Second harmonic generation microscopy investigation of the crystalline ultrastructure of three barley starch lines affected by hydration

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

Beccles triple post alignment, Beccles Marshes, Suffolk: excavation and palaeoenvironmental analysis of an Iron Age Wetland site

This paper describes the results of two seasons of excavation and associated palaeoenvironmental analyses of a wetland site on Beccles Marshes, Beccles, Suffolk. The site has been identified as a triple post alignment of oak timbers (0.6–2.0 m long), over 100 m in length, and 3–4 m wide, running north-west to south-east towards the River Waveney. It was constructed in a single phase which has been dated dendrochronologically to 75 BC, although discrete brushwood features identified as possible short trackways have been dated by radiocarbon to both before and after the alignment was built. It is unclear if the posts ever supported a superstructure but notches (‘halving lap joints’) in some of the posts appear to have held timbers to support the posts and/or aid in their insertion. In addition, fragments of both Iron Age and Romano-British pottery were recovered. A substantial assemblage of worked wooden remains appears to reflect the construction of the post row itself and perhaps the on-site clearance of floodplain vegetation. This assemblage also contains waste material derived from the reduction splitting of timbers larger than the posts of the alignment, but which have not been recovered from the site. Environmental analyses indicate that the current landscape context of the site with respect to the River Waveney is probably similar to that which pertained in prehistory. The coleoptera (beetle) record illustrates a series of changes in the on-site vegetation in the period before, during and after the main phase of human activity which may be related to a range of factors including floodplain hydrology and anthropogenic utilisation of Beccles Marshes. The possible form and function of the site is discussed in relation to the later prehistoric period in Suffolk.</jats:p

A Review of Starch Biosynthesis in Relation to the Building Block-Backbone Model

Starch is a water-insoluble polymer of glucose synthesized as discrete granules inside the stroma of plastids in plant cells. Starch reserves provide a source of carbohydrate for immediate growth and development, and act as long term carbon stores in endosperms and seed tissues for growth of the next generation, making starch of huge agricultural importance. The starch granule has a highly complex hierarchical structure arising from the combined actions of a large array of enzymes as well as physicochemical self-assembly mechanisms. Understanding the precise nature of granule architecture, and how both biological and abiotic factors determine this structure is of both fundamental and practical importance. This review outlines current knowledge of granule architecture and the starch biosynthesis pathway in relation to the building block-backbone model of starch structure. We highlight the gaps in our knowledge in relation to our understanding of the structure and synthesis of starch, and argue that the building block-backbone model takes accurate account of both structural and biochemical data

Starch Biosynthesis in Crop Plants

Starch is a water-insoluble polyglucan synthesized inside the plastids of plant tissues to provide a store of carbohydrate. Starch harvested from plant storage organs has probably represented the major source of calories for the human diet since before the dawn of civilization. Following the advent of agriculture and the building of complex societies, humans have maintained their dependence on high-yielding domesticated starch-forming crops such as cereals to meet food demands, livestock production, and many non-food applications. The top three crops in terms of acreage are cereals, grown primarily for the harvestable storage starch in the endosperm, although many starchy tuberous crops also provide an important source of calories for various communities around the world. Despite conservation in the core structure of the starch granule, starches from different botanical sources show a high degree of variability, which is exploited in many food and non-food applications. Understanding the factors underpinning starch production and its final structure are of critical importance in guiding future crop improvement endeavours. This special issue contains reviews on these topics and is intended to be a useful resource for researchers involved in improvement of starch-storing crops

Starch Biosynthesis in the Developing Endosperms of Grasses and Cereals

The starch-rich endosperms of the Poaceae, which includes wild grasses and their domesticated descendents the cereals, have provided humankind and their livestock with the bulk of their daily calories since the dawn of civilization up to the present day. There are currently unprecedented pressures on global food supplies, largely resulting from population growth, loss of agricultural land that is linked to increased urbanization, and climate change. Since cereal yields essentially underpin world food and feed supply, it is critical that we understand the biological factors contributing to crop yields. In particular, it is important to understand the biochemical pathway that is involved in starch biosynthesis, since this pathway is the major yield determinant in the seeds of six out of the top seven crops grown worldwide. This review outlines the critical stages of growth and development of the endosperm tissue in the Poaceae, including discussion of carbon provision to the growing sink tissue. The main body of the review presents a current view of our understanding of storage starch biosynthesis, which occurs inside the amyloplasts of developing endosperms

Method for identifying the phosphorylation site of Maize Starch Synthase I

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