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Rengasamy Ramamoorthy, Bhushan Vishal, Srinivasan Ramachandran, Prakash P Kumar
Ds insertion in rice OsPS1-F gene results in semi-dwarf plants with reduced tiller number and grain yield, while genetic complementation with OsPS1-F rescued the mutant phenotype. Photosynthetic electron transport is regulated in the chloroplast thylakoid membrane by multi-protein complexes. Studies about photosynthetic machinery and its subunits in crop plants are necessary, because they could be crucial for yield enhancement in the long term. Here, we report the characterization of OsPS1-F (encoding Oryza sativa PHOTOSYSTEM 1-F subunit) using a single copy Ds insertion rice mutant line...
November 17, 2017: Plant Cell Reports
Alonso M Acuña, Pascal van Alphen, Filipe Branco Dos Santos, Rienk van Grondelle, Klaas J Hellingwerf, Ivo H M van Stokkum
Cyanobacterial thylakoid membranes are known to host photosynthetic and respiratory complexes. This hampers a straight forward interpretation of the highly dynamic fluorescence originating from photosynthetic units. The present study focuses on dark-to-light transitions in whole cells of a PSI-deficient mutant of the cyanobacterium Synechocystis sp. PCC 6803. The time-dependent cellular fluorescence spectrum has been measured, while having previously exposed the cells to different conditions that affect respiratory activity...
November 11, 2017: Biochimica et Biophysica Acta
Maithili Krishnan, Geri F Moolenaar, Karthick Babu Sai Sankar Gupta, Nora Goosen, Anjali Pandit
Plants adapt to fluctuating light conditions by a process called non-photochemical quenching (NPQ), where membrane protein PsbS plays a crucial role and transforms a change in the pH-gradient across the thylakoid membrane under excess light conditions into a photoprotective state, leading to de-excitation of antenna chlorophylls. The PsbS activation mechanism is elusive and has been proposed to involve a monomerization step and protonation of specific residues. To elucidate its function, it is essential to produce PsbS in large quantities, stabilize PsbS in a membrane-mimicking environment and analyze its pH-dependent conformational structure...
November 9, 2017: Scientific Reports
Cheng Xingxing, Liu Jiuyang, Zhang Huan, Li Fudong, Zhang Shuya, Xu Min, Ruan Ke, Wang Yuhua, Fu Aigen
Proper biogenesis and maintenance of photosynthetic thylakoid membrane complexes are essential for the photosynthetic light reactions. A thylakoid lumenal protein, Psb27, plays a vital role in assembly or/and maintenance of photosystem II (PSII). In cyanobacteria, it is a small lipoprotein docked to the lumenal side of PSII, and functions in the assembly of the Mn4Ca cluster and in the PSII repair cycle. However, Psb27 from Arabidopsis thaliana is not a lipoprotein, and it is involved in PSII repair and acclimation to fluctuating light stress, suggesting a functional divergence between Arabidopsis Psb27 and cyanobacterial Psb27s...
November 2, 2017: Photosynthesis Research
Soomin Park, Alexandra L Fischer, Zhirong Li, Roberto Bassi, Krishna K Niyogi, Graham R Fleming
Nonphotochemical quenching mechanisms regulate light harvesting in oxygenic photosynthesis. Measurement techniques for nonphotochemical quenching have typically focused on downstream effects of quenching, such as measuring reduced chlorophyll fluorescence. Here, to directly measure a species involved in quenching, we report snapshot transient absorption (TA) spectroscopy, which rapidly tracks carotenoid radical cation signals as samples acclimate to excess light. The formation of zeaxanthin radical cations, which is possible evidence of zeaxanthin-chlorophyll charge-transfer (CT) quenching, was investigated in spinach thylakoids...
November 2, 2017: Journal of Physical Chemistry Letters
Qingen Da, Ting Sun, Menglong Wang, Honglei Jin, Mengshu Li, Dongru Feng, Jinfa Wang, Hong-Bin Wang, Bing Liu
M-type thioredoxins are required to regulate zeaxanthin epoxidase activity and to maintain the steady-state level of the proton motive force, thereby influencing NPQ properties under low-light conditions in Arabidopsis. Non-photochemical quenching (NPQ) helps protect photosynthetic organisms from photooxidative damage via the non-radiative dissipation of energy as heat. Energy-dependent quenching (qE) is a major constituent of NPQ. However, the mechanism underlying the regulation of qE is not well understood...
October 28, 2017: Plant Cell Reports
Jian Zhang, Jianwei Xiao, Yuqian Li, Bodan Su, Huimin Xu, Xiaoyi Shan, Chengwei Song, Jianbo Xie, Ruili Li
The chloroplast, as the photosynthetic organelle of plants, plays a crucial role in plant development. Extensive studies have been conducted on chloroplast development; however, the related regulatory mechanism still remains elusive. Here, we characterized a mutant with defective chloroplasts in Arabidopsis, termed pigment-defective mutant3 (pdm3), which exhibits a distinct albino phenotype in leaves, eventually leading to pdm3 seedling lethality under autotrophic growth conditions. Electron microscopy demonstrated that the number of thylakoids was reduced and the structure of those thylakoids was disrupted in the pdm3 mutant, which eventually led to the breakdown of chloroplasts...
October 19, 2017: Journal of Experimental Botany
Győző Garab, Bettina Ughy, Pieter de Waard, Parveen Akhtar, Uroš Javornik, Christos Kotakis, Primož Šket, Václav Karlický, Zuzana Materová, Vladimír Špunda, Janez Plavec, Herbert van Amerongen, László Vígh, Henk Van As, Petar H Lambrev
Chloroplast thylakoid membranes contain virtually all components of the energy-converting photosynthetic machinery. Their energized state, driving ATP synthesis, is enabled by the bilayer organization of the membrane. However, their most abundant lipid species is a non-bilayer-forming lipid, monogalactosyl-diacylglycerol; the role of lipid polymorphism in these membranes is poorly understood. Earlier (31)P-NMR experiments revealed the coexistence of a bilayer and a non-bilayer, isotropic lipid phase in spinach thylakoids...
October 17, 2017: Scientific Reports
Dilek Killi, Matthew Haworth
Quinoa (Chenopodium quinoa Willd.) has been proposed as a hardy alternative to traditional grain crops in areas with warm-to-hot climates that are likely to experience increased drought and salt stress in the future. We characterised the diffusive and metabolic limitations to photosynthesis in quinoa exposed to drought and salt stress in isolation and combination. Drought-induced pronounced stomatal and mesophyll limitations to CO₂ transport, but quinoa retained photosynthetic capacity and photosystem II (PSII) performance...
October 17, 2017: Plants (Basel, Switzerland)
Joanna Grzyb, Katarzyna Gieczewska, Justyna Łabuz, Olga Sztatelman
Direct interaction of ferredoxin:NADP(+) oxidoreductase (FNR) with thylakoid membranes was postulated as a part of the cyclic electron flow mechanism. In vitro binding of FNR to digalactosyldiacylglycerol and monogalactosyldiacylglycerol membranes was also shown. In this paper we deal with the latter interaction in more detail describing the effect for two FNR forms of Synechocystis PCC 6803. The so-called short FNR (sFNR) is homologous to FNR from higher plant chloroplasts. The long FNR (lFNR) form contains an additional domain, responsible for the interaction with phycobilisomes...
October 13, 2017: Biochimica et Biophysica Acta
Tinghong Tan, Yanni Sun, Shishuai Luo, Chao Zhang, Huapeng Zhou, Honghui Lin
Boea hygrometrica (B. hygrometrica) can tolerate severe desiccation and resume photosynthetic activity rapidly upon water availability. However, little is known about the mechanisms by which B. hygrometrica adapts to dehydration and resumes competence upon rehydration. Here we determine how B. hygrometrica deals with oxidative stress, excessive excitation/electron pressures as well as photosynthetic apparatus modulation during dehydration/rehydration. By measuring ROS generation and scavenging efficiency, we found that B...
November 1, 2017: Plant & Cell Physiology
Nancy Ruiz-Lau, Ángela Sáez, Mónica Lanza, Begoña Benito
K+ is widely used by plant cells, whereas Na+ can easily reach toxic levels during plant growth, which typically occurs in saline environments; however, the effects and functions in the chloroplast have been only roughly estimated. Traditionally, the occurrence of ionic fluxes across the chloroplast envelope or the thylakoid membranes has been mostly deduced from physiological measurements or from knowledge of chloroplast metabolism. However, many of the proteins involved in these fluxes have not yet been characterized...
October 3, 2017: Plant & Cell Physiology
Selene Casella, Fang Huang, David Mason, Guo-Yan Zhao, Giles N Johnson, Conrad W Mullineaux, Lu-Ning Liu
The structural dynamics and flexibility of cell membranes play fundamental roles in the functions of the cells, i.e., signaling, energy transduction, and physiological adaptation. The cyanobacterial thylakoid membrane represents a model membrane that can conduct both oxygenic photosynthesis and respiration simultaneously. In this study, we conducted direct visualization of the global organization and mobility of photosynthetic complexes in thylakoid membranes from a model cyanobacterium, Synechococcus elongatus PCC 7942, using high-resolution atomic force, confocal, and total internal reflection fluorescence microscopy...
November 6, 2017: Molecular Plant
Ryoichi Sato, Masaru Kono, Kyohei Harada, Hiroyuki Ohta, Shinichi Takaichi, Shinji Masuda
Plants have mechanisms allowing them to acclimate to intense light conditions, which involves the dissipation of excess light energy. These mechanisms allow plants to perform photosynthesis efficiently and, therefore, must be accurately and precisely controlled. However, how plants dissipate excess light energy has yet to be fully elucidated. Herein we report the identification of a gene, which we named Fluctuating-Light-Acclimation Protein1 (FLAP1), that is conserved in oxygenic phototrophs. We show that Arabidopsis FLAP1 is associated with chloroplast thylakoid and envelope membranes and that the flap1 mutant shows delayed non-photochemical quenching (NPQ) relaxation during induction of photosynthesis at moderate light intensity...
September 1, 2017: Plant & Cell Physiology
Marisa S Otegui
Chloroplast degradation during natural or stress-induced senescence requires the participation of both plastidic and extraplastidic degradative pathways. As part of the extraplastidic pathways, chloroplasts export stroma, envelope, and thylakoid proteins in membrane-bound organelles that are ultimately degraded in vacuoles. Some of these pathways, such as the formation of senescence-associated vacuoles (SAVs) and CV-containing vesicles (CCVs), do not depend on autophagy, whereas delivery of Rubisco-containing bodies (RCBs), ATI1-PS (ATG8-interacting Protein 1) bodies, and small starch-like granule (SSLG) bodies is autophagy dependent...
July 22, 2017: Journal of Experimental Botany
Rajneesh Singhal, Donna E Fernandez
Membrane proteins that are imported into chloroplasts must be accurately routed in order to establish and maintain the highly differentiated membranes characteristic of these organelles. Little is known about the targeting information or pathways involved, especially in the case of proteins with multiple transmembrane domains. We have studied targeting of the SCY components of the two SEC translocases in chloroplasts. SCY1 and SCY2 share a similar, highly conserved structure with 10 transmembrane domains, but are targeted to different membranes: the thylakoids and inner envelope, respectively...
September 13, 2017: Journal of Experimental Botany
Pernille Vængebjerg Boutrup, Øjvind Moestrup, Urban Tillmann, Niels Daugbjerg
A gymnodinioid photosynthetic dinoflagellate was isolated from Argentina and examined by light and electron microscopy and analysis of nuclear-encoded LSU rDNA. Kirithra asteri gen. et sp. nov. was proposed as morphology and molecular phylogeny separated this dinoflagellate from others within the family Ceratoperidiniaceae. Cells were surrounded by a hyaline amphiesma comprising polygonal vesicles. Each vesicle contained a honeycomb and a trilaminar structure. An anterior sulcal extension ending in a complete circle formed the apical structure complex (ASC), which characterizes Ceratoperidiniaceae...
September 9, 2017: Protist
Yang-Er Chen, Jun-Mei Cui, Yan-Qiu Su, Chao-Ming Zhang, Jie Ma, Zhong-Wei Zhang, Ming Yuan, Wen-Juan Liu, Huai-Yu Zhang, Shu Yuan
Reversible phosphorylation of proteins and the assembly of thylakoid complexes are the important protective mechanism against environmental stresses in plants. This research was aimed to investigate the different responses of the antioxidant defense system and photosystem II (PSII) to osmotic stress between drought-resistant and drought-susceptible wheat cultivars. Results showed that the decrease in PSII photochemistry and six enzyme activities was observed in drought-susceptible wheat compared with drought-resistant wheat under osmotic stress...
October 5, 2017: Scientific Reports
Chunyu Zhang, Cong Li, Jun Liu, Yandong Lv, Chunsheng Yu, Hongyu Li, Tao Zhao, Bin Liu, Jianhua Zhang
Water deprivation causes substantial losses in crop yields around the world. In this study, we show that when overexpressed in transgenic rice (Oryza sativa), the bZIP transcription factor OsABF1 confers distinctly different drought-tolerance phenotypes when tethered to the transcriptional activator VP16 versus the transcriptional repressor EAR. We performed chromatin immunoprecipitation sequencing (ChIP-seq) and RNA sequencing (RNA-seq) assays on transgenic rice lines and determined that OsABF1 binds to DNA sequences containing an ACGT core motif...
July 20, 2017: Journal of Experimental Botany
Marjaana Rantala, Mikko Tikkanen, Eva-Mari Aro
Conversion of solar energy into chemical energy in plant chloroplasts concomitantly modifies the thylakoid architecture and hierarchical interactions between pigment-protein complexes. Here, the thylakoids were isolated from light-acclimated Arabidopsis leaves and investigated with respect to the composition of the thylakoid protein complexes and their association into higher molecular mass complexes, the largest one comprising both photosystems (PSII and PSI) and light-harvesting chlorophyll a/b-binding complexes (LHCII)...
October 4, 2017: Plant Journal: for Cell and Molecular Biology
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