Phosphorylated derivatives of the cytokinins,zeatin and its 9-β-d-ribofuranoside,naturally occurring adenine and adenosine derivatives with plant cell-division promoting activity

Zusammenfassung Zeatin-ribosid-5-phosphat wurde einerseits durch Umsetzung von 6-Chlorpurin-ribotid mit trans-4-Amino-2-methylbuten-(2)-ol-(1) und andererseits durch Behandlung von Isopropyliden-zeatin-ribosid mit Pyrophosphorylchlorid hergestellt. Die Phosphorylierung des Isopropylidenderivats in Pyridin ergab ein Allylpyridiniumderivat, dessen Struktur spektroskopisch und durch Abbau bewiesen wurde.     

Behavioural ecology: transient sexual mimicry leads to fertilization

Sexual mimicry among animals is widespread, but does it impart a fertilization advantage in the widely accepted 'sneak-guard' model of sperm competition? Here we describe field results in which a dramatic facultative switch in sexual phenotype by sneaker-male cuttlefish leads to immediate fertilization success, even in the presence of the consort male. These results are surprising, given the high rate at which females reject copulation attempts by males, the strong mate-guarding behaviour of consort males, and the high level of sperm competition in this complex mating system.     

Deficiency of glutaredoxin 5 reveals Fe-S clusters are required for vertebrate haem synthesis

Iron is required to produce haem and iron-sulphur (Fe-S) clusters, processes thought to occur independently. Here we show that the hypochromic anaemia in shiraz (sir) zebrafish mutants is caused by deficiency of glutaredoxin 5 (grx5), a gene required in yeast for Fe-S cluster assembly. We found that grx5 was expressed in erythroid cells of zebrafish and mice. Zebrafish grx5 rescued the assembly of grx5 yeast Fe-S, showing that the biochemical function of grx5 is evolutionarily conserved. In contrast to yeast, vertebrates use iron regulatory protein 1 (IRP1) to sense intracellular iron and regulate mRNA stability or the translation of iron metabolism genes. We found that loss of Fe-S cluster assembly in sir animals activated IRP1 and blocked haem biosynthesis catalysed by aminolaevulinate synthase 2 (ALAS2). Overexpression of ALAS2 RNA without the 5' iron response element that binds IRP1 rescued sir embryos, whereas overexpression of ALAS2 including the iron response element did not. Further, antisense knockdown of IRP1 restored sir embryo haemoglobin synthesis. These findings uncover a connection between haem biosynthesis and Fe-S clusters, indicating that haemoglobin production in the differentiating red cell is regulated through Fe-S cluster assembly.     

Sexual behaviour: rapid speciation in an arthropod

Theory predicts that sexual behaviour in animals can evolve rapidly, accelerating the rate of species formation. Here we estimate the rate of speciation in Laupala, a group of forest-dwelling Hawaiian crickets that is characterized primarily through differences in male courtship song. We find that Laupala has the highest rate of speciation so far recorded in arthropods, supporting the idea that divergence in courtship or sexual behaviour drives rapid speciation in animals.     

A Systemic Exploration of Lesotho’s Basic Education through Interactive Management

Lesotho is an inland country striving to improve its economy. Accessible education is perceived as an effective approach to economic growth. Over the years, various projects were commenced to improve Lesotho’s basic education provision. However, the progress is not satisfactory or stable. This paper argues for systemic thinking and adopts Warfield’s interactive management to identify the difficulties in Lesotho’s education projects. Interactive management can help stakeholders to identify system elements, structure the relationship between systems elements and produce a diagraph representing the system in question. The core mechanism of interactive management is a binary matrix which can infer the existence of a relationship between system elements, provided that the relationship is transitive. Four root problems were identified through the interactive management process: ‘board members not educated’, ‘poor service delivery by the Ministry of Education and Training to teachers’, ‘food insecurity’ and ‘reduced and standardisation of school fees at post primary schools’. The developed model demonstrates how system elements are interconnected. The model has potential to be used as a starting point for the Lesotho government to manage on its basic education problems through the identified root causes.     

Concise representations for association rules in multi-level datasets

Association rule mining plays an important role in knowledge and information discovery. Often for a dataset, a huge number of rules can be extracted, but many of them are redundant, especially in the case of multi-level datasets. Mining non-redundant rules is a promising approach to solve this problem. However, existing work (Pasquier et al. 2005, Xu & Li 2007) is only focused on single level datasets. In this paper, we firstly present a definition for redundancy and a concise representation called Reliable basis for representing non-redundant association rules, then we propose an extension to the previous work that can remove hierarchically redundant rules from multi-level datasets. We also show that the resulting concise representation of non-redundant association rules is lossless since all association rules can be derived from the representation. Experiments show that our extension can effectively generate multilevel non-redundant rules.