A molecular and structural characterization of senescing Arabidopsis siliques and comparison of transcriptional profiles with senescing petals and leaves

Senescence of plant organs is a genetically controlled process that regulates cell death to facilitate nutrient recovery and recycling, and frequently precedes, or is concomitant with, ripening of reproductive structures. In Arabidopsis thaliana, the seeds are contained within a silique, which is itself a photosynthetic organ in the early stages of development and undergoes a programme of senescence prior to dehiscence. A transcriptional analysis of the silique wall was undertaken to identify changes in gene expression during senescence and to correlate these events with ultrastructural changes. The study revealed that the most highly up-regulated genes in senescing silique wall tissues encoded seed storage proteins, and the significance of this finding is discussed. Global transcription profiles of senescing siliques were compared with those from senescing Arabidopsis leaf or petal tissues using microarray datasets and metabolic pathway analysis software (MapMan). In all three tissues, members of NAC and WRKY transcription factor families were up-regulated, but components of the shikimate and cell-wall biosynthetic pathways were down-regulated during senescence. Expression of genes encoding ethylene biosynthesis and action showed more similarity between senescing siliques and petals than between senescing siliques and leaves. Genes involved in autophagy were highly expressed in the late stages of death of all plant tissues studied, but not always during the preceding remobilization phase of senescence. Analyses showed that, during senescence, silique wall tissues exhibited more transcriptional features in common with petals than with leaves. The shared and distinct regulatory events associated with senescence in the three organs are evaluated and discussed.

Excess open solar magnetic flux from satellite data: 1. Analysis of the third perihelion Ulysses pass

We use the third perihelion pass by the Ulysses spacecraft to illustrate and investigate the “flux excess” effect, whereby open solar flux estimates from spacecraft increase with increasing heliocentric distance. We analyze the potential effects of small-scale structure in the heliospheric field (giving fluctuations in the radial component on timescales smaller than 1 h) and kinematic time-of-flight effects of longitudinal structure in the solar wind flow. We show that the flux excess is explained by neither very small-scale structure (timescales < 1 h) nor by the kinematic “bunching effect” on spacecraft sampling. The observed flux excesses is, however, well explained by the kinematic effect of larger-scale (>1 day) solar wind speed variations on the frozen-in heliospheric field. We show that averaging over an interval T (that is long enough to eliminate structure originating in the heliosphere yet small enough to avoid cancelling opposite polarity radial field that originates from genuine sector structure in the coronal source field) is only an approximately valid way of allowing for these effects and does not adequately explain or account for differences between the streamer belt and the polar coronal holes.

Time series analysis of lava flux

We have applied time series analytical techniques to the flux of lava from an extrusive eruption. Tilt data acting as a proxy for flux are used in a case study of the May–August 1997 period of the eruption at Soufrière Hills Volcano, Montserrat. We justify the use of such a proxy by simple calibratory arguments. Three techniques of time series analysis are employed: spectral, spectrogram and wavelet methods. In addition to the well-known ~9-hour periodicity shown by these data, a previously unknown periodic flux variability is revealed by the wavelet analysis as a 3-day cycle of frequency modulation during June–July 1997, though the physical mechanism responsible is not clear. Such time series analysis has potential for other lava flux proxies at other types of volcanoes.

Analysis of time-related metabolic fluctuations induced by ethionine in the rat

The time-course of metabolic events following response to a model hepatotoxin ethionine (800 mg/kg) was investigated over a 7 day period in rats using high-resolution (1)H NMR spectroscopic analysis of urine and multivariate statistics. Complementary information was obtained by multivariate analysis of (1)H MAS NMR spectra of intact liver and by conventional histopathology and clinical chemistry of blood plasma. (1)H MAS NMR spectra of liver showed toxin-induced lipidosis 24 h postdose consistent with the steatosis observed by histopathology, while hypertaurinuria was suggestive of liver injury. Early biochemical changes in urine included elevation of guanidinoacetate, suggesting impaired methylation reactions. Urinary increases in 5-oxoproline and glycine suggested disruption of the gamma-glutamyl cycle. Signs of ATP depletion together with impairment of the energy metabolism were given from the decreased levels in tricarboxylic acid cycle intermediates, the appearance of ketone bodies in urine, the depletion of hepatic glucose and glycogen, and also hypoglycemia. The observed increase in nicotinuric acid in urine could be an indication of an increase in NAD catabolism, a possible consequence of ATP depletion. Effects on the gut microbiota were suggested by the observed urinary reductions in the microbial metabolites 3-/4-hydroxyphenyl propionic acid, dimethylamine, and tryptamine. At later stages of toxicity, there was evidence of kidney damage, as indicated by the tubular damage observed by histopathology, supported by increased urinary excretion of lactic acid, amino acids, and glucose. These studies have given new insights into mechanisms of ethionine-induced toxicity and show the value of multisystem level data integration in the understanding of experimental models of toxicity or disease.

Integrated cytokine and metabolic analysis of pathological responses to parasite exposure in rodents

Parasitic infections cause a myriad of responses in their mammalian hosts, on immune as well as on metabolic level. A multiplex panel of cytokines and metabolites derived from four parasite-rodent models, namely, Plasmodium berghei-mouse, Trypanosoma brucei brucei-mouse, Schistosoma mansoni-mouse, and Fasciola hepatica-rat were statistically coanalyzed. 1H NMR spectroscopy and multivariate statistical analysis were used to characterize the urine and plasma metabolite profiles in infected and noninfected animals. Each parasite generated a unique metabolic signature in the host. Plasma cytokine concentrations were obtained using the ‘Meso Scale Discovery’ multi cytokine assay platform. Multivariate data integration methods were subsequently used to elucidate the component of the metabolic signature which is associated with inflammation and to determine specific metabolic correlates with parasite-induced changes in plasma cytokine levels. For example, the relative levels of acetyl glycoproteins extracted from the plasma metabolite profile in the P. berghei-infected mice were statistically correlated with IFN-γ, whereas the same cytokine was anticorrelated with glucose levels. Both the metabolic and the cytokine data showed a similar spatial distribution in principal component analysis scores plots constructed for the combined murine data, with samples from all infected animals clustering according to the parasite species and whereby the protozoan infections (P. berghei and T. b. brucei) grouped separately from the helminth infection (S. mansoni). For S. mansoni, the main infection-responsive cytokines were IL-4 and IL-5, which covaried with lactate, choline, and D-3-hydroxybutyrate. This study demonstrates that the inherently differential immune response to single and multicellular parasites not only manifests in the cytokine expression, but also consequently imprints on the metabolic signature, and calls for in-depth analysis to further explore direct links between immune features and biochemical pathways.

Sensitivity analysis of an ocean carbon cycle model in the North Atlantic: an investigation of parameters affecting the air-sea CO2 flux, primary production and export of detritus

The sensitivity of the biological parameters in a nutrient-phytoplankton-zooplankton-detritus (NPZD) model in the calculation of the air-sea CO2 flux, primary production and detrital export is analysed. We explore the effect on these outputs of variation in the values of the twenty parameters that control ocean ecosystem growth in a 1-D formulation of the UK Met Office HadOCC NPZD model used in GCMs. We use and compare the results from one-at-a-time and all-at-a-time perturbations performed at three sites in the EuroSITES European Ocean Observatory Network: the Central Irminger Sea (60° N 40° W), the Porcupine Abyssal Plain (49° N 16° W) and the European Station for Time series in the Ocean Canary Islands (29° N 15° W). Reasonable changes to the values of key parameters are shown to have a large effect on the calculation of the air-sea CO2 flux, primary production, and export of biological detritus to the deep ocean. Changes in the values of key parameters have a greater effect in more productive regions than in less productive areas. The most sensitive parameters are generally found to be those controlling well-established ocean ecosystem parameterisations widely used in many NPZD-type models. The air-sea CO2 flux is most influenced by variation in the parameters that control phytoplankton growth, detrital sinking and carbonate production by phytoplankton (the rain ratio). Primary production is most sensitive to the parameters that define the shape of the photosynthesis-irradiance curve. Export production is most sensitive to the parameters that control the rate of detrital sinking and the remineralisation of detritus.

Moving towards a more mechanistic approach in the determination of soil heat flux from remote measurements - II. Diurnal shape of soil heat flux

For vegetated surfaces, calculation of soil heat flux, G, with the Exact or Analytical method requires a harmonic analysis of below-canopy soil surface temperature, to obtain the shape of the diurnal course of G. When determining G with remote sensing methods, only composite (vegetation plus soil) radiometric brightness temperature is available. This paper presents a simple equation that relates the sum of the harmonic terms derived for the composite radiometric surface temperature to that of belowcanopy soil surface temperature. The thermal inertia, Gamma(,) for which a simple equation has been presented in a companion paper, paper I, is used to set the magnitude of G. To assess the success of the method proposed in this paper for the estimation of the diurnal shape of G, a comparison was made between 'remote' and in situ calculated values from described field sites. This indicated that the proposed method was suitable for the estimation of the shape of G for a variety of vegetation types and densities. The approach outlined in paper I, to obtain Gamma, was then combined with the estimated harmonic terms to predict estimates of G, which were compared to values predicted by empirical remote methods found in the literature. This indicated that the method proposed in the combination of papers I and II gave reliable estimates of G, which, in comparison to the other methods, resulted in more realistic predictions for vegetated surfaces. This set of equations can also be used for bare and sparsely vegetated soils, making it a universally applicable method. (C) 2007 Elsevier B.V. All rights reserved.

Remote estimation of thermal inertia and soil heat flux for bare soil

A method is presented which allows thermal inertia (the soil heat capacity times the square root of the soil thermal diffusivity, C(h)rootD(h)), to be estimated remotely from micrometeorological observations. The method uses the drop in surface temperature, T-s, between sunset and sunrise, and the average night-time net radiation during that period, for clear, still nights. A Fourier series analysis was applied to analyse the time series of T-s . The Fourier series constants, together with the remote estimate of thermal inertia, were used in an analytical expression to calculate diurnal estimates of the soil heat flux, G. These remote estimates of C(h)rootD(h) and G compared well with values derived from in situ sensors. The remote and in situ estimates of C(h)rootD(h) both correlated well with topsoil moisture content. This method potentially allows area-average estimates of thermal inertia and soil heat flux to be derived from remote sensing, e.g. METEOSAT Second Generation, where the area is determined by the sensor's height and viewing angle. (C) 2003 Elsevier B.V. All rights reserved.

Understanding electron heat flux signatures in the solar wind

Suprathermal electrons (E > 80 eV) carry heat flux away from the Sun. Processes controlling the heat flux are not well understood. To gain insight into these processes, we model heat flux as a linear dependence on two independent parameters: electron number flux and electron pitch angle anisotropy. Pitch angle anisotropy is further modeled as a linear dependence on two solar wind components: magnetic field strength and plasma density. These components show no correlation with number flux, reinforcing its independence from pitch angle anisotropy. Multiple linear regression applied to 2 years of Wind data shows good correspondence between modeled and observed heat flux and anisotropy. The results suggest that the interplay of solar wind parameters and electron number flux results in distinctive heat flux dropouts at heliospheric features like plasma sheets but that these parameters continuously modify heat flux. This is inconsistent with magnetic disconnection as the primary cause of heat flux dropouts. Analysis of fast and slow solar wind regimes separately shows that electron number flux and pitch angle anisotropy are equally correlated with heat flux in slow wind but that number flux is the dominant correlative in fast wind. Also, magnetic field strength correlates better with pitch angle anisotropy in slow wind than in fast wind. The energy dependence of the model fits suggests different scattering processes in fast and slow wind.

A multispacecraft analysis of a small-scale transient entrained by solar wind streams

The images taken by the Heliospheric Imagers (HIs), part of the SECCHI imaging package onboard the pair of STEREO spacecraft, provide information on the radial and latitudinal evolution of the plasma compressed inside corotating interaction regions (CIRs). A plasma density wave imaged by the HI instrument onboard STEREO-B was found to propagate towards STEREO-A, enabling a comparison between simultaneous remotesensing and in situ observations of its structure to be performed. In situ measurements made by STEREO-A show that the plasma density wave is associated with the passage of a CIR. The magnetic field compressed after the CIR stream interface (SI) is found to have a planar distribution. Minimum variance analysis of the magnetic field vectors shows that the SI is inclined at 54° to the orbital plane of the STEREO-A spacecraft. This inclination of the CIR SI is comparable to the inclination of the associated plasma density wave observed by HI. A small-scale magnetic cloud with a flux rope topology and radial extent of 0.08 AU is also embedded prior to the SI. The pitch-angle distribution of suprathermal electrons measured by the STEREO-A SWEA instrument shows that an open magnetic field topology in the cloud replaced the heliospheric current sheet locally. These observations confirm that HI observes CIRs in difference images when a small-scale transient is caught up in the compression region.

Factors controlling the distribution of ozone in the West African lower troposphere during the AMMA (African Monsoon Multidisciplinary Analysis) wet season campaign

Ozone and its precursors were measured on board the Facility for Airborne Atmospheric Measurements (FAAM) BAe 146 Atmospheric Research Aircraft during the monsoon season 2006 as part of the African Monsoon Multidisciplinary Analysis (AMMA) campaign. One of the main features observed in the west African boundary layer is the increase of the ozone mixing ratios from 25 ppbv over the forested area (south of 12° N) up to 40 ppbv over the Sahelian area. We employ a two-dimensional (latitudinal versus vertical) meteorological model coupled with an O3-NOx-VOC chemistry scheme to simulate the distribution of trace gases over West Africa during the monsoon season and to analyse the processes involved in the establishment of such a gradient. Including an additional source of NO over the Sahelian region to account for NO emitted by soils we simulate a mean NOx concentration of 0.7 ppbv at 16° N versus 0.3 ppbv over the vegetated region further south in reasonable agreement with the observations. As a consequence, ozone is photochemically produced with a rate of 0.25 ppbv h−1 over the vegetated region whilst it reaches up to 0.75 ppbv h−1 at 16° N. We find that the modelled gradient is due to a combination of enhanced deposition to vegetation, which decreases the ozone levels by up to 11 pbbv, and the aforementioned enhanced photochemical production north of 12° N. The peroxy radicals required for this enhanced production in the north come from the oxidation of background CO and CH4 as well as from VOCs. Sensitivity studies reveal that both the background CH4 and partially oxidised VOCs, produced from the oxidation of isoprene emitted from the vegetation in the south, contribute around 5–6 ppbv to the ozone gradient. These results suggest that the northward transport of trace gases by the monsoon flux, especially during nighttime, can have a significant, though secondary, role in determining the ozone gradient in the boundary layer. Convection, anthropogenic emissions and NO produced from lightning do not contribute to the establishment of the discussed ozone gradient.

Effects of host plant drought stress on the performance of the bird cherry-oat aphid, Rhopalosiphum padi (L.): a mechanistic analysis

1. The growth (increase in height and leaf number) of four grass species was reduced by a -0.5 MPa drought stress, but the performance of an associated herbivore, Rhopalosiphum padi (L.), was not affected consistently. The intrinsic rate of increase of R. padi was reduced by drought stress on three grass species, including Dactylis glomerata (L.), but was unaffected on Arrhenatherum elatius (L.). Therefore, there is no general relationship in the effect of plant drought on an insect herbivore, even among closely related host plant species. 2. Drought stress increased the quality of plant phloem sap, as indicated by increased sieve element osmotic pressure and essential amino acid concentrations. Thus, diet quality could not account for the reduced performance of R. padi under drought stress. The concentration of essential amino acids in the phloem of well-watered A. elatius was, however, lower than that of well-watered D. glomerata, correlating with the decreased performance of aphids on well-watered A. elatius. 3. There were no differences in aphid feeding duration between watering treatments or plant species but sap ingestion rates were reduced significantly under drought stress. 4. Using the measure of dietary amino acid concentrations and the estimate of sap ingestion, the essential amino acid flux through aphids was calculated. Compared with the flux through aphids feeding on well-watered D. glomerata, there was a reduction in aphids feeding on drought-stressed D. glomerata and drought-stressed A. elatius due to lower sap ingestion rates. The flux through aphids on well-watered A. elatius was also reduced due to low phloem essential amino acid concentrations. Thus, the performance of an aphid is correlated with the availability and accessibility of essential amino acids.

Relationships between transition period diet, metabolic parameters and fertility in lactating dairy cows

Cows in severe negative energy balance after calving have reduced fertility, mediated by metabolic signals influencing the reproductive system. We hypothesised that transition diet could alter metabolic status after calving, and thus influence fertility. Multiparous dairy cows were assigned to four transition groups 6 weeks pre-calving and fed: (a) basal control diet (n = 10); (b) basal diet plus barley (STARCH, n = 10); (c) basal diet plus Soypass (high protein, HiPROT, n = 11); or (d) no transition management (NoTRANS, n = 9). All cows received the same lactational diet. Blood samples, body weights and condition scores (BCS) were collected weekly. Fertility parameters were monitored using milk progesterone profiles and were not affected by transition diet. Data from all cows were then combined and analysed according to the pattern of post-partum ovarian activity. Cows with low progesterone profiles had significantly lower insulin-like growth factor-I (IGF-I) and insulin concentrations accompanied by reduced dry matter intakes (DMIs), BCS and body weight. Cows with prolonged luteal activity (PLA) were older and tended to have lower IGF-I. Analysis based on the calving to conception interval revealed that cows which failed to conceive (9/40) also had reduced IGF-I, BCS and body weight. Fertility was, therefore, decreased in cows which were in poor metabolic status following calving. This was reflected in reduced circulating IGF-I concentrations and compromised both ovarian activity and conception. There was little effect of the transition diets on these parameters. (C) 2003 Elsevier Science Inc. All rights reserved.

Metabolic profiles and progesterone cycles in first lactation dairy cows

This study investigated the ovarian function, metabolic profiles and fertility in first lactation Holstein-Friesian dairy cows (mean 305 day milk yield: 7417 +/- 191 kg, n = 37). Reproductive profiles obtained from milk progesterone analysis were categorized into normal (n = 17) and four abnormal profiles (delayed ovulation, DOV1, n = 9; DOV2, n = 2; persistent corpus luteum, PCL1, n = 6; PCL2, n = 4; 1: immediately post-calving, 2: subsequent cycles). Fifty-five percent of cows had abnormal profiles with half of these being categorized as DOV1. Fertility of DOV1 and DOV2 cows was reduced whereas PCL1 and PCL2 cows had similar reproductive competence to normal profile cows. DOV1 animals had higher milk energy values, lower energy balances, lower dry matter intakes (DMI) and greater body weight and body condition score (BCS) losses post-calving than normal profile animals. DOV1 animals also had lower insulin-like growth factor-I (IGF-I) and higher betahydroxybutyrate (BHB) concentrations and tended to have the lower insulin and glucose concentrations in the pre-service period than normal profile cows. All PCL animals had vulval discharges postpartum. Despite this, the DMI, body weight and BCS changes, IGF-I concentrations and fertility of PCL1 animals was similar to normal profile cows. In conclusion, the high prevalence of delayed ovulation post-calving (DOV1) in primiparous high yielding cows lasted long enough (71 +/- 8.3 days) to have a detrimental impact on fertility and was associated with significant physiological changes. This study did not establish any detrimental effects of PCL profiles on fertility or production parameters. (C) 2002 Elsevier Science Inc. All rights reserved.

First lactation ovarian function in dairy heifers in relation to prepubertal metabolic profiles

The aim of this study was to determine whether any differences in the GH-IGF-I axis in juvenile calves were predictive of fertility problems as adult cows. Endogenous metabolic hormone profiles before and after feeding and the response to a GH-releasing factor (GRF) challenge were measured in prepubertal (6 month) dairy calves. These metabolic parameters were subsequently related to physical characteristics at puberty and to ovarian function during the first lactation. Milk progesterone analysis was used to categorize the animals into those with normal progesterone profiles following calving (n = 17) and those that developed delayed ovulation (DOV1, n = 9) or persistent corpus luteum (PCL1, n = 6) profiles. There were associations between prepubertal GH parameters, glucose and non-esterified fatty acid (NEFA) concentrations and the body condition score at which the animals attained puberty. The calves which subsequently developed DOV1 profiles as cows tended to have a higher GH pulse amplitude during fasting than normal profile animals, they did not show the anticipated decrease in circulating glucose concentrations following a post-prandial rise in insulin and they also had the lowest IGF-I concentrations. The calves that later developed PCL1 had a significantly larger GH pulse amplitude and pulse area than normal profile animals in the fed period and had the highest IGF-I concentrations. There were no differences in prepubertal insulin or NEFA concentrations or in the GH response to a GRF challenge between the different progesterone profile categories. Plasma IGF-I concentrations in prepubertal animals were positively correlated with their post-calving concentrations, whereas glucose concentrations had a negative correlation between these time-periods. These results suggested that the different juvenile endocrine profiles of the DOV1 cows may predispose them to a higher rate of tissue mobilization during lactation and a consequent reduction in fertility, while altered GH and IGF-I levels in PCL1 cows may later contribute to the maintenance of the persistent corpus luteum. Therefore metabolic differences in prepubertal calves were later reflected by altered reproductive function during the first lactation.