Overexpression of Hydroxynitrile Lyase in Cassava Roots Elevates Protein and Free Amino Acids while Reducing Residual Cyanogen Levels

Cassava is the major source of calories for more than 250 million Sub-Saharan Africans, however, it has the lowest protein-to-energy ratio of any major staple food crop in the world. A cassava-based diet provides less than 30% of the minimum daily requirement for protein. Moreover, both leaves and roots contain potentially toxic levels of cyanogenic glucosides. The major cyanogen in cassava is linamarin which is stored in the vacuole. Upon tissue disruption linamarin is deglycosylated by the apolplastic enzyme, linamarase, producing acetone cyanohydrin. Acetone cyanohydrin can spontaneously decompose at pHs >5.0 or temperatures >35°C, or is enzymatically broken down by hydroxynitrile lyase (HNL) to produce acetone and free cyanide which is then volatilized. Unlike leaves, cassava roots have little HNL activity. The lack of HNL activity in roots is associated with the accumulation of potentially toxic levels of acetone cyanohydrin in poorly processed roots. We hypothesized that the over-expression of HNL in cassava roots under the control of a root-specific, patatin promoter would not only accelerate cyanogenesis during food processing, resulting in a safer food product, but lead to increased root protein levels since HNL is sequestered in the cell wall. Transgenic lines expressing a patatin-driven HNL gene construct exhibited a 2–20 fold increase in relative HNL mRNA levels in roots when compared with wild type resulting in a threefold increase in total root protein in 7 month old plants. After food processing, HNL overexpressing lines had substantially reduced acetone cyanohydrin and cyanide levels in roots relative to wild-type roots. Furthermore, steady state linamarin levels in intact tissues were reduced by 80% in transgenic cassava roots. These results suggest that enhanced linamarin metabolism contributed to the elevated root protein levels

De geprotocolleerde Interapy-behandeling van depressie via het internet; resultaten van een gerandomiseerde trial

Psychologische behandelingen via internet bieden een nieuwe mogelijkheid voor de geestelijke gezondheidszorg. In samenwerking met de Stichting Mentrum ggz Amsterdam heeft Interapy een behandeling voor depressie via internet opgezet. De behandeling bestaat uit cognitief-gedragstherapeutische interventies, zoals psycho-educatie, schrijfopdrachten, registratie, activatie, het uitdagen van negatieve automatische gedachten en terugvalpreventie. Dit artikel beschrijft de procedure, de behandeling en de resultaten van een vergelijkende studie onder cliënten die matig tot ernstig depressief waren. De cliënten die direct actief werden behandeld (N = 32) verbeterden significant meer dan de cliënten in de psycho-educatieconditie (N = 14). Deze tweede groep kreeg de actieve behandeling ongeveer twaalf weken later. De effecten waren groot. In de actief behandelde groep liet 75 procent van de cliënten klinisch relevante verbetering zien, in de psycho-educatieconditie was dat percentage 36. Uit de follow-up na zes weken bleek dat de verbeteringen standhielden

Cyanotypic frequencies in adjacent and mixed populations of Trifolium occidentale Coombe and Trifolium repens L. are regulated by different mechanisms.

The cyanogenic polymorphism in Trifolium repens is caused by the variation in two genes, the interaction of which produces four distinct cyanotypes. Along the Atlantic coasts of Bretagne, T. repens is sometimes found in populations mixed with the related species Trifolium occidentale, although the latter species usually occurs only in a narrow fringe along the coast, whereas T. repens is a more inland species. No plants of T. occidentale have ever been reported to have linamarase activity. Indeed, of 763 T. occidentale plants studied, none contained linamarase activity. However, the variation in the proportion of cyanotypes in T. repens was enormous, even between sites less than 2 km apart. Our results confirm the presumption that T. repens and T. occidentale are indeed separate species. Both the fact that T. occidentale plants never contain linamarase activity, and the difference in proportion of plants with cyanoglucosides in mixed stands show that gene flow between the species must be rare. These dissimilar distributions strongly indicate that cyanotypic frequencies in adjacent and mixed populations of the very closely related species T. occidentale and T. repens are regulated by different mechanisms. (C) 2000 Elsevier Science Ltd