A cybernetic model to predict the effect of freely available nitrogen substrate on rifamycin B production in complex media

It is well-known that secondary metabolite production is repressed by excess nitrogen substrate available in the fermentation media. Although the nitrogen catabolite repression has been known, quantitative process models have not been reported to represent this phenomenon in complex medium. In this paper, we present a cybernetic model for rifamycin B production via Amycolatopsis mediterranei S699 in complex medium, which is typically used in industry. Nitrogen substrate is assumed to be present in two forms in the medium; available nitrogen (S _ANS) such as free amino acids and unavailable nitrogen (S _UNS) such as peptides and proteins. The model assumes that an inducible enzyme catalyzes the conversion of S _UNS to S _ANS. Although S _ANS is required for growth and product formation, high concentrations were found to inhibit rifamycin production. To experimentally validate the model, five different organic nitrogen sources were used that differ in the ratio of S _ANS/S _UNS. The model successfully predicts higher rifamycin B productivity for nitrogen sources that contain lower initial S _ANS. The higher productivity is attributed to the sustained availability of S _ANS at low concentration via conversion of S _UNS to S _ANS, thereby minimizing the effects of nitrogen catabolite repression on rifamycin production. The model can have applications in model-based optimization of substrate feeding recipe and in monitoring and control of fed batch processes.     

BMI and Waist Circumference as Predictors of Well‐being in Older Adults: Findings From the English Longitudinal Study of Ageing

The aim of this study is to examine the association of BMI and waist circumference (WC), with a quality of life (QoL) indicator designed for older ages (CASP19), and with depressive symptoms (Centre for Epidemiologic Studies Depression Scale). We included 8,688 individuals aged ≥52 years who participants of Wave 2 (2004–2005) and Wave 3 (2006–2007) of the English Longitudinal Study of Ageing (ELSA). To explore cross‐sectional relationships (2004–2005), we fitted regression models for BMI and WC (included simultaneously) as our predictors of QoL and depressive symptoms adjusted for covariates. To explore longitudinal relationships, BMI and waist at baseline (2004–2005) were related to the each outcome variable measured at follow‐up (2006–2007), and adjusted for baseline characteristics (2004–2005). For a given BMI, larger WC was associated with lower QoL and higher risk of depressive symptoms for women in cross‐sectional and longitudinal analyses. By contrast for a given WC increased BMI for women was positively associated with QoL and lower odds of depressive symptoms. In men, for a given BMI, increased WC was related to QoL only cross‐sectionally; neither WC nor BMI at baseline were associated with depressive symptoms (cross‐sectionally or longitudinally). In conclusion among older people, for a given BMI, increased WC was related with higher risk of poor QoL and, for women, of depressive symptoms; whereas for a given WC, increased BMI had a protective effect on QoL for women.     

Development and molecular characterization of wheat--Aegilops kotschyi addition and substitution lines with high grain protein, iron, and zinc

Over two billion people, depending largely on staple foods, suffer from deficiencies in protein and some micronutrients such as iron and zinc. Among various approaches to overcome protein and micronutrient deficiencies, biofortification through a combination of conventional and molecular breeding methods is the most feasible, cheapest, and sustainable approach. An interspecific cross was made between the wheat cultivar 'Chinese Spring' and Aegilops kotschyi Boiss. accession 396, which has a threefold higher grain iron and zinc concentrations and about 33% higher protein concentration than wheat cultivars. Recurrent backcrossing and selection for the micronutrient content was performed at each generation. Thirteen derivatives with high grain iron and zinc concentrations and contents, ash and ash micronutrients, and protein were analyzed for alien introgression. Morphological markers, high molecular weight glutenin subunit profiles, anchored wheat microsatellite markers, and GISH showed that addition and substitution of homoeologous groups 1, 2, and 7 chromosomes of Ae. kotschyi possess gene(s) for high grain micronutrients. The addition of 1U/1S had high molecular weight glutenin subunits with higher molecular weight than those of wheat, and the addition of 2S in most of the derivatives also enhanced grain protein content by over 20%. Low grain protein content in a derivative with a 2S-wheat translocation, waxy leaves, and absence of the gdm148 marker strongly suggests that the gene for higher grain protein content on chromosome 2S is orthologous to the grain protein QTL on the short arm of group 2 chromosomes.     

Overexpression of WsSGTL1 Gene of Withania somnifera Enhances Salt Tolerance,Heat Tolerance and Cold Acclimation Ability in Transgenic Arabidopsis Plants

Background

Sterol glycosyltrnasferases (SGT) are enzymes that glycosylate sterols which play important role in plant adaptation to stress and are medicinally important in plants like Withania somnifera. The present study aims to find the role of WsSGTL1 which is a sterol glycosyltransferase from W. somnifera, in plant’s adaptation to abiotic stress.

Methodology

The WsSGTL1 gene was transformed in Arabidopsis thaliana through Agrobacterium mediated transformation, using the binary vector pBI121, by floral dip method. The phenotypic and physiological parameters like germination, root length, shoot weight, relative electrolyte conductivity, MDA content, SOD levels, relative electrolyte leakage and chlorophyll measurements were compared between transgenic and wild type Arabidopsis plants under different abiotic stresses - salt, heat and cold. Biochemical analysis was done by HPLC-TLC and radiolabelled enzyme assay. The promoter of the WsSGTL1 gene was cloned by using Genome Walker kit (Clontech, USA) and the 3D structures were predicted by using Discovery Studio Ver. 2.5.

Results

The WsSGTL1 transgenic plants were confirmed to be single copy by Southern and homozygous by segregation analysis. As compared to WT, the transgenic plants showed better germination, salt tolerance, heat and cold tolerance. The level of the transgene WsSGTL1 was elevated in heat, cold and salt stress along with other marker genes such as HSP70, HSP90, RD29, SOS3 and LEA4-5. Biochemical analysis showed the formation of sterol glycosides and increase in enzyme activity. When the promoter of WsSGTL1 gene was cloned from W. somnifera and sequenced, it contained stress responsive elements. Bioinformatics analysis of the 3D structure of the WsSGTL1 protein showed functional similarity with sterol glycosyltransferase AtSGT of A. thaliana.

Conclusions

Transformation of WsSGTL1 gene in A. thaliana conferred abiotic stress tolerance. The promoter of the gene in W.somnifera was found to have stress responsive elements. The 3D structure showed functional similarity with sterol glycosyltransferases.     

Effects of NaCl and iso-osmotic PEG stress on growth,osmolytes accumulation and antioxidant defense in cultured sugarcane cells

In order to discriminate between the ionic and osmotic components of salt stress, sugarcane (Saccharum officinarum L. cv. Co 86032) calli were cultured on media containing NaCl or polyethylene glycol (PEG) 8000 that exerted the same osmotic pressure (−0.7 MPa). PEG stress exposure for 15 days led to significant growth reduction and loss in water content than salt stressed and control tissues. Osmotic adjustment (OA) was observed in callus tissues grown on salt, but was not evident in callus grown on PEG. Oxidative damage to membranes, estimated in terms of accumulation of thiobarbituric acid reactive substances-TBARS and electrolytic leakage was significantly higher in both the stressed calli than the control however, the extent of damage was more in the PEG stressed calli. The stressed callus tissues showed inhibition of ascorbate peroxidase activity, while catalase activity was increased. These results indicate sensitivity of cells to PEG-mediated stress than salt stress and differences in their OA to these two stress conditions. The sensitivity to the osmotic stress indicate that expression of the stress tolerance response requires the coordinated action of different tissues in a plant and hence was not expressed at the cellular level.