basic Biology, Okazaki, 444-8585, Japan
| | - Yoshitaka Nishiyama
- Department of Biochemistry and Molecular Biology and Institute for Environmental Science and Technology, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama, 338-8570, Japan
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3
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Sun Y, Zerges W. Translational regulation in chloroplasts for development and homeostasis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2015; 1847:809-20. [PMID: 25988717 DOI: 10.1016/j.bbabio.2015.05.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Revised: 04/13/2015] [Accepted: 05/10/2015] [Indexed: 11/16/2022]
Abstract
Chloroplast genomes encode 100-200 proteins which function in photosynthesis, the organellar genetic system, and other pathways and processes. These proteins are synthesized by a complete translation system within the chloroplast, with bacterial-type ribosomes and translation factors. Here, we review translational regulation in chloroplasts, focusing on changes in translation rates which occur in response to requirements for proteins encoded by the chloroplast genome for development and homeostasis. In addition, we delineate the developmental and physiological contexts and model organisms in which translational regulation in chloroplasts has been studied. This article is part of a Special Issue entitled: Chloroplast biogenesis.
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Affiliation(s)
- Yi Sun
- Biology Department and Center for Structural and Functional Genomics, Concordia University, 7141 Sherbrooke W., Montreal, Quebec H4B 1R6, Canada
| | - William Zerges
- Biology Department and Center for Structural and Functional Genomics, Concordia University, 7141 Sherbrooke W., Montreal, Quebec H4B 1R6, Canada.
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4
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Abstract
Overall translational machinery in plastids is similar to that of E. coli. Initiation is the crucial step for translation and this step in plastids is somewhat different from that of E. coli. Unlike the Shine-Dalgarno sequence in E. coli, cis-elements for translation initiation are not well conserved in plastid mRNAs. Specific trans-acting factors are generally required for translation initiation and its regulation in plastids. During translation elongation, ribosomes pause sometimes on photosynthesis-related mRNAs due probably to proper insertion of nascent polypeptides into membrane complexes. Codon usage of plastid mRNAs is different from that of E. coli and mammalian cells. Plastid mRNAs do not have the so-called rare codons. Translation efficiencies of several synonymous codons are not always correlated with codon usage in plastid mRNAs.
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Hu YY, Fan DY, Losciale P, Chow WS, Zhang WF. Whole-tissue determination of the rate coefficients of photoinactivation and repair of photosystem II in cotton leaf discs based on flash-induced P700 redox kinetics. PHOTOSYNTHESIS RESEARCH 2013; 117:517-528. [PMID: 23589088 DOI: 10.1007/s11120-013-9822-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 04/02/2013] [Indexed: 06/02/2023]
Abstract
Using radioactively labelled amino acids to investigate repair of photoinactivated photosystem II (PS II) gives only a relative rate of repair, while using chlorophyll fluorescence parameters yields a repair rate coefficient for an undefined, variable location within the leaf tissue. Here, we report on a whole-tissue determination of the rate coefficient of photoinactivation k i , and that of repair k r in cotton leaf discs. The method assays functional PS II via a P700 kinetics area associated with PS I, as induced by a single-turnover, saturating flash superimposed on continuous background far-red light. The P700 kinetics area, directly proportional to the oxygen yield per single-turnover, saturating flash, was used to obtain both k i and k r . The value of k i , directly proportional to irradiance, was slightly higher when CO2 diffusion into the abaxial surface (richer in stomata) was blocked by contact with water. The value of k r , sizable in darkness, changed in the light depending on which surface was blocked by contact with water. When the abaxial surface was blocked, k r first peaked at moderate irradiance and then decreased at high irradiance. When the adaxial surface was blocked, k r first increased at low irradiance, then plateaued, before increasing markedly at high irradiance. At the highest irradiance, k r differed by an order of magnitude between the two orientations, attributable to different extents of oxidative stress affecting repair (Nishiyama et al., EMBO J 20: 5587-5594, 2001). The method is a whole-tissue, convenient determination of the rate coefficient of photoinactivation k i and that of repair k r .
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Affiliation(s)
- Yuan-Yuan Hu
- The Key Laboratory of Oasis Eco-agriculture, Xinjiang Production and Construction Group, Shihezi University, Shihezi, 832003, People's Republic of China
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6
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Huang W, Zhang SB, Cao KF. The different effects of chilling stress under moderate light intensity on photosystem II compared with photosystem I and subsequent recovery in tropical tree species. PHOTOSYNTHESIS RESEARCH 2010; 103:175-82. [PMID: 20221850 DOI: 10.1007/s11120-010-9539-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2009] [Accepted: 02/20/2010] [Indexed: 05/09/2023]
Abstract
Tropical plants are sensitive to chilling temperatures above zero but it is still unclear whether photosystem I (PSI) or photosystem II (PSII) of tropical plants is mainly affected by chilling temperatures. In this study, the effect of 4 degrees C associated with various light densities on PSII and PSI was studied in the potted seedlings of four tropical evergreen tree species grown in an open field, Khaya ivorensis, Pometia tomentosa, Dalbergia odorifera, and Erythrophleum guineense. After 8 h chilling exposure at the different photosynthetic flux densities of 20, 50, 100, 150 micromol m(-2) s(-1), the maximum quantum yield of PSII (F (v) /F (m)) in all of the four species decreased little, while the quantity of efficient PSI complex (P (m)) remained stable in all species except E. guineense. However, after chilling exposure under 250 micromol m(-2) s(-1) for 24 h, F (v) /F (m) was severely photoinhibited in all species whereas P (m) was relative stable in all plants except E. guineense. At the chilling temperature of 4 degrees C, electron transport from PSII to PSI was blocked because of excessive reduction of primary electron acceptor of PSII. F (v) /F (m) in these species except E. guineense recovered to approximately 90% after 8 h recovery in low light, suggesting the dependence of the recovery of PSII on moderate PSI and/or PSII activity. These results suggest that PSII is more sensitive to chilling temperature under the moderate light than PSI in tropical trees, and the photoinhibition of PSII and closure of PSII reaction centers can serve to protect PSI.
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Affiliation(s)
- Wei Huang
- Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, 666303, Mengla, Yunnan, China.
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7
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Oguchi R, Jia H, Barber J, Chow WS. Recovery of photoinactivated photosystem II in leaves: retardation due to restricted mobility of photosystem II in the thylakoid membrane. PHOTOSYNTHESIS RESEARCH 2008; 98:621-629. [PMID: 18807208 DOI: 10.1007/s11120-008-9363-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2008] [Accepted: 09/01/2008] [Indexed: 05/26/2023]
Abstract
The functionality of photosystem II (PS II) following high-light pre-treatment of leaf segments at a chilling temperature was monitored as F(v)/F(m), the ratio of variable to maximum chlorophyll fluorescence in the dark-adapted state and a measure of the optimal photochemical efficiency in PS II. Recovery of PS II functionality in low light (LL) and at a favourable temperature was retarded by (1) water stress and (2) growth in LL, in both spinach and Alocasia macrorrhiza L. In spinach leaf segments, water stress per se affected neither F(v)/F(m) nor the ability of the adenosine triphosphate (ATP) synthase to be activated by far-red light for ATP synthesis, but it induced chloroplast shrinkage as observed in frozen and fractured samples by scanning electron microscopy. A common feature of water stress and growth of plants in LL is the enhanced anchoring of PS II complexes, either across the shrunken lumen in water-stress conditions or across the partition gap in larger grana due to growth in LL. We suggest that such enhanced anchoring restricts the mobility of PS II complexes in the thylakoid membrane system, and hence hinders the lateral migration of photoinactivated PS II reaction centres to the stroma-located ribosomes for repair.
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Affiliation(s)
- Riichi Oguchi
- Research School of Biological Sciences, The Australian National University, Canberra, ACT 0200, Australia
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8
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Translation and translational regulation in chloroplasts. CELL AND MOLECULAR BIOLOGY OF PLASTIDS 2007. [DOI: 10.1007/4735_2007_0234] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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9
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Takahashi S, Murata N. Glycerate-3-phosphate, produced by CO2 fixation in the Calvin cycle, is critical for the synthesis of the D1 protein of photosystem II. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2006; 1757:198-205. [PMID: 16551463 DOI: 10.1016/j.bbabio.2006.02.002] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2005] [Revised: 02/02/2006] [Accepted: 02/07/2006] [Indexed: 10/25/2022]
Abstract
We demonstrated recently that, in intact cells of Chlamydomonas reinhardtii, interruption of CO2 fixation via the Calvin cycle inhibits the synthesis of proteins in photosystem II (PSII), in particular, synthesis of the D1 protein, during the repair of PSII after photodamage. In the present study, we investigated the mechanism responsible for this phenomenon using intact chloroplasts isolated from spinach leaves. When CO2 fixation was inhibited by exogenous glycolaldehyde, which inhibits the phosphoribulokinase that synthesizes ribulose-1,5-bisphosphate, the synthesis de novo of the D1 protein was inhibited. However, when glycerate-3-phosphate (3-PGA), which is a product of CO2 fixation in the Calvin cycle, was supplied exogenously, the inhibitory effect of glycolaldehyde was abolished. A reduced supply of CO2 also suppressed the synthesis of the D1 protein, and this inhibitory effect was also abolished by exogenous 3-PGA. These findings suggest that the supply of 3-PGA, generated by CO2 fixation, is important for the synthesis of the D1 Protein. It is likely that 3-PGA accepts electrons from NADPH and decreases the level of reactive oxygen species, which inhibit the synthesis of proteins, such as the D1 protein.
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10
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Baena-González E, Aro EM. Biogenesis, assembly and turnover of photosystem II units. Philos Trans R Soc Lond B Biol Sci 2002; 357:1451-9; discussion 1459-60. [PMID: 12437884 PMCID: PMC1693054 DOI: 10.1098/rstb.2002.1141] [Citation(s) in RCA: 176] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Assembly of photosystem II, a multiprotein complex embedded in the thylakoid membrane, requires stoichiometric production of over 20 protein subunits. Since part of the protein subunits are encoded in the chloroplast genome and part in the nucleus, a signalling network operates between the two genetic compartments in order to prevent wasteful production of proteins. Coordinated synthesis of proteins also takes place among the chloroplast-encoded subunits, thus establishing a hierarchy in the protein components that allows a stepwise building of the complex. In addition to this dependence on assembly partners, other factors such as the developmental stage of the plastid and various photosynthesis-related parameters exert a strict control on the accumulation, membrane targeting and assembly of the PSII subunits. Here, we briefly review recent results on this field obtained with three major approaches: biogenesis of photosystem II during the development of chloroplasts from etioplasts, use of photosystem II-specific mutants and photosystem II turnover during its repair cycle.
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Affiliation(s)
- Elena Baena-González
- Department of Biology, Plant Physiology and Molecular Biology, University of Turku, FIN-20014 Turku, Finland
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11
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Abstract
The evolution of eukaryotes was punctuated by invasions of the bacteria that have evolved to mitochondria and plastids. These bacterial endosymbionts founded major eukaryotic lineages by enabling them to carry out aerobic respiration and oxygenic photosynthesis. Yet, having evolved as free-living organisms, they were at first poorly adapted organelles. Although mitochondria and plastids have integrated within the physiology of eukaryotic cells, this integration has probably been constrained by the high level of complexity of their bacterial ancestors and the inability of gradual evolutionary processes to drastically alter complex systems. Here, I review complex processes that directly involve translation of plastid mRNAs and how they could constrain transfer to the nucleus of the genes encoding them.
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Affiliation(s)
- William Zerges
- Biology Dept, Concordia University, 1455 Maisonneuve West, Montreal, Quebec, Canada H3G 1M8.
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12
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Mühlbauer SK, Eichacker LA. Light-dependent formation of the photosynthetic proton gradient regulates translation elongation in chloroplasts. J Biol Chem 1998; 273:20935-40. [PMID: 9694842 DOI: 10.1074/jbc.273.33.20935] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Upon transfer of lysed chloroplasts from darkness to light, the accumulation of membrane and stromal chloroplast proteins is strictly regulated at the level of translation elongation. In darkness, translation elongation is retarded even in the presence of exogenously added ATP and dithiothreitol. In the light, addition of the electron transport inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethyl urea inhibits translation elongation even in the presence of ATP. This inhibition can be overcome by addition of artificial electron donors in the presence of light, but not in darkness. Electron flow between photosystem II and I induced by far red light of 730 nm is sufficient for the activation of translation elongation. This activation can also be obtained by electron donors to photosystem I, which transport protons into the thylakoid lumen. Release of the proton gradient by uncouplers prevents the light-dependent activation of translation elongation. Also, the induction of translation activation is switched off rapidly upon transfer from light to darkness. Hence, we propose that the formation of a photosynthetic proton gradient across the thylakoid membrane activates translation elongation in chloroplasts.
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Affiliation(s)
- S K Mühlbauer
- Department of Botany, University of Munich, 80638 München, Menzinger Strasse 67, Federal Republic of Germany
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13
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He Q, Vermaas W. Chlorophyll a availability affects psbA translation and D1 precursor processing in vivo in Synechocystis sp. PCC 6803. Proc Natl Acad Sci U S A 1998; 95:5830-5. [PMID: 9576970 PMCID: PMC20465 DOI: 10.1073/pnas.95.10.5830] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Transcript accumulation and translation of psbA as well as processing of the D1 precursor protein were investigated in relation to chlorophyll availability in vivo in cyanobacterial strains lacking photosystem I (PS I). The psbA transcript level was almost independent of chlorophyll availability and was approximately 3-fold lower in darkness than in continuous light (5 microE m-2 s-1). Upon illumination, it reached a steady-state level within several hours. Upon growth under light-activated heterotrophic growth conditions (LAHG) in the PS I-less strain, D1 synthesis occurred immediately upon illumination. However, in PS I-less/chlL- cells, which lacked the light-independent chlorophyll biosynthesis pathway and had very low chlorophyll levels after LAHG growth, very little D1 synthesis occurred upon illumination, and the synthesis rate increased with time. This result suggests a translational control of D1 biosynthesis related to chlorophyll availability. Upon illumination, initially a high level of the nonprocessed D1 precursor was observed by pulse labeling and immunodetection in LAHG-grown PS I-less/chlL- cells but not in PS I-less cells. A significant amount of the D1 precursor eventually was processed to mature D1, and the half-life of the D1 precursor decreased as the chlorophyll content of the cells increased. The D1 processing enzyme CtpA was found to be present at similar levels regardless illumination or chlorophyll levels. We conclude that, directly or indirectly, chlorophyll availability is needed for D1 translation as well as for efficient processing of the D1 precursor.
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Affiliation(s)
- Q He
- Department of Plant Biology and Center for the Study of Early Events in Photosynthesis, Arizona State University, Box 871601, Tempe, AZ 85287-1601, USA
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14
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Hirose T, Sugiura M. Both RNA editing and RNA cleavage are required for translation of tobacco chloroplast ndhD mRNA: a possible regulatory mechanism for the expression of a chloroplast operon consisting of functionally unrelated genes. EMBO J 1997; 16:6804-11. [PMID: 9362494 PMCID: PMC1170284 DOI: 10.1093/emboj/16.22.6804] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Tobacco chloroplast genes encoding a photosystem I component (psaC) and a NADH dehydrogenase subunit (ndhD) are transcribed as a dicistronic pre-mRNA which is then cleaved into short mRNAs. An RNA protection assay revealed that the cleavage occurs at multiple sites in the intercistronic region. There are two possible initiation codons in the tobacco ndhD mRNA: the upstream AUG and the AUG created by RNA editing from the in-frame ACG located 25 nt downstream. Using the chloroplast in vitro translation system, we found that translation begins only from the edited AUG. The extent of ACG to AUG editing is partial and depends on developmental and environmental conditions. In addition, the in vitro assay showed that the psaC/ndhD dicistronic mRNA is not functional and that the intercistronic cleavage is a prerequisite for both ndhD and psaC translation. Using a series of mutant mRNAs, we showed that an intramolecular interaction between an 8 nt sequence in the psaC coding region and its complementary 8 nt sequence in the 5' ndhD UTR is the negative element for translation of the dicistronic mRNA. A possible mechanism in which the differential expression of the chloroplast operon consists of functionally unrelated genes is discussed.
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Affiliation(s)
- T Hirose
- Center for Gene Research, Nagoya University, Nagoya 464-01, Japan
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15
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Kettunen R, Pursiheimo S, Rintamäki E, Van Wijk KJ, Aro EM. Transcriptional and translational adjustments of psbA gene expression in mature chloroplasts during photoinhibition and subsequent repair of photosystem II. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 247:441-8. [PMID: 9249058 DOI: 10.1111/j.1432-1033.1997.00441.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The D1 reaction centre protein of photosystem II (PSII), encoded by the plastid psbA gene, has the highest turnover rate of all thylakoid proteins, due to light-induced damage to D1. The expression of the psbA gene was studied in chloroplasts of fully developed pea (Pisum sativum L.) leaves during high-light photoinhibitory treatment and subsequent restoration of PSII function at low light. psbA transcript levels were determined and the translational activity was followed by in vivo pulse-labelling, by in vitro translations with intact chloroplasts, and by run-off translations on isolated thylakoid membranes. PSII photochemical efficiency was determined in vivo by monitoring the ratio of variable fluorescence to maximal fluorescence (F(V)/F(M)). Enhanced D1 synthesis in pea leaves, upon a shift first from darkness to growth light and subsequently to high light, was accompanied by a substantial increase in the total number of pshA transcripts and by the accumulation of psbA mRNA x initiation complexes on thylakoid membrane. This suggested that high-light illumination increased the transcriptional activity of the psbA gene in mature leaves, and that enhanced translational initiation of psbA mRNA was followed by docking of the initiation complexes to the thylakoid membrane. The high-light-induced increase in the number of thylakoid-associated psbA mRNA x initiation complexes, occurred in parallel with enhanced in vivo D1 synthesis. This, however, did not result in an enhanced accumulation of D1 translation products in in vitro run-off translations when pea leaves were shifted from growth light to high light. This may suggest that at high light only a portion of thylakoid-associated psbA mRNA can be under translational elongation at a given moment. When the leaves were shifted from high light to low light to allow repair of PSII, thylakoid-associated psbA mRNA was rapidly released from the membrane and the high-light-induced pool of psbA transcripts was degraded. The synthesis of the D1 protein decreased on the same time scale. However, the restoration of PSII photochemical function, measured as F(V)/F(M), took a substantially longer time. It is concluded that during changing light conditions, mature leaves are able to adjust psbA gene expression both at the transcriptional and at the translational level.
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Affiliation(s)
- R Kettunen
- Department of Biology, University of Turku, Finland
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16
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van Wijk KJ, Eichacker L. Light is required for efficient translation elongation and subsequent integration of the D1-protein into photosystem II. FEBS Lett 1996; 388:89-93. [PMID: 8690097 DOI: 10.1016/0014-5793(96)00540-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The light dependence of translation and successive assembly of the D1 reaction center protein into Photosystem II subcomplexes was followed in fully developed chloroplasts isolated from the dark phase of diurnally grown spinach. The incorporation of synthesized D1 protein into Photosystem II (PSII) was analyzed by fractionation of radiolabeled unassembled protein and PSII (sub)complexes on sucrose density gradients. The ribosomes with attached nascent chains were recovered as pellets in the same gradients, and nascent chains of the D1 protein were immunoprecipitated. The analysis showed that absence of light during translation leads to an increased accumulation of polysome-bound D1 translation intermediates, indicating that light is required for efficient elongation of the D1 protein. The accumulation of the D1 protein and CP43 decreased three-fold in darkness, whereas accumulation of the D2 reaction center protein was not affected by light. In addition, light was also required for efficient incorporation of the D1 protein into the PSII core complex. In darkness, the newly synthesized D1 protein accumulated predominantly as unassembled protein or in PSII subcomplexes smaller than 100 kDa.
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Affiliation(s)
- K J van Wijk
- Department of Biochemistry, Arrhenius Laboratories, Stockholm University, Sweden
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17
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Tyystjärvi T, Mulo P, Mäenpää P, Aro EM. D1 polypeptide degradation may regulate psbA gene expression at transcriptional and translational levels in Synechocystis sp. PCC 6803. PHOTOSYNTHESIS RESEARCH 1996; 47:111-120. [PMID: 24301819 DOI: 10.1007/bf00016174] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/1995] [Accepted: 11/20/1995] [Indexed: 06/02/2023]
Abstract
Light has been suggested to regulate both synthesis and degradation of the Photosystem II (PS II) reaction centre polypeptide D1, encoded by the psbA gene. The modified degradation rate of the D1 polypeptide in site-directed Synechocystis sp PCC 6803 D1 mutants CA1 [del(E242-E244);Q241H], E243K and E229D has provided a tool to determine whether the rate of D1 polypeptide synthesis is directly regulated by light-intensity-related factors or by a control mechanism mediated by light-dependent degradation of the D1 polypeptide. In vivo accumulation of [(35)S] methionine into the D1 polypeptide was found to correlate with D1 polypeptide degradation rather than with incident irradiance. This suggests that the degradation rate of the D1 polypeptide regulates its own synthesis at translational level. Furthermore, several fold differences in the psbA mRNA levels were measured between D1 mutant strains, indicating that the psbA gene transcription is not solely under light control.
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Affiliation(s)
- T Tyystjärvi
- Department of Biology, University of Turku, BioCity A 6th floor, Tykistökatu 6, FIN-20520, Turku, Finland
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18
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van Wijk KJ, Knott TG, Robinson C. Evidence for SecA- and delta pH-independent insertion of D1 into thylakoids. FEBS Lett 1995; 368:263-6. [PMID: 7628618 DOI: 10.1016/0014-5793(95)00668-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Many nuclear-encoded proteins are targeted into chloroplast thylakoids by an azide sensitive Sec-related mechanism or by a delta pH-driven mechanism. In this report, the requirements for the integration of chloroplast-encoded thylakoid proteins have been analysed in pulse-labeled intact chloroplasts. We show that the integration of the photosystem II reaction centre protein, D1, continues in the absence of a delta pH and in the presence of azide. A range of other proteins are similarly targeted to thylakoids in the presence of azide, suggesting that the SecA-related mechanism is not widely used for the targeting of chloroplast-encoded proteins.
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Affiliation(s)
- K J van Wijk
- Department of Biological Sciences, University of Warwick, Coventry, UK
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Nixon PJ, Komenda J, Barber J, Deak Z, Vass I, Diner BA. Deletion of the PEST-like region of photosystem two modifies the QB-binding pocket but does not prevent rapid turnover of D1. J Biol Chem 1995; 270:14919-27. [PMID: 7797471 DOI: 10.1074/jbc.270.25.14919] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The rapid turn-over of the D1 polypeptide of the photosystem two complex has been suggested to be due to the presence of a "PEST"-like sequence located between putative transmembrane helices IV and V of D1 (Greenberg, B. M., Gaba, V., Mattoo, A. K. and Edelman, M. (1987) EMBO J. 6, 2865-2869). We have tested this hypothesis by constructing a deletion mutant (delta 226-233) of the cyanobacterium Synechocystis sp. PCC 6803 in which residues 226-233 of the D1 polypeptide, containing the PEST-like sequence, have been removed. The resulting mutant, delta PEST, is able to grow photoautotrophically and give light-saturated rates of oxygen at wild type levels. However electron transfer on the acceptor side of the complex is perturbed. Analysis of cells by thermoluminescence and by monitoring the decay in quantum yield of variable fluorescence following saturating flash excitation indicates that Q-B, but not Q-A, is destabilized in this mutant. Electron transfer on the donor side of photosystem two remains largely unchanged in the mutant. Turnover of the D1 polypeptide as examined by pulse-chase experiments using [35S]methionine was enhanced in the delta PEST mutant compared to strain TC31 which is the wild type control. We conclude that the PEST sequence is not absolutely required for turnover of the D1 polypeptide in vivo although deletion of residues 226-233 does have an effect on the redox equilibrium between QA and QB.
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Affiliation(s)
- P J Nixon
- Wolfson Laboratories, Biochemistry Department, Imperial College of Science, Technology and Medicine, London, United Kingdom
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van Wijk KJ, Nilsson LO, Styring S. Synthesis of reaction center proteins and reactivation of redox components during repair of photosystem II after light-induced inactivation. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)46939-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Cánovas PM, Barber J. Detection of a 10 kDa breakdown product containing the C-terminus of the D1-protein in photoinhibited wheat leaves suggests an acceptor side mechanism. FEBS Lett 1993; 324:341-4. [PMID: 8405378 DOI: 10.1016/0014-5793(93)80147-m] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Photoinhibition of intact leaves of wheat generates a 10 kDa breakdown product which is clearly observed both at 4 degrees C and 25 degrees C. Selective immunoblotting has shown that the 10 kDa fragment contains the C-terminus of the D1-protein and, under the conditions employed, supports an acceptor side mechanism for photoinhibition in vivo. Although a corresponding 23 kDa N-terminal D1-fragment was not detected our results are consistent with the argument that the primary cleavage site is in the loop joining putative transmembrane segments IV and V.
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Affiliation(s)
- P M Cánovas
- Wolfson Laboratories, Biochemistry Department, Imperial College of Science, Technology and Medicine, London, UK
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