Honest sexual signalling mediated by parasite and testosterone effects on oxidative balance

Extravagant ornaments evolved to advertise their bearers'' quality, the honesty of the signal being ensured by the cost paid to produce or maintain it. The oxidation handicap hypothesis (OHH) proposes that a main cost of testosterone-dependent ornamentation is oxidative stress, a condition whereby the production of reactive oxygen and nitrogen species (ROS/RNS) overwhelms the capacity of antioxidant defences. ROS/RNS are unstable, very reactive by-products of normal metabolic processes that can cause extensive damage to key biomolecules (cellular proteins, lipids and DNA). Oxidative stress has been implicated in the aetiology of many diseases and could link ornamentation and genetic variation in fitness-related traits. We tested the OHH in a free-living bird, the red grouse. We show that elevated testosterone enhanced ornamentation and increased circulating antioxidant levels, but caused oxidative damage. Males with smaller ornaments suffered more oxidative damage than those with larger ornaments when forced to increase testosterone levels, consistent with a handicap mechanism. Parasites depleted antioxidant defences, caused oxidative damage and reduced ornament expression. Oxidative damage extent and the ability of males to increase antioxidant defences also explained the impacts of testosterone and parasites on ornamentation within treatment groups. Because oxidative stress is intimately linked to immune function, parasite resistance and fitness, it provides a reliable currency in the trade-off between individual health and ornamentation. The costs induced by oxidative stress can apply to a wide range of signals, which are testosterone-dependent or coloured by pigments with antioxidant properties.     

Nonglucosylated oligosaccharides are transferred to protein in MI8-5 Chinese hamster ovary cells

A CHO mutant MI8-5 was found to synthesize Man9-GlcNAc2-P-P-dolichol rather than Glc3Man9GlcNAc2-P-P-dolichol as the oligosaccharide-lipid intermediate in N-glycosylation of proteins. MI8-5 cells were incubated with labeled mevalonate, and the prenol was found to be dolichol. The mannose-labeled oligosaccharide released from oligosaccharide-lipid of MI8-5 cells was analyzed by HPLC and alpha-mannosidase treatment, and the data were consistent with a structure of Man9GlcNAc2. In addition, MI8-5 cells did not incorporate radioactivity into oligosaccharide- lipid during an incubation with tritiated galactose, again consistent with MI8-5 cells synthesizing an unglucosylated oligosaccharide-lipid. MI8-5 cells had parental levels of glucosylphosphoryldolichol synthase activity. However, in two different assays, MI8-5 cells lacked dolichol- P-Glc:Man9GlcNAc2-P-P-dolichol glucosyltransferase activity. MI8-5 cells were found to synthesize glucosylated oligosaccharide after they were transfected with Saccharomyces cerevisiae ALG 6, the gene for dolichol-P-Glc:Man9GlcNAc2-P-P-dolichol glucosyltransferase. MI8-5 cells were found to incorporate mannose into protein 2-fold slower than parental cells and to approximately a 2-fold lesser extent.      

Effects of rhizoma peanut cultivars (Arachis glabrata Benth.) on the soil bacterial diversity and predicted function in nitrogen fixation

There is a growing awareness of the importance of soil microorganisms in agricultural management practices. Currently, much less is known about whether different crop cultivar has an effect on the taxonomic structure and diversity, and specific functions of soil bacterial communities. Here, we examined the changes of the diversity and composition and enzyme‐encoding nitrogenase genes in a long‐term field experiment with seven different rhizoma peanut cultivars in southeastern USA, coupling high‐throughput 16S rRNA gene sequencing and the sequence‐based function prediction with Tax4Fun. Of the 32 phyla detected (Proteobacteria class), 13 were dominant: Acidobacteria, Alphaproteobacteria, Actinobacteria, Betaproteobacteria, Bacteroidetes, Verrucomicrobia, Gammaproteobacteria, Deltaproteobacteria, Gemmatimonadetes, Firmicutes, Nitrospirae, Chloroflexi, and Planctomycetes (relative abundance >1%). We found no evidence that the diversity and composition of bacterial communities were significantly different among different cultivars, but the abundance of some dominant bacterial groups that have N‐fixation potentials (at broad or fine taxonomic level) and predicted abundances of some enzyme‐encoding nitrogenase genes showed significant across‐cultivar differences. The nitrogenase genes were notably abundant in Florigraze and Latitude soils while remarkably lower in Arbook and UF_TITO soils when compared with other cultivars, indicating different nitrogen fixation potentials among different cultivars. The findings also suggest that the abundance of certain bacterial taxa and the specific function bacteria perform in ecosystems can have an inherent association. Our study is helpful to understand how microbiological responses and feedback to different plant genotypes through the variation in structure and function of their communities in the rhizosphere.     

A genomic approach to isoflavone biosynthesis in kudzu (<Emphasis Type="Italic">Pueraria lobata</Emphasis>)

Roots of kudzu (Pueraria lobata) are a rich source of isoflavone O- and C-glycosides. Although O-glycosylation of (iso)flavonoids has been well characterized at the molecular level, no plant isoflavonoid C-glycosyltransferase genes have yet been isolated. To address the biosynthesis of kudzu isoflavonoids, we generated 6,365 high-quality expressed sequence tags (ESTs) from a subtraction cDNA library constructed using RNA from roots that differentially accumulate puerarin. The ESTs were clustered into 722 TCs and 3,913 singletons, from which 15 family I glycosyltransferases (UGTs) were identified. Hierarchical clustering analysis of the expression patterns of these UGTs with isoflavone synthase (IFS) in a range of tissues identified UGTs with potential functions in isoflavone glycosylation. The open reading frames of these UGTs were expressed in E. coli for functional analysis, and one was shown to preferentially glycosylate isoflavones at the 7-O-position. In addition, ESTs corresponding to chalcone synthase, chalcone reductase, chalcone isomerase (CHI) and 2-hydroxyisoflavanone dehydratase were identified. Recombinant CHI proteins had high activities with both 6′-deoxy- and 6′-hydroxy chalcones, typical of Type II CHIs. Establishment of this EST database and identification of genes associated with kudzu isoflavone biosynthesis and glycosylation provide a new resource for metabolic engineering of bioactive kudzu isoflavones.     

Mutations in a Conserved Domain of E. coli MscS to the Most Conserved Superfamily Residue Leads to Kinetic Changes

In Escherichia coli (E. coli) the mechanosensitive channel of small conductance, MscS, gates in response to membrane tension created from acute external hypoosmotic shock, thus rescuing the bacterium from cell lysis. E. coli MscS is the most well studied member of the MscS superfamily of channels, whose members are found throughout the bacterial and plant kingdoms. Homology to the pore lining helix and upper vestibule domain of E. coli MscS is required for inclusion into the superfamily. Although highly conserved, in the second half of the pore lining helix (TM3B), E. coli MscS has five residues significantly different from other members of the superfamily. In superfamilies such as this, it remains unclear why variations within such a homologous region occur: is it tolerance of alternate residues, or does it define functional variance within the superfamily? Point mutations (S114I/T, L118F, A120S, L123F, F127E/K/T) and patch clamp electrophysiology were used to study the effect of changing these residues in E. coli MscS on sensitivity and gating. The data indicate that variation at these locations do not consistently lead to wildtype channel phenotypes, nor do they define large changes in mechanosensation, but often appear to effect changes in the E. coli MscS channel gating kinetics.     

Chimpanzee fetal G gamma and A gamma globin gene nucleotide sequences provide further evidence of gene conversions in hominine evolution

The fetal globin genes G gamma and A gamma from one chromosome of a chimpanzee (Pan troglodytes) were sequenced and found to be closely similar to the corresponding genes of man and the gorilla. These genes contain identical promoter and termination signals and have exons 1 and 2 separated by the conserved short intron 1 (122 bp) and exons 2 and 3 separated by the more rapidly evolving, larger intron 2 (893 bp and 887 bp in chimpanzee G gamma and A gamma, respectively). Each intron 2 has a stretch of simple sequence DNA (TG)n serving possibly as a "hot spot" for recombination. The two chimpanzee genes encode polypeptide chains that differ only at position 136 (glycine in G gamma and alanine in A gamma) and that are identical to the corresponding human chains, which have aspartic acid at position 73 and lysine at 104 in contrast to glycine and arginine at these respective positions of the gorilla A gamma chain. Phylogenetic analysis by the parsimony method revealed four silent (synonymous) base substitutions in evolutionary descent of the chimpanzee G gamma and A gamma codons and none in the human and gorilla codons. These Homininae (Pan, Homo, Gorilla) coding sequences evolved at one-tenth the average mammalian rate for nonsynonymous and one-fourth that for synonymous substitutions. Three sequence regions that were affected by gene conversions between chimpanzee G gamma and A gamma loci were identified: one extended 3' of the hot spot with G gamma replaced by the A gamma sequence, another extended 5' of the hot spot with A gamma replaced by G gamma, and the third conversion extended from the 5' flanking to the 5' end of intron 2, with G gamma replaced here by the A gamma sequence. A conversion similar to this third one has occurred independently in the descent of the gorilla genes. The four previously identified conversions, labeled C1-C4 (Scott et al. 1984), were substantiated with the addition of the chimpanzee genes to our analysis (C1 being shared by all three hominines and C2, C3, and C4 being found only in humans). Thus, the fetal genes from all three of these hominine species have been active in gene conversions during the descent of each species.      

“Girney” vocalizations among Japanese macaque females: Context and function

One vocalization in the Japanese macaque (Macaca fuscata) system of communication is the “girney.” Previous studies indicated that the “girney” is used for short range communication and that it tends to occur when subordinate animals approach and groom dominant ones and when females without infants approach females who have infants. Data were collected on the social behavior of adult female Japanese monkeys of the Arashiyama-A troop in Texas in order to test those results. The study indicates that “girneys” are the most frequently occurring vocalizations of females during and following the birth season and that they occur primarily in two contexts. Those are the proximity of a female to another female with a new infant and the proximity of a lower ranking animal to a higher ranking one. The contexts are ones in which the risk of aggression is high, and the “girneys” appear to function as appeasement gestures to reduce the risk.     

Voltage-induced gating of the mechanosensitive MscL ion channel reconstituted in a tethered lipid bilayer membrane

The mechanosensitive (MS) ion channel is gated by changes in bilayer deformation. It is functional without the presence of any other proteins and gating of the channel has been successfully achieved using conventional patch clamping techniques where a voltage has been applied together with a pressure over the membrane. Here, we have for the first time analyzed the large conducting (MscL) channel in a supported membrane using only an external electrical field. This was made possible using a newly developed technique utilizing a tethered lipid bilayer membrane (tBLM), which is part of an engineered microelectronic array chip. Single ion channel activity characteristic for MscL was obtained, albeit with lower conductivity. The ion channel was gated using solely a transmembrane potential of 300 mV. Computations demonstrate that this amount of membrane potential induces a membrane tension of 12 dyn/cm, equivalent to that calculated to gate the channel in patch clamp from pressure-induced stretching of the bilayer. These results strengthen the supposition that the MscL ion channel gates in response to stress in the lipid membrane rather than pressure across it. Furthermore, these findings illustrate the possibility of using the MscL as a release valve for engineered membrane devices; one step closer to mimicking the true function of the living cell.