Uphill energy transfer in photosystem I from <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis>. Time-resolved fluorescence measurements at 77 K

Energetic properties of chlorophylls in photosynthetic complexes are strongly modulated by their interaction with the protein matrix and by inter-pigment coupling. This spectral tuning is especially striking in photosystem I (PSI) complexes that contain low-energy chlorophylls emitting above 700 nm. Such low-energy chlorophylls have been observed in cyanobacterial PSI, algal and plant PSI–LHCI complexes, and individual light-harvesting complex I (LHCI) proteins. However, there has been no direct evidence of their presence in algal PSI core complexes lacking LHCI. In order to determine the lowest-energy states of chlorophylls and their dynamics in algal PSI antenna systems, we performed time-resolved fluorescence measurements at 77 K for PSI core and PSI–LHCI complexes isolated from the green alga Chlamydomonas reinhardtii. The pool of low-energy chlorophylls observed in PSI cores is generally smaller and less red-shifted than that observed in PSI–LHCI complexes. Excitation energy equilibration between bulk and low-energy chlorophylls in the PSI–LHCI complexes at 77 K leads to population of excited states that are less red-shifted (by ~?12 nm) than at room temperature. On the other hand, analysis of the detection wavelength dependence of the effective trapping time of bulk excitations in the PSI core at 77 K provided evidence for an energy threshold at ~?675 nm, above which trapping slows down. Based on these observations, we postulate that excitation energy transfer from bulk to low-energy chlorophylls and from bulk to reaction center chlorophylls are thermally activated uphill processes that likely occur via higher excitonic states of energy accepting chlorophylls.     

An individual-level selection model for the apparent altruism exhibited by cellular slime moulds

In Dictyostelium discoideum, cells that become part of the stalk or basal disc display behaviour that can be interpreted as altruistic. Atzmony et al. (Curr Sci 72:142–145, 1997) had hypothesised that this behaviour could be the outcome of an adaptive strategy based on differing intrinsic quality as reflected by phenotypes that indicate differences in potential for survival and reproduction, followed by intercellular competition among amoebae of differing qualities. Low-quality amoebae would have a poor chance of succeeding in the competition to form spores; they could enhance their chances of survival by adopting a presumptive stalk strategy. Here we extend the hypothesis by making use of recent findings. Our approach is based on the view that an evolutionary explanation for the apparent altruism of stalk cells in D. discoideum must apply broadly to other cellular slime moulds (CSMs) that exhibit stalk cell death. Further, it must be capable of being modified to cover social behaviour in CSMs with an extracellular stalk, as well as in sorocarpic amoebae whose stalk cells are viable. With regard to D. discoideum, we suggest that (a) differentiation-inducing factor, thought of as a signal that inhibits amoebae from forming spores and induces them to differentiate into basal disc cells, is better viewed as a mediator of competition among post-aggregation amoebae and (b) the products of the ‘recognition genes’, tgrB and tgrC, allow an amoeba to assess its quality relative to that of its neighbours and move to a position within the aggregate that optimises its reproductive fitness. From this perspective, all cells behave in a manner that is ‘selfish’ rather than ‘altruistic’, albeit with different expectations of success.     

Aloe Emodin Reduces Phthiodiolone Dimycocerosate Potentiating Vancomycin Susceptibility on Mycobacteria

Treatment of tuberculosis still represent a major public health issue. The emergence of multi-and extensively-drug resistant (MDR and XDR) Mycobacterium tuberculosis clinical strains further pinpoint the urgent need for new anti-tuberculous drugs. We previously showed that vancomycin can target mycobacteria lacking cell wall integrity, especially those lacking related phthiocerol and phthiodolone dimycocerosates, PDIM A and PDIM B, respectively. As aloe emodin was previously hypothesized to be able to target the synthesis of mycobacterial cell wall lipids, we tested its ability to potentiate glycopeptides antimycobacterial activity. The aloe emodin with the vancomycin induced a combination effect beyond simple addition, close to synergism, at a concentration lower to reported IC₅₀ cytotoxic value, on M. bovis BCG and on H37Rv M. tuberculosis. Interestingly, out of six MDR and pre-XDR clinical strains, one showed a strong synergic susceptibility to the drug combination. Mycobacterial cell wall lipid analyses highlighted a selective reduction of PDIM B by aloe emodin.     

Presence of bark influences the succession of cryptogamic wood-inhabiting communities on conifer fallen logs

Predictors of cryptogamic wood-inhabiting communities need to be examined to understand the drivers of forest biodiversity. We estimated the influence of bark cover on the wood-inhabiting vegetation on conifer logs in early stages of epixylic succession in mature European boreal and hemi-boreal forests. Abundance of substrate groups with respect to log attributes was estimated with generalized linear and generalized linear mixed models. The structure and composition of epixylic communities was analysed using non-metric multidimensional scaling with subsequent environmental fitting. The abundance of true epixylics was inversely related to bark cover. In the first stage, bark cover did not influence the abundance of epiphytes and epigeous species; positively influenced the abundance of facultative epixylics on spruce logs and negatively influenced it on pine logs. In the second stage, the effect of bark cover was positive for epiphytes and epigeous species on spruce logs and for facultative epixylics independent of log species identity and negative for epigeous species on pine logs. Generalist species did not depend on bark cover. Total cover of wood-inhabiting vegetation was marginally influenced by bark cover. The effect of bark cover on epixylic vegetation at community level was negligible. In general, bark cover favours the establishment and growth of species with low substrate specificity. This preference may lead to either burial of logs by epigeous bryophytes, or facilitation of succession towards the dominance of ground vegetation.     

Biotic Potential of a Short-Horned Grasshopper, <Emphasis Type="Italic">Oxya hyla hyla</Emphasis> Serville (Orthoptera: Acrididae) to Assess Its Biomass Producing Capacity

The growth of fishery and animal husbandry is being hindered by the scarcity of protein rich feed ingredients. Being rich in protein grasshoppers may be an alternative source of protein rich feed ingredients and hence rearing of these insects is essential for sustainable supply of insect biomass to the feed industry. The success of biomass production through insect rearing depends on the reproductive potentiality, rate of survival and growth of that particular insect. This study examines the biotic potential, fecundity, fertility, nymph mortality, life span and biomass production ability of a multivoltine grasshopper, Oxya hyla hyla (Serville, 1931) under semi-controlled condition. The grasshoppers are reared in 35 ± 2 °C temperature and 12L: 12D photoperiod and provided with food as fresh leaves of Cynodon dactylon (L.) Pers. to nymphs and Sorghum halepense (L.) Pers. to the adults. The result shows that a single pair of O. hyla hyla can lay on average 69.87 eggs in 4.96 ± 0.43 egg pods of which 7.37 ± 0.92 % eggs and 8.26 ± 0.99 % nymphs do not survive. The remaining survived nymphs metamorphose to 27.8 ± 3.35 male and 32.6 ± 3.21 female adults which produce a biomass of 18.48 ± 1.67 g wet weight. Thus a mass scale rearing of this insect may produce good amount of insect biomass which may be usable for fish and animal feed.     

Surface display of ACC deaminase on endophytic <Emphasis Type="Italic">Enterobacteriaceae</Emphasis> strains to increase saline resistance of host rice sprouts by regulating plant ethylene synthesis

Background

Most endophytic bacteria in consortia, which provide robust and broad metabolic capacity, are attractive for applications in plant metabolic engineering. The aim of this study was to investigate the effects of engineered endophytic bacterial strains on rice sprout ethylene level and growth under saline stress. A protocol was developed to synthesize engineered strains by expressing bacterial 1-aminocyclopropane-1-carboxylate (ACC) deaminase gene on cells of endophytic Enterobacter sp. E5 and Kosakonia sp. S1 (denoted as E5P and S1P, respectively).

Results

Results showed that ACC deaminase activities of the engineered strains E5P and S1P were significantly higher than those of the wild strains E5 and S1. About 32–41% deaminase was expressed on the surface of the engineered strains. Compared with the controls without inoculation, inoculation with the wild and engineered strains increased the deaminase activities of sprouts. Inoculation with the engineered strains increased 15–21% more deaminase activities of sprouts than with the wild strains, and reduced the ethylene concentrations of sprouts more significantly than with wild strains (P < 0.05). Inoculation with the wild and engineered strains promoted the growth of sprouts, while the promoting effects were more profound with the engineered strains than with the wild strains. The engineered strains improved saline resistance of sprouts under salt concentrations from 10 to 25 g L^?1. The engineered strains promoted longer roots and shoots than the wild strains under the salt stresses, indicating that the ACC deaminases on the endophytic bacterial cells could result in plant-produced ACC degradation and inhibit plant ethylene formation.

Conclusions

The protocols of expressing enzymes on endophytic bacterial cells showed greater potentials than those of plant over-expressed enzymes to increase the efficiency of plant metabolic pathways.

     

Isolation of DNA for RAPD analysis from dry leaf material of some<Emphasis Type="Italic">Hesperis</Emphasis> L. specimens

An improved protocol for the isolation of DNA from dry material of someHesperis specimens is described. The isolated DNA is suitable for random amplification of polymorphic DNA (RAPD) analysis. Different DNA extraction protocols were examined to determine which might yield DNA from dry leaf tissue ofHesperis specimens. The methods examined include the protocols with hexadecyltrimethylammonium bromide (CTAB) described by Doyle and Doyle (1987); sodium dodecyl sulfate (SDS) by Dellaporta et al. (1983); and CTAB and SDS, the modified minipreparation, by Dellaporta et al (1983). None of these procedures yielded DNA of suitable purity for RAPD assay. We established an improved procedure involving CTAB and enzymatic digestion of proteins and RNA. The recovery of DNA with an average yield of 25 mg/g of leaf material was possible with this procedure. RAPD bands, which could be used to distinguish amongHesperis specimens, were generated.     

Longitudinal analytical approaches to genetic data

Background

Longitudinal phenotypic data provides a rich potential resource for genetic studies which may allow for greater understanding of variants and their covariates over time. Herein, we review 3 longitudinal analytical approaches from the Genetic Analysis Workshop 19 (GAW19). These contributions investigated both genome-wide association (GWA) and whole genome sequence (WGS) data from odd numbered chromosomes on up to 4 time points for blood pressure–related phenotypes. The statistical models used included generalized estimating equations (GEEs), latent class growth modeling (LCGM), linear mixed-effect (LME), and variance components (VC). The goal of these analyses was to test statistical approaches that use repeat measurements to increase genetic signal for variant identification.

Results

Two analytical methods were applied to the GAW19: GWA using real phenotypic data, and one approach to WGS using 200 simulated replicates. The first GWA approach applied a GEE-based model to identify gene-based associations with 4 derived hypertension phenotypes. This GEE model identified 1 significant locus, GRM7, which passed multiple test corrections for 2 hypertension-derived traits. The second GWA approach employed the LME to estimate genetic associations with systolic blood pressure (SBP) change trajectories identified using LCGM. This LCGM method identified 5 SBP trajectories and association analyses identified a genome-wide significant locus, near ATOX1 (p?=?1.0E^?8). Finally, a third VC-based model using WGS and simulated SBP phenotypes that constrained the β coefficient for a genetic variant across each time point was calculated and compared to an unconstrained approach. This constrained VC approach demonstrated increased power for WGS variants of moderate effect, but when larger genetic effects were present, averaging across time points was as effective.

Conclusion

In this paper, we summarize 3 GAW19 contributions applying novel statistical methods and testing previously proposed techniques under alternative conditions for longitudinal genetic association. We conclude that these approaches when appropriately applied have the potential to: (a) increase statistical power; (b) decrease trait heterogeneity and standard error; (c) decrease computational burden in WGS; and (d) have the potential to identify genetic variants influencing subphenotypes important for understanding disease progression.

     

Plant cytochrome P450s: nomenclature and involvement in natural product biosynthesis

Cytochrome P450s constitute the largest family of enzymatic proteins in plants acting on various endogenous and xenobiotic molecules. They are monooxygenases that insert one oxygen atom into inert hydrophobic molecules to make them more reactive and hydro-soluble. Besides for physiological functions, the extremely versatile cytochrome P450 biocatalysts are highly demanded in the fields of biotechnology, medicine, and phytoremediation. The nature of reactions catalyzed by P450s is irreversible, which makes these enzymes attractions in the evolution of plant metabolic pathways. P450s are prime targets in metabolic engineering approaches for improving plant defense against insects and pathogens and for production of secondary metabolites such as the anti-neoplastic drugs taxol or indole alkaloids. The emerging examples of P450 involvement in natural product synthesis in traditional medicinal plant species are becoming increasingly interesting, as they provide new alternatives to modern medicines. In view of the divergent roles of P450s, we review their classification and nomenclature, functions and evolution, role in biosynthesis of secondary metabolites, and use as tools in pharmacology.