GABA Receptors and the Pharmacology of Sleep

Current GABAergic sleep-promoting medications were developed pragmatically, without making use of the immense diversity of GABAA receptors. Pharmacogenetic experiments are leading to an understanding of the circuit mechanisms in the hypothalamus by which zolpidem and similar compounds induce sleep at α2βγ2-type GABAA receptors. Drugs acting at more selective receptor types, for example, at receptors containing the α2 and/or α3 subunits expressed in hypothalamic and brain stem areas, could in principle be useful as hypnotics/anxiolytics. A highly promising sleep-promoting drug, gaboxadol, which activates αβδ-type receptors failed in clinical trials. Thus, for the time being, drugs such as zolpidem, which work as positive allosteric modulators at GABAA receptors, continue to be some of the most effective compounds to treat primary insomnia

Microsatellite segregation analysis and cytogenetic evidence for tetrasomic inheritance in the American yam Dioscorea tridifa and a new basic chromosome number in the Dioscoreae

International audienceDespite the economic and cultural importance of the indigenous “Amerindian” yam Dioscorea trifida, very little is known about their origin, phylogeny, diversity and genetics. Consequently, conventional breeding efforts for the selection of D. trifida genotypes resistant to potyviruses which are directly involved in the regression of this species have been seriously limited. Our objective of this paper is to contribute to the clarification of the cytogenetic status, i.e., inheritance and chromosome number. Our results provide genetic evidence supporting tetrasomic behaviour of the genome of D. trifida based on chromosomal segregation pattern analysis using eight SSRs markers in three different crosses. This is the first reliable evidence of an autopolyploid species in the genus Dioscorea. The second major result in this study is the revealing of a new base chromosome number in the botanical section Macrogynodium to which D. trifida belongs. To date, our assumptions about the ploidy level of yams are based on the observations that the basic chromosome number is 10 or 9, and D. trifida was described as octoploid. The chromosome number of D. trifida accessions was also assessed using somatic chromosomic count techniques. Flow cytometry did not show significant variation of 2C DNA content among 80 accessions indicating homogeneity of the ploidy level of the cultivated D. trifida. This suggests that autotetraploidy is well established as well as the rule for the cultivated pool of D. trifida, even if the direct diploid ancestor remains to be identified. The data presented in this paper are significant and important for the effective breeding and conservation of the species and for elucidating the phylogeny and the origins of the yam and the evolution of the genus Dioscorea

Contribution of genetic resources to grain storage protein composition and wheat quality

The technological quality of wheat flour is defined by a range of dough characteristics relevant to the breadmaking processes and practices of individual countries and for particular products. The influence of storage protein diversity on wheat quality has been widely documented in the last three decades. The present chapter focuses on several aspects of wheat quality that merit more attention. The huge genetic diversity of wheat storage proteins means that all the possible allelic combinations and their interactions are too numerous to be tested in terms of their influence on the major quality parameters. However it is still relevant to describe the variation in rheological and viscoelastic properties of gluten in relation to its component proteins, glutenin and gliadin. Although gluten plays a major role in determining the properties of dough, the abundance of the two major storage protein fractions does not solely explain the observed variation in those properties. We therefore examine the influence of some genetic factors, including those affecting the protein composition, on the variation in the glutenin polymer sizes. Some examples will be given to illustrate how end-use quality can be improved by taking advantage of the available genetic resources in parallel with molecular genome analyses with the dual aim of widening the scope of characteristics that can be harnessed in breeding and ensuring consistent wheat quality in changing agro-climatic situations. The known alleles of the major genes are highlighted in the context of the challenges that the research community is facing regarding wheat allele nomenclature, exchange of gene bank material and the numerous quality attributes of interest. Finally, important research objectives are proposed for breeding future wheats with grain protein quality and technological properties tailored for different food products