Long term studies on bone mineral changes during different lactations in Swedish dairy cattle

Changes in the bone mineral content (BMG) during the first 4 lactations were continuously studied between July 1977 and February 1982 in a total number of 103 dairy cows of different breeds and rearing intensities. The BMG was measured by dichromatic photon absorptiometry in 2 coccygeal vertebrae. Although great individual variations were found, the changes in BMG during the lactation followed a typical pattern with high values during the dry period and low values after calving and during mid-lactation. The influence of body weight on the BMC value is discussed. The changes in BMC were more accentuated during the first lactation, as compared to the subsequent lactations. This could indicate a metabolically more active skeleton in younger cows. In this study no difference in BMC pattern was observed between cows affected or not affected by parturient paresis.     

Genome-wide insertional mutagenesis of Arabidopsis thaliana

Over 225,000 independent Agrobacterium transferred DNA (T-DNA) insertion events in the genome of the reference plant Arabidopsis thaliana have been created that represent near saturation of the gene space. The precise locations were determined for more than 88,000 T-DNA insertions, which resulted in the identification of mutations in more than 21,700 of the approximately 29,454 predicted Arabidopsis genes. Genome-wide analysis of the distribution of integration events revealed the existence of a large integration site bias at both the chromosome and gene levels. Insertion mutations were identified in genes that are regulated in response to the plant hormone ethylene.     

Resistant starch in cereals: Exploiting genetic engineering and genetic variation

Some of the starch consumed by humans is not digested in the small intestine. Such starch, known as resistant starch, is fermented in the large intestine and leads to the production of short chain fatty acids. Increased consumption of resistant starch is associated with improved cardio-vascular health. A high proportion of amylose in the starch consumed is correlated with increased resistant starch but other unknown aspects of starch structure may also influence the digestibility of starch. Detailed investigation of the starch biosynthetic pathway has revealed that reducing the activity of specific isoforms of branching enzymes and starch synthases can lead to increased amylose. Methods to alter the expression of and detect mutations in targeted genes involved are discussed.     

Increased accuracy of starch granule type quantification using mixture distributions

Background

The proportion of granule types in wheat starch is an important characteristic that can affect its functionality. It is widely accepted that granule types are either large, disc-shaped A-type granules or small, spherical B-type granules. Additionally, there are some reports of the tiny C-type granules. The differences between these granule types are due to its carbohydrate composition and crystallinity which is highly, but not perfectly, correlated with the granule size. A majority of the studies that have considered granule types analyse them based on a size threshold rather than chemical composition. This is understandable due to the expense of separating starch into different types. While the use of a size threshold to classify granule type is a low-cost measure, this results in misclassification. We present an alternative, statistical method to quantify the proportion of granule types by a fit of the mixture distribution, along with an R package, a web based app and a video tutorial for how to use the web app to enable its straightforward application.

Results

Our results show that the reliability of the genotypic effects increase approximately 60% using the proportions of the A-type and B-type granule estimated by the mixture distribution over the standard size-threshold measure. Although there was a marginal drop in reliability for C-type granules. The latter is likely due to the low observed genetic variance for C-type granules.

Conclusions

The determination of the proportion of granule types from size-distribution is better achieved by using the mixing probabilities from the fit of the mixture distribution rather than using a size-threshold.

     

Structural and molecular basis of starch viscosity in hexaploid wheat

Wheat starch is considered to have a low paste viscosity relative to other starches. Consequently, wheat starch is not preferred for many applications as compared to other high paste viscosity starches. Increasing the viscosity of wheat starch is expected to increase the functionality of a range of wheat flour-based products in which the texture is an important aspect of consumer acceptance (e.g., pasta, and instant and yellow alkaline noodles). To understand the molecular basis of starch viscosity, we have undertaken a comprehensive structural and rheological analysis of starches from a genetically diverse set of wheat genotypes, which revealed significant variation in starch traits including starch granule protein content, starch-associated lipid content and composition, phosphate content, and the structures of the amylose and amylopectin fractions. Statistical analysis highlighted the association between amylopectin chains of 18-25 glucose residues and starch pasting properties. Principal component analysis also identified an association between monoesterified phosphate and starch pasting properties in wheat despite the low starch-phosphate level in wheat as compared to tuber starches. We also found a strong negative correlation between the phosphate ester content and the starch content in flour. Previously observed associations between internal starch granule fatty acids and the swelling peak time and pasting temperature have been confirmed. This study has highlighted a range of parameters associated with increased starch viscosity that could be used in prebreeding/breeding programs to modify wheat starch pasting properties.