The steady state kinetics of some biological systems: III. Thermodynamic aspects

Some thermodynamic aspects of steady systems are considered. The time rates of changes, “flux”, of various thermodynamic quantities are formulated. In particular the free energy flux in the steady state, the difference between the free energy flux in the steady and time dependent states and the change in free energy flux upon transition between steady states are discussed. Equations are derived which exhibit the formal similarities and differences between the free energy flux and the conventional free energy change. The temperature dependence of the steady state rate is examined and conditions for “mastery” by a single step discussed. A brief discussion of the role ofrate in the coupling of exergonic and endergonic reactions is given.     

Energy dependant plant stress acclimation

Plants may live and grow under suboptimal environmental conditions having certain biochemical and metabolic adaptations that facilitate their survival. Plant “metabolic flexibility” consists of the accomplishment of the same step in a metabolic pathway in a variety of different ways. Pyrophosphate which works as an energy donor when cellular ATP pools become diminished during stresses, alternative glycolytic reactions that bypass ATP-requiring steps, additional pathways for electron transport in plant mithocondria and the salvage pathways are some of the aspects related to “energetic flexibility”. This key feature that plays an important role in plant acclimation to stress can be an important target for engineering enhanced stress tolerance in crop plants.     

Association between contrasting methane emissions of two rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) cultivars from the irrigated agroecosystem of northeast India and their growth and photosynthetic characteristics

Over two consecutive years in the North Bank Plain Zone of Assam, India, during the spring growing season (February–June) of- 2006 and 2007 we examined effects of morpho-physiological characteristics of rice (Oryza sativa L.) plants in relation to methane (CH₄) emission from paddy fields. Traditional cultivar “Agni” and modern improved cultivar “Ranjit” were grown in light textured loamy soil under irrigation. A higher seasonal integrated methane flux (E _sif) was recorded from “Agni” compared to “Ranjit”. Both cultivars exhibited an emission peak during active vegetative growth and a second peak at panicle initiation. Leaf and tiller number, leaf area, length, and volume of root were greater in “Agni”, but grain yield and yield-related parameters such as increased photosynthate partitioning to panicles at the expense of roots were greater in “Ranjit”. “Ranjit” also photosynthesed faster than “Agni” during panicle development but slower than “Agni” at tillering. In both the years, a higher soil organic carbon content was recorded in plots of “Agni”. Our results suggest that in “Agni” enhanced diversion of photosynthate to roots resulted in more substrate being available to methanogenic bacteria in the rhizosphere. Additionally, the more extensive vegetative growth of this cultivar may enhance methane transport from the soil to the above-ground atmosphere.     

The evolution of “egalitarian” and “despotic” social systems among macaques

Recent studies of captive macaques have revealed considerable inter-species differences in dominance styles among females. In “egalitarian” species such as stumptail (Macaca arctoides) or tonkean macaques (M. tonkeana), social interactions are more symmetrical and less kin-biased than in “despotic” species such as Japanese (M. fuscata) or rhesus macaques (M. mulatta). Field observations of moor macaques (M. maurus), close relatives of tonkean macaques, suggest that tolerance during feeding characterizes their egalitarian dominance style in the natural habitat. Although it has been proposed that communal defense against other groups may be the main selective force in the evolution of egalitarian dominance style among females, few field data support this prediction. A game theory analysis showed that both an “egalitarian” strategy and a “despotic” strategy are possible evolutionarily stable strategies (ESS) under certain conditions. The difference in dominance styles might reflect the difference in ESS. This means that an egalitarian dominance style can emerge without strong between-group contest competition. A phylogenetic comparison among macaques suggests that despotic dominance styles very likely evolved from egalitarian dominance styles. In the future, primate socioecological studies should pay more attention to the evolutionary history of each species.     

A “Nonsterile” Method for Selecting and Growing <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> Transformants (T<Subscript>2</Subscript> Transgenic Lines) Resistant to Kanamycin

A breakthrough in transgenic Arabidopsis thaliana research was the development of the floral dip transformation protocol, a simple and reliable method of obtaining transformants, T₁ transgenic lines, at high efficiency while avoiding the use of tissue culture. However, the traditional protocol (a “sterile” method) of obtaining T₂ transgenic lines has not evolved along with improvements in transformation technology as it continues to be laborious and time-consuming. In this study, we report on the development of an improved protocol (a “nonsterile” method) for selecting and growing A. thaliana transformants (T₂ transgenic lines) resistant to kanamycin under nonsterile conditions. This protocol involves the use of a simple yet specialized device that will aid in solium selection of T₂ transgenic lines that can be rapidly grown in a hydroponic system. The “nonsterile” method reduces labor and time involved as compared to the “sterile” method; moreover, it is easy to set up and maintain. This method may also be applicable to other selecting agents, and perhaps to other plants.     

A mathematical model of decision-making neural circuits controlling behavioral model selection

Mathematical models of mutually interacting reverberatory neural circuits exhibit decision-making properties that can account for behavioral mode selection in terms of identifiable neural subsystems and measurable variables, without the need for invoking concepts such as “drive,” “motivation,” or “instinct”. The models can account for an animal's ability to persist in a given behavioral mode under appropriate stimulus conditions and to rapidly switch modes in response to significant stimulus changes via the properties of stable steady states, thresholds for steady-state transitions, and the lack of intrinsic oscillations.     

Interaction of cycles

We discuss under the McCulloch and Pitts assumptions for neural nets a circuit consisting ofk cycles such that one cycle is activated by an outside stimulus and sends an impulse to a second cycle which in its turn sends an impulse to the next cycle, etc., up to thekth cycle, which sends an impulse to a response. We thus have a “series” ofk cycles “interacting”. We give several theorems regarding the response patterns of such circuits under the additional constraint that the stimulus acts but once, and at the time it acts the circuit is at rest.     

Insect octopamine receptors: a new classification scheme based on studies of cloned Drosophila G-protein coupled receptors

Summary Insect octopamine receptors are G-protein coupled receptors. They can be coupled to second messenger pathways to mediate either increases or decreases in intracellular cyclic AMP levels or the generation of intracellular calcium signals. Insect octopamine receptors were originally classified on the basis of second messenger changes induced in a variety of intact tissue preparations. Such a classification system is problematic if more than one receptor subtype is present in the same tissue preparation. Recent progress on the cloning and characterization in heterologous cell systems of octopamine receptors from Drosophila and other insects is reviewed. A new classification system for insect octopamine receptors into “α-adrenergic-like octopamine receptors (OctαRs)”, “β-adrenergic-like octopamine receptors (OctβRs)” and “octopamine/tyramine (or tyraminergic) receptors” is proposed based on their similarities in structure and in signalling properties with vertebrate adrenergic receptors. In future studies on the molecular basis of octopamine signalling in individual tissues it will be essential to identify the relative expression levels of the different classes of octopamine receptor present. In addition, it will be essential to identify if co-expression of such receptors in the same cells results in the formation of oligomeric receptors with specific emergent pharmacological and signalling properties.     

Salt tolerance in Lycopersicon species VI. Genotype-by-salinity interaction in quantitative trait loci detection: constitutive and response QTLs

 A study of genotype-by-salinity interaction was carried out to compare the behavior of quantitative trait loci (QTLs) in two F₂ populations derived from crosses between the cherry tomato, Lycopersicon esculentum Mill. var. cerasiforme, and two wild relatives Lycopersicon pimpinellifolium (Jusl.) Mill. and Lycopersicon chesmannii f. minor (Hook. f.) Mull., grown at two environmental conditions (optimum and high salinity). QTLs for earliness and fruit yield could be classified into four groups: “response-sensitive”, those detected only under control conditions or whose contribution significantly decreased in salinity; “response-tolerant”, detected only in salinity or in which the direction of their additive effects changed; “constitutive”, detected in both growing conditions; and “altered” QTLs, those where the degree of dominance changed according to the presence or absence of salt. Epistatic interactions were also influenced by the salt treatment. This differential allele effect at some (non-constitutive) QTLs induced by salt stress will make selection under an “optimum environment” unfruitful for the “response-tolerant” QTLs. Similarly, selection under salinity will ignore “response-sensitive” QTLs. Given that salinity is highly variable in the field, marker-assisted selection should take into account not only the “response-tolerant” but also the “response-sensitive” QTLs although there might be cases where selection in some QTLs for both conditions is not feasible. Comparing both populations, very few QTLs showed the same behavior. Received: 5 August 1996 / Accepted: 25 October 1996     

Biotechnology of flavours—the next generation

Volatile organic chemicals (flavours, aromas) are the sensory principles of many consumer products and govern their acceptance and market success. Flavours from microorganisms compete with the traditional agricultural sources. Screening for overproducers, elucidation of metabolic pathways and precursors and application of conventional bioengineering has resulted in a set of more than 100 commercial aroma chemicals derived via biotechnology. Various routes may lead to volatile metabolites: De novo synthesis from elementary biochemical units, degradation of larger substrates such as lipids, and functionalization of immediate flavour precursor molecules. More recently, the field was stimulated by the increasing preference of alienated consumers for products bearing the label “natural”, and by the vivid discussion on healthy and “functional” food ingredients. The unmistakable call for sustainable sources and environmentally friendly production is forcing the industry to move towards a greener chemistry. Progress is expected from the toolbox of genetic engineering which is expected to help in identifying metabolic bottlenecks and in creating novel high-yielding strains. Bioengineering, in a complementary way, provides promising technical options, such as improved substrate dosage, gas-phase or two-phase reactions and in situ product recovery.     

<Emphasis Type="Italic">In vitro</Emphasis>–<Emphasis Type="Italic">ex vitro</Emphasis> salt (NaCl) tolerance of cassava (<Emphasis Type="Italic">Manihot esculenta</Emphasis> Crantz) plants

Three cassava clones (SOM-1, “05”, and “50”) were cultured in vitro on MS medium plus sucrose (30 g L⁻¹) and myo-inositol (100 mg L⁻¹) without plant growth regulators and with additions of 0 (control), 0.5, 1, 1.5, 2, 2.5, and 3 g L⁻¹ NaCl to test their salt tolerance. The same cassava clones were cultivated in greenhouse conditions on a sandy soil substratum and irrigated with 20% strength Hoagland solution, and additions of 0, 4, and 8 g L⁻¹ of NaCl. Salinity negatively affected the survival, development, leaf water content, and mineral composition (mainly by accumulation of Cl and Na) of both in vitro and ex vitro plants, but with different intensity in each clone. In both conditions of culture (in vitro and ex vitro) clone SOM-1, from a desert arid saline zone of Somalia, was the most tolerant and clone “05”, from a rainy region of Ivory Coast, the most sensitive. Clone “50” tolerance to in vitro salt treatments, although lower, was not significantly different from that of SOM-1 but the ex vitro response was similar to “05”. In general, there was a correlation between in vitro and ex vitro behavior of the cassava plant regarding salt tolerance, which would allow the in vitro culture method to be used for selection of salt-tolerant plants of this crop.     

Salt tolerance in Lycopersicon spp. VII. Pleiotropic action of genes controlling earliness on fruit yield

 The change from vegetative to reproductive development (earliness) in Lycopersicon chesmannii line L2 was delayed for 20 weeks when compared to other Lycopersicon species under greenhouse conditions. The interspecific hybrid of L. chesmannii L2 and L. esculentum E9, a cherry tomato cultivar, also showed this delay in reproductive development. The distribution of this character in the F₂-derived population showed a bimodal shape, plants could be scored easily as “early” or “late” in two nutrient conditions (optimum and high salinity). A QTL with major effects on earliness was detected in salinity, which explained 35.6% of the phenotypic variation. The effect of this QTL greatly diminished under control conditions, indicating differences in the genetic control of earliness between treatments. ACC synthase or phytochrome B2 are the products of candidate genes for such a major QTL. Other QTLs with minor effects, and epistatic interactions, are also involved in earliness under both conditions. A “late” F₂ subpopulation yielded twice as much as an “early” F₂; conversely, “early” plants were taller than “late” plants, regardless of the treatment. QTL analysis, carried out in both subpopulations, showed that yield differences may be explained by chesmannii alleles showing negative additive effects at some QTLs only in the “early” subpopulation. The effect of population subdivision on QTL analysis was investigated by computer simulations to show sample-size or random effects; thus, important pleiotropic or regulatory effects of genes controlling earliness on yield that affect QTL analysis, have been reveiled. Therefore alleles controlling earliness in L. chesmannii have to be taken into account for a more efficient utilization of the genetic resources of this species. Received: 30 June 1998 / Accepted: 31 August 1998     

Orchestrated downregulation of genes involved in oxidative metabolic pathways in obese vs. lean high-fat young male consumers

There are major variations in the susceptibility to weight gain among individuals under similar external influences (decreased physical activity and excessive calorie intake), depending on the genetic background. In the present study, we performed a microarray analysis and real-time PCR validations in order to find out differential gene expression in subcutaneous abdominal adipose tissue from two groups of subjects that despite living in similar environmental conditions such as a habitual high-fat dietary intake (energy as fat >40%) and similar moderate physical activity, some of them were successfully “resistant” (lean) to weight gain, while others were “susceptible” to fat deposition (obese). The classification of up- and downregulated genes into different categories, together with the analysis of the altered biochemical pathways, revealed a coordinated downregulation of catabolic pathways operating in the mitochondria: fatty acid β oxidation (P = 0.008), tricarboxylic acid cycle (P = 0.001), and electron transport chain (P = 0.012). At the same time, glucose metabolism (P = 0.010) and fatty acid biosynthesis (P = 0.011) pathways were also downregulated in obese compared to lean subjects. In conclusion, our data showed an orchestrated downregulation of nuclear-encoded mitochondrial gene expression. These genes are involved in cellular respiration and oxidative metabolic pathways and could play a role in the susceptibility to weight gain in some individuals.     

Maternal effects on offspring growth and development depend on environmental quality in the frogBombina orientalis

Summary Differences in maternal investment and initial offspring size can have important consequences for offspring growth and development. To examine the effects of initial size variability in the frogBombina orientalis, we reared larvae (N=360) in one of two treatments representing different levels of environmental quality. We used snout-vent length at the feeding stage (stage 25, Gosner 1960) as a measure of maternal investment. In a “low quality” treatment, larvae were reared with two conspecific tadpoles and food was limited, whereas in a “high quality” treatment, larvae were reared individually and were fed ad libitum. Among tadpoles reared in the low quality treatment, individuals that were initially small had smaller body sizes through metamorphosis and longer larval periods than individuals that were initially large. Among tadpoles reared in the high quality treatment, initial size had only a weak influence on later larval size, and did not significantly affect metamorphic size of the duration of the larval period. This interaction between maternal investment and rearing conditions suggests that production of initially small offspring could be advantageous if these offspring develop in relatively benign environments, but disadvantageous if environments are more severe. These findings are discussed in light of previous studies that have demonstrated such interactions in organisms with complex life cycles.     

Expression of phytoene synthase gene (Psy) is enhanced during fruit ripening of Cara Cara navel orange (Citrus sinensis Osbeck)

Citrus is an important fruit crop as regards accumulation of carotenoids. In plant carotenoid biosynthesis, phytoene synthase gene (Psy) plays a key role in catalyzing the head-to-head condensation of geranylgeranyl diphosphate molecules to produce colorless phytoene. In the present paper, we reported the phytoene contents determination and characterization of Psy during fruit ripening of “Washington” navel orange and its red-fleshed mutant “Cara Cara”. Results showed that phytoene was exclusively accumulated in peel and pulp of “Cara Cara”. Although phytoene was observed accumulating with fruit ripening of “Cara Cara”, the contents in pulp were 10 times higher than those in peel. The isolated two Psy cDNAs were both 1520 bp in full length, containing 436 deduced amino acid residues, with a different amino acid at 412th. Genomic hybridization results showed that one or two copies might be present in “Cara Cara” and “Washington” genomes. During “Cara Cara” and “Washington” fruit coloration, expression of Psy was observed to be up-regulated, as revealed by tissue specific profiles in the flavedo, albedo, segment membrane and juice sacs. However, Psy expression in albedo of “Cara Cara” was higher than that in “Washington”, as evidenced by phytoene accumulation in the peel.     

Mobilization of a Hobo-related Sequence in the Genome of Drosophila simulans

The hobo transposable element can occur under three forms in the Drosophila genome: as a complete element (also called canonical), as internally deleted copies, or as hobo-related sequences (relics). Some evidence indicated that canonical elements and internally deleted copies are recent acquisitions of Drosophila genomes, while the “relics” are old components, normally degenerated and immobile. Here we present the characterization of a hobo-related sequence, found in the genome of a hypermutable strain of D. simulans, which insertion into the white locus raised a de novo white mutation. It is a shorter hobo related element presenting, overall, roughly 18% of divergence at the DNA level from the canonical hobo, with many indels that make clear this element is defective. However, its ITRs and flanking regions are extremely conserved. This is the first hobo “relic” showed to be mobilizable. We suggest, and point up some evidences, toward the idea that this sequence could have been mobilized by the canonical element. The presence of a similar “relic” element in D. sechellia allows us to suggest that these elements have been maintained mobilizable since the time of divergence between these species.     

Estimation of relative contribution of “mobile phycobilisome” and “energy spillover” in the light–dark induced state transition in Spirulina platensis

Previously, it was clarified that phycobilisome (PBS) mobility and energy spillover were both involved in light-to-dark induced state transitions of intact Spirulina platensis cells. In this work, by taking advantage of the characteristic fluorescence spectra of photosystem I (PSI) trimers and monomers as indicators, the relative contributions for the “mobile PBS” and “energy spillover” are quantitatively estimated by separating the fluorescence contribution of PBS mobility from that of PSI oligomeric change. Above the phase transition temperature (T _PT) of the membrane lipids, the relative proportion of the contributions is invariable with 65% of “mobile PBS” and 35% of “energy spillover”. Below T _PT, the proportion for the “mobile PBS” becomes larger under lowering temperature even reaching 95% with 5% “energy spillover” at 0°C. It is known that lower temperature leads to a further light state due to a more reduced or oxidized PQ pool. Based on the current result, it can be deduced that disequilibrium of the redox state of the PQ pool will trigger PBS movement instead of change in the PSI oligomeric state.     

Biocatalytic ketone reduction—a powerful tool for the production of chiral alcohols—part II: whole-cell reductions

The tricarboxylic acid (TCA) cycle is an energy-producing pathway for aerobic organisms. However, it is widely accepted that the phylogenetic origin of the TCA cycle is the reductive TCA cycle, which is a non-Calvin-type carbon-dioxide-fixing pathway. Most of the enzymes responsible for the oxidative and reductive TCA cycles are common to the two pathways, the difference being the direction in which the reactions operate. Because the reductive TCA cycle operates in an energetically unfavorable direction, some specific mechanisms are required for the reductive TCA-cycle-utilizing organisms. Recently, the molecular mechanism for the “citrate cleavage reaction” and the “reductive carboxylating reaction from 2-oxoglutarate to isocitrate” in Hydrogenobacter thermophilus have been demonstrated. Both of these reactions comprise two distinct consecutive reactions, each catalyzed by two novel enzymes. Sequence analyses of the newly discovered enzymes revealed phylogenetic and functional relationships between other TCA-cycle-related enzymes. The occurrence of novel enzymes involved in the citrate-cleaving reaction seems to be limited to the family Aquificaceae. In contrast, the key enzyme in the reductive carboxylation of 2-oxoglutarate appears to be more widely distributed in extant organisms. The four newly discovered enzymes have a number of potential biotechnological applications.     

Foliage consumption and larval development of parasitized and unparasitized soybean looper,Pseudoplusia includens [Lep.: Noctuidae], reared on a resistant soybean genotype and effects on an associated parasitoid,Compidosoma truncatellum [Hym.: Encyrtidae]

Field grown foliage from the resistant soybean [Glycine max (L.) Merrill] breeding line GAT “81–327” and the susceptible cultivar “Ransom” was used to rear unparasitized larvae of the soybean looper (SBL),Pseudoplusia includens (Walker), and larvae parasitized byCopidosoma truncatellum (Dalman). SBL larvae, whether parasitized or not, consumed more foliage when fed “Ransom”. Unparasitized larvae reared on “81–327” had longer developmental times and suffered greater mortality than unparasitized larvae reared on “Ransom”. Parasitization of SBL larvae byC. truncatellum increased total foliage consumption of both soybean lines. Parasitized larvae reared on the resistant “81–327” weighed less and yielded fewer parasitoid adults.

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Résumé Des larves dePseudoplusia includens (Walker) parasitées ou non parCopidosoma truncatellum (Dalman) ont été nourries des feuilles de deux lignées de soja [Glycine max (L.) Merrill] l'une, GAT “81–327” résistante et l'autre, “Ransom” sensible. Les larves deP. includens qu'elles soient parasitées ou non consommaient plus de feuillage lorsqu'elles étaient nourries de la lignée “Ransom”. Les larves non parasitées élevées sur “81–327” avaient un cycle de développement beaucoup plus long et un taux de mortalité beaucoup plus élevé que les larves non parasitées élevées comparativement sur feuilles de “Ransom”. Par contre, les larves parasitées manifestaient une consommation accrue du feuillage des deux lignées de soja. Les larves parasitées élevées sur les feuilles de la variété résistante GAT “81–327” pesaient moins et produisaient moins également de parasites adultes.

     

Decline in energy storage in the Antarctic minke whale (<Emphasis Type="Italic">Balaenoptera bonaerensis</Emphasis>) in the Southern Ocean

The annual trend in energy storage in the Antarctic minke whale was examined using catch data from all 18 survey years in the Japanese Whale Research Program (JARPA). Regression analyses clearly showed that blubber thickness, girth and fat weight have been decreasing for nearly 2 decades. The decrease per year is estimated at approximately 0.02 cm for mid-lateral blubber thickness and 17 kg for fat weight, corresponding to 9% for both measurements over the 18-year period. Furthermore, “date”, “extent of diatom adhesion”, “sex”, “body length”, “fetus length”, “latitude”, “age” and “longitude” were all identified as partially independent predictors of blubber thickness. The direct interpretation of this substantial decline in energy storage in terms of food availability is difficult, since no long-term krill abundance series is available. However, an increase in the abundance of krill feeders other than minke whales and a resulting decrease in the krill population must be considered as a likely explanation.