Recombination and base composition: the case of the highly self-fertilizing plant Arabidopsis thaliana

BACKGROUND: Rates of recombination can vary among genomic regions in eukaryotes, and this is believed to have major effects on their genome organization in terms of base composition, DNA repeat density, intron size, evolutionary rates and gene order. In highly self-fertilizing species such as Arabidopsis thaliana, however, heterozygosity is expected to be strongly reduced and recombination will be much less effective, so that its influence on genome organization should be greatly reduced. RESULTS: Here we investigated theoretically the joint effects of recombination and self-fertilization on base composition, and tested the predictions with genomic data from the complete A. thaliana genome. We show that, in this species, both codon-usage bias and GC content do not correlate with the local rates of crossing over, in agreement with our theoretical results. CONCLUSIONS: We conclude that levels of inbreeding modulate the effect of recombination on base composition, and possibly other genomic features (for example, transposable element dynamics). We argue that inbreeding should be considered when interpreting patterns of molecular evolution

Ascorbic acid causes spuriously low blood glucose measurements

CITATION: Strijdom, J.G., Marais, B.J. & Koeslag, J.H. 1993. Ascorbic acid causes spuriously low blood glucose measurements. S Afr Med J, 83(1):64-65.The original publication is available at http://www.samj.org.za[No abstract available]Publisher’s versio

Natural variation in abiotic stress responsive gene expression and local adaptation to climate in Arabidopsis thaliana.

Gene expression varies widely in natural populations, yet the proximate and ultimate causes of this variation are poorly known. Understanding how variation in gene expression affects abiotic stress tolerance, fitness, and adaptation is central to the field of evolutionary genetics. We tested the hypothesis that genes with natural genetic variation in their expression responses to abiotic stress are likely to be involved in local adaptation to climate in Arabidopsis thaliana. Specifically, we compared genes with consistent expression responses to environmental stress (expression stress responsive, "eSR") to genes with genetically variable responses to abiotic stress (expression genotype-by-environment interaction, "eGEI"). We found that on average genes that exhibited eGEI in response to drought or cold had greater polymorphism in promoter regions and stronger associations with climate than those of eSR genes or genomic controls. We also found that transcription factor binding sites known to respond to environmental stressors, especially abscisic acid responsive elements, showed significantly higher polymorphism in drought eGEI genes in comparison to eSR genes. By contrast, eSR genes tended to exhibit relatively greater pairwise haplotype sharing, lower promoter diversity, and fewer nonsynonymous polymorphisms, suggesting purifying selection or selective sweeps. Our results indicate that cis-regulatory evolution and genetic variation in stress responsive gene expression may be important mechanisms of local adaptation to climatic selective gradients

The NOMA track module on nutrition, human rights and governance: Part 2. A transnational curriculum using a human rights-based approach to foster key competencies in nutrition professionals

Background. In response to the challenge of the global health needs of the 21st century, four academic institutions in Norway, South Africa and Uganda,each offering a Master’s degree in nutrition, collaboratively developed the NOrwegian MAsters (NOMA) track module on nutrition, human rights andgovernance, integrating a human rights-based approach into graduate education in nutrition.Objective. To capture students’ perceptions about the NOMA track module, focusing on the development of key competencies.Methods. Employing a qualitative approach, 20 (91% response rate) in-depth telephonic interviews were conducted with participating students, voicerecorded and transcribed. Through an inductive process, emerging themes were used to compile a code list for content analysis of the transcribed text. Relevant themes were reported according to the professionals’ roles described by the CanMEDS competency framework.Results. Participation in the module enhanced key competencies in the students, e.g. communication skills and the adoption of a holistic approach tointeraction with people or communities. Their role as collaborator was enhanced by their learning to embrace diversity and cultural differences and similarities. Students had to adapt to different cultures and educational systems. They were inspired to contribute in diverse contexts and act as agents for change in the organisations in which they may work or act as leaders or co-ordinators during interaction with community groups and policy makers. Higher education institutions offering transnational modules should support lecturers to manage the inherent diversity in the classroom as a way of enhancing student performance.Conclusion. The development of future transprofessional modules will benefit from the inclusion of desirable key competencies as part of the moduleoutcomes by following a competency by design process

The neural correlates of intimate partner violence in women

Objective: To examine hippocampal volume and white matter tracts in women with and without intimate partner violence (IPV). Method: Nineteen women with IPV exposure in the last year, and 21 women without IPV exposure in the last year underwent structural magnetic resonance imaging (MRI) including diffusion tensor imaging (DTI) sequences. Additional data on alcohol use and presence of psychiatric disorder was collected. Differences in fractional anisotropy (FA) between the two groups were examined, using a statistical model that included demographic measures, alcohol use and psychiatric disorder. Results: IPV subjects did not demonstrate significantly different hippocampal volumes compared to subjects without recent IPV. FA was, however, significantly reduced in the body of the corpus callosum of IPV subjects. Adjusting for age, alcohol use, smoking and psychiatric diagnosis did not change the significance of the result. Conclusion: Data on hippocampal volume in IPV are inconsistent, perhaps reflecting the fact that multiple factors influence this measure. Reduced FA in the body of the corpus callosum in IPV suggests altered integrity of this white matter tract; additional work is needed to address the underlying mechanisms and clinical correlates of this finding.Key Words: Corpus callosum; Hippocampal volume; Intimate partner violence; Neuroimagin

The neural correlates of intimate partner violence in women

Objective: To examine hippocampal volume and white matter tracts in women with and without intimate partner violence (IPV). Method: Nineteen women with IPV exposure in the last year, and 21 women without IPV exposure in the last year underwent structural magnetic resonance imaging (MRI) including diffusion tensor imaging (DTI) sequences. Additional data on alcohol use and presence of psychiatric disorder was collected. Differences in fractional anisotropy (FA) between the two groups were examined, using a statistical model that included demographic measures, alcohol use and psychiatric disorder. Results: IPV subjects did not demonstrate significantly different hippocampal volumes compared to subjects without recent IPV. FA was, however, significantly reduced in the body of the corpus callosum of IPV subjects. Adjusting for age, alcohol use, smoking and psychiatric diagnosis did not change the significance of the result. Conclusion: Data on hippocampal volume in IPV are inconsistent, perhaps reflecting the fact that multiple factors influence this measure. Reduced FA in the body of the corpus callosum in IPV suggests altered integrity of this white matter tract; additional work is needed to address the underlying mechanisms and clinical correlates of this finding