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Kamat PK, Rai S, Swarnkar S, Shukla R, Nath C. Molecular and Cellular Mechanism of Okadaic Acid (OKA)-Induced Neurotoxicity: A Novel Tool for Alzheimer’s Disease Therapeutic Application. Mol Neurobiol 2014; 50:852-65. [DOI: 10.1007/s12035-014-8699-4] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2013] [Accepted: 03/24/2014] [Indexed: 12/31/2022]
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Huang J, Qin F, Zang G, Kang Z, Zou H, Hu F, Yue C, Li X, Wang G. Mutation of OsDET1 increases chlorophyll content in rice. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2013; 210:241-249. [PMID: 23849131 DOI: 10.1016/j.plantsci.2013.06.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2013] [Revised: 05/27/2013] [Accepted: 06/02/2013] [Indexed: 06/02/2023]
Abstract
As an important agronomic trait, the chlorophyll (Chl) content is closely related to photosynthesis in plants. A rice mutant Gc (Oryza sativa indica) was characterized previously by its enhanced Chl content (Chl b and total Chl) and exaggerated photosynthetic rate. Here, we describe the enhanced Chl content was caused by a mutation in the rice homolog of the DE-ETIOLATED1 (DET1) known to be involved in light transduction and morphogenesis in Arabidopsis and tomato. Sequence analysis revealed that the Gc mutant carried two fragment-insertions and a fragment-deletion upstream of the start codon of OsDET1, which led to enhance mRNA levels of OsDET1. Besides, the Gc mutant harbored a single T-to-C base transversion in the seventh exon of OsDET1, which resulted in leucine(328) to serine(328) localized in the highly conserved region. Genetic complementation demonstrated that OsDET1 mutation conferred the enhanced Chl content in the Gc mutant leaf. OsDET1 was richly expressed in green tissues, and its expression seems to be under circadian control. OsDET1-GFP fusion protein in onion epidermal cells showed that OsDET1 localized to the nucleus. These results indicated that OsDET1 mutation in Gc mutant increases Chl content in rice, which might be fundamental for enhanced photoresponsiveness.
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Affiliation(s)
- Junli Huang
- Key Laboratory of Biorheological Science and Technology, Ministry of Education, Bioengineering College, Chongqing University, 174 Shazheng Street, Shapingba District, Chongqing 400030, China
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Liere K, Weihe A, Börner T. The transcription machineries of plant mitochondria and chloroplasts: Composition, function, and regulation. JOURNAL OF PLANT PHYSIOLOGY 2011; 168:1345-60. [PMID: 21316793 DOI: 10.1016/j.jplph.2011.01.005] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2010] [Revised: 01/07/2011] [Accepted: 01/10/2011] [Indexed: 05/04/2023]
Abstract
Although genomes of mitochondria and plastids are very small compared to those of their bacterial ancestors, the transcription machineries of these organelles are of surprising complexity. With respect to the number of different RNA polymerases per organelle, the extremes are represented on one hand by chloroplasts of eudicots which use one bacterial-type RNA polymerase and two phage-type RNA polymerases to transcribe their genes, and on the other hand by Physcomitrella possessing three mitochondrial RNA polymerases of the phage type. Transcription of genes/operons is often driven by multiple promoters in both organelles. This review describes the principle components of the transcription machineries (RNA polymerases, transcription factors, promoters) and the division of labor between the different RNA polymerases. While regulation of transcription in mitochondria seems to be only of limited importance, the plastid genes of higher plants respond to exogenous and endogenous cues rather individually by altering their transcriptional activities.
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Affiliation(s)
- Karsten Liere
- Institut für Biologie/Genetik, Humboldt-Universität zu Berlin, Chausseestrasse 117, Berlin, Germany
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Schweer J, Türkeri H, Link B, Link G. AtSIG6, a plastid sigma factor from Arabidopsis, reveals functional impact of cpCK2 phosphorylation. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2010; 62:192-202. [PMID: 20088902 PMCID: PMC2988416 DOI: 10.1111/j.1365-313x.2010.04138.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2009] [Accepted: 12/23/2009] [Indexed: 05/17/2023]
Abstract
Plastids contain sigma factors, i.e. gene-regulatory proteins for promoter binding and transcription initiation. Despite the physical and functional similarity shared with their prokaryotic counterparts, the plant sigma factors have distinguishing features: most notably the existence of a variable extra sequence comprising their N-terminal portions. This distinct architecture is reflected by functional differences, including phosphorylation control by organellar protein kinase(s) closely related to nucleocytosolic, rather than bacterial-type, enzymes. In particular, cpCK2, a nuclear-coded plastid-targeted casein kinase 2, has been implicated as a key component in plant sigma factor phosphorylation and transcriptional regulation (Eur. J. Biochem. 269, 2002, 3329; Planta, 219, 2004, 298). Although this notion is based mainly on biochemical evidence and in vitro systems, the recent availability of Arabidopsis sigma knock-out lines for complementation by intact and mutant sigma cDNAs has opened up new strategies for the study of transcription regulatory mechanisms in vivo. Using Arabidopsis sigma factor 6 (AtSIG6) as a paradigm, we present data suggesting that: (i) this factor is a substrate for regulatory phosphorylation by cpCK2 both in vitro and in vivo; (ii) cpCK2 phosphorylation of SIG6 occurs at multiple sites, which can widely differ in their effect on the visual and/or molecular phenotype; (iii) in vivo usage of the perhaps most critical cpCK2 site defined by Ser174 requires (pre-)phosphorylation at the n + 3 serine residue Ser177, pointing to 'pathfinder' kinase activity capable of generating a functional cpCK2 substrate site.
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Affiliation(s)
| | | | | | - Gerhard Link
- *For correspondence (fax: +49 234 321 4188; e-mail )
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Pedmale UV, Liscum E. Regulation of Phototropic Signaling in Arabidopsis via Phosphorylation State Changes in the Phototropin 1-interacting Protein NPH3. J Biol Chem 2007; 282:19992-20001. [PMID: 17493935 DOI: 10.1074/jbc.m702551200] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phototropism, or the directional growth (curvature) of various organs toward or away from incident light, represents a ubiquitous adaptive response within the plant kingdom. This response is initiated through the sensing of directional blue light (BL) by a small family of photoreceptors known as the phototropins. Of the two phototropins present in the model plant Arabidopsis thaliana, phot1 (phototropin 1) is the dominant receptor controlling phototropism. Absorption of BL by the sensory portion of phot1 leads, as in other plant phototropins, to activation of a C-terminal serine/threonine protein kinase domain, which is tightly coupled with phototropic responsiveness. Of the five phot1-interacting proteins identified to date, only one, NPH3 (non-phototropic hypocotyl 3), is essential for all phot1-dependent phototropic responses, yet little is known about how phot1 signals through NPH3. Here, we show that, in dark-grown seedlings, NPH3 exists as a phosphorylated protein and that BL stimulates its dephosphorylation. phot1 is necessary for this response and appears to regulate the activity of a type 1 protein phosphatase that catalyzes the reaction. The abrogation of both BL-dependent dephosphorylation of NPH3 and development of phototropic curvatures by protein phosphatase inhibitors further suggests that this post-translational modification represents a crucial event in phot1-dependent phototropism. Given that NPH3 may represent a core component of a CUL3-based ubiquitin-protein ligase (E3), we hypothesize that the phosphorylation state of NPH3 determines the functional status of such an E3 and that differential regulation of this E3 is required for normal phototropic responsiveness.
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Affiliation(s)
- Ullas V Pedmale
- Division of Biological Sciences and the Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, Missouri 65211, USA
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6
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Transcription and transcriptional regulation in plastids. CELL AND MOLECULAR BIOLOGY OF PLASTIDS 2007. [DOI: 10.1007/4735_2007_0232] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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Irihimovitch V, Stern DB. The sulfur acclimation SAC3 kinase is required for chloroplast transcriptional repression under sulfur limitation in Chlamydomonas reinhardtii. Proc Natl Acad Sci U S A 2006; 103:7911-6. [PMID: 16672369 PMCID: PMC1472544 DOI: 10.1073/pnas.0511042103] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Sulfur (S) deprivation responses have been studied extensively in algae and land plants; however, little is known of the signals that link perception of S status to chloroplast gene expression. Here, we have compared the chloroplast S limitation response in WT vs. sac1 and sac3 sulfur acclimation mutants of the green alga Chlamydomonas reinhardtii. We provide evidence that in the WT, chloroplast transcriptional activity rapidly decreases after removal of S from the medium, leading to reduced transcript accumulation. This decrease correlates with reduced abundance of a sigma70-like factor, Sig1, which is most likely the unique chloroplast transcription specificity factor. We further show that reduced transcription activity and diminished Sig1 accumulation are mediated by the SAC3 gene product, a putative Snf1-type Ser/Thr kinase previously shown to have both positive and negative effects on nuclear gene expression. Inclusion of the protein kinase inhibitor 6-dimethylaminopurine during S limitation yielded a pattern of expression that was largely similar to that seen in the sac3 mutant, lending support to the hypothesis that Sac3 kinase activation leads to transcriptional repression and Sig1 proteolysis. The finding that Sac3 regulates chloroplast gene expression suggests that it has a previously unknown role in integrating the S limitation response in multiple subcellular compartments.
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Affiliation(s)
- Vered Irihimovitch
- Boyce Thompson Institute for Plant Research, Cornell University, Tower Road, Ithaca, NY 14853
| | - David B. Stern
- Boyce Thompson Institute for Plant Research, Cornell University, Tower Road, Ithaca, NY 14853
- *To whom correspondence should be addressed. E-mail:
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Shiina T, Tsunoyama Y, Nakahira Y, Khan MS. Plastid RNA polymerases, promoters, and transcription regulators in higher plants. INTERNATIONAL REVIEW OF CYTOLOGY 2005; 244:1-68. [PMID: 16157177 DOI: 10.1016/s0074-7696(05)44001-2] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Plastids are semiautonomous plant organelles exhibiting their own transcription-translation systems that originated from a cyanobacteria-related endosymbiotic prokaryote. As a consequence of massive gene transfer to nuclei and gene disappearance during evolution, the extant plastid genome is a small circular DNA encoding only ca. 120 genes (less than 5% of cyanobacterial genes). Therefore, it was assumed that plastids have a simple transcription-regulatory system. Later, however, it was revealed that plastid transcription is a multistep gene regulation system and plays a crucial role in developmental and environmental regulation of plastid gene expression. Recent molecular and genetic approaches have identified several new players involved in transcriptional regulation in plastids, such as multiple RNA polymerases, plastid sigma factors, transcription regulators, nucleoid proteins, and various signaling factors. They have provided novel insights into the molecular basis of plastid transcription in higher plants. This review summarizes state-of-the-art knowledge of molecular mechanisms that regulate plastid transcription in higher plants.
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Affiliation(s)
- Takashi Shiina
- Faculty of Human Environment, Kyoto Prefectural University, Kyoto 606-8522, Japan
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Zerges W, Wang S, Rochaix JD. Light activates binding of membrane proteins to chloroplast RNAs in Chlamydomonas reinhardtii. PLANT MOLECULAR BIOLOGY 2002; 50:573-585. [PMID: 12369632 DOI: 10.1023/a:1020246007858] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Several membrane proteins were previously shown to bind to the 5' leader of the chloroplast psbC mRNA in the unicellular eukaryotic alga Chlamydomonas reinhardtii. This study showed that these proteins have affinity for AU-rich RNAs, as determined by competition experiments. In addition, their binding activities are enhanced 13-15-fold by light, and a 46 kDa protein is activated within 1-10 min. This activation could be mediated by the modulation of ADP pools by the light-dependent reactions of photosynthesis and ATP synthase because (1) two inhibitors that block ATP synthesis also prevent this activation and (2) ADP inhibits the RNA-binding activity of this protein in vitro. An inhibitor of Photosystem II diminishes this induction, suggesting that reducing potential generated by the photosynthetic electron transport chain modulates this RNA-binding activity. The RNA-binding activities of two proteins (of 46 and 47 kDa) are inhibited by Mg-protoporphyrin IX methyl ester in vitro suggesting they could be regulated by these intermediates in the chlorophyll biosynthetic pathway.
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Affiliation(s)
- William Zerges
- Biology Department, Concordia University, Montreal, Canada.
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Tsunoyama Y, Morikawa K, Shiina T, Toyoshima Y. Blue light specific and differential expression of a plastid sigma factor, Sig5 in Arabidopsis thaliana. FEBS Lett 2002; 516:225-8. [PMID: 11959137 DOI: 10.1016/s0014-5793(02)02538-3] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The transcription of plastid gene psbD is under the control of the BLRP (blue-light-responsive promoter) recognized by plastid-encoded RNA polymerase, in which nuclear-encoded sigma factors play a crucial role in the promoter recognition. We examined the effects of light on mRNA levels of six different SIG genes in Arabidopsis and found that blue light extensively induced the accumulation of SIG5 transcripts, but red light did not. The blue light specificity was not observed in the accumulations of remaining five SIG genes. The blue light dependency of the SIG5 expression well explains the light-dependent behavior of the psbD BLRP.
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Affiliation(s)
- Yuichi Tsunoyama
- Radioisotope Research Center, Kyoto University, Kitashirakawa-oiwake-cho, Kyoto 606-8502, Sakyo-ku, Japan
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Thum KE, Kim M, Christopher DA, Mullet JE. Cryptochrome 1, cryptochrome 2, and phytochrome a co-activate the chloroplast psbD blue light-responsive promoter. THE PLANT CELL 2001; 13:2747-60. [PMID: 11752385 PMCID: PMC139486 DOI: 10.1105/tpc.010345] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2001] [Accepted: 09/07/2001] [Indexed: 05/20/2023]
Abstract
The reaction center core of photosystem II is composed of two chlorophyll binding proteins, D1 and D2, that are encoded by the chloroplast genes psbA and psbD. These chlorophyll binding proteins are damaged during photochemistry, especially under high irradiance. Photosystem II function is maintained under these conditions through turnover and resynthesis of D1 and D2. Blue light-activated transcription of psbD from a special light-responsive promoter is part of the repair system. In this study, light-activated chloroplast and psbD transcription were studied after dark adaptation of 21-day-old light-grown Arabidopsis plants. Illumination of dark-adapted plants with red light increased chloroplast transcription activity and transcription from the psbD light-responsive promoter. Blue light further increased chloroplast transcription activity and stimulated differential transcription from the psbD light-responsive promoter. Photoreceptor mutants showed that blue light-specific activation of chloroplast transcription and the psbD light-responsive promoter involve cryptochrome 1 (cry1) or cryptochrome 2 (cry2) and phytochrome A (phyA). Blue light-induced activation of the psbD light-responsive promoter was normal in det2-1 and hy5-1 but attenuated in det3-1. Therefore, cry1/cry2/phyA-mediated blue light activation of the psbD light-responsive promoter in 21-day-old Arabidopsis plants does not involve hy5, a transcription factor that mediates other phyA and blue light-induced responses.
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Affiliation(s)
- K E Thum
- Department of Biochemistry and Biophysics, Texas A & M University, College Station, Texas 77843, USA
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12
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Thum KE, Kim M, Christopher DA, Mullet JE. Cryptochrome 1, cryptochrome 2, and phytochrome a co-activate the chloroplast psbD blue light-responsive promoter. THE PLANT CELL 2001. [PMID: 11752385 DOI: 10.1105/tpc.13.12.2747] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The reaction center core of photosystem II is composed of two chlorophyll binding proteins, D1 and D2, that are encoded by the chloroplast genes psbA and psbD. These chlorophyll binding proteins are damaged during photochemistry, especially under high irradiance. Photosystem II function is maintained under these conditions through turnover and resynthesis of D1 and D2. Blue light-activated transcription of psbD from a special light-responsive promoter is part of the repair system. In this study, light-activated chloroplast and psbD transcription were studied after dark adaptation of 21-day-old light-grown Arabidopsis plants. Illumination of dark-adapted plants with red light increased chloroplast transcription activity and transcription from the psbD light-responsive promoter. Blue light further increased chloroplast transcription activity and stimulated differential transcription from the psbD light-responsive promoter. Photoreceptor mutants showed that blue light-specific activation of chloroplast transcription and the psbD light-responsive promoter involve cryptochrome 1 (cry1) or cryptochrome 2 (cry2) and phytochrome A (phyA). Blue light-induced activation of the psbD light-responsive promoter was normal in det2-1 and hy5-1 but attenuated in det3-1. Therefore, cry1/cry2/phyA-mediated blue light activation of the psbD light-responsive promoter in 21-day-old Arabidopsis plants does not involve hy5, a transcription factor that mediates other phyA and blue light-induced responses.
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Affiliation(s)
- K E Thum
- Department of Biochemistry and Biophysics, Texas A & M University, College Station, Texas 77843, USA
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Chang SC, Cho MH, Kang BG, Kaufman PB. Changes in starch content in oat (Avena sativa) shoot pulvini during the gravitropic response. JOURNAL OF EXPERIMENTAL BOTANY 2001; 52:1029-1040. [PMID: 11432919 DOI: 10.1093/jexbot/52.358.1029] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In order to determine if components of the signal transduction pathway are involved in starch metabolism during the gravitropic response, the effects of inhibitors of phosphoprotein phosphatases and protein kinases (OA), and calcium channel blockers (LaCl3), on gravitropic bending and starch levels in gravisensitive node/pulvini of oat shoots were examined. Among the compounds tested, okadaic acid (OA) and lanthanum chloride (LaCl3) showed the strongest inhibitory effects on the negative gravitropic curvature response in oat shoot node/pulvini. At the same time, they caused a rapid loss of starch in graviresponding pulvini based on a quantitative analysis of starch levels in the bending tissues over 48 h periods. These two compounds act initially to block the net increase in starch content that occurs during the early stages (0-9 h) in graviresponding oat shoot pulvini. As a result, starch levels drop precipitously in shoots treated with OA and LaCl3, starting at time zero of gravistimulation by reorientation. These findings suggest that protein dephosphorylation and calcium play a role in starch metabolism in oat shoot pulvini in response to a gravistimulation signal. They also indicate that the amount of starch present in the chloroplast gravisensors in oat shoot pulvini may determine the rate of upward bending in graviresponding pulvini.
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Affiliation(s)
- S C Chang
- Molecular, Cellular and Developmental Biology Group, Department of Biology, University of Michigan, Ann Arbor, Michigan 48109-1048, USA
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Kovacheva S, Ryberg M, Sundqvist C. ADP/ATP and protein phosphorylation dependence of phototransformable protochlorophyllide in isolated etioplast membranes. PHOTOSYNTHESIS RESEARCH 2000; 64:127-36. [PMID: 16228451 DOI: 10.1023/a:1006451824312] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The effects of modulated ADP/ATP and NADPH/NADP(+) ratios, and of protein kinase inhibitors, on the in vitro reformation of phototransformable protochlorophyllide, i.e. the aggregated ternary complexes between NADPH, protochlorophyllide, and NADPH-protochlorophyllide oxidoreductase (POR, EC 1.3.1.33), in etioplast membranes isolated from dark-grown wheat (Triticum aestivum) were investigated. Low temperature fluorescence emission spectra (-196 degrees C) were used to determine the state of the pigments. The presence of spectral intermediates of protochlorophyllide and the reformation of phototransformable protochlorophyllide were reduced at high ATP, but favoured by high ADP. Increased ADP level partly prevented the chlorophyllide blue-shift. The protein kinase inhibitor K252a prevented reformation of phototransformable protochlorophyllide without showing any effect on the chlorophyllide blue-shift. Addition of NADPH did not overcome the inhibition. The results indicate that protein phosphorylation plays a role in the conversion of the non-phototransformable protochlorophyllide to POR-associated phototransformable protochlorophyllide. The possible presence of a plastid ADP-dependent kinase, the activity of which favours the formation of PLBs, is discussed. Reversible protein phosphorylation is suggested as a regulatory mechanism in the prolamellar body formation and its light-dependent dispersal by affecting the membrane association of POR. By the presence of a high concentration of phototransformable protochlorophyllide, prolamellar bodies can act as light sensors for plastid development. The modulation of plastid protein kinase and protein phosphatase activities by the NADPH/NADP(+) ratio is suggested.
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Affiliation(s)
- S Kovacheva
- Botanical Institute, Department of Plant Physiology, Göteborg University, Box 461, SE 405 30, Göteborg, Sweden
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Tsolakis G, Parashi E, Galland P, Kotzabasis K. Blue light signaling chains in Phycomyces: phototransduction of carotenogenesis and morphogenesis involves distinct protein kinase/phosphatase elements. Fungal Genet Biol 1999; 28:201-13. [PMID: 10669585 DOI: 10.1006/fgbi.1999.1175] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Carotenogenesis and morphogenesis represent two of the several responses sensitive to blue light which characterize the lower eukaryote Phycomyces blakesleeanus. Speculating that reversible phosphorylation may be an intracellular event beyond the photoperception step, we resorted to the use of first-choice inhibitors of protein phosphatases and protein kinases. The mycelial beta-carotene content of dark-grown cultures was induced by all agents administered, while the morphogenic output showed the typical trend effected by light only with one of the protein kinase inhibitors. Our data provide convincing evidence that protein phosphorylation plays a regulatory role in photocarotenogenesis and photomorphogenesis of Phycomyces. According to the model we propose, the putative signaling elements involved are anticipated to have a repressive function in the dark so that the responses are maintained in the "off" mode until the moment photon information has to flow through the regulatory circuit.
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Affiliation(s)
- G Tsolakis
- Department of Biology, University of Crete, Heraklion, Crete, 71409, Greece
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Abstract
A great variety of cellular functions are regulated by protein serine/threonine phosphatases (PP). This review summarises the current knowledge of the structural features, patterns of expression and involvement in signal transduction pathways of protein serine/threonine phosphatases related to PP5 and RdgC. Designated now as PP5/RdgC subfamily by P. T. W. Cohen in her 1997 study published in Trends in Biochemical Sciences, (Vol. 22, pp. 245-251), this heterogeneous group comprises phosphatases PP5/PPT, containing regulatory domains with tetratricopeptide repeats, RdgC/PPEF, which possess Ca2+-binding EF hand-type sites, and, recently discovered in plants, PP7. PP5 is ubiquitously expressed and appears to be a multifunctional phosphatase involved in a number of different signalling pathways. In contrast, expression of RdgC/PPEF phosphatases and PP7 is confined primarily to specialised sensory cells in animals and plants, respectively, which may be indicative of their more specialised roles in sensory signal transduction.
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Affiliation(s)
- A V Andreeva
- Research School of Biological and Molecular Sciences, Oxford Brookes University, Headington, UK.
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Abstract
C4 plants, including maize, Flaveria, amaranth, sorghum, and an amphibious sedge Eleocharis vivipara, have been employed to elucidate the molecular mechanisms and signaling pathways that control C4 photosynthesis gene expression. Current evidence suggests that pre-existing genes were recruited for the C4 pathway after acquiring potent and surprisingly diverse regulatory elements. This review emphasizes recent advances in our understanding of the creation of C4 genes, the activities of the C4 gene promoters consisting of synergistic and combinatorial enhancers and silencers, the use of 5' and 3' untranslated regions for transcriptional and posttranscriptional regulations, and the function of novel transcription factors. The research has also revealed new insights into unique or universal mechanisms underlying cell-type specificity, coordinate nuclear-chloroplast actions, hormonal, metabolic, stress and light responses, and the control of enzymatic activities by phosphorylation and reductive processes.
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Affiliation(s)
- Jen Sheen
- Department of Molecular Biology, Department of Genetics, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114; e-mail:
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Abstract
The nuclear genome of the model plant Arabidopsis thaliana contains a small gene family consisting of three genes encoding RNA polymerases of the single-subunit bacteriophage type. There is evidence that similar gene families also exist in other plants. Two of these RNA polymerases are putative mitochondrial enzymes, whereas the third one may represent the nuclear-encoded RNA polymerase (NEP) active in plastids. In addition, plastid genes are transcribed from another, entirely different multisubunit eubacterial-type RNA polymerase, the core subunits of which are encoded by plastid genes [plastid-encoded RNA polymerase (PEP)]. This core enzyme is complemented by one of several nuclear-encoded sigma-like factors. The development of photosynthetically active chloroplasts requires both PEP and NEP. Most NEP promoters show certain similarities to mitochondrial promoters in that they include the sequence motif 5'-YRTA-3' near the transcription initiation site. PEP promoters are similar to bacterial promoters of the -10/-35 sigma 70 type.
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Affiliation(s)
- W R Hess
- Institute of Biology, Humboldt University, Berlin, Germany
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Kim M, Thum KE, Morishige DT, Mullet JE. Detailed architecture of the barley chloroplast psbD-psbC blue light-responsive promoter. J Biol Chem 1999; 274:4684-92. [PMID: 9988705 DOI: 10.1074/jbc.274.8.4684] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The photosystem II reaction center chlorophyll protein D2, is encoded by the chloroplast gene psbD. PsbD is transcribed from at least three different promoters, one which is activated by high fluence blue light. Sequences within 130 base pairs (bp) of the psbD blue light-responsive promoter (BLRP) are highly conserved in higher plants. In this study, the structure of the psbD BLRP was analyzed in detail using deletion and site-directed mutagenesis and in vitro transcription. Deletion analysis showed that a 53-bp DNA region of the psbD BLRP, from -57 to -5, was sufficient for transcription in vitro. Mutation of a putative prokaryotic -10 element (TATTCT) located from -7 to -12 inhibited transcription from the psbD BLRP. In contrast, mutation of a putative prokaryotic -35 element, had no influence on transcription. Mutation of a TATATA sequence located between the barley psbA -10 and -35 elements significantly reduced transcription from this promoter. However, site-directed mutation of sequences located between -35 and -10 had no effect on transcription from the psbD BLRP. Transcription from the psbD BLRP was previously shown to require a 22-bp sequence, termed the AAG-box, located between -36 and -57. The AAG-box specifically binds the protein complex AGF. Site-directed mutagenesis identified two different sequence motifs in the AAG-box that are important for transcription in vitro. Based on these results, we propose that positive factors bind to the AAG-box and interact with the chloroplast-encoded RNA polymerase to promote transcription from the psbD BLRP. Transcription from the psbD BLRP is thus similar to type II bacterial promoters that use activating proteins to stimulate transcription. Transcription of the psbD BLRP was approximately 6. 5-fold greater in plastid extracts from illuminated versus dark-grown plants. This suggests that light-induced activation of this promoter in vivo involves factors interacting with the 53-bp psbD BLRP in vitro.
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Affiliation(s)
- M Kim
- Department of Biochemistry and Biophysics, Crop Biotechnology Center, Texas A & M University, College Station, Texas 77843, USA
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Kim M, Christopher DA, Mullet JE. ADP-Dependent phosphorylation regulates association of a DNA-binding complex with the barley chloroplast psbD blue-light-responsive promoter. PLANT PHYSIOLOGY 1999; 119:663-70. [PMID: 9952463 PMCID: PMC32144 DOI: 10.1104/pp.119.2.663] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/1998] [Accepted: 11/06/1998] [Indexed: 05/20/2023]
Abstract
The chloroplast gene psbD encodes D2, a chlorophyll-binding protein located in the photosystem II reaction center. Transcription of psbD in higher plants involves at least three promoters, one of which is regulated by blue light. The psbD blue-light-regulated promoter (BLRP) consists of a -10 promoter element and an activating complex, AGF, that binds immediately upstream of -35. A second sequence-specific DNA-binding complex, PGTF, binds upstream of AGF between -71 and -100 in the barley (Hordeum vulgare) psbD BLRP. In this study we report that ADP-dependent phosphorylation selectively inhibits the binding of PGTF to the barley psbD BLRP. ATP at high concentrations (1-5 mM) inhibits PGTF binding, but in the presence of phosphocreatine and phosphocreatine kinase, this capacity is lost, presumably due to scavenging of ADP. ADP inhibits PGTF binding at relatively low concentrations (0.1 mM), whereas other nucleotides are unable to mediate this response. ADP-mediated inhibition of PGTF binding is reduced in the presence of the protein kinase inhibitor K252a. This and other results suggest that ADP-dependent phosphorylation of PGTF (or some associated protein) inhibits binding of PGTF to the psbD BLRP and reduces transcription. ADP-dependent phosphorylation is expected to increase in darkness in parallel with the rise in ADP levels in chloroplasts. ADP-dependent phosphorylation in chloroplasts may, therefore, in coordination, inactivate enzymes involved in carbon assimilation, protein synthesis, and transcription during diurnal light/dark cycles.
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Affiliation(s)
- M Kim
- Department of Biochemistry and Biophysics, Crop Biotechnology Center, Texas A&M University, College Station, Texas 77843, USA
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Nakahira Y, Baba K, Yoneda A, Shiina T, Toyoshima Y. Circadian-regulated transcription of the psbD light-responsive promoter in wheat chloroplasts. PLANT PHYSIOLOGY 1998; 118:1079-88. [PMID: 9808753 PMCID: PMC34781 DOI: 10.1104/pp.118.3.1079] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/1998] [Accepted: 08/17/1998] [Indexed: 05/20/2023]
Abstract
The level of mRNAs derived from the plastid-encoded psbD light-responsive promoter (LRP) is controlled by a circadian clock(s) in wheat (Triticum aestivum). The circadian oscillations in the psbD LRP mRNA level persisted for at least three cycles in continuous light and for one cycle in continuous dark, with maxima in subjective morning and minima in subjective early night. In vitro transcription in chloroplast extracts revealed that the circadian cycles in the psbD LRP mRNA level were dominantly attributed to the circadian-regulated transcription of the psbD LRP. The effects of various mutations introduced into the promoter region on the psbD LRP activity in vitro suggest the existence of two positive elements located between -54 and -36, which generally enhance the transcription activity, and an anomalous core promoter structure lacking the functional "-35" element, which plays a crucial role in the circadian fluctuation and light dependency of psbD LRP transcription activity.
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Affiliation(s)
- Y Nakahira
- Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-nihonmatu-cho, Sakyo-ku, Kyoto 606-8501, Japan
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García-Fernández JM, Hess WR, Houmard J, Partensky F. Expression of the psbA gene in the marine oxyphotobacteria Prochlorococcus spp. Arch Biochem Biophys 1998; 359:17-23. [PMID: 9799555 DOI: 10.1006/abbi.1998.0862] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The oxygenic photosynthetic prokaryotes Prochlorococcus marinus SS120 (CCMP1375) and Prochlorococcus sp. MED4 (CCMP 1378) were previously shown to exhibit different pigmentation and ecophysiological characteristics. The former strain has a much lower divinyl-Chl a to b ratio and is adapted to lower photon flux densities than the latter. In contrast to the cyanobacteria examined so far, both strains possess only one copy of the psbA gene, encoding the D1 protein of photosystem II core. In acclimated steady-state cultures, psbA transcript levels were always higher at high irradiances in both strains. Upon a shift from low to high light, the psbA transcript levels increased in both strains but more quickly in MED4 than in SS120. They decreased during the opposite shift. Iron-starved MED4 cells overexpressed psbA at all assayed irradiances, suggesting that this species, representative of populations from naturally iron-depleted oceanic areas, may have developed a particular compensation mechanism. The similar effects of DCMU and DBMIB on the expression of psbA suggest that light regulation of psbA in Prochlorococcus may be mediated by the electron transport chain. The energy state of cells could, however, also be involved in this regulation, since cultures of both strains subjected to darkness showed psbA levels significantly lower when glucose was added.
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Affiliation(s)
- J M García-Fernández
- Observatoire Océanologique de Roscoff, CNRS et Université Paris 6, Station Biologique BP 74, Roscoff Cedex, F-29682, France.
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Shiina T, Allison L, Maliga P. rbcL Transcript levels in tobacco plastids are independent of light: reduced dark transcription rate is compensated by increased mRNA stability. THE PLANT CELL 1998; 10:1713-22. [PMID: 9761797 PMCID: PMC143938 DOI: 10.1105/tpc.10.10.1713] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The plastid rbcL gene, encoding the large subunit of ribulose-1, 5-bisphosphate carboxylase, in higher plants is transcribed from a sigma70 promoter by the eubacterial-type RNA polymerase. To identify regulatory elements outside of the rbcL -10/-35 promoter core, we constructed transplastomic tobacco plants with uidA reporter genes expressed from rbcL promoter derivatives. Promoter activity was characterized by measuring steady state levels of uidA mRNA on RNA gel blots and by measuring promoter strength in run-on transcription assays. We report here that the rbcL core promoter is sufficient to obtain wild-type rates of transcription. Furthermore, the rates of transcription were up to 10-fold higher in light-grown leaves than in dark-adapted plants. Although the rates of transcription were lower in the dark, rbcL mRNA accumulated to similar levels in light-grown and dark-adapted leaves. Accumulation of uidA mRNA from most rbcL promoter deletion derivatives directly reflected the relative rates of transcription: high in the light-grown and low in the dark-adapted leaves. However, uidA mRNA accumulated to high levels in a light-independent fashion as long as a segment encoding a stem-loop structure in the 5' untranslated region was included in the promoter construct. This finding indicates that lower rates of rbcL transcription in the dark are compensated by increased mRNA stability.
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MESH Headings
- Base Sequence
- DNA Primers/genetics
- DNA, Plant/genetics
- Darkness
- Drug Stability
- Gene Expression
- Genes, Plant
- Genes, Reporter
- Light
- Molecular Sequence Data
- Plant Proteins/genetics
- Plants, Genetically Modified
- Plants, Toxic
- Plastids/genetics
- Promoter Regions, Genetic
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Plant/genetics
- RNA, Plant/metabolism
- Ribulose-Bisphosphate Carboxylase/genetics
- Sequence Homology, Nucleic Acid
- Nicotiana/genetics
- Nicotiana/metabolism
- Nicotiana/radiation effects
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Affiliation(s)
- T Shiina
- Waksman Institute, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, New Jersey 08854-8020, USA
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Christopher DA, Hoffer PH. DET1 represses a chloroplast blue light-responsive promoter in a developmental and tissue-specific manner in Arabidopsis thaliana. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 1998; 14:1-11. [PMID: 9681024 DOI: 10.1046/j.1365-313x.1998.00078.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The chloroplast psbD-psbC loci, which encode the D2 and CP43 subunits of the photosystem II reaction center, respectively, are regulated by a blue light-responsive promoter (BLRP). It has recently been shown in barley seedlings that activation of psbD-psbC transcription by blue light involves inhibition of a protein kinase that represses the BLRP in the dark. To elucidate further the photosensory pathways regulating the psbD BLRP, the effects of three nuclear mutations on the expression of the BLRP in chloroplasts of Arabidopsis thaliana were examined. The mutants used included the det1-1 and det1-6 alleles for the nuclear protein DET1, involved in repressing photomorphogenesis, and the cry1 gene for the blue light photoreceptor, cryptochrome (CRY1), involved in hypocotyl elongation. The BLRP was not significantly expressed in cotyledons of light-grown wild-type seedlings, unlike the light-responsive expression of the chloroplast, psbA and rbcL, and nuclear, Lhcb and Chs, genes. Analysis of the mutants revealed that DET1 represses transcription from the BLRP in a developmental and tissue-specific manner, which is unique from the effects that DET1 has on other light-regulated promoters. In addition, the cry1 mutation did not reduce the expression of the BLRP in response to blue light. This suggests that the BLRP is regulated by a different photosensory system relative to CRY1. A model is proposed involving blue light, DET1 and phytochrome in regulating transcription from the psbD BLRP.
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Affiliation(s)
- D A Christopher
- Department of Plant Molecular Physiology, University of Hawaii at Manoa, Honolulu 96822, USA.
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Hoffer PH, Christopher DA. Structure and blue-light-responsive transcription of a chloroplast psbD promoter from Arabidopsis thaliana. PLANT PHYSIOLOGY 1997; 115:213-22. [PMID: 9306699 PMCID: PMC158477 DOI: 10.1104/pp.115.1.213] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
We characterized the effects of light on psbD transcription and mRNA levels during chloroplast development in Arabidopsis thaliana. After 6 to 12 hours of illumination of dark-grown seedlings, two psbD mRNAs were detected and their 5' ends were mapped to positions -550 and -190 bp upstream from the psbD translational start codon. Their kinetics of accumulation resembled the accumulation of chloroplast psbA and rbcL mRNAs but differed from the accumulation of the nuclear-encoded Lhcb and Chs mRNAs. A third psbD mRNA with its 5' ends at position -950 accumulated after illumination of > 180 h. The 5' ends of this transcript were mapped to a nucleotide sequence that is highly conserved with functional sequences in the barley (Hordeum vulgare) blue-light-responsive promoter (BLRP). Transcription from the Arabidopsis psbD promoter was 3-fold higher in blue relative to red light, whereas red and blue light affected total chloroplast, rbcL, and 16S rDNA transcription similarly. This study shows that transcription of Arabidopsis psbD is mediated by a BLRP and suggests that psbD genes in other land plants are regulated by a common blue-light-signaling pathway. Isolating the BLRP from Arabidopsis will allow molecular genetic studies aimed at identifying the pertinent photoreceptor and components of this phototransduction pathway.
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MESH Headings
- Adaptation, Physiological
- Arabidopsis/genetics
- Arabidopsis/metabolism
- Arabidopsis/radiation effects
- Base Sequence
- Cloning, Molecular
- DNA Primers/genetics
- DNA, Chloroplast/genetics
- Evolution, Molecular
- Genes, Plant/radiation effects
- Light
- Molecular Sequence Data
- Photosynthetic Reaction Center Complex Proteins/genetics
- Photosystem II Protein Complex
- Polymerase Chain Reaction
- Promoter Regions, Genetic/radiation effects
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Plant/genetics
- RNA, Plant/metabolism
- Sequence Homology, Nucleic Acid
- Transcription, Genetic/radiation effects
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Affiliation(s)
- P H Hoffer
- Department of Plant Molecular Physiology, University of Hawaii at Manoa, Honolulu 96822, USA
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