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A structural re-modeling of the thylakoid system, including granum size and regularity, occurs in chlorophyll-deficient wheat mutants affected by photosynthetic membrane over-reduction. In the chloroplast of land plants, the thylakoid system is defined by appressed grana stacks and unstacked stroma lamellae. This study focuses on the variations of the grana organization occurring in outdoor-grown wheat mutants characterized by low chlorophyll content and a tendency for photosynthetic membrane over-reduction. Triticum aestivum ANK-32A and Triticum durum ANDW-7B were compared to their corresponding WT lines, NS67 and LD222, respectively. Electron micrographs of chloroplasts were used to calculate grana ultrastructural parameters. Photosynthetic parameters were obtained by modulated chlorophyll fluorescence and applying Light Curves (LC) and Rapid Light Curves (RLC) protocols. For each photosynthetic parameter, the difference Δ(RLC-LC) was calculated to evaluate the flexible response to light in the examined lines. In the mutants, fewer and smaller disks formed grana stacks characterized by a marked increase in lateral and cross-sectional irregularity, both negatively correlated with the number of layers per granum. A relationship was found between membrane over-reduction and granum structural irregularity. The possible acclimative significance of a greater proportion of stroma-exposed grana domains in relieving the excess electron pressure on PSI is discussed. [ABSTRACT FROM AUTHOR]

With the idea of knowing the impact of the research carried out by the professors in the Psychology degree 1 of the University Center of Health Sciences 2, of the University of Guadalajara 3, located in the city of Guadalajara in the state of Jalisco, Mexico, the university authorities decided to carry out an evaluation process from the previous analysis of the options of accreditation agencies at international level and in which they decided to opt for the organization GRANA 4, which means: "generator of resources for accreditation in the nations of America", its methodology is based on a decimal system of qualitative and quantitative evaluation composed of 10 headings or dimensions, 100 items and 1000 indicators of second and third generation. Its supporting references and context are based on the following organizations: UNESCO 5, OECD 6, WTO 7, World Bank 8, Bologna Declaration 9, among others. During the evaluation process, the computer platform SIEVAS10 is used, which means: evaluation and follow-up system "that facilitates the filling out and the evaluation process during its stages and allows interaction among evaluators. The tools it has to facilitate the evaluation are: meanings, contexts, bibliographic references, glossary, decimal scale to qualify quality levels, fields to integrate strengths, weaknesses, the permanent improvement plan and formats to integrate statistics in retrospective and prospective. The system facilitates the computer availability to incorporate evidentiary documents and web sites that help the evaluation process. It also has graphs that are automatically built as the evaluation is incorporated into the platform. There are 10 processes to carry out the entire evaluation process, starting with the internal evaluation, then the external evaluation, concluding with the delivery of results and the permanent improvement plan (PMP). The internal evaluation was carried out by a committee of the evaluated institution composed of: 3 professors, 2 managers, 1 student and linked to the processes graduates and employers associated with the program to be evaluated. The external evaluators came from 3 countries 11 : Argentina, Venezuela and Spain with expertise in the discipline evaluated and with experience in evaluation processes in the field of the discipline either in their country or region of origin.e evaluators. The basis of the article focuses on the dimension or item 2 called: "impact of research on training", which is made up of 10 items and 100 indicators according to the GRANA model. This process had a duration of 6 months starting in June 2015 and concluding on January 15, 2016. Currently, the PMP of this Bachelor's Degree is being implemented in accordance with the improvement proposals suggested by the expert evaluation committee. [ABSTRACT FROM AUTHOR]

With the idea of knowing the impact on society that the degree in Psychology from the University Center for Health Sciences, of the University of Guadalajara, located in the city of Guadalajara in the state of Jalisco, Mexico, has had, the university authorities decided to take carried out a reassessment process from the previous analysis of the options of accreditation agencies at the international level and in which it decided to opt for the GRANA organization, which means: "Generator of resources for accreditation in the nations of America", its methodology It is based on a decimal system of qualitative and quantitative evaluation made up of 10 categories or dimensions, 100 items and 1000 second and third generation indicators. Its references for support and context are based on the organizations of: UNESCO, OECD, WTO, the World Bank and the Bologna Declaration, among others. During the evaluation process, the SIEVAS computer platform is used, which means: evaluation and follow-up system "that facilitates the completion and evaluation process during its stages and allows interaction between evaluators. The tools it has to facilitate the evaluation are: meanings, contexts, bibliographical references, glossary, decimal scale to qualify quality levels, fields to integrate strengths, weaknesses, the permanent improvement plan and formats to integrate statistics in retrospect and prospective. The system facilitates computer availability to incorporate supporting documents and websites that help the evaluation process. It also has graphs that are built automatically as the evaluation is incorporated into the platform. There are 10 processes to carry out the entire evaluation process, starting with the internal evaluation, then with the external evaluation, concluding with the delivery of results and the permanent improvement plan (PMP). The internal evaluation was carried out by a committee of the evaluated institution composed of: 3 professors, 2 directors, 1 student and linked to the processes of graduates and employers associated with the program to be evaluated. Meanwhile, the external evaluators came from 3 countries11: Argentina, Italy, Mexico and Spain with a specialty in the discipline evaluated and with experience in evaluation processes in the field of the discipline, either in their country or region of origin. The basis of the article focuses on the dimension or item 1 called: "social impact of training". It is made up of 10 items and 100 indicators according to the GRANA model. This process lasted 8.5 months, starting on February 10, 2021 and ending on October 29, 2021. The PMP of this Bachelor's Degree is currently in operation in accordance with the improvement proposals suggested by the expert evaluation committee. [ABSTRACT FROM AUTHOR]

En este artículo se estudia el aprovechamiento de la grana en Andalucía Occidental durante el siglo XV. El valor de la grana, que sirve para obtener el preciado color rojo para teñir lanas y sedas, permite reflexionar sobre la conexión existente entre los ecosistemas donde se recogía este recurso natural, los campesinos, la gobernanza de las ciudades y pueblos y el interés del mercado.

Apple skin contains several groups of strongly absorbing cell organelles with pigments that change dynamically in type and concentration during fruit maturation. Chlorophylls and carotenoids, both primarily involved in photosynthesis, are found in the grana of chloroplasts, while anthocyanin vacuolar inclusions (AVIs) accumulate for light protection in red-skinned cultivars. A Mie model describing light scattering by absorbing spherical particles in a non-absorbing medium allowed to theoretically investigate the explicit influence of grana and AVIs on the effective scattering coefficient μ s ′ and the absorption coefficient μ a . The reconstruction of the complex refractive indices of the organelles predicted anomalous dispersion, i.e., a local increase in the real part of the refractive index in the spectral regions with high chlorophyll and anthocyanin absorption, in agreement with the Kramers–Kronig relations. As a result, peaks in μ s ′ were predicted to be shifted to longer wavelengths compared to the corresponding μ a bands. This selective scattering effect was confirmed experimentally with integrating sphere measurements for red- or green-skinned apple samples of the cultivars 'Elstar', 'Gala' or 'Jonagold'. Comparison between simulations and measurements indicated that the Soret bands of chlorophyll a and chlorophyll b are at 435 nm and 469 nm, respectively, and overlap with the absorption of carotenoids, whose red-most edge is at 488 nm. For anthocyanin absorption, a pronounced blue shift from 550 to 520 nm was observed, indicating structural or chemical changes of AVIs. [ABSTRACT FROM AUTHOR]

Este artículo revisa la historia de los judíos sefardíes en Túnez, conocidos también por los nombres de grana, liorneses o portugueses. En la primera parte, presentamos el estado de la cuestión de la historiografía relativa a los sefardíes tunecinos. A continua­ción, investigamos los itinerarios de los sefardíes que fueron expulsados a Túnez. Se puede hablar de dos principales itinerarios: el primero, de los que marcharon a Túnez después la expulsión de España y de Portugal a fines del siglo XV y principios del XVI; el segundo, de los que llegaron al país en el siglo XVII principalmente desde Livorno. Por último, estudiamos los diferentes aspectos del asentamiento de los sefardíes en Túnez, es decir, la llegada de los expulsados al país y la posición del Estado Hafsí y los beyes; sus relaciones y comunicaciones sociales y económicas con la mayoría musul­mana, los moriscos, y los judíos locales (tuansa). Este estudio se basa en una rica bibliografía sobre los judíos tunecinos en general, además de otras fuentes: principalmente, el diario inédito de fray Francisco Ximénez, pero también otros textos españoles, así como documentos producidos por la comunidad portuguesa junto con algunas fuentes tunecinas locales.

The aim of the present study was to investigate the photosynthetic properties and transcriptomic profiles of wildtype and chlorophyll (Chl) b-lacking rice (Oryza sativa L.). The plastid ultrastructure of the Chl b-lacking rice (i.e., loss of starch granules, abundant vesicles, and abundant plastoglobuli) indicated abnormal plastid development, whereas the analysis of transcriptome profiles and differentially expressed genes revealed that gene encoding PsbR (PSII core protein) was downregulated in the mutant, thereby reducing the Chl accumulation of the mutant. Meanwhile, in regards to Chl biosynthesis and degradation pathways, GluTR gene was downregulated, whereas UROD, CPOX, and MgCH genes were upregulated. The qPCR results were generally consistent with those of the transcription analysis, except for the finding that NOL genes, which regulate Chl b degradation, were upregulated. These results suggest that both the reduction in Chl accumulation and increase in conversion rate of Chl b to Chl a caused Chl a/b ratio amplification in mutant. The present study also provides evidence for Chl b degradation via pheophorbide b.

Iron (Fe) is an essential micronutrient whose availability is limiting in many soils. During Fe deficiency, plants alter the expression of many genes to increase Fe uptake, distribution, and utilization. In a genetic screen for suppressors of Fe sensitivity in the E3 ligase mutant bts-3, we isolated an allele of the bHLH transcription factor (TF) ILR3, ilr3-4. We identified a striking leaf bleaching phenotype in ilr3 mutants that was suppressed by limiting light intensity, indicating that ILR3 is required for phototolerance during Fe deficiency. Among its paralogs that are thought to be partially redundant, only ILR3 was required for phototolerance as well as repression of genes under Fe deficiency. A mutation in the gene-encoding PYE, a known transcriptional repressor under Fe deficiency, also caused leaf bleaching. We identified singlet oxygen as the accumulating reactive oxygen species (ROS) in ilr3-4 and pye, suggesting photosensitivity is due to a PSII defect resulting in ROS production. During Fe deficiency, ilr3-4 and pye chloroplasts retain normal ultrastructure and, unlike wild type (WT), contain stacked grana similar to Fesufficient plants. Additionally, we found that the D1 subunit of PSII is destabilized in WT during Fe deficiency but not in ilr3-4 and pye, suggesting that PSII repair is accelerated during Fe deficiency in an ILR3- and PYE-dependent manner. Collectively, our results indicate that ILR3 and PYE confer photoprotection during Fe deficiency to prevent the accumulation of singlet oxygen, potentially by promoting reduction of grana stacking to limit excitation and facilitate repair of the photosynthetic machinery. [ABSTRACT FROM AUTHOR]

Granum is a basic structural unit of the thylakoid membrane network of plant chloroplasts. It is composed of multiple flattened membranes forming a stacked arrangement of a cylindrical shape. Grana membranes are composed of lipids and tightly packed pigment-protein complexes whose primary role is the catalysis of photosynthetic light reactions. These membranes are highly dynamic structures capable of adapting to changing environmental conditions by fine-tuning photochemical efficiency, manifested by the structural reorganization of grana stacks. Due to a nanometer length scale of the structural granum features, the application of high-resolution electron microscopic techniques is essential for a detailed analysis of the granum architecture. This mini-review overviews recent approaches to quantitative grana structure analyses from electron microscopy data, highlighting the basic manual measurements and semi-automated workflows. We outline and define structural parameters used by different authors, for instance, granum height and diameter, thylakoid thickness, end-membrane length, Stacking Repeat Distance, and Granum Lateral Irregularity. This article also presents insights into efficient and effective measurements of grana stacks visualized on 2D micrographs. The information on how to correctly interpret obtained data, taking into account the 3D nature of grana stacks projected onto 2D space of electron micrograph, is also given. Grana ultrastructural observations reveal key features of this intriguing membrane arrangement, broadening our knowledge of the thylakoid network's remarkable plasticity. [ABSTRACT FROM AUTHOR]

Granum is a basic structural unit of the thylakoid membrane network of plant chloroplasts. It is composed of multiple flattened membranes forming a stacked arrangement of a cylindrical shape. Grana membranes are composed of lipids and tightly packed pigment-protein complexes whose primary role is the catalysis of photosynthetic light reactions. These membranes are highly dynamic structures capable of adapting to changing environmental conditions by fine-tuning photochemical efficiency, manifested by the structural reorganization of grana stacks. Due to a nanometer length scale of the structural granum features, the application of high-resolution electron microscopic techniques is essential for a detailed analysis of the granum architecture. This mini-review overviews recent approaches to quantitative grana structure analyses from electron microscopy data, highlighting the basic manual measurements and semi-automated workflows. We outline and define structural parameters used by different authors, for instance, granum height and diameter, thylakoid thickness, end-membrane length, Stacking Repeat Distance, and Granum Lateral Irregularity. This article also presents insights into efficient and effective measurements of grana stacks visualized on 2D micrographs. The information on how to correctly interpret obtained data, taking into account the 3D nature of grana stacks projected onto 2D space of electron micrograph, is also given. Grana ultrastructural observations reveal key features of this intriguing membrane arrangement, broadening our knowledge of the thylakoid network’s remarkable plasticity.

Extreme temperatures have become a threat to crop yields. To maintain plant growth and yield, chlorophyll (Chl) biosynthesis plays a crucial role in adaptation to temperature stress. This study investigated the influence of temperature on the biosynthesis and characteristics of pigments (Chl a, Chl b, and carotenoids) in the leaves of Chl b-lacking mutant rice (Chlorina 1, ch1) and wild-type rice (Norin No.8, wt). The ch1 showed thinner stacked grana caused by a decrease in thylakoid membranes per granum at 15 °C, whereas the destacked grana were observed at 35 °C after 12 h incubation. However, the grana are stacked normally, along with the absence of Chl b, and a significantly decreased amount of Chl a in both wt and ch1 were observed after heat stress exposure, demonstrating that light-harvesting complex II proteins are involved in grana stacking. Ch1 was sensitive to 15 °C during the first 4 h of incubation but it subsequently adapted to the cold environment. In addition, there were no significant differences in the photosynthesis between wt and ch1 after 12 h incubation at 35 °C. Differentially expressed gene (DEGs) analysis revealed that GluRS expression decreased, which resulted in a decline in Chl biosynthesis in wt and ch1 at 35 °C. At 8 h and 12 h, there were no significant differences in the expression of DEGs involved in Chl biosynthesis and degradation between wt and ch1 at 15 °C. ALAD expression in wt and ch1 at 15 °C decreased until it was undetectable. These findings suggested that ch1 may adapt to temperatures ranging from 15 °C to 35 °C.

The OBJECTIVE: Academic dishonesty is still a concern of researchers in various parts of the world. This is because there are still many academicians doing this unethical behavior. Do we examine how Grit plays a role in academic dishonesty? Does Grit predict Academic Achievement? Does Gender moderate the influence of Grit towards Academic Dishonesty?. MATERIALS AND METHODS: A quantitative approach is used in this research. A total of 408 students in Indonesia participated (M = 95; F = 313). The measuring instrument used is the Academic Dishonesty Scale adapted from Ampuni et al. (2019) with a = 0.860 and the Grit Scale for Children and Adult used by Wahidah (2019) with a = 0.727. RESULTS AND DISCUSSION: The results show that all research variables influence academic dishonesty. Even the influence of Grit, Gender, and academic achievement together is the greatest academic dishonesty. However, Gender was unable to moderate the influence of Grit toward academic dishonesty. CONCLUSIONS: We conclude that students who have Grit will reduce the tendency to behave in unethical behavior in academics, in this case, academic dishonesty. [ABSTRACT FROM AUTHOR]

Extreme temperatures have become a threat to crop yields. To maintain plant growth and yield, chlorophyll (Chl) biosynthesis plays a crucial role in adaptation to temperature stress. This study investigated the influence of temperature on the biosynthesis and characteristics of pigments (Chl a, Chl b, and carotenoids) in the leaves of Chl b-lacking mutant rice (Chlorina 1, ch1) and wild-type rice (Norin No.8, wt). The ch1 showed thinner stacked grana caused by a decrease in thylakoid membranes per granum at 15 °C, whereas the destacked grana were observed at 35 °C after 12 h incubation. However, the grana are stacked normally, along with the absence of Chl b, and a significantly decreased amount of Chl a in both wt and ch1 were observed after heat stress exposure, demonstrating that light-harvesting complex II proteins are involved in grana stacking. Ch1 was sensitive to 15 °C during the first 4 h of incubation but it subsequently adapted to the cold environment. In addition, there were no significant differences in the photosynthesis between wt and ch1 after 12 h incubation at 35 °C. Differentially expressed gene (DEGs) analysis revealed that GluRS expression decreased, which resulted in a decline in Chl biosynthesis in wt and ch1 at 35 °C. At 8 h and 12 h, there were no significant differences in the expression of DEGs involved in Chl biosynthesis and degradation between wt and ch1 at 15 °C. ALAD expression in wt and ch1 at 15 °C decreased until it was undetectable. These findings suggested that ch1 may adapt to temperatures ranging from 15 °C to 35 °C. [ABSTRACT FROM AUTHOR]

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Non-photochemical quenching (NPQ) is an important photoprotective mechanism in plants and algae. Although the process is extensively studied, little is known about its relationship with ultrastructural changes of the thylakoid membranes. In order to better understand this relationship, we studied the effects of illumination on the organization of thylakoid membranes in Monstera deliciosa leaves. This evergreen species is known to exhibit very large NPQ and to possess giant grana with dozens of stacked thylakoids. It is thus ideally suited for small-angle neutron scattering measurements (SANS)—a non-invasive technique, which is capable of providing spatially and statistically averaged information on the periodicity of the thylakoid membranes and their rapid reorganizations in vivo. We show that NPQ-inducing illumination causes a strong decrease in the periodic order of granum thylakoid membranes. Development of NPQ and light-induced ultrastructural changes, as well as the relaxation processes, follow similar kinetic patterns. Surprisingly, whereas NPQ is suppressed by diuron, it impedes only the relaxation of the structural changes and not its formation, suggesting that structural changes do not cause but enable NPQ. We also demonstrate that the diminishment of SANS peak does not originate from light-induced redistribution and reorientation of chloroplasts inside the cells.

The aim of the present study was to investigate the photosynthetic properties and transcriptomic profiles of wildtype and chlorophyll (Chl) b-lacking rice (Oryza sativa L.). The plastid ultrastructure of the Chl b-lacking rice (i.e., loss of starch granules, abundant vesicles, and abundant plastoglobuli) indicated abnormal plastid development, whereas the analysis of transcriptome profiles and differentially expressed genes revealed that gene encoding PsbR (PSII core protein) was downregulated in the mutant, thereby reducing the Chl accumulation of the mutant. Meanwhile, in regards to Chl biosynthesis and degradation pathways, GluTR gene was downregulated, whereas UROD, CPOX, and MgCH genes were upregulated. The qPCR results were generally consistent with those of the transcription analysis, except for the finding that NOL genes, which regulate Chl b degradation, were upregulated. These results suggest that both the reduction in Chl accumulation and increase in conversion rate of Chl b to Chl a caused Chl a/b ratio amplification in mutant. The present study also provides evidence for Chl b degradation via pheophorbide b. [ABSTRACT FROM AUTHOR]

In vascular plants, the thylakoid architecture is dominated by the highly structured multiple membrane layers known as grana. The structural diversity of the thylakoid system among plant species is mainly determined by the adaptation to the growth light regime, according to a paradigm stating that shade-tolerant species are featured by a high membrane extension with an enhanced number of thylakoid layers per granum. In this study, the thylakoid system was analysed in Selaginella martensii Spring, a shade-adapted rainforest species belonging to lycophytes, a diminutive plant lineage, sister clade of all other vascular plants (euphyllophytes, including ferns and seed plants). The species is characterized by giant cup-shaped chloroplasts in the upper epidermis and, quantitatively less important, disk-shaped chloroplasts in the mesophyll and lower epidermis. The study aimed at the quantitative assessment of the thylakoid appression exploiting a combination of complementary methods, including electron microscopy, selective thylakoid solubilisation, electron paramagnetic resonance, and simultaneous analysis of fast chlorophyll a fluorescence and P700 redox state. With a chlorophyll a / b ratio of 2.6 and PSI/PSII ratio of 0.31, the plant confirmed two typical hallmarks of shade-adaptation. The morphometric analysis of electron micrographs revealed a 33% fraction of non-appressed thylakoid domains. However, contrasting with the structural paradigm of thylakoid shade-adaptation in angiosperms, S. martensii privileges the increase in the granum diameter in place of the increase in the number of layers building the granum. The very wide grana diameter, 727 nm on average, largely overcame the threshold of 500 nm currently hypothesized to allow an effective diffusion of long-range electron carriers. The fraction of non-appressed membranes based on the selective solubilisation of thylakoids with digitonin was 26%, lower than the morphometric determination, indicating the presence of non-appressed domains inaccessible to the detergent, most probably because of the high three-dimensional complexity of the thylakoid system in S. martensii. Particularly, strong irregularity of grana stacks is determined by assembling thylakoid layers of variable width that tend to slide apart from each other as the number of stacked layers increases. • Selaginella martensii shows photosynthetic hallmarks of shade adaptation. • Wide grana diameter prevails over the stacking of several layers. • 500 nm is not an upper threshold to the granum diameter. • Strong irregularity of grana leads to a structurally complex thylakoid system. • Not all stroma-exposed thylakoid domains are accessible to digitonin. [ABSTRACT FROM AUTHOR]

Build-up of the energized state of thylakoid membranes and the synthesis of ATP are warranted by organizing their bulk lipids into a bilayer. However, the major lipid species of these membranes, monogalactosyldiacylglycerol, is a non-bilayer lipid. It has also been documented that fully functional thylakoid membranes, in addition to the bilayer, contain an inverted hexagonal (HII) phase and two isotropic phases. To shed light on the origin of these non-lamellar phases, we performed 31P-NMR spectroscopy experiments on sub-chloroplast particles of spinach: stacked, granum and unstacked, stroma thylakoid membranes. These membranes exhibited similar lipid polymorphism as the whole thylakoids. Saturation transfer experiments, applying saturating pulses at characteristic frequencies at 5 °C, provided evidence for distinct lipid phases—with component spectra very similar to those derived from mathematical deconvolution of the 31P-NMR spectra. Wheat-germ lipase treatment of samples selectively eliminated the phases exhibiting sharp isotropic peaks, suggesting easier accessibility of these lipids compared to the bilayer and the HII phases. Gradually increasing lipid exchanges were observed between the bilayer and the two isotropic phases upon gradually elevating the temperature from 5 to 35 °C, suggesting close connections between these lipid phases. Data concerning the identity and structural and functional roles of different lipid phases will be presented in the accompanying paper.

In 1980, Wildman et al. (Bot Gaz 141: 24-36) proposed a three-dimensional model for chloroplast structure whereby the grana were arranged in non-overlapping rows, like beads on a string. This string-of-grana model was developed from phase microscope analysis of living cells and partially disrupted, isolated chloroplasts. However, models based on analyses by various electron microscope (EM) techniques (which inevitably encompass a relatively small fraction of the whole chloroplast) indicated that grana are interconnected in all directions by intergranal lamellae and not just along a single 'string.' Hence the string-of-grana model was not widely accepted. Recently, confocal laser scanning microscopy (CLSM) of both living and fixed cells, which gives views of the three-dimensional disposition of grana by imaging Photosystem II fluorescence over much larger sample volumes, that is, the entire chloroplast, has revealed that, although many grana are apparently not in any discernible arrangement, some are indeed present in strings of varying lengths in a range of taxa. The topic therefore warrants revisiting, using techniques, for example, such as EM tomography to assess the degree of variation in the geometry of intergranal connections in whole chloroplasts, and its possible functional consequences and developmental origins.

Abstract Diatoms show a special organisation of their plastid membranes, such that their thylakoids span the entire plastid in bands of three. While in higher plants the interaction of the light harvesting complex II and photosystem II with divalent cations (especially Mg2+) was found to take part in the interplay of electrostatic attraction and repulsion in grana membrane appression, for diatoms the key players in maintaining proper membrane distances were not identified so far. In this work, we investigated the changes in the thylakoid architecture of Thalassiosira pseudonana in reaction to different salts by using circular dichroism and fluorescence spectroscopy in combination with other techniques. We show that divalent cations have an important influence on optimal pigment organisation and thus also on maintaining membrane appression. Thereby, monovalent cations are far less effective. The concentration needed is in a physiological range and fits well with the values obtained for higher plant grana stacking, despite the fact that strict protein segregation as seen in higher plant grana is missing. Graphical abstract Unlabelled Image Highlights • Mg2+ participates in the regulation of diatom thylakoid membrane distances. • Optimal cation concentrations are in the same range as in higher plants grana. • Higher salt concentrations lead to reversible increase of the interthylakoidal space. • The inner four core thylakoid membranes resemble grana in their adhesion behaviour. [ABSTRACT FROM AUTHOR]

LHCI, the peripheral antenna system of Photosystem I, includes four light-harvesting proteins (Lhca1-Lhca4) in higher plants, all of which are devoid in the Arabidopsis thaliana knock-out mutant ΔLhca. PSI absorption cross-section was reduced in the mutant, thus affecting the redox balance of the photosynthetic electron chain and resulting in a more reduced PQ with respect to the wild type. ΔLhca plants developed compensatory response by enhancing LHCII binding to PSI. However, the amplitude of state transitions, as measured from changes of chlorophyll fluorescence in vivo, was unexpectedly low than the high level of PSI-LHCII supercomplex established. In order to elucidate the reasons for discrepancy, we further analyzed state transition in ΔLhca plants. The STN7 kinase was fully active in the mutant as judged from up-regulation of LHCII phosphorylation in state II. Instead, the lateral heterogeneity of thylakoids was affected by lack of LHCI, with LHCII being enriched in stroma membranes with respect to the wild type. Re-distribution of this complex affected the overall fluorescence yield of thylakoids already in state I and minimized changes in RT fluorescence yield when LHCII did connect to PSI reaction center. We conclude that interpretation of chlorophyll fluorescence analysis of state transitions becomes problematic when applied to mutants whose thylakoid architecture is significantly modified with respect to the wild type. [ABSTRACT FROM AUTHOR]

The effects of sucrose (Suc) on the ultrastructure of photosynthetic apparatus (PSA) and its functional characteristics were investigated in chilling-tolerant Snowdrop (Galanthus nivalis L.). On the first stage of the experiments, the plants were acclimated at +5 °C and then their detached leaves were subjected to low temperatures (-5 or -15 °C) in the presence of Suc (0.02 or 0.1 M). The electron microscopic analysis showed that Suc treatment at +5 °C induced granal thylakoid elongation and reduction of number of thylakoids. At negative temperatures, the number of thylakoids per granum and the height of grana increased after Suc treatment. The data obtained by method of slow induction chlorophyll fluorescence showed that sharp drop in functional parameters (Fv/Fm, qP, and ETR) with decrease in temperature from +5 to -15 °C was prevented in part by treating of leaves with 0.02 M Suc and, to a large extent, after exposure of leaves in 0.1 M Suc solution. Non-photochemical quenching of fluorescence increased with decrease in the temperature to -15 °C and stabilized with Suc-treatment. The effect of Suc on G. nivalis PSA ultrastructure and functioning suggests that their chloroplasts are capable of osmotic adjustment in response to cold stress. [ABSTRACT FROM AUTHOR]

It is well established that the majority of energy-converting photosynthetic protein complexes in plant thylakoid membrane are nonhomogenously distributed between stacked and unstacked membrane regions. Yet, the sublocalization of the central cytochrome b 6 f complex remains controversial. We present a structural model that explains the variation in cytochrome b 6 f sublocalization data. Small changes in the distance between adjacent membranes in stacked grana regions either allow or restrict access of cytochrome b 6 f complexes to grana. If the width of the gap falls below a certain threshold, then the steric hindrance prevents cytochrome b 6 f access to grana. Evidence is presented that the width of stromal gap is variable, demonstrating that the postulated mechanism can regulate the lateral distribution of the cytochrome b 6 f complexes. [ABSTRACT FROM AUTHOR]

With the idea of knowing the impact on society that has had a degree in Psicología1 University Science Center health2 University of Guadalajara3, located in the city of Guadalajara Jalisco, Mexico state, the university authorities decided to take a process of evaluation from the previous analysis of options accrediting agencies internationally and in which it decided to opt for GRANA4 organization, which means "generating resources for accreditation in the nations of America", its methodology decimal system based on a qualitative and quantitative assessment consists of 10 items or dimensions, 100 items and 1000 indicators of second and third generation. Their referents support and context are based on organizations: the UNESCO5, the OCDE6, OMC7 the Mundial8 Bank and the declaration of Bolonia9 among others. During the evaluation process it is used SIEVAS10 computing platform which means monitoring and evaluation system "which facilitates filling and evaluation process during its stages and allows interaction between evaluators. Its tools to facilitate evaluation are: meanings, contexts, references, glossary, decimal scale to rate levels of quality, fields to integrate the strengths, weaknesses, plan continuous improvement and formats for integrating statistics retrospective and prospectively. The computer system provides availability to include supporting documents and websites that help the evaluation process. It also features graphics that are built automatically as the platform evaluation is incorporated. There are 10 processes for the entire evaluation process, starting with internal assessment, after the external evaluation, concluding with the delivery of results and continuous improvement plan (PMP). The internal evaluation was conducted by a committee of the institution evaluated consisting of: 3 teachers, 2 managers, 1 students and graduates processes and linked to employers associated with the program to be evaluated. While, external evaluators were from 3 countries11: Argentina, Venezuela and Spain specializing in the discipline assessed with experience in evaluation processes in the field of discipline either in their country or region of origin. The basis of the article focuses on the dimension or category 1 called "social impact of training". That is formed of 10 items and 100 indicators according to GRANA model. This process lasted 6 months starting in June 2015 and ending on 15 January 2016. He is currently running the PMP led this degree in line with improvement proposals suggested by the expert committee evaluator. [ABSTRACT FROM AUTHOR]

The most enigmatic feature of mature thylakoids of Angiosperms is the presence of piles of membranous discs forming the cylindrical structures known as grana. Although some models aim to elucidate their formation, until now the mechanism governing the architecture of thylakoid stacks remains obscure. In this work a new model is presented aiming to explain the way thylakoids stack. In comparison with previous models, this model proposes a dynamic mechanism for the rapid selfassembly of thylakoid stacks and their subsequent disassembly under the influence of a variety of physicochemical factors and is consistent with the evolutionary origin of these membranes and their ontogenetic continuity. The model proposes that, under the influence of attractive electrostatic forces, the membranes come closer in a parallel alignment and the photosystem II/light harvesting complexes migrate laterally forming circular aggregates. Finally the thylakoids rotate around the vertical axis of the superimposed aggregates, under the action of a torque.

In NADP-malic enzyme (NADP-ME) type C4 plants, MC chloroplasts have well-developed grana, whereas BSC chloroplasts are generally characterized by highly reduced grana. In the previous study, salt treatment induced granal development in BSC chloroplasts of Zea mays, an NADP-ME type C4 plant. Therefore, we examined the effects of salinity stress on the granal structure of BSC chloroplasts in seven other C4 species belonging to the NADP-ME type. The plants were grown in soil and after a certain period of time, they were treated with 3% NaCl for 5 d. Ultrastructure and quantitative properties of chloroplasts at the middle part of leaf tissues were investigated. In BSC chloroplasts of all the C4 species, almost no structural damage was observed, but the development of granal stacking was induced under salinity condition. Granal indices and appressed thylakoid density of BSC chloroplasts in the salt-treated plants were higher than those in the control plants. In all the species, the structure of MC chloroplasts was more or less damaged by salt stress; thylakoids were swollen and chloroplast envelope was disorganized. These results suggest that the granal development in BSC chloroplasts and the high damage of MC chloroplasts are common features of NADP-ME type C4 plants under salinity stress.

The most enigmatic feature of mature thylakoids of Angiosperms is the presence of piles of membranous discs forming the cylindrical structures known as grana. Although some models aim to elucidate their formation, until now the mechanism governing the architecture of thylakoid stacks remains obscure. In this work a new model is presented aiming to explain the way thylakoids stack. In comparison with previous models, this model proposes a dynamic mechanism for the rapid selfassembly of thylakoid stacks and their subsequent disassembly under the influence of a variety of physicochemical factors and is consistent with the evolutionary origin of these membranes and their ontogenetic continuity. The model proposes that, under the influence of attractive electrostatic forces, the membranes come closer in a parallel alignment and the photosystem II/light harvesting complexes migrate laterally forming circular aggregates. Finally the thylakoids rotate around the vertical axis of the superimposed aggregates, under the action of a torque. [ABSTRACT FROM AUTHOR]

El insento (D. Coccus) es una especie de las plagas de ciertas especies de cactáceas de las cuales se obtiene un valioso colorante rojo que es utilizado en la industria textil, alimentaria, cosmética y famaceutica. Para obtener el articulo completo pueden contactar al Editor de la Revista Ecosistemas y Recursos Agropecuarios en el siguiente correo electrónico era@ujat.mx y se les enviará sin algún costo.

The light-harvesting antenna of higher plant photosystem II ( LHCII) is the major photosynthetic membrane component encoded by an entire family of homologous nuclear genes. On the contrary, the great majority of proteins of photosystems and electron transport components are encoded by the chloroplast genome. In this work, we succeeded in gradually inhibiting the expression of the chloroplast genes that led to the disappearance of the photosystem complexes, mimicking almost total photoinhibition. The treated plants, despite displaying only some early signs of senescence, sustained their metabolism and growth for several weeks. The only major remaining membrane component was LHCII antenna that formed superstructures - stacks of dozens of thylakoids or supergrana. Freeze-fracture electron microscopy revealed specific organization, directly displaying frequently bifurcated membranes with reduced or totally absent photosystem II ( PSII) reaction centre complexes. Our findings show that it is possible to accumulate large amounts of light-harvesting membranes, organized into three-dimensional structures, in the absence of reaction centre complexes. This points to the reciprocal role of LHCII and PSII in self-assembly of the three-dimensional matrix of the photosynthetic membrane, dictating its size and flexible adaptation to the light environment. [ABSTRACT FROM AUTHOR]

Chloroplasts utilize photons from solar radiation to synthesize energy-rich molecules of ATPs and NADPHs, which are further used in active cellular processes. Multiprotein complexes (MPCs), including photosystems (PSII and PSI), and the cellular architecture responsible for generation of the proton motive force and the subsequent photophosphorylation, mediate the task of ATP and NADPH synthesis. Both photosystems and other multiprotein assemblies are embedded in thylakoid membranes. Advances in techniques used to study structural biology, biophysics, and comparative genomics and proteomics have enabled us to gain insights of structure, function, and localization of each individual component of the photosynthetic apparatus. An efficient coordination among MPCs is essential for normal functioning of photosynthesis, but there are various stressors that might directly or indirectly interact with photosynthetic components and processes. Cadmium is one of the toxic heavy metals that interact with photosynthetic components and damage photosystems and other MPCs in thylakoids. In plants, iron deficiency shows similar symptoms as those caused by Cd. Our article provides a general overview of chloroplast structure and a critical account of Cd-induced changes in photosystems and other MPCs in thylakoids, and suggests the possible mechanisms involved in mediating these changes. The connection between Cd-induced Fe deficiency and the elevated Cd toxicity under the Fe-deficient condition was also discussed. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the significance of blue light (B) in the growth and photosynthetic capacity of cucumber. Gas exchange, chlorophyll (Chl) fluorescence kinetics, chloroplast ultrastructure, and leaf growth were investigated to explore the influence of three different light qualities of light emitting diodes (LEDs) on plant morphogenesis and the development of photosynthetic apparatus in cucumber ( Cucumis sativus) leaves from emergence to full expansion under weak light [50 μmol(photon) m s]. We found that B could significantly increase the leaf area (LA), shoot elongation, Chl a/ b, net photosynthetic rate, and stomatal conductance ( g). In addition, the comparisons of maximal quantum yield of PSII photochemistry and the photosynthetic performance index between B-, W (white light)-, and R (red light)-grown leaves suggested that B was essential for the development of photosynthetic apparatus under weak light. B-grown leaves had the lowest Chl content under weak light, however, they had well-developed chloroplasts with the highest degree of stacked lamellae and the lowest starch accumulation. This could explain to a considerable extent the highest net photosynthetic rate per Chl unit. The results demonstrated that B optimized photosynthetic performance by improving the photosynthetic rate, increasing LA, and prolonging active photosynthesis duration under low irradiance. Therefore B is necessary to ensure healthy development of chloroplasts and highly efficient photosynthetic functions in cucumbers under a weak light environment. More importantly, our study also provided theoretical and technical support for the development of light environmental control technology. [ABSTRACT FROM AUTHOR]

The reaction center-binding D1 protein of Photosystem II is damaged by excessive light, which leads to photoinhibition of Photosystem II. The damaged D1 protein is removed immediately by specific proteases, and a metalloprotease FtsH located in the thylakoid membranes is involved in the proteolytic process. According to recent studies on the distribution and organization of the protein complexes/supercomplexes in the thylakoid membranes, the grana of higher plant chloroplasts are crowded with Photosystem II complexes and light-harvesting complexes. For the repair of the photodamaged D1 protein, the majority of the active hexameric FtsH proteases should be localized in close proximity to the Photosystem II complexes. The unstacking of the grana may increase the area of the grana margin and facilitate easier access of the FtsH proteases to the damaged D1 protein. These results suggest that the structural changes of the thylakoid membranes by light stress increase the mobility of the membrane proteins and support the quality control of Photosystem II. [ABSTRACT FROM AUTHOR]

Background Grana and starch are major functional structures for photosynthesis and energy storage of plant, respectively. Both exhibit highly ordered molecular structures and appear as micrometer-sized granules inside chloroplasts. In order to distinguish grana and starch, we used multiphoton microscopy, with simultaneous acquisition of two-photon fluorescence (2PF) and second harmonic generation (SHG) signals. SHG is sensitive to crystallized structures while 2PF selectively reveals the distribution of chlorophyll. Result Three distinct microstructures with different contrasts were observed, i.e. "SHG dominates", "2PF dominates", and "SHG collocated with 2PF". It is known that starch and grana both emit SHG due to their highly crystallized structures, and no autofluorescence is emitted from starch, so the "SHG dominates" contrast should correspond to starch. The contrast of "SHG collocated with 2PF" is assigned to be grana, which exhibit crystallized structure with autofluorescent chlorophyll. The "2PF dominates" contrast should correspond to stroma thylakoid, which is a non-packed membrane structure with chrolophyll. The contrast assignment is further supported by fluorescence lifetime measurement. Conclusion We have demonstrated a straightforward and noninvasive method to identify the distribution of grana and starch within an intact leaf. By merging the 2PF and SHG images, grana, starch and stroma thylakoid can be visually distinguished. This approach can be extended to the observation of 3D grana distribution and their dynamics in living plants. [ABSTRACT FROM AUTHOR]

The chloroplasts of land plants contain internal membrane systems, the thylakoids, which are arranged in stacks called grana. Because grana have not been found in Cyanobacteria, the evolutionary origin of genes controlling the structural and functional diversification of thylakoidal membranes in land plants remains unclear. The angulata10-1 (anu10-1) mutant, which exhibits pale-green rosettes, reduced growth, and deficient leaf lateral expansion, resulting in the presence of prominent marginal teeth, was isolated. Palisade cells in anu10-1 are larger and less packed than in the wild type, giving rise to large intercellular spaces. The ANU10 gene encodes a protein of unknown function that localizes to both chloroplasts and amyloplasts. In chloroplasts, ANU10 associates with thylakoidal membranes. Mutant anu10-1 chloroplasts accumulate H2O2, and have reduced levels of chlorophyll and carotenoids. Moreover, these chloroplasts are small and abnormally shaped, thylakoidal membranes are less abundant, and their grana are absent due to impaired thylakoid stacking in the anu10-1 mutant. Because the trimeric light-harvesting complex II (LHCII) has been reported to be required for thylakoid stacking, its levels were determined in anu10-1 thylakoids and they were found to be reduced. Together, the data point to a requirement for ANU10 for chloroplast and mesophyll development. [ABSTRACT FROM AUTHOR]

The role of thylakoid grana still remains enigmatic. Here, we outline current research on the structural dynamics and biogenesis of land plant thylakoids and discuss recent developments.Thylakoids of land plants have a bipartite structure, consisting of cylindrical grana stacks, made of membranous discs piled one on top of the other, and stroma lamellae which are helically wound around the cylinders. Protein complexes predominantly located in the stroma lamellae and grana end membranes are either bulky [photosystem I (PSI) and the chloroplast ATP synthase (cpATPase)] or are involved in cyclic electron flow [the NAD(P)H dehydrogenase (NDH) and PGRL1–PGR5 heterodimers], whereas photosystem II (PSII) and its light-harvesting complex (LHCII) are found in the appressed membranes of the granum. Stacking of grana is thought to be due to adhesion between Lhcb proteins (LHCII or CP26) located in opposed thylakoid membranes. The grana margins contain oligomers of CURT1 proteins, which appear to control the size and number of grana discs in a dosage- and phosphorylation-dependent manner. Depending on light conditions, thylakoid membranes undergo dynamic structural changes that involve alterations in granum diameter and height, vertical unstacking of grana, and swelling of the thylakoid lumen. This plasticity is realized predominantly by reorganization of the supramolecular structure of protein complexes within grana stacks and by changes in multiprotein complex composition between appressed and non-appressed membrane domains. Reversible phosphorylation of LHC proteins (LHCPs) and PSII components appears to initiate most of the underlying regulatory mechanisms. An update on the roles of lipids, proteins, and protein complexes, as well as possible trafficking mechanisms, during thylakoid biogenesis and the de-etiolation process complements this review. [ABSTRACT FROM PUBLISHER]

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Photosynthetic membrane sacs (thylakoids) of plants form granal stacks interconnected by nonstacked thylakoids, thereby being able to fine-tune (i) photosynthesis, (ii) photoprotection and (iii) acclimation to the environment. Growth in low light leads to the formation of large grana, which sometimes contain as many as 160 thylakoids. The net surface charge of thylakoid membranes is negative, even in low-light-grown plants; so an attractive force is required to overcome the electrostatic repulsion. The theoretical van derWaals attraction is, however, at least 20-fold too small to play the role. We determined the enthalpy change, in the spontaneous stacking of previously unstacked thylakoids in the dark on addition of Mg2+, to be zero or marginally positive (endothermic). The Gibbs free-energy change for the spontaneous process is necessarily negative, a requirement that can be met only by an increase in entropy for an endothermic process. We conclude that the dominant attractive force in thylakoid stacking is entropy-driven. Several mechanisms for increasing entropy upon stacking of thylakoid membranes in the dark, particularly in low-light plants, are discussed. In the light, which drives the chloroplast far away from equilibrium, granal stacking accelerates non-cyclic photophosphorylation, possibly enhancing the rate at which entropy is produced. [ABSTRACT FROM AUTHOR]

The distinctive lateral organization of the protein complexes in the thylakoid membrane investigated by Jan Anderson and co-workers is dependent on the balance of various attractive and repulsive forces. Modulation of these forces allows critical physiological regulation of photosynthesis that provides efficient light-harvesting in limiting light but dissipation of excess potentially damaging radiation in saturating light. The light-harvesting complexes (LHCII) are central to this regulation, which is achieved by phosphorylation of stromal residues, protonation on the lumen surface and de-epoxidation of bound violaxanthin. The functional flexibility of LHCII derives from a remarkable pigment composition and configuration that not only allow efficient absorption of light and efficient energy transfer either to photosystem II or photosystem I core complexes, but through subtle configurational changes can also exhibit highly efficient dissipative reactions involving chlorophyll--xanthophyll and/or chlorophyll--chlorophyll interactions. These changes in function are determined at a macroscopic level by alterations in protein-protein interactions in the thylakoid membrane. The capacity and dynamics of this regulation are tuned to different physiological scenarios by the exact protein and pigment content of the light-harvesting system. Here, the molecular mechanisms involved will be reviewed, and the optimization of the light-harvesting system in different environmental conditions described. [ABSTRACT FROM AUTHOR]

Long-term acclimation of shade versus sun plants modulates the composition, function and structural organization of the architecture of the thylakoid membrane network. Significantly, these changes in the macroscopic structural organization of shade and sun plant chloroplasts during long-term acclimation are also mimicked following rapid transitions in irradiance: reversible ultrastructural changes in the entire thylakoid membrane network increase the number of grana per chloroplast, but decrease the number of stacked thylakoids per granum in seconds to minutes in leaves. It is proposed that these dynamic changes depend on reversible macro-reorganization of some light-harvesting complex IIb and photosystem II supracomplexes within the plant thylakoid network owing to differential phosphorylation cycles and other biochemical changes known to ensure flexibility in photosynthetic function in vivo. Some lingering grana enigmas remain: elucidation of the mechanisms involved in the dynamic architecture of the thylakoid membrane network under fluctuating irradiance and its implications for function merit extensive further studies. [ABSTRACT FROM AUTHOR]