Louse (Insecta : Phthiraptera) mitochondrial 12S rRNA secondary structure is highly variable

Lice are ectoparasitic insects hosted by birds and mammals. Mitochondrial 12S rRNA sequences obtained from lice show considerable length variation and are very difficult to align. We show that the louse 12S rRNA domain III secondary structure displays considerable variation compared to other insects, in both the shape and number of stems and loops. Phylogenetic trees constructed from tree edit distances between louse 12S rRNA structures do not closely resemble trees constructed from sequence data, suggesting that at least some of this structural variation has arisen independently in different louse lineages. Taken together with previous work on mitochondrial gene order and elevated rates of substitution in louse mitochondrial sequences, the structural variation in louse 12S rRNA confirms the highly distinctive nature of molecular evolution in these insects

Minimal energy foldings of eukaryotic mRNAs form a separate leader domain

We have investigated the minimal energy foldings of 38 mature mRNAs, including the globin family, the insulins, the growth hormones and interleukin-2, and have compared these foldings with those of fully and partly randomised sequences. The mRNAs differ from the random sequences in that they form a separate leader hairpin of 40–60 nucleotides, with the initiation codon typically located downstream of this hairpin, followed by a main fold in which a region flanking the initiation codon is basepaired with the trailer: resulting in a close proximity of the 5′ and 3′ end of the mRNA. The formation of this conformation depends not only—or primarily—on the structure of the leader, but on both the leader and trailer sequence and their interaction with the coding sequence. Thus if, as the frequent occurrence of this pattern suggests, the secondary structure of the leader regions plays a role in the initiation of translation, possibly accounting for the specificity of initiation and the different translational efficiencies of various mRNAs, we expect that these features may be influenced both by leader and trailer mutants

Modernizing Agriculture through a ‘new’ Green Revolution: The Limits of the Crop Intensification Program in Rwanda

Pendant les dernières dix années, les secteurs agricoles des pays Africains ont connu un nombre important d’initiatives pour la promotion d’une ‘nouvelle’ Révolution Verte pour le continent. A cause de la faible productivité de leurs activités agricoles, en fait, il est demandé aux petits producteurs africains de rattraper leur désavantage par rapport aux pays de la Révolution Verte. Cet article est une contribution au débat sur la nouvelle Révolution Verte en Afrique. L’article analyse le Programme d’Intensification des Cultures rwandais (Crop Intensification Program, CIP) en tant qu’étude de cas de l’application du modèle de la Révolution Verte. La discussion présentée dans cet article dérive d’un effort de recherche à trois niveaux : macro, meso et micro. L’analyse révèle que le CIP ne prend pas en considérations les résultats des expériences précédentes de Révolution Verte, en particulier pour ce qui concerne des questions de différentiation sociale, de durabilité environnementale et de création et diffusion des connaissances.Over the past decade, African agriculture sectors have been the object of numerous initiatives advancing a ‘new’ Green Revolution for the continent. The low productivity of African small-holders is attributed to the low use of modern, improved agricultural inputs. In short, African countries are expected to catch up with the Green Revolution in other parts of the world. This paper is a contribution to the debate on the new African Green Revolution. We analyse the Rwandan Crop Intensification Program (CIP) as a case-study of the application of the African Green Revolution model. The paper is based on research at the macro, meso and micro level. We argue that the CIP fails to draw lessons from previous Green Revolution experiences in terms of its effects on social differentiation, on ecological sustainability, and on knowledge exchange and creation