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[en] The Andes-endemic Barnadesioideae lineage is the oldest surviving and phylogenetically basal subfamily of the Asteraceae (Compositae), a prolific group of flowering plants with world-wide distribution (∼24,000 species) marked by a rich diversity of sesquiterpene lactones (STLs). Intriguingly, there is no evidence that members of the Barnadesioideae produce STLs, specialized metabolites thought to have contributed to the adaptive success of the Asteraceae family outside South America. The biosynthesis of STLs requires the intimate expression and functional integration of germacrene A synthase (GAS) and germacrene A oxidase (GAO) to sequentially cyclize and oxidize farnesyl diphosphate into the advanced intermediate germacrene A acid leading to diverse STLs. Our previous discovery of GAO activity conserved across all major subfamilies of Asteraceae, including the phylogenetically basal lineage of Barnadesioideae, prompted further investigation of the presence of the gateway GAS in Barnadesioideae. Herein we isolated two terpene synthases (BsGAS1/BsGAS2) from the basal Barnadesia spinosa (Barnadesioideae) that displayed robust GAS activity when reconstituted in yeast and characterized in vitro. Despite the apparent lack of STLs in the Barnadesioideae, this work unambiguously confirms the presence of GAS in the basal genera of the Asteraceae. Phylogenetic analysis reveals that the two BsGASs fall into two distinct clades of the Asteraceae's GASs, and BsGAS1 clade is only retained in the evolutionary closer Cichorioideae subfamily, implicating BsGAS2 is likely the ancestral base of most GASs found in the lineages outside the Barnadesioideae. Taken together, these results show the enzymatic capacities of GAS and GAO emerged prior to the subsequent radiation of STL-producing Asteraceae subfamilies. - Highlights: • Sesquiterpene lactones are characteristic metabolites in Asteraceae family. • Barnadesioideae is the basal lineage of all Asteraceae plants, producing sesquiterpene lactones. • Two germacrene A synthases (GASs) were identified and characterized from Barnadesia spinosa. • A phylogenetic analysis showed two sub-clades of GASs have evolved in Asteraceae. • GAS enzymes evolved prior to the divergence and global dispersal of the modern Asteraceae.
[en] This paper concerns technology and technology transfers which are becoming increasingly important for developing countries, especially those in South America. The author also points out that developed countries have not implemented the United Nations resolutions concerning dissemination of knowledge on advanced technologies. He stresses that if South American States wish to obtain assistance with nuclear technology from developed countries they should sign and ratify the Non-Proliferation Treaty and the Tlatelolco Treaty. (NEA)
[fr]Cette communication traite de la technologie et des transferts de technologie dont l'importance va en augmentant pour les pays en voie de developpement et notamment les pays latino-americains. L'auteur signale aussi l'inexecution de la part des nations developpees des resolutions adoptees par les Nations Unies visant a diffuser les connaissances technologiques avancees. Il insiste aussi sur le fait que si les Etats latino-americains veulent recevoir l'aide des pays developpes dans le domaine de la technologie nucleaire ils devraient conclure et ratifier le Traite de non-proliferation et le Traite de Tlatelolco
[en] To the south of the San franciscana plate a number of tectonically interdigitated suspect terranes create a complex geological situation in which intercalated ancient, metasedimentary, metavolcanic, composite and granitic terranes are tectonically repeated. These terranes are briefly discussed here together with possible interpretations. (author)
[en] The complexity of the admixture dynamics that shaped American populations is unveiled by Ongaro et al., where genetic data for more than 12,000 individuals from the continents are investigated. This study evaluates the dramatic impact of events after the colonial era, revealing a spatial and temporal heterogeneity and mirroring historical records. © 2019 Elsevier Ltd The human genetic diversity of the Americas has been affected by several events of gene flow that have continued since the colonial era and the Atlantic slave trade. Moreover, multiple waves of migration followed by local admixture occurred in the last two centuries, the impact of which has been largely unexplored. Here, we compiled a genome-wide dataset of ∼12,000 individuals from twelve American countries and ∼6,000 individuals from worldwide populations and applied haplotype-based methods to investigate how historical movements from outside the New World affected (1) the genetic structure, (2) the admixture profile, (3) the demographic history, and (4) sex-biased gene-flow dynamics of the Americas. We revealed a high degree of complexity underlying the genetic contribution of European and African populations in North and South America, from both geographic and temporal perspectives, identifying previously unreported sources related to Italy, the Middle East, and to specific regions of Africa. © 2019 Elsevier Ltd