Evolutionary conflicts: rapid suppression of a male-killer

Conflicts between and within species can drive fast evolutionary change. A recent study has documented remarkably rapid counter-adaptations in the wild to an extreme sex-ratio distortion caused by a bacterial symbiont.     

Ant semiochemicals limit apterous aphid dispersal

Some organisms can manipulate the nervous systems of others or alter their physiology in order to obtain benefit. Ants are known to limit alate aphid dispersal by physically removing wings and also through chemical manipulation of the alate developmental pathway. This results in reduced dispersal and higher local densities of aphids, which benefit ants in terms of increased honeydew and prey availability. Here, we show that the walking movement of mutualistic apterous aphids is also reduced by ant semiochemicals. Aphids walk slower and their dispersal from an unsuitable patch is hampered by ants. If aphid walking dispersal has evolved as a means of natural enemy escape, then ant chemicals may act as a signal indicating protection; hence, reduced dispersal could be adaptive for aphids. If, however, dispersal is primarily a means to reduce competition or to maintain persistent metapopulations, then manipulation by ants could be detrimental. Such manipulation strategies, common in host-parasite and predator-prey interactions, may be more common in mutualism than expected.     

Chemically inducible expression of the PHB biosynthetic pathway in <Emphasis Type="Italic">Arabidopsis</Emphasis>

Arabidopsis plants were transformed with a multi-gene construct for expression of the polyhydroxybutyrate (PHB) biosynthetic pathway containing a gene switch that can be activated by commercially available non-steroidal ecdysone analogs approved for use on some crops as pesticides. T(1) progeny of transgenic Arabidopsis plants were isolated and screened for PHB production in the presence of ecdysone analogs. T(2) progeny derived from selected T(1) lines were subjected to further analysis by comparing PHB production levels prior to treatment with inducing agent and 21 days after initiation of induction. Significant PHB production was delayed in many of the engineered plants until after induction. PHB levels of up to 14.3% PHB per unit dry weight were observed in young leaves harvested from engineered T(2) plants after applications of the commercial ecdysone analog Mimic. PHB in older leaves reached levels of up to 7% PHB per unit dry weight. This study represents a first step towards engineering a chemically inducible gene switch for PHB production in plants using inducing agents that are approved for field use.     

5-Lipoxygenase: regulation of expression and enzyme activity

5-Lipoxygenase (5-LO) catalyzes the first two steps in the biosynthesis of leukotrienes, a group of pro-inflammatory lipid mediators derived from arachidonic acid. Leukotriene antagonists are used in the treatment of asthma, and the potential role of leukotrienes in atherosclerosis, another chronic inflammatory disease, has recently received considerable attention. In addition, some possible effects of 5-LO metabolites in tumorigenesis have emerged. Thus, knowledge of the biochemistry of this enzyme has potential implications for the treatment of various diseases. Recent advances have expanded our understanding of the regulatory mechanisms underlying the expression and control of 5-LO activity. With regard to the control of enzyme activity, many of these findings focus on the N-terminal domain of 5-LO.     

Decoding the mannitol enigma in filamentous fungi

Mannitol is a 6-carbon polyol that is among the most abundant biochemical compounds in the biosphere. Mannitol has been ascribed a multitude of roles in filamentous fungi including carbohydrate storage, reservoir of reducing power, stress tolerance and spore dislodgement and/or dispersal. The advancement of genetic manipulation techniques in filamentous fungi has rapidly accelerated our understanding of the roles and metabolism of mannitol. The targeted deletion of genes encoding proteins of mannitol metabolism in several fungi, including phytopathogens, has proven that the metabolism of mannitol does not exist as a cycle and that many of the postulated roles are unsupported. These recent studies have provided a much needed focus on this mysterious metabolite and make this a fitting time to review the roles and metabolism of mannitol in filamentous fungi.     

Mimetics of the tri- and tetrasaccharide epitope of GQ1balpha as myelin-associated glycoprotein (MAG) ligands

The synthesis of phenoxyphenyl, phenoxybenzyl, biphenyl, and phenyltriazole substituted sialic acid derivatives as mimics of the tri- and tetrasaccharide epitopes of GQ1balpha is described. These synthetically easily available sialosides show comparable or even enhanced affinity to MAG compared with the natural tri- and tetrasaccharide epitopes and form a new class of potential MAG antagonists.     

Voltammetric detection of single base-pair mismatches and quantification of label-free target ssDNA using a competitive binding assay

The application of electrochemical techniques for DNA detection is motivated by their potential to detect hybridisation events in a more rapid, simplistic and cost-effective manner compared to conventional optical assays. Here, we present an electrochemical DNA sensor for the specific and quantitative detection of single-stranded DNA (ssDNA). Probe oligonucleotides were immobilised onto thin gold film electrodes by a 5'-thiol-linker. Hybridisation was detected by means of the electroactive redox-marker methylene blue (MB) covalently attached to the 5'-end of the target ssDNA and voltammetric techniques. MB-labeled target ssDNA was recognised down to 30 pmol. By application of a competitive binding assay, non-labeled ssDNA was detected down to 3 pmol. In addition, the DNA-modified electrodes were capable of sensing single base-pair mismatches at different positions within the sequence of the hybridised double-stranded DNA (dsDNA).     

HPLC-photodiode array detection analysis of curcuminoids in Curcuma species indigenous to Indonesia

An optimized HPLC method with photodiode array detection was developed and applied to analyse the curcuminoids curcumin, demethoxycurcumin, and bis-demethoxycurcumin in rhizomes of Curcuma mangga Val &. v. Zijp, C. heyneana Val. & v. Zijp, C. aeruginosa Roxb. and C. soloensis Val. (Zingiberaceae), indigenous to Indonesia. The method was validated with an isocratic system, a short run time of 10 min and a baseline separation. The curcuminoid content was 0.18-0.47% for C. mangga, 0.98-3.21% for C. heyneana, 0.02-0.03% for C. aeruginosa and 0.40% for C. soloensis.