Are prions a relic of an early stage of peptide evolution?

The rather unique properties of prions and their presence in very different kinds of living species suggest that this type of molecule was created at a very early stage of evolution and may even represent a relic from a time where peptide evolution was ongoing and RNA/DNA did not yet exist. A comparison of the most frequently occurring amino acid sequences in known prions with the sequences preferentially formed in the salt-induced peptide formation reaction, the most simple mechanism enabling the formation of peptides under primitive earth conditions, shows a remarkable coincidence that strongly supports this hypothesis.     

Selective control of Microcystis using an amino acid – a laboratory assay

An amino acid (L-lysine) was screened against eighteen strains ofCyanophyceae, Bacillariophyceae and Chlorophyceae. OnlyMicrocystis strains (Cyanophyceae) were sensitive tolysine; other strains were not affected. Cells of sevenMicrocystis strains (10⁶ cellsmL^–1) were completely killed within 48h by lysine at concentrations between 0.6 and 5.0 mgL^–1. Two Microcystis strains wereinhibited by 92 and 98 %. Similar results were obtained when lysine malonateandlysine copper were used as algicides. Microcystis specieswere killed by lysine malonate at concentrations between 0.6 and 5 mgL^–1, and by lysine copper at concentrations between 0.5and 20 mg L^–1.     

Insulin secretion: Feed-forward control of insulin biosynthesis?

It has long been accepted wisdom that insulin secreted from islet beta cells has either no effect, or an inhibitory feedback effect, on insulin synthesis and secretion. Recent work suggests, instead, that secreted insulin acts directly on beta cells, via its own receptor, to enhance insulin production in an autocrine feed-forward loop.     

Aminoacylation of the anticodon stem by a tRNA-synthetase paralog: relic of an ancient code?

The activation and charging of amino acids onto the acceptor stems of their cognate tRNAs are the housekeeping functions of aminoacyl-tRNA synthetases. The availability of whole genome sequences has revealed the existence of synthetase-like proteins that have other functions linked to different aspects of cell metabolism and physiology. In eubacteria, a paralog of glutamyl-tRNA synthetase, which lacks the tRNA-binding domain, was found to aminoacylate tRNA(Asp) not on the 3'-hydroxyl group of the acceptor stem but on a cyclopentene diol of the modified nucleoside queuosine present at the wobble position of anticodon loop. This modified nucleoside might be a relic of an ancient code.     

Dinoflagellate ribosomal RNA; an evolutionary relic?

The apparent molecular weights of the rRNA subunits of the dinoflagellate Peridinium cinctum fa. westii were determined by polyacrylamide gel electrophoresis to obtain an indication of its evolutionary status. The apparent molecular weights of the Peridinium light and heavy rRNA subunits were 0.7 and 1.23 X 10(6) respectively. The light rRNA is therefore typically eukaryotic but the heavy rRNA has a significantly lower MW than previously reported for higher eukaryotes which range from 1.3 to 1.75 X 10(6) depending on their evolutionary position. Thus by this criterion Peridinium is similar to red algae and may represent a eukaryotic stage, lower than fungi or green plants.     

Biochemical control of xylan biosynthesis - which end is up?

Xylans are major components of land plant secondary cell walls and are required for normal plant growth and development. Secondary walls also account for the bulk of lignocellulosic biomass, a potential feedstock for large-scale production of biofuels. Glucuronoxylan and arabinoxylan affect the conversion of lignocellulosic biomass to fermentable sugar, a crucial and expensive step in biofuel production. Thus, knowledge of xylan biosynthesis may provide tools to modify secondary cell wall structure and thereby improve the bioprocessing characteristics of biomass. Recent studies have shown that glucuronoxylan structure and biosynthesis are far more complex than previously appreciated and the number of glycosyltransferases implicated in this process continues to increase. New hypotheses regarding the mechanisms of glucuronoxylan biosynthesis challenge some widely held views.     

Floristic affinities of an inselberg archipelago in the southern Namib desert—relic of the past,centre of endemism or nothing special?

The floral composition of an inselberg archipelago in the southern Namib desert was investigated with regard to species diversity, geographic range of the species, habitat niches, seed dispersal abilities and plant herbivore defence. Although no endemic species were found, the archipelago forms an extreme and often isolated outlier for a large number of species in their distribution area. The hypothesis is proposed that the isolated extreme habitat allowed survival of relic populations due to low immigration rate and low competition. The high proportion of species favouring long-range dispersal might explain the lack of endemic species as well as the large contribution of species at their distributional boundary.     

Using human brain lesions to infer function: a relic from a past era in the fMRI age?

Recent technological advances, such as functional imaging techniques, allow neuroscientists to measure and localize brain activity in healthy individuals. These techniques avoid many of the limitations of the traditional method for inferring brain function, which relies on examining patients with brain lesions. This has fueled the zeitgeist that the classical lesion method is an inferior and perhaps obsolescent technique. However, although the lesion method has important weaknesses, we argue that it complements the newer activation methods (and their weaknesses). Furthermore, recent developments can address many of the criticisms of the lesion method. Patients with brain lesions provide a unique window into brain function, and this approach will fill an important niche in future research.     

The sulfide binding function of annelid hemoglobins: relic of an old biosystem?

Invertebrates living in sulfide-rich environments have developed different strategies of coping with sulfide toxicity. Some bivalves and annelids have hemoglobins that are capable of binding sulfide for detoxification and/or transporting it to internal bacterial symbionts. Annelids living in the sulfide-rich environments have giant (approximately 3.6 MDa) hemoglobin, consisting of 144 globin chains arranged in a hexagonal bilayer structure held together by 36 nonglobin linker chains. Some globin chains contain either a free cysteine residue at positions Cys+1 or at position Cys+11 relative to the E7 distal residue in the E helix and EF interhelical region, respectively, which bind sulfide. The hexagonal bilayer hemoglobins of annelids living in environments lacking sulfide, do not have the corresponding free cysteine residues and cannot bind sulphide. Given that the early stages of life occurred under anoxic conditions in the presence of sulfide, it is possible that the sulfide binding function from modern annelid globins inhabiting sulphide rich habitats is an evolutionary relic. This proposal seems supported by the recent finding of "protoglobins" which also have a corresponding cysteine residue in Archea known to exist in hyperthermophilic and sulfide-rich environments.     

Regulatory network of tetrapyrrole biosynthesis – studies of intracellular signalling involved in metabolic and developmental control of plastids

Plant tetrapyrrole metabolism is located in two different organelles and distributes end products into the whole cell. A complex regulatory network is involved to prevent metabolic imbalance and inefficient allocation of intermediates as well as to correlate the metabolic activities with organelle development. This review presents new findings about the control of tetrapyrrole biosynthesis and addresses the question of which regulatory principles are involved in controlling the expression of the participating enzymes and the metabolic flow in the entire pathway. It is suggested that functional organelles are required for nuclear gene expression and that metabolic signals participate in a signalling cascade transferring information from plastids to the nucleus. Recent reports about plastid-localised control mechanisms for plant tetrapyrrole metabolism are summarised and compared with results obtained in experiments on nucleus-plastid communication.     

Concerning the mechanism and control of α-amyrin biosynthesis

Experiments have shown that the variation in the ratios of α- to β-amyrin which are found in plants is not controlled by S-adenosylmethionine. The radioactive compound produced in peas after feeding with radioactive methionine is 24-methylene-lanosterol.     

Rubisco activase: an enzyme with a temperature‐dependent dual function?

Heat treatment of intact spinach leaves was found to induce a unique thylakoid membrane association of an approximately 40 kDa stromal protein. This protein was identified as rubisco activase. Most of the rubisco activase was sequestered to the thylakoid membrane, particularly to the stroma-exposed regions, during the first 10 min of heat treatment at 42 degrees C. At lower temperatures (38-40 degrees C) the association of rubisco activase with the thylakoid membrane occurred more slowly. The temperature-dependent association of rubisco activase with the thylakoid membrane was due to a conformational change in the rubisco activase itself, not to heat-induced alterations in the thylakoid membrane. Association of the 41 kDa isoform of rubisco activase occurred first, followed by the binding of the 45 kDa isoform to the thylakoid membrane. Fractionation of thylakoid membranes revealed a specific association of rubisco activase with thylakoid-bound polysomes. Our results suggest a temperature-dependent dual function for rubisco activase. At optimal temperatures it functions in releasing inhibitory sugar phosphates from the active site of Rubisco. During a sudden and unexpected exposure of plants to heat stress, rubisco activase is likely to manifest a second role as a chaperone in association with thylakoid-bound ribosomes, possibly protecting, as a first aid, the thylakoid associated protein synthesis machinery against heat inactivation.     

Biological tools for control of larval stages of malaria vectors – a review

The two main interventions presently being deployed for control of malaria vectors, that is, long-lasting insecticide-treated bed nets (LLINs) and indoor residual spraying (IRS) involve the use of chemical insecticides and target adult mosquitoes. Meanwhile, the potential of larval control is increasingly being acknowledged for the reduction of insecticide-resistant and/or exophagic Anopheles populations. Larval control has proven to be cost-effective and ideal for localities where mosquito-breeding sites are well defined and approachable. Utilising biological control tools to control anopheline larvae can lower the problem of resistance development, a common feature of chemical control. Fortunately, there are many options of biological larval control tools. Besides their direct impact on mortality, the effects of these tools can reach beyond the larval stage. Anopheline adults that develop from larvae exposed to biological control tools, such as entomopathogenic fungi, show reduced longevity, fecundity and susceptibility to Plasmodium infections. Combining two or more larval control tools can increase their efficacy against anopheline larvae. However, despite the identification of larval control potential in the laboratory, and in few cases in the field, many potential biological control tools have not been utilised to their fullest extent. This review provides an overview of the existing and potential biological larval control options for malaria vectors and discusses the advantages and requirements to develop them for malaria vector control.