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This study investigates carbon partitioning in the developing endosperm of a European variety of spring wheat subjected to moderately elevated daytime temperatures (27°C/16°C d/night) from anthesis to grain maturity. Elevated daytime temperatures caused significant reductions in both fresh and dry weights and reduced the starch content of harvested grains compared to plants grown under a 20°C/16°C d/night regimen. Accelerated grain development caused by elevated temperatures was accounted for by representing plant development as thermal time (°C DPA). We examined the effects of high-temperature stress (HTS) on the uptake and partitioning of [U-14C]-sucrose supplied to isolated endosperms. HTS caused reduced sucrose uptake into developing endosperms from the second major grain-filling stage (approximately 260°C DPA) up to maturity. Enzymes involved in sucrose metabolism were unaffected by HTS, whereas key enzyme activities involved in endosperm starch deposition such as ADP-glucose pyrophosphorylase and soluble isoforms of starch synthase were sensitive to HTS throughout grain development. HTS caused a decrease in other major carbon sinks such as evolved CO2, ethanol-soluble material, cell walls and protein. Despite reductions in the labeling of carbon pools caused by HTS, the relative proportions of sucrose taken up by endosperm cells allocated to each cellular pool remain unchanged, except for evolved CO2, which increased under HTS and may reflect enhanced respiratory activity. The results of this study show that moderate temperature increases can cause significant yield reductions in some temperate wheat cultivars chiefly through three effects: reduced sucrose uptake by the endosperm, reduced starch synthesis and increased partitioning of carbon into evolved CO2.

Accurate estimation of the static and dynamic wind loads on heliostats based on detailed measurement and characterisation of turbulence is crucial to avoid structural failure and reduce the cost of the structural heliostat components. Wind load predictions for heliostats are not specified in design standards for buildings because of a heliostat’s non-standard shape and the variations of wind velocity and turbulence in the lowest 10 m of the atmospheric boundary layer (ABL). This paper reviews the static and dynamic wind loads on heliostats in the most unfavourable operating and stow positions, with a focus on the aerodynamic effects related to the heliostat structural component geometry, turbulence parameters in the ABL and field spacing. An increased resolution of field-scale wind measurements at heliostat field sites is recommended to fully characterise the ABL turbulence, as the high-intensity gusts over shorter durations at heights below 10 m lead to high-amplitude displacements with larger frequencies than observed in standard building structures. Increased understanding and development of aerodynamic wind load predictions for heliostats, based on their critical scaling parameters and local wind conditions, would increase the accuracy of annual field efficiency models through an improved resolution of operating load data and reduce the capital cost of structural components in power tower plants.

Starch synthesis is an elaborate process employing several isoforms of starch synthases (SSs), starch branching enzymes (SBEs) and debranching enzymes (DBEs). In cereals, some starch biosynthetic enzymes can form heteromeric complexes whose assembly is controlled by protein phosphorylation. Previous studies suggested that SSIIa forms a trimeric complex with SBEIIb, SSI, in which SBEIIb is phosphorylated. This study investigates the post-translational modification of SSIIa, and its interactions with SSI and SBEIIb in maize amyloplast stroma. SSIIa, immunopurified and shown to be free from other soluble starch synthases, was shown to be readily phosphorylated, affecting Vmax but with minor effects on substrate Kd and Km values, resulting in a 12-fold increase in activity compared with the dephosphorylated enzyme. This ATP-dependent stimulation of activity was associated with interaction with SBEIIb, suggesting that the availability of glucan branching limits SSIIa and is enhanced by physical interaction of the two enzymes. Immunoblotting of maize amyloplast extracts following non-denaturing polyacrylamide gel electrophoresis identified multiple bands of SSIIa, the electrophoretic mobilities of which were markedly altered by conditions that affected protein phosphorylation, including protein kinase inhibitors. Separation of heteromeric enzyme complexes by GPC, following alteration of protein phosphorylation states, indicated that such complexes are stable and may partition into larger and smaller complexes. The results suggest a dual role for protein phosphorylation in promoting association and dissociation of SSIIa-containing heteromeric enzyme complexes in the maize amyloplast stroma, providing new insights into the regulation of starch biosynthesis in plants.

This paper investigated the influence of the turbulent wind fluctuations in the lowest 10 m of the atmospheric boundary layer (ABL), depending on the surface roughness of the terrain surrounding a heliostat field, on the required dimensions and material cost of the structural heliostat components to resist the combined bending and torsional stresses due to the design wind loads. Turbulence data in the lowest 10 m of the full-scale ABL from ESDU 85020 were correlated with peak wind load coefficients on model-scale heliostats in wind tunnel experiments to determine the design wind loads as a function of heliostat size and terrain roughness. The results highlight the large dependence of wind loads and cost on terrain roughness with increasing heliostat size. The increasing mass of steel per unit area in the pedestal, torque tube and support mass led to their relative contribution increasing from 18% of the total specific cost of a 25 m2 heliostat to 34% of the total cost of a 150 m2 heliostat. The effect of the increasing turbulence characteristics in a high-roughness terrain resulted in a 10% increase in the total cost of a 25 m2 heliostat and a 13% increase in the total cost of a 150 m2 heliostat. An improved understanding of the influence of ABL turbulence on the design wind loads on full-scale heliostats can therefore allow the dimensions of structural components and the respective material cost of manufacturing to be optimised for the local wind conditions and terrain at different sites.

Starch branching enzymes (SBEs) are one of the major classes of enzymes that catalyze starch biosynthesis in plants. Here, we utilized the clustered regularly interspaced short palindromic repeats–CRISPR associated protein 9 (CRISPR–Cas9)-mediated gene editing system to investigate the effects of SBE mutation on starch structure and turnover in the oilseed crop Brassica napus. Multiple single-guide RNA (sgRNA) expression cassettes were assembled into a binary vector and two rounds of transformation were employed to edit all six BnaSBE genes. All mutations were heterozygous monoallelic or biallelic, and no chimeric mutations were detected from a total of 216 editing events. Previously unannotated gene duplication events associated with two BnaSBE genes were characterized through analysis of DNA sequencing chromatograms, reflecting the complexity of genetic information in B. napus. Five Cas9-free homozygous mutant lines carrying two to six mutations of BnaSBE were obtained, allowing us to compare the effect of editing different BnaSBE isoforms. We also found that in the sextuple sbe mutant, although indels were introduced at the genomic DNA level, an alternate transcript of one BnaSBE2.1 gene bypassed the indel-induced frame shift and was translated to a modified full-length protein. Subsequent analyses showed that the sextuple mutant possesses much lower SBE enzyme activity and starch branching frequency, higher starch-bound phosphate content, and altered pattern of amylopectin chain length distribution relative to wild-type (WT) plants. In the sextuple mutant, irregular starch granules and a slower rate of starch degradation during darkness were observed in rosette leaves. At the pod-filling stage, the sextuple mutant was distinguishable from WT plants by its thick main stem. This work demonstrates the applicability of the CRISPR–Cas9 system for the study of multi-gene families and for investigation of gene-dosage effects in the oil crop B. napus. It also highlights the need for rigorous analysis of CRISPR–Cas9-mutated plants, particularly with higher levels of ploidy, to ensure detection of gene duplications.

Non-uniform pressure distributions on the heliostat surface due to turbulence in the atmospheric boundary layer (ABL) have a significant impact on the maximum bending moments about the hinge of and pedestal base of a conventional pedestal-mounted heliostat. This paper correlates the movement of the centre of pressure due to the mean and peak pressure distributions with the hinge and overturning moment coefficients using high-frequency pressure and force measurements on a scale-model heliostat within two simulated ABLs generated in a wind tunnel. The positions of the centre of pressure were calculated for a range of heliostat elevation-azimuth configurations using a similar analogy to those in ASCE 7-02 for monoslope-roof buildings, ASCE 7-16 for rooftop solar panels, and in the literature on flat plates. It was found that the maximum hinge moment is strongly correlated to the centre of pressure movement from the heliostat central elevation axis. Application of stow and operating load coefficients to a full-scale 36 m2 heliostat showed that the maximum hinge moment remains below the stow hinge moment at maximum operating design gust wind speeds of 29 m/s in a suburban terrain and 33 m/s in a desert terrain. The operating hinge moments at elevation angles above 45° are less than 60% of the stow loads with a constant 40 m/s design wind speed. The results in the current study can be used to determine heliostat configurations and appropriate design wind speeds in different terrains leading to the maximum design wind loads on the elevation drive and foundation.

This paper investigated the integral length scales of turbulence in a low-roughness atmospheric surface layer (ASL), characterised by very smooth terrain in the Utah desert during near-neutral cond...

The correlation between turbulence intensity and length scale and the lift force on a horizontal flat plate in an atmospheric boundary layer flow is investigated in this study. Experiments were conducted in a large-scale wind tunnel to measure the peak loads on flat plate models of various chord length dimensions at different heights within simulated atmospheric boundary layers. The peak lift force coefficient on the flat plates was correlated with both turbulence intensity and length scale. The results show that the peak lift force coefficient on the flat plate is a function of vertical integral length scale ( L w x ) and vertical turbulence intensity ( I w ) in terms of a parameter defined as I w ( L w x c ) 2.4 , where c is the chord length of the plate. An increase in this turbulence parameter from 0.005 to 0.054, increases the peak lift force coefficient from 0.146 to 0.787. The established relationship is then used to predict the peak wind loads on full-scale heliostats within the atmospheric surface layer as a case study. It is found that decreasing the ratio of heliostat height to the chord length dimension of the mirror panel from 0.5 to 0.2 leads to a reduction of 80% in the peak stow lift force coefficient, independent of the terrain roughness.

During the operation of a concentrating solar thermal (CST) power tower plant, heliostat mirrors inclined at different angles act as bluff bodies that are exposed to large drag loads from the wind. This experimental study investigates the aerodynamic loads on a heliostat in a tandem configuration, to determine the significance of the shielding effect from an upstream heliostat. To understand the effect of turbulence on the peak wind loads, scale-model heliostats with square facets were positioned within a part-depth atmospheric boundary layer (ABL) with a Power Law velocity profile. Peak drag coefficients on the instrumented downstream heliostat in the tandem configuration were normalized with respect to those on a single (isolated) heliostat. A range of tandem configurations were tested to determine the effects of elevation angle, azimuth angle, and gap spacing between the tandem heliostats. Findings show that peak drag loads are reduced by up to 60% on the downstream heliostat relative to an isolated heliostat at an elevation angle of 90 Â ° and a gap spacing of two chord lengths, but at higher gap spacing the shielding effect is either marginal or non-existent. Peak hinge moment coefficients on a downstream heliostat in tandem are up to seven times the load on an isolated heliostat, with the maximum occurring at 90 Â ° elevation and 180 Â ° azimuth. Base-overturning moment coefficients are less affected, as the changes in the centre of pressure location are relatively small compared to the length of the support pylon. Strouhal number analysis of the fluctuating surface pressures indicated that the dominant frequency of the pressure spectra on the downstream heliostat is over three times the value on an isolated heliostat at 45 Â ° elevation and azimuth angles. Hence, both static and dynamic effects must be considered separately in the wind load design for heliostats at typical operating angles.

summary Sphagnum cuspidatum Hoffm. was collected from a remote site in N. Wales, and a polluted site in the S. Pennines. When added to artificial rainwater solution, HSO3− was oxidized to SO42−. The rate at which this oxidation occurred was modified differentially by the mosses from the two sites. S. cuspidatum from the S. Pennines promoted a rapid oxidation rate and disappearance of HSO3− was complete in 6 h. S. cuspidatum from N. Wales, on the other hand, achieved a very slow oxidation rate and HSO3− persisted in solution for more than 24 h. Prolonged exposure to HSO3− in the Welsh material caused damage to, and eventual death of, this material but not of the S. Pennine moss. The rates of HSO3− oxidation promoted by the mosses from the two sites appear to be related to the concentration of the transition metal ions, Fe(III), Mn(II), and Cu(II), present on the cell-wall cation-exchange sites. These metals, particularly Fe, present on the surface of the S. Pennine material catalysed a rapid chemical oxidation of HSO3− to SO42−. The increased levels of transition metals associated with the S. Pennine moss originate in the peat as a legacy of past pollution events at this site. Levels of Fe were approximately 100 times greater than those for Mn or Cu and 5–10 times higher on the S. Pennine moss than on that from N. Wales. Removal of these metal ions (using EDTA) from the surface of the S. Pennine material removed the HSO3− oxidizing ability of the moss, leading eventually to cell death. The ability to withstand high levels of HSO3− was conferred upon the Welsh moss by supplying Fe(m) in artificial rainwater solution under laboratory conditions. Transplanting Sphagnum from the Welsh to the S. Pennine site gave rise to a similar response. Nomenclature of mosses follows Smith (1978).

summary Shoots of Sphagnum cuspidatum Hoffm. were collected from two sites: one, a relatively unpolluted site in N. Wales, remote from pollution sources and the other, a grossly polluted site in the South Pennines.* Material from both sites was grown in the laboratory and exposed to artificial rainwater solution with and without bisulphite (HSO3) amendment (0.1 mM). Effects of exposure to HSO3 for up to 21 days on growth, photosynthesis, chlorophyll a fluorescence and chlorophyll concentrations were studied in the two Sphagnum populations. Application of HSO3 produced significantly less than maximum growth in Sphagnum from both sites. This effect was far greater, however, in the material from the unpolluted Welsh site. Photosynthesis in the Welsh material treated with HSO3 decreased steadily with time; after 21 days of exposure, photosynthetic oxygen evolution had ceased. This decrease was accompanied by a decrease in fluorescence quenching (as [(P – T)/P]), suggesting a gradual loss of water-splitting activity. In contrast, HSO3 initially stimulated photosynthesis in Sphagnum from the polluted site. Chlorophyll concentration was decreased in Spliagmtm from both sites in the presence of HSO3 Possible mechanisms of tolerance to HSO3 are discussed.

Manipulation of turbulence within an atmospheric boundary layer flow by application of woven wire mesh fences is investigated. Turbulence properties behind fences of different porosities and mesh opening widths were determined from velocity measurements in a wind tunnel. It is found that with the application of a fence with a porosity of 0.46, the streamwise turbulence intensity can be reduced from the inflow level of 12.5%–8.8% and the integral length scale can be reduced from 380 to 270 mm. The results show that behind the mesh fences turbulence kinetic energy decays as a power law function of the downstream distance for all wire mesh fences tested in the wind tunnel. The decay rate of turbulence kinetic energy is faster, and a larger reduction in the integral length scale is achieved for fences with porosities between 0.46 and 0.64 compared to higher porosities of between 0.73 and 0.75. Porosity of the woven wire meshes is found to be the key parameter which influences their turbulence reduction performance. In the end, application of the wire mesh fences for reduction of wind loads on solar panels and heliostats is discussed. Evaluation of wind loads based on the reduction of turbulence intensity and integral length scale shows that up to 48% and 53% reduction in peak drag and lift forces on a heliostat, respectively, can be achieved with application of mesh fences.

This paper investigated the dynamic fluctuations of the high-frequency surface pressure and force measurements on an instrumented scale-model heliostat within a turbulent ABL generated in a wind tunnel. Peak aerodynamic load coefficients on the model heliostat calculated following the equivalent static wind load method were consistent with previous wind tunnel studies in the literature. The dynamic analysis of the hinge, azimuth and overturning moments in the current study showed that there are a range of critical load cases and heliostat configurations that need to be considered to investigate the dynamic loading on the elevation and azimuth drives of a heliostat. Quasi-steady variation of the fluctuating peak loads following a Gaussian distribution was found to under-predict the maximum hinge and overturning moments in operating and stow configurations. It is therefore recommended that the analysis of instantaneous loads on the elevation drive and pedestal foundation is carried out for an improved estimation of the heliostat design wind loads.

The Sucrose Non-fermenting-1-Related Protein Kinase 1 (SnRK1) is a highly conserved heterotrimeric protein kinase in plants. It possesses a catalytic subunit (α) and two regulatory subunits (β and γ). The effects of altered expression of AKINβ1 on carbohydrate metabolism and gene expression in leaves were investigated in an Arabidopsis T-DNA insertion mutant. The contents of key intermediates in the tricarboxylic acid (TCA) cycle of the mutant leaves were markedly reduced throughout the diurnal cycle, coupled with a decrease in measurable respiration rate. Compared to wild-type, 2485 genes and 188 genes were expressed differentially in leaves of the akinβ1 mutant in response to light and darkness respectively. Among these, several genes exhibited very substantial decreases in expression. Notably, expression of particular isoforms of multigene families involved in malate and lipid metabolism, and nitrate uptake showed decreases of 40-240 fold during the light period, but not during darkness. The subcellular localization of AKINβ1 and the regulatory function of N-myristoylation on the subcellular localization of AKINβ1 were investigated, showing that AKINβ1 localizes to Golgi. A model is hypothesized to explain the effects of AKINβ1 on metabolism and gene expression in Arabidopsis.

The unsteady surface pressure distribution on heliostats in a tandem arrangement is investigated in this experimental study. The differential pressure on the panel of a heliostat model is measured for a range of gaps between the two tandem heliostats, varying from 1 to 7 times the chord length dimension of the panel. The heliostat models are placed in a simulated turbulent atmospheric boundary layer in the University of Adelaide wind tunnel. The measured surface pressures are analysed and compared with those of a single heliostat, at three elevation angles of 30°, 60° and 90°. The results showed that the peak pressure distribution on the tandem heliostat differs significantly from the single heliostat. Regions of large-magnitude pressure occur near the edges of the panel at smaller gap ratios. Large unsteady variations of the position of the centre of pressure are found for the tandem heliostat at gap ratios equal to and less than 5, which lead to an increase of the hinge moment relative to the single heliostat. The peak hinge moment coefficient on a tandem heliostat is found to be 40% and 70% larger than the coefficient on the single heliostat at elevation angles of 30° and 60°, respectively. The results therefore indicate the importance of the unsteady wind loads in different rows of a field for the design of heliostats as they vary significantly from the loads on a single heliostat dependent on the field arrangement.

This paper investigates the effects of turbulence in the atmospheric boundary layer (ABL) on the peak wind loads on heliostats in stow position in isolation and in tandem configurations with respect to the critical scaling parameters of the heliostats. The heliostats were exposed to a part-depth ABL in a wind tunnel using two configurations of spires and roughness elements to generate a range of turbulence intensities and integral length scales. Force measurements on different-sized heliostat mirrors at a range of heights found that both peak lift and hinge moments were reduced by up to 30% on the second tandem heliostat when the spacing between the heliostat mirrors was close to the mirror chord length and converged to the isolated heliostat values when the spacing was greater than 5 times the chord length. Peak wind loads on the tandem heliostat were above those on an isolated heliostat for an integral-length-scale-to-chord-length ratio L u x / c of less than 5, whereas tandem loads were 30% lower than an isolated heliostat at L u x / c of 10. The reduced loads on the tandem heliostat corresponded to a shift to higher frequencies of the fluctuating pressure spectra, due to the break-up of large eddies by the upstream heliostat.

This study investigates the dependence of peak wind load coefficients on a heliostat in stow position on turbulence characteristics in the atmospheric surface layer, such that the design wind loads, and thus the size and cost of heliostats, can be further optimised. Wind tunnel experiments were carried out to measure wind loads and pressure distributions on a heliostat in stow position exposed to gusty wind conditions in a simulated part-depth atmospheric boundary layer (ABL). Force measurements on different-sized heliostat mirrors at a range of heights found that both peak lift and hinge moment coefficients, which are at least 10 times their mean coefficients, could be optimised by stowing the heliostat at a height equal to or less than half that of the mirror facet chord length. Peak lift and hinge moment coefficients increased linearly and approximately doubled in magnitude as the turbulence intensity increased from 10% to 13% and as the ratio of integral length scale to mirror chord length L u x / c increased from 5 to 10, compared to a 25% increase with a 40% increase in freestream Reynolds number. Pressure distributions on the stowed heliostat showed the presence of a high-pressure region near the leading edge of the heliostat mirror that corresponds to the peak power spectra of the fluctuating pressures at low frequencies of around 2.4 Hz. These high pressures caused by the break-up of large vortices at the leading edge are most likely responsible for the peak hinge moment coefficients and the resonance-induced deflections and stresses that can lead to structural failure during high-wind events.

Starch commands a central role in the carbon budget of the majority of plants on earth, and its biological role changes during development and in response to the environment. Throughout the life of a plant, starch plays a dual role in carbon allocation, acting as both a source, releasing carbon reserves in leaves for growth and development, and as a sink, either as a dedicated starch store in its own right (in seeds and tubers), or as a temporary reserve of carbon contributing to sink strength, in organs such as flowers, fruits, and developing non-starchy seeds. The presence of starch in tissues and organs thus has a profound impact on the physiology of the growing plant as its synthesis and degradation governs the availability of free sugars, which in turn control various growth and developmental processes. This review attempts to summarize the large body of information currently available on starch metabolism and its relationship to wider aspects of carbon metabolism and plant nutrition. It highlights gaps in our knowledge and points to research areas that show promise for bioengineering and manipulation of starch metabolism in order to achieve more desirable phenotypes such as increased yield or plant biomass.

This experimental study outlines a method to calculate the design wind loads on heliostats, based on peak wind load coefficients reported in the heliostat literature and aerodynamic shape factors derived from high-frequency pressure measurements on an isolated heliostat at different elevation and azimuth angles in a boundary layer wind tunnel. The results show that the aerodynamic shape factors are largest for a range of heliostat configurations, including elevation angles of 15°, 30° and 45°and azimuth angles of 0° and 45°. The distribution of shape factors indicates that the leading edge of the heliostat is most vulnerable to wind-induced mirror damage in this range of critical elevation angles for heliostat design wind loads. The method proposed in the current study for heliostats conforms to the procedure used in design wind codes and standards for buildings and roof-mounted solar panels.

Physical properties of resistant starch (RS) were examined in a range of barley genotypes to determine the contribution of starch and seed physical characteristics to the RS component. Thirty-three barley genotypes were studied, which varied significantly in their RS, amylose, and starch contents and grain yield. From 33 genotypes, 13 exhibiting high RS were selected for detailed physicochemical analysis of starch. In high-RS varieties, granule size and number were unimodal, compared with normal starches from a reference genotype, which showed a bimodal distribution. Principal component analysis (PCA) showed that a higher content of granules

Starch synthesis requires several enzymatic activities including branching enzymes (BEs) responsible for the formation of α(1 → 6) linkages. Distribution and number of these linkages are further controlled by debranching enzymes that cleave some of them, rendering the polyglucan water-insoluble and semi-crystalline. Although the activity of BEs and debranching enzymes is mandatory to sustain normal starch synthesis, the relative importance of each in the establishment of the plant storage polyglucan (i.e. water insolubility, crystallinity and presence of amylose) is still debated. Here, we have substituted the activity of BEs in Arabidopsis with that of the Escherichia coli glycogen BE (GlgB). The latter is the BE counterpart in the metabolism of glycogen, a highly branched water-soluble and amorphous storage polyglucan. GlgB was expressed in the be2 be3 double mutant of Arabidopsis, which is devoid of BE activity and consequently free of starch. The synthesis of a water-insoluble, partly crystalline, amylose-containing starch-like polyglucan was restored in GlgB-expressing plants, suggesting that BEs' origin only has a limited impact on establishing essential characteristics of starch. Moreover, the balance between branching and debranching is crucial for the synthesis of starch, as an excess of branching activity results in the formation of highly branched, water-soluble, poorly crystalline polyglucan.

The mean and spectral characteristics of turbulence in the wake flow of a flat plate model resembling a heliostat in the atmospheric boundary layer flow are investigated in a wind tunnel experiment. Mean velocity and turbulence kinetic energy were characterized in the wake of a heliostat model at three elevation angles up to a distance of eight times the characteristic dimension of the heliostat panel. An increase in turbulence intensity and kinetic energy was found in the wake flow, reaching a peak at a distance equal to approximately twice the characteristic dimension of the heliostat panel. Furthermore, spectral and wavelet analysis of velocity fluctuations in the wake showed that the dominant mechanism in the immediate downstream of the plate was the breakdown of large inflow turbulence structures to smaller scales. In the end, the wake-induced turbulence patterns and wind loads in a heliostat field were discussed. It was found that compared to a heliostat at the front row, the heliostats positioned in high-density regions of a field were subjected to a higher turbulence intensity and, consequently, larger dynamic wind loading. The results show that it is necessary to consider the increased unsteady wind loads for the design of a heliostat in high-density regions of a field, where the gap between the rows is less than three-times the characteristic length of the heliostat panel.

Starch synthase 2 (SS2) is an important enzyme in leaf starch synthesis, elongating intermediate-length glucan chains. Loss of SS2 results in a distorted starch granule phenotype and altered physiochemical properties, highlighting its importance in starch biosynthesis, however, the post-translational regulation of SS2 is poorly understood. In this study, a combination of bioinformatic and in vitro analysis of recombinant SS2 was used to identify and characterize SS2 post-translational regulatory mechanisms. The SS2 N-terminal region, comprising the first 185 amino acids of the mature protein sequence, was shown to be highly variable between species, and was predicted to be intrinsically disordered. Intrinsic disorder in proteins is often correlated with protein phosphorylation and protein-protein interactions. Recombinant Arabidopsis thaliana SS2 formed homodimers that required the N-terminal region, but N-terminal peptides could not form stable homodimers alone. Recombinant SS2 was shown to be phosphorylated by chloroplast protein kinases and recombinant casein kinase II at two N-terminal serine residues (S63, S65), but mutation of these phosphorylation sites (Ser>Ala) revealed that they are not required for homo-dimerization. Heteromeric enzyme complex (HEC) formation between SS2 and SBE2.2 was shown to be ATP-dependent. However, SS2 homo-dimerization and protein phosphorylation are not required for its interaction with SBE2.2, as truncation of the SS2 N-terminus did not disrupt ATP-dependent HEC assembly. SS2 phosphorylation had no affect on its catalytic activity. Intriguingly, the removal of the N-terminal region of SS2 resulted in a 47-fold increase in its activity. As N-terminal truncation disrupted dimerization, this suggests that SS2 is more active when monomeric, and that transitions between oligomeric state may be a mechanism for SS2 regulation.

This paper assesses the influence on the levelised cost of electricity (LCOE) of the design wind speed at which heliostats in concentrating solar thermal (CST) power tower (PT) plants are stowed. Lowering the design wind speed for parking heliostats in the stow position reduces the cost of the heliostat field at the expense of a reduction in the energy harvested. However, both influences are highly non-linear and also vary from site to site, so that new understanding is needed to guide the optimisation of this parameter. The capacity factor and the power output for a PT plant without thermal storage are calculated for six locations by mapping hourly solar irradiance data to the Weibull probability distribution of mean wind speed. The cost of materials for the heliostat components and their sensitivity to heliostat size are estimated as a function of the design (stow) wind speed based on the specification of the structural design for quasi-static wind loads. The sensitivity of the LCOE to the design is assessed statistically. The results show that the materials cost of structural components in larger heliostats are most sensitive to the design wind speed, so that a 34% reduction in cost can be achieved by lowering the design wind speed from 15 m/s to 10 m/s. In contrast, the optimum design wind speed for smaller heliostats between 20 m 2 and 50 m 2 is typically above 10 m/s. The LCOE can be reduced by as much as 18% by lowering the design wind speed from the maximum recorded wind speeds at the three Australian sites. Hence there is significant economic benefit from optimising the minimum design at sites with high wind speeds.

© 2017 IOP Publishing Ltd and Sissa Medialab srl. We describe improvements in CCD performance that have been achieved on 4k×4k, (15 μm)2-pixel, fully depleted CCDs for the Dark Energy Spectroscopic Instrument (DESI) [1]. With respect to our previous work on CCDs for the Dark Energy Camera and the Baryon Oscillation Spectroscopic Survey, our goals for the DESI CCD development were to improve read noise and quantum efficiency, improve the astrometric precision, and decrease pixel-size variations. We report experimental results on recently fabricated CCDs to be used in DESI.

Dynamic amplification and gust effects from turbulence can increase wind loads significantly over and above the static wind loads that have been used for heliostat design. This paper presents the results of analyzing the relationship between gust factor and turbulence intensity within the atmospheric boundary layer (ABL) based on the high fidelity measurements of wind velocity at the SLTEST facility in the Utah desert. Results showed that there are distinct characteristics of a low roughness ABL that deviate from semi-empirical relationships derived for open country and urban terrains with larger surface roughness heights. The analysis also indicated that gust factor is increased by 2.4% when lowering the gust period from 3s to 1s in the low roughness field experiment ABL, compared to a 3.6% increase in a suburban terrain at a 10m height. Although 3s gust periods are recommended in AS/NZS 1170.2 [1], comparison of gust factor data with a 1s gust period is recommended particularly in high roughness ABLs su...

The velocity fluctuations within the atmospheric boundary layer (ABL) and the wind direction are two important parameters which affect the resulting loads on the heliostats. In this study, the drag force on a square heliostat within the ABL at different turbulence intensities is simulated. To this end, numerical analysis of the wind loads have been conducted by implementing the three-dimensional Embedded Large Eddy Simulation (ELES). The results prove that in contrast with other models which are too dissipative for highly turbulent flow, the present model can accurately predict boundary effects and calculate the peak loads on heliostat at different elevation angles and turbulence intensities. Therefore, it is recommended that the model is used as a tool to provide new information about the relationship between wind loads and turbulence structures within ABL such as vortex length scale.

Protein–protein interactions between starch phosphorylase (SP) and other starch biosynthetic enzymes were investigated using isolated maize endosperm amyloplasts and a recombinant maize enzyme. Plastidial SP is a stromal enzyme existing as a multimeric protein in amyloplasts. Biochemical analysis of the recombinant maize SP indicated that the tetrameric form was catalytically active in both glucan-synthetic and phosphorolytic directions. Protein–protein interaction experiments employing the recombinant SP as an affinity ligand with amyloplast extracts showed that the multimeric state of SP determined interactions with other enzymes of the starch biosynthetic pathway. The monomeric form of SP interacts with starch branching enzyme I (SBEI) and SBEIIb, whereas only SBEI interacts with the tetrameric form of SP. In all cases, protein–protein interactions were broken when amyloplast lysates were dephosphorylated in vitro, and enhanced following pre-treatment with ATP, suggesting a mechanism of protein complex formation regulated by protein phosphorylation. In vitro protein phosphorylation experiments with [γ-32P]-ATP show that SP is phosphorylated by a plastidial protein kinase. Evidence is presented which suggests SBEIIb modulates the catalytic activity of SP through the formation of a heteromeric protein complex.

Starch-branching enzymes (SBEs) are one of the four major enzyme classes involved in starch biosynthesis in plants and algae, and their activities play a crucial role in determining the structure and physical properties of starch granules. SBEs generate α-1,6-branch linkages in α-glucans through cleavage of internal α-1,4 bonds and transfer of the released reducing ends to C-6 hydroxyls. Starch biosynthesis in plants and algae requires multiple isoforms of SBEs and is distinct from glycogen biosynthesis in both prokaryotes and eukaryotes which uses a single branching enzyme (BE) isoform. One of the unique characteristics of starch structure is the grouping of α-1,6-branch points in clusters within amylopectin. This is a feature of SBEs and their interplay with other starch biosynthetic enzymes, thus facilitating formation of the compact water-insoluble semicrystalline starch granule. In this respect, the activity of SBE isoforms is pivotal in starch granule assembly. SBEs are structurally related to the α-amylase superfamily of enzymes, sharing three domains of secondary structure with prokaryotic Bes: the central (β/α)8 -barrel catalytic domain, an NH2 -terminal domain involved in determining the size of α-glucan chain transferred, and the C-terminal domain responsible for catalytic capacity and substrate preference. In addition, SBEs have conserved plant-specific domains, including phosphorylation sites which are thought to be involved in regulating starch metabolism. SBEs form heteromeric protein complexes with other SBE isoforms as well as other enzymes involved in starch synthesis, and assembly of these protein complexes is regulated by protein phosphorylation. Phosphorylated SBEIIb is found in multienzyme complexes with isoforms of glucan-elongating starch synthases, and these protein complexes are implicated in amylopectin cluster formation. This review presents a comparative overview of plant SBEs and includes a review of their properties, structural and functional characteristics, and recent developments on their post-translational regulation.

Mismatch of turbulence spectra from the corresponding full-scale conditions is a common challenge in wind tunnel modelling of unsteady wind loads on small-scale structures, such as solar panels, heliostats and low-rise buildings. Understanding the effect of this mismatch on the unsteady wind loads is necessary for providing an accurate estimation of wind loads on full-scale structures. The correlation between the turbulence spectra and the unsteady wind loads in wind tunnel measurements is investigated in this study through measurement of unsteady lift and drag forces on horizontal and vertical flat plates. It was found through spectral analysis that the turbulent eddies in the range of reduced frequencies between 0.01 and 1 contributed the most to the unsteady wind loads. An approach for wind tunnel modelling was proposed in which the geometric scaling ratio of each model is determined based on the analysis of the turbulence power spectrum as a function of reduced frequency. The suitable geometric scaling ratio should be then chosen such that the turbulence spectrum as a function of reduced frequency is the closest match to that at full-scale for reduced frequencies between approximately 0.01 and 1.

Protein-protein interactions among enzymes of amylopectin biosynthesis were investigated in developing wheat (Triticum aestivum) endosperm. Physical interactions between starch branching enzymes (SBEs) and starch synthases (SSs) were identified from endosperm amyloplasts during the active phase of starch deposition in the developing grain using immunoprecipitation and cross-linking strategies. Coimmunoprecipitation experiments using peptide-specific antibodies indicate that at least two distinct complexes exist containing SSI, SSIIa, and either of SBEIIa or SBEIIb. Chemical cross linking was used to identify protein complexes containing SBEs and SSs from amyloplast extracts. Separation of extracts by gel filtration chromatography demonstrated the presence of SBE and SS forms in protein complexes of around 260 kD and that SBEII forms may also exist as homodimers. Analysis of cross-linked 260-kD aggregation products from amyloplast lysates by mass spectrometry confirmed SSI, SSIIa, and SBEII forms as components of one or more protein complexes in amyloplasts. In vitro phosphorylation experiments with γ-32P-ATP indicated that SSII and both forms of SBEII are phosphorylated. Treatment of the partially purified 260-kD SS-SBE complexes with alkaline phosphatase caused dissociation of the assembly into the respective monomeric proteins, indicating that formation of SS-SBE complexes is phosphorylation dependent. The 260-kD SS-SBEII protein complexes are formed around 10 to 15 d after pollination and were shown to be catalytically active with respect to both SS and SBE activities. Prior to this developmental stage, SSI, SSII, and SBEII forms were detectable only in monomeric form. High molecular weight forms of SBEII demonstrated a higher affinity for in vitro glucan substrates than monomers. These results provide direct evidence for the existence of protein complexes involved in amylopectin biosynthesis.

The Australian Solar Thermal Research Initiative (ASTRI) aims to develop a high optical quality heliostat with target cost – manufactured, installed and operational – of 90 AUD/m2. Three different heliostat design concepts are described, each with features identified during a prior scoping study as having the potential to contribute to cost reduction compared to the current state-of-the-art. The three concepts which are being developed will be down-selected to a single concept for testing in late 2016. The heliostat concept development work is supported by technology development streams, developing novel sandwich panel mirror facet structures, analysing and testing wind loads on heliostats in both stow and operation positions, and developing new heliostat field layouts and software tools for optical analysis of heliostats design concepts Refereed/Peer-reviewed

The sugary-2 mutation in maize (Zea mays L.) is a result of the loss of catalytic activity of the endosperm-specific SS (starch synthase) IIa isoform causing major alterations to amylopectin architecture. The present study reports a biochemical and molecular analysis of an allelic variant of the sugary-2 mutation expressing a catalytically inactive form of SSIIa and sheds new light on its central role in protein–protein interactions and determination of the starch granule proteome. The mutant SSIIa revealed two amino acid substitutions, one being a highly conserved residue (Gly522→Arg) responsible for the loss of catalytic activity and the inability of the mutant SSIIa to bind to starch. Analysis of protein–protein interactions in sugary-2 amyloplasts revealed the same trimeric assembly of soluble SSI, SSIIa and SBE (starch-branching enzyme) IIb found in wild-type amyloplasts, but with greatly reduced activities of SSI and SBEIIb. Chemical cross-linking studies demonstrated that SSIIa is at the core of the complex, interacting with SSI and SBEIIb, which do not interact directly with each other. The sugary-2 mutant starch granules were devoid of amylopectin-synthesizing enzymes, despite the fact that the respective affinities of SSI and SBEIIb from sugary-2 for amylopectin were the same as observed in wild-type. The data support a model whereby granule-bound proteins involved in amylopectin synthesis are partitioned into the starch granule as a result of their association within protein complexes, and that SSIIa plays a crucial role in trafficking SSI and SBEIIb into the granule matrix.

Amylose extender (ae(-)) starches characteristically have modified starch granule morphology resulting from amylopectin with reduced branch frequency and longer glucan chains in clusters, caused by the loss of activity of the major starch branching enzyme (SBE), which in maize endosperm is SBEIIb. A recent study with ae(-) maize lacking the SBEIIb protein (termed ae1.1 herein) showed that novel protein-protein interactions between enzymes of starch biosynthesis in the amyloplast could explain the starch phenotype of the ae1.1 mutant. The present study examined an allelic variant of the ae(-) mutation, ae1.2, which expresses a catalytically inactive form of SBEIIb. The catalytically inactive SBEIIb in ae1.2 lacks a 28 amino acid peptide (Val272-Pro299) and is unable to bind to amylopectin. Analysis of starch from ae1.2 revealed altered granule morphology and physicochemical characteristics distinct from those of the ae1.1 mutant as well as the wild-type, including altered apparent amylose content and gelatinization properties. Starch from ae1.2 had fewer intermediate length glucan chains (degree of polymerization 16-20) than ae1.1. Biochemical analysis of ae1.2 showed that there were differences in the organization and assembly of protein complexes of starch biosynthetic enzymes in comparison with ae1.1 (and wild-type) amyloplasts, which were also reflected in the composition of starch granule-bound proteins. The formation of stromal protein complexes in the wild-type and ae1.2 was strongly enhanced by ATP, and broken by phosphatase treatment, indicating a role for protein phosphorylation in their assembly. Labelling experiments with [γ-(32)P]ATP showed that the inactive form of SBEIIb in ae1.2 was phosphorylated, both in the monomeric form and in association with starch synthase isoforms. Although the inactive SBEIIb was unable to bind starch directly, it was strongly associated with the starch granule, reinforcing the conclusion that its presence in the granules is a result of physical association with other enzymes of starch synthesis. In addition, an Mn(2+)-based affinity ligand, specific for phosphoproteins, was used to show that the granule-bound forms of SBEIIb in the wild-type and ae1.2 were phosphorylated, as was the granule-bound form of SBEI found in ae1.2 starch. The data strongly support the hypothesis that the complement of heteromeric complexes of proteins involved in amylopectin synthesis contributes to the fine structure and architecture of the starch granule.

Multiple forms of starch synthases (EC 2.4.1.21) are critical for the synthesis of starch in higher plants. These enzymes catalyze the extension of linear glucan chains by the transfer of glucose from the nucleotide sugar ADPglucose. Recombinant maize starch synthase I (rSSI) was purified from Escherichia coli in order to study the regulation of this enzyme by protein phosphorylation. The rSSI was phosphorylated in vitro by incubation with [γ 32P]-ATP and maize amyloplast lysates, which were used as a source of protein kinase. Maximal phosphorylation of rSSI was achieved within 20 minutes, and there was no noticeable change in the amount of phosphorylation beyond this time. Phosphoamino acid analysis of rSSI indicated phosphorylation of one or more serine residues. In order to purify and identify the phosphopeptides, phosphorylated rSSI was digested with trypsin to yield smaller peptides, which were then concentrated using Immobilized Metal Affinity Chromatography (IMAC). Potential phosphopeptides eluting from the IMAC column were purified and putatively identified using reversed phase (C18 column) High Pressure Liquid Chromatography (HPLC). They were then analyzed by mass spectrometry using Matrix-Assisted Laser Desorption/Ionization-Time of Flight (MALDI-TOF) which yielded the mass of potential phosphopeptides.

Thick, fully depleted p-channel charge-coupled devices (CCDs) have been developed at the Lawrence Berkeley National Laboratory (LBNL). These CCDs have several advantages over conventional thin, n-channel CCDs, including enhanced quantum efficiency and reduced fringing at near-infrared wavelengths and improved radiation tolerance. Here we report results from the irradiation of CCDs with 12.5 and 55 MeV protons at the LBNL 88-Inch Cyclotron and with 0.1-1 MeV electrons at the LBNL Co60 source. These studies indicate that the LBNL CCDs perform well after irradiation, even in the parameters in which significant degradation is observed in other CCDs: charge transfer efficiency, dark current, and isolated hot pixels. Modeling the radiation exposure over a six-year mission lifetime with no annealing, we expect an increase in dark current of 20 e/pixel/hr, and a degradation of charge transfer efficiency in the parallel direction of 3e-6 and 1e-6 in the serial direction. The dark current is observed to improve with an annealing cycle, while the parallel CTE is relatively unaffected and the serial CTE is somewhat degraded. As expected, the radiation tolerance of the p-channel LBNL CCDs is significantly improved over the conventional n-channel CCDs that are currently employed in space-based telescopes such as the Hubble Space Telescope., 11 pages, 10 figures, submitted to IEEE Transactions

Most of the carbon used for starch biosynthesis in cereal endosperms is derived from ADP-glucose (ADP-Glc) synthesized by extra-plastidial AGPase activity, and imported directly across the amyloplast envelope. The properties of the wheat endosperm amyloplast ADP-Glc transporter were analysed with respect to substrate kinetics and specificities using reconstituted amyloplast envelope proteins in a proteoliposome-based assay system, as well as with isolated intact organelles. Experiments with liposomes showed that ADP-Glc transport was dependent on counter-exchange with other adenylates. Rates of ADP-Glc transport were highest with ADP and AMP as counter-exchange substrates, and kinetic analysis revealed that the transport system has a similar affinity for ADP and AMP. Measurement of ADP and AMP efflux from intact amyloplasts showed that, under conditions of ADP-Glc-dependent starch biosynthesis, ADP is exported from the plastid at a rate equal to that of ADP-Glc utilization by starch synthases. Photo-affinity labelling of amyloplast membranes with the substrate analogue 8-azido-[alpha-P-32]ADP-Glc showed that the polypeptide involved in substrate binding is an integral membrane protein of 38 kDa. This study shows that the ADP-Glc transporter in cereal endosperm amyloplasts imports ADP-Glc in exchange for ADP which is produced as a by-product of the starch synthase reaction inside the plastid.

In this study, the functional properties of A- and B-type wheat starch granules from two commercial wheat flours were investigated for digestibility in vitro, chemical composition (e.g., amylose, protein, and ash content), gelatinization, retrogradation, and pasting properties. The branch chain length and chain length distribution of these A- and B-type wheat starch granules were also determined using high-performance anion exchange chromatography (HPAEC). Wheat starches with different granular sizes not only had different degrees of enzymatic hydrolysis and thermal and pasting properties, but also different molecular characteristics. Different amylose content, protein content, and branch chain length of amylopectin in A- and B-type wheat starch granules could also be the major factors besides granular size for different digestibility and other functional properties of starch. The data indicate that different wheat cultivars with different proportion of A- and B-type granular starch could result ...

The Dark Energy Camera is a new imager with a 2.2-degree diameter field of view mounted at the prime focus of the Victor M. Blanco 4-meter telescope on Cerro Tololo near La Serena, Chile. The camera was designed and constructed by the Dark Energy Survey Collaboration, and meets or exceeds the stringent requirements designed for the wide-field and supernova surveys for which the collaboration uses it. The camera consists of a five element optical corrector, seven filters, a shutter with a 60 cm aperture, and a CCD focal plane of 250 micron thick fully-depleted CCDs cooled inside a vacuum Dewar. The 570 Mpixel focal plane comprises 62 2kx4k CCDs for imaging and 12 2kx2k CCDs for guiding and focus. The CCDs have 15 microns x15 microns pixels with a plate scale of 0.263 arc sec per pixel. A hexapod system provides state-of-the-art focus and alignment capability. The camera is read out in 20 seconds with 6-9 electrons readout noise. This paper provides a technical description of the camera's engineering, construction, installation, and current status., Comment: submitted to AJ Corresponding Authors H. T. Diehl (diehl@fnal.gov)

Starch synthesis requires several enzymatic activities including branching enzymes (BEs) responsible for the formation of α(1→6) linkages. Distribution and number of these linkages are further controlled by debranching enzymes (DBEs) that cleave some of them, rendering the polyglucan water-insoluble and semi-crystalline. Although the activity of BEs and DBEs is mandatory to sustain normal starch synthesis, the relative importance of each in the establishment of the plant storage polyglucan (i.e. water-insolubility, crystallinity, presence of amylose) is still debated. Here, we have substituted the activity of BEs inArabidopsiswith that of theEscherichia coliglycogen branching enzyme (GlgB). The latter is the BE counterpart in the metabolism of glycogen, a highly branched water-soluble and amorphous storage polyglucan. GlgB was expressed in thebe2 be3double mutant ofArabidopsisthat is devoid of BE activity and consequently free of starch. The synthesis of a water-insoluble, partly crystalline, amylose-containing starch-like polyglucan was restored in GlgB-expressing plants, suggesting that BEs origin only have a limited impact on establishing essential characteristics of starch. Moreover, the balance between branching and debranching is crucial for the synthesis of starch, as an excess of branching activity results in the formation of highly branched, water-soluble, poorly crystalline polyglucan.

Highlight Starch biosynthetic enzymes in rice endosperm are physically associated with each other and form enzymatically active multiple protein–protein complexes, several of which were common to cereals while others were unique., Amylopectin is a highly branched, organized cluster of glucose polymers, and the major component of rice starch. Synthesis of amylopectin requires fine co-ordination between elongation of glucose polymers by soluble starch synthases (SSs), generation of branches by branching enzymes (BEs), and removal of misplaced branches by debranching enzymes (DBEs). Among the various isozymes having a role in amylopectin biosynthesis, limited numbers of SS and BE isozymes have been demonstrated to interact via protein–protein interactions in maize and wheat amyloplasts. This study investigated whether protein–protein interactions are also found in rice endosperm, as well as exploring differences between species. Gel permeation chromatography of developing rice endosperm extracts revealed that all 10 starch biosynthetic enzymes analysed were present at larger molecular weights than their respective monomeric sizes. SSIIa, SSIIIa, SSIVb, BEI, BEIIb, and PUL co-eluted at mass sizes >700kDa, and SSI, SSIIa, BEIIb, ISA1, PUL, and Pho1 co-eluted at 200–400kDa. Zymogram analyses showed that SSI, SSIIIa, BEI, BEIIa, BEIIb, ISA1, PUL, and Pho1 eluted in high molecular weight fractions were active. Comprehensive co-immunoprecipitation analyses revealed associations of SSs–BEs, and, among BE isozymes, BEIIa–Pho1, and pullulanase-type DBE–BEI interactions. Blue-native-PAGE zymogram analyses confirmed the glucan-synthesizing activity of protein complexes. These results suggest that some rice starch biosynthetic isozymes are physically associated with each other and form active protein complexes. Detailed analyses of these complexes will shed light on the mechanisms controlling the unique branch and cluster structure of amylopectin, and the physicochemical properties of starch.

We have identified a novel means to achieve substantially increased vegetative biomass and oilseed production in the model plant Arabidopsis thaliana. Endogenous isoforms of starch branching enzyme (SBE) were substituted by either one of the endosperm-expressed maize (Zea mays L.) branching isozymes, ZmSBEI or ZmSBEIIb. Transformants were compared with the starch-free background and with the wild-type plants. Each of the maize-derived SBEs restored starch biosynthesis but both morphology and structure of starch particles were altered. Altered starch metabolism in the transformants is associated with enhanced biomass formation and more-than-trebled oilseed production while maintaining seed oil quality. Enhanced oilseed production is primarily due to an increased number of siliques per plant whereas oil content and seed number per silique are essentially unchanged or even modestly decreased. Introduction of cereal starch branching isozymes into oilseed plants represents a potentially useful strategy to increase biomass and oilseed production in related crops and manipulate the structure and properties of leaf starch.

Second harmonic generation (SHG) microscopy is employed to study changes in crystalline organization due to altered gene expression and hydration in barley starch granules. SHG intensity and susceptibility ratio values (R'(SHG)) are obtained using reduced Stokes-Mueller polarimetric microscopy. The maximum R'(SHG) values occur at moderate moisture indicating the narrowest orientation distribution of nonlinear dipoles from the cylindrical axis of glucan helices. The maximum SHG intensity occurs at the highest moisture and amylopectin content. These results support the hypothesis that SHG is caused by ordered hydrogen and hydroxyl bond networks which increase with hydration of starch granules. (C) 2015 Optical Society of America

Starch biosynthesis requires the ordered assembly of glucose units into amylose and amylopectin from ADPglucose. Whilst amylose has a relatively simple linear structure, the synthesis of amylopectin requires the formation of regular, repeating clusters of glucan chains. These clusters have a 9 nm periodicity and comprise a crystalline, alpha helical region and an amorphous branched region, a unit which is repeated many times over to give rise to blocklets of amylopectin. Although the individual enzymes of starch biosynthesis have been studied extensively, our knowledge of the mechanisms which give rise to this highly ordered structure is limited. There is an increasing body of literature which has demonstrated that several reactions are regulated post-translationally, including via redox modulation, protein-protein interactions and protein phosphorylation. This chapter summarises our current knowledge of these mechanisms and offers a model of how they serve to coordinate the biosynthesis of amylopectin in particular.