bluuebunny/crossref_metadata_2025 huggingface dataset:
Anti‐NANP antibody and treatment efficacy in patients with acute uncomplicated falciparum malaria attacks
Authors: Robert V. , Roeffen W. , Brasseur P. , Aribot G. , Verhave J.P. , Roussilhon C.
Published: March 2003

African patients originating from the hypoendemic, urban area of Greater Dakar (Senegal, West Africa) who presented with an acute Plasmodium falciparum infection were studied using an in‐vivo chloroquine sensitivity assay for 28 days. Forty‐seven patients with acute malaria infections were treated with 25 mg/body weight of chloroquine. Adequate responses to treatment were observed in 24 patients (51%), whereas 23 (49%) were resistant. On the day of admission, these two groups of patients were comparable with respect to age, level of parasitemia and delay before initiation of treatment, but not with respect to gametocyte prevalence which was higher in patients resistant to therapy (48%) than in those who responded to treatment (17%). In order to evaluate whether the therapeutic response was associated with any given specific immune response, antibody activities against different stages of the parasite cycle were evaluated: anti‐NANP repeats (i.e. antisporozoite stage antigen), anti‐Pfs 45 kDa (i.e. antigametocyte stage antigen), and anti‐MSP3 (i.e. antimerozoite stage antigen) antibodies were measured by ELISA at day 0 (i.e. on the day of admission and before initiation of treatment), day 7 and day 28. No significant differences between treatment‐sensitive and treatment‐resistant infections were observed for antibody prevalences and optical densities, except at day 0, when the prevalence of antibodies against NANP repeats was 2.4 times more frequent in the group of patients with a propitious response to treatment: 62.5% of the patients with an infection sensitive to chloroquine had anti‐NANP antibodies, whereas only 26.1% of the patients resistant to chloroquine treatment had such a humoral response. These observations are discussed in relation to (1) the finding that gametocyte prevalence was markedly increased at a time when resistance to antimalarial treatment was observed; (2) the possibility that the efficacy of the therapeutic response could be the result of the combined effects of treatment and the individual immune status of the patients at the time of drug cure; and (3) the presence of detectable anti‐NANP activity as potential indicator of the level of premunition acquired in an area of low and seasonal malaria transmission.
Suppression of macrophage interleukin‐12 and tumour necrosis factor‐α production in mice infected with Toxocara canis
Authors: Kuroda Etsushi , Yoshida Yasuhiro , Shan Bao En , Yamashita Uki
Published: March 2003

Toxocara canis induces a predominantly Th2 type response with enhanced amounts of interleukin (IL)‐4 and reduced amounts of interferon (IFN)‐γ in infected mice. In this study, we investigated the macrophage function of T. canis‐infected mice from the standpoint of cytokine production. C3H/HeN mice were infected with T. canis by oral administration of embryonated eggs. Ten days after infection, macrophages were obtained from spleen and peritoneal cavity, were cultured with lipopolysaccharide, and cytokines in the culture supernatant were evaluated with enzyme‐linked immunosorbent assay. Macrophages from T. canis‐infected mice produced IL‐1 and IL‐6 equvalent to macrophages from normal mice. The production of IL‐10 and tumour growth factor (TGF)‐β was enhanced, but IL‐12 and tumour necrosis factor (TNF)‐α production was diminished. The addition of IFN‐γ, anti‐IL‐10 antibody, anti‐TGF‐β antibody or indomethacin did not restore the production of IL‐12 and TNF‐α by macrophages from T. canis‐infected mice. Furthermore, the stimulation of normal macrophages with T. canis antigen in vitro induced IL‐1α, IL‐6, IL‐10 and TGF‐β, but not IL‐12 and TNF‐α. These results indicate that cytokine producing pattern of macrophages is altered by T. canis‐infection, and this altered macrophage function may play an important role in the modification of the immune response to T. canis.
Immunogenicity of recombinant fragments of Plasmodium falciparum acidic basic repeat antigen produced in Escherichia coli
Authors: Kushwaha Ashima , Rao Prakash P.L. , Suresh R.padma , Chauhan V.S.
Published: March 2003

The acidic basic repeat antigen (ABRA) of Plasmodium falciparum is a potential vaccine candidate against erythrocytic stages of malaria. We report, for the first time, the immunological characteristics of recombinant ABRA constructs. The recombinant proteins representing different fragments of ABRA were expressed in Escherichia coli, either as fusions with maltose binding protein or as 6X histidine tagged molecules, and purified by affinity chromatography. Immunogenicity studies with these constructs in rabbits and mice indicated that the N‐terminal region is the least immunogenic part of ABRA. T‐cell proliferation experiments in mice immunized with these constructs revealed that the T‐cell epitopes were localized in the middle portion of the protein. More importantly, the purified immunoglobulin G specific to middle and C‐terminal fragments prevented parasite growth at levels approaching 80–90%. We found that these proteins were also recognized by sera from P. falciparum‐infected patients from Rourkela, a malaria endemic zone of India. Our immunogenicity results suggest that potential of ABRA as a vaccine candidate antigen should be investigated further.
Changes in the mouse sciatic nerve action potential after epineural injection of sera from Trypanosoma cruzi infected mice
Authors: Tekiel V. , Losavio A. , Jones M. , Muchnik S. , González‐Cappa S.M.
Published: March 2003

Pathology of chronic Chagas' disease involves peripheral nervous system (PNS) compromise. A high prevalence of antibodies reacting with nervous system antigens has been found in the sera of patients and infected animals, although their physiological role in mediating PNS tissue damage is unknown. Here, we demonstrate that epineural injection of sera from Trypanosoma cruzi infected mice affects the characteristics of the sciatic nerve action potential (SNAP) depending on the parasite strain. Sera from mice infected with the reticulotropic/neurotropic RA strain with reactivity against sciatic nerve (RA/Ne+ sera) induced delays on latency and diminished amplitudes 4 days after injection. Sera from mice infected with the myotropic CA‐I strain failed to affect SNAP. Purified immunoglobulin (Ig)G from RA/Ne+ also diminished the amplitude of SNAP. Deposits of IgG labelling axonal fibres and/or myelin sheaths were detected in nerves injected with RA/Ne+ sera. No major histological damage or parasite DNA was found in those nerves. The SNAP changes after sera injection were similar to those observed in mice injected with trypomastigotes in the epineurum 17 days before and in chronically infected animals. This investigation suggests that autoantibodies triggered as a consequence of T. cruzi infection are able to mediate, at least in part, the electrophysiological abnormalities observed in PNS during the course of Chagas' disease.
Cellular responses to Schistosoma japonicum cathepsin D aspartic protease
Authors: Verity Christiana K. , Mcmanus Donald P. , Brindley Paul J.
Published: March 2003

Lymphocyte proliferation and cytokine production were measured in groups of mice vaccinated (but not subsequently challenge infected) with recombinant forms of Schistosoma japonicum cathepsin D aspartic protease, rSjASP1 (expressed in bacteria; enzymatically inactive) and rSjASP2 (expressed in insect cells; enzymatically active). Both forms of the schistosome enzyme induced significant proliferation of splenocytes recovered from vaccinated mice, and expression of interferon (IFN)‐γ, interleukin (IL)‐4 and IL‐10 mRNA in these cells was detected using reverse transcriptase‐polymerase chain reaction. Secretion of IFN‐γ, IL‐4 and IL‐10 by splenocytes from vaccinated mice was confirmed and quantified using enzyme‐linked immunosorbent assay. IFN‐γ was the most abundant cytokine produced, followed by IL‐4 and IL‐10 in rank order. These findings indicated that vaccination of mice with the schistosome protease induces a mixed Th1/Th2 cytokine response, which may explain the modest level of protection after challenge infection in cathepsin d‐vaccinated mice, reported previously.
Increased levels of interleukin‐12 in Plasmodium falciparum malaria: correlation with the severity of disease
Authors: Malaguarnera Lucia , Imbesi Rosa Maria , Pignatelli Salvatore , Simporè Jacques , Malaguarnera Mariano , Musumeci Salvatore
Published: March 2003

Interleukin (IL)‐12, produced by mononuclear phagocytes, activates the T‐helper 1 (Th1) cells and helps, as a mediator, the innate immune response to intracellular microbes. In Plasmodium falciparum infection, this proinflammatory cytokine has immunoregulatory functions with effects on the immune response to the blood stage of disease, but also induces protection and reduces malarial anaemia. In this study, the levels of IL‐12 were determined in 73 African children, aged 2–144 months (median 19·5 months), who had severe or mild P. falciparum malaria. IL‐12 was determined using the enzyme‐linked immunosorbent assay. The levels of IL‐12 were found to be significantly elevated (21·6 ± 18·3 pg/ml) in patients who suffered less severely from the disease. In contrast, the levels of IL‐12 were found to be lower (13·1 ± 7·11 pg/ml) in patients who suffered more severely from the disease.
Impact of dietary sterols on life‐history traits of a caterpillar
Authors: BEHMER SPENCER , GREBENOK ROBERT
Published: March 2003

Although lepidopteran larvae have been shown to metabolise a number of different phytosterols, their life‐history traits in response to these different phytosterols may vary with the species. Using the specialist moth, Plutella xylostella (Linaeus) (Lepidoptera), growth, development and fecundity on artificial diets containing host and non‐host phytosterols were measured over two generations. Because of the nature of the experimental design, maternal effects linked to dietary sterol could be assessed. In both generations, survival was highest on diets containing sitosterol as the primary phytosterol. A significant decrease in survival on stigmasterol, a non‐host phytosterol, was observed between generations. As expected, survival on a control diet with only trace‐sterols decreased between generations. Larval duration and pupal duration in both generations was longest on the diets containing the non‐host phytosterols, stigmasterol and spinasterol, and on the trace‐sterol diet. Finally, fecundity was affected by dietary sterol. In the first generation, fewer viable eggs were produced on the stigmasterol and trace‐sterol diets than on wheatgerm control diet. In both generations, dietary sterol significantly influenced percentage egg viability. Overall, these results indicate that differences in phytosterol structure can have pronounced effects on life‐history traits, especially when they are projected to the population level. The implications of these results are discussed with respect to phytosterol use by phytophagous insects and their host plant affiliations.
Feeding rates and carbohydrate metabolism by Bemisia tabaci (Homoptera: Aleyrodidae) on different quality phloem saps
Authors: ISAACS RUFUS , BYRNE DAVID N. , HENDRIX DONALD L.
Published: March 2003

Abstract.The effects of water stress on phloem sap quality of the melon, Cucumis melo, and how this, in turn, has an impact on the sweet potato whitefly, Bemisia tabaci were studied. Melon plants were grown under watering regimes that produced plants with or without water stress. Plants showed strong developmental responses to the treatments; water‐stressed plants were shorter, with fewer, smaller leaves than those without stress. There was, however, no effect of plant water stress on the development period of whiteflies feeding on these plants, or on the weights of male or female adults. Honeydew production was used as an indirect measure to test whether the absence of insect developmental or behavioural effects was due to differential phloem sap ingestion. Feeding rates on the stressed plants were almost half those on unstressed plants, and there was also variation in the daily pattern of honeydew production. Phloem sap and honeydew were analysed to determine why the feeding behaviours differed. Amino acid composition of the phloem sap was similar in both groups of plants, but carbohydrate concentrations were greater in water‐stressed plants, indicating that lower feeding rates may have been due either to the physical or nutritional quality of the phloem sap. The honeydew of insects that were feeding on water‐stressed plants contained a greater concentration of carbohydrate than those on unstressed plants, and was composed of a significantly greater proportion of glucose and the disaccharide, trehalulose. This isomerization of more complex sugars from those in the diet suggests that B. tabaci uses a mechanism of osmoregulation to actively maintain its internal water status. It is concluded that transient conditions of water stress in this host plant do not affect the development of B. tabaci, due to physiological and behavioural changes in response to diets with different nutritional and physical properties. The implications of this finding for the feeding biology of B. tabaci on desert‐grown crops are discussed.
Qualitative aspects of sperm stock in males and females from Eupelmus orientalis and Dinarmus basalis (Hymenoptera: Chalcidoidea) as revealed by dual fluorescence
Authors: Damiens David , Bressac Christophe , Brillard Jean‐Pierre , Chevrier Claude
Published: March 2003

Abstract The quality of a sperm population can be characterized physiologically and its fecundity predicted by its viable : non‐viable sperm ratio. To improve the knowledge of reproductive strategies in two ectoparasitoid hymenopteran species, Eupelmus orientalis Crawford (Hymenoptera: Eupelmidae) and Dinarmus basalis Rondani (Hymenoptera: Pteromalidae), the assessment of sperm viability using the dual fluorescence staining procedure SYBR‐14 : propidium iodide was developed. The aim of the study was to provide a comparative test in vitro applicable to both sexes to study the evolution of sperm quality at various stages of the reproductive processes. The reliability of propidium iodide to detect non‐viable sperm (stained in red) was confirmed in both species on the basis of two stress tests (ethanol and Triton X‐100) but our study also revealed that propidium iodide concentrations must be adequately adjusted for each single species. This experiment also demonstrated the physiological heterogeneity of sperm populations in E. orientalis and D. basalis males and females. In both species, 40% of the sperm in the seminal vesicles was found to be non‐viable. By contrast with E. orientalis, the populations of non‐viable sperm estimated from the seminal vesicles of D. basalis were found to be strongly different from those observed in the spermatheca. From the present results, the population of viable sperm detected in the spermatheca of females from both species proved a reliable predictor of fertilization achieved in ovipositing females.
Similar temperature requirement for sugar accumulation and for the induction of new forms of sucrose phosphate synthase and amylase in cold‐stored potato tubers
Authors: Deiting U. , Zrenner R. , Stitt M.
Published: March 2003

The onset of sugar accumulation in cold‐stored potato tubers coincides with an activation of sucrose phosphate synthase (SPS) and the appearance of a new form of amylase (Hill et al. 1996; Nielsen et al. 1997). To provide more evidence that these changes are involved in the regulation of cold‐induced sugar accumulation we have compared the temperature dependence of sugar accumulation with the temperature dependence of changes in SPS and amylase activity. To do this, we investigated: sugars and metabolites; SPS activity, protein and transcript; invertase activity; and amylolytic activity and amylase forms, during the first 10 d after transferring tubers from room temperature to 3, 5, 7, 9 and 11 °C. After 10 d there was negligible accumulation of sugars at 11, 9 and 7 °C, and a large accumulation at 5 and 3 °C. Activation of SPS was assayed by comparing activity in an assay with limiting substrates and phosphate and an assay with saturating substrate concentrations. The activation state increased slightly at 7 °C, 3‐ to 4‐fold at 5 °C and 5‐ to 6‐fold at 3 °C. The cold‐induced change in the kinetic properties of SPS was accompanied by the appearance of a new form of SPS with a slightly higher apparent molecular weight, and by an increase of the SPS transcript. The changes in SPS protein and transcript showed the same temperature dependence as the changes in the kinetic properties. Total starch hydrolysing enzyme activity was unaltered at 7°C, increased at 5°C and increased further (up to 7‐ to 8‐fold) at 3 °C. The increase in amylolytic activity correlated with the appearance of a new amylase band on zymograms. Acid invertase activity showed a similar increase at 3, 5, and 7°C, and it did not correlate with the total sugar accumulation. The cold‐induced accumulation of sugar can be reversed by transferring tubers back to warmer temperatures. We compared the decline of sugar levels with the changes of SPS, amylolytic activity and metabolites at various times (up to 14 d) after transfer of tubers from a 4 °C storage (for 14 d) back to 20°C. SPS activation state is reversed and the cold‐induced form of SPS virtually disappears during the first 2–4 d at 20 °C. The cold‐induced amylase activity also vanishes within 2–4 d.
Estimating the cost of flowering in a grapefruit tree
Authors: Bustan A. , Goldschmidt E. E.
Published: March 2003

The objective of the present study is to evaluate a Citrus tree's investment in the flowering process in relation to its photoassimilate resources, as a part of its annual reproductive effort. The overall requirement for carbohydrate of a single flower of grapefruit (Citrus paradisi Macf. cv. ‘Marsh seedless’) is evaluated as 8·33 × 10–3 mol C over 3 weeks. The direct cost of production of a single flower is estimated to be 5·75 × 10–3 mol C, most of which is allocated to the petals, anthers and style — organs designated to abscise. About 2·58 × 10–3 mol C is consumed by respiration not associated with growth processes. Growth respiration (Rg) occurs mostly during early stages of flower growth and development. However, the total respiration rate increases sharply during anthesis, when growth processes have almost ceased. Ethylene evolution also reaches remarkably high rates during anthesis. High temperatures increase the rate of flower respiration (Q10 = 2·12) but shorten the duration of flowering. A grapefruit tree may bear each year 20 000–50 000 flowers, only 0·5–2·5% of which develop into mature fruit. The amount of carbohydrate invested each year in bloom at the whole‐tree level is 166–400 mol C per tree (depending on the number of flowers), amounting to 10–20% of the carbohydrate consumed for fruit growth. The overall daily demand for carbohydrate by the flowers of a grapefruit tree during anthesis may exceed the daily carbohydrate production by the leaves. High temperatures lead to a further increase in the daily demand for carbohydrate. In such cases, the management of flowering must rely on carbohydrate reserves recruited from other tree organs. The ecophysiological and evolutionary aspects of Citrus flowering are discussed.
Carbon mobilization in shoot parts and roots of wheat during grain filling: assessment by 13C/12C steady‐state labelling, growth analysis and balance sheets of reserves
Authors: Gebbing T. , Schnyder H. , Kühbauch W.
Published: March 2003

cv, cultivar δ, deviation of C isotope composition from a standard Δ, C isotope discrimination WSC, water soluble carbohydrates  Steady‐state labelling of all post‐anthesis photosynthate of wheat was performed to assess the mobilization of pre‐anthesis C (C fixed prior to anthesis) in vegetative plant parts during grain filling. Results were compared with estimates obtained by indirect approaches to mobilization of pre‐anthesis C: ‘classical’ growth analysis and balance sheets of water soluble carbohydrates (WSC) and protein. Experiments were performed with two spring wheat cultivars grown with differential nitrogen fertilizer supply in 1991 and 1992. The fraction of pre‐anthesis C mobilized in above‐ground vegetative biomass ranged between 24 and 34% of total C present at anthesis. Treatment effects on mobilization of pre‐anthesis C in total above‐ground vegetative biomass were closely related (r2 = 0·89) to effects on mobilization of WSC‐C plus protein‐C (estimated as N mobilized × 3·15). On average, 81% of pre‐anthesis C mobilization was attributable to the balance of pre‐anthesis WSC (48%) and protein (33%) between anthesis and maturity. In roots, WSC and protein mobilization accounted for only 29% of the loss of pre‐anthesis C. Notably, mobilization of pre‐anthesis C was 1·4–2·6 times larger than the net loss of C from above‐ground vegetative biomass between anthesis and maturity. This discrepancy was mainly due to post‐anthesis C accumulation in glumes and stem. Post‐anthesis C accumulation was related to continued synthesis of structural biomass after anthesis and accounted for a mean 15% of total C contained in above‐ground vegetative plant parts at maturity. A close correspondence between net loss of C and mobilization of pre‐anthesis C was only apparent in leaf blades and leaf sheaths. Although balance sheets of WSC and protein also underrated the mobilization of pre‐anthesis C by ≈ 19%, they gave a much better estimate of pre‐anthesis C mobilization than growth analysis.
The effects of light on induction, time courses, and kinetic patterns of net nitrate uptake in barley
Authors: Peuke A. D. , Jeschke W. D.
Published: March 2003

Barley seedlings (Hordeum vulgare L.) were grown hydroponically with (induced) or without (uninduced) nitrate in a light/dark cycle with high photon flux density to determine the effects of light on time courses, induction and kinetics of net nitrate uptake. Nitrate uptake was induced by external nitrate in both light and dark and was prevented by 1 mol m–3 p‐fluorophenylalanine. In high light, nitrate uptake was about 2‐fold higher than in low light. During time course experiments the uptake rates oscillated due to daily light–dark changes. Rates of nitrate uptake also increased at about 2200 h during continuous darkness. This increase coincided approximately with the time at which the dark period started during the previous culture of the plants, indicating that it was due to a mechanism associated with an endogenous diurnal rhythm. When calculating the kinetics of nitrate uptake, a model with two saturable systems, including a high‐affinity system (HATS) and a low‐affinity system (LATS), gave the best fit to data in all treatments. The apparent affinity of the HATS ranged from 7·7 to 12·2 mmol m–3 in induced plants in all light conditions. The effect of light on the HATS was mainly an increase of apparent Vmax in the step from low to high light. In uninduced plants the HATS operated at a very low activity which was strongly enhanced during induction. Interpretation of the calculated kinetics of the LATS was much more difficult on the basis of net uptake data. The apparent affinity of the LATS increased from 24·3 mol m–3 in low light up to 0·17 mol m–3 after acceleration in high light. These extreme changes in apparent affinity of the LATS could not be explained satisfactorily, and the nature of this system is also discussed with respect to the method used.
Genetic analysis of the roles of phytochromes A and B1 in the reversed gravitropic response of the lz‐2 tomato mutant
Authors: BEHRINGER F. J. , LOMAX T. L.
Published: March 2003

The lz‐2 mutation in tomato (Lycopersicon esculentum) causes conditional reversal of shoot gravitropism by light. This response is mediated by phytochrome. To further elicit the mechanism by which phytochrome regulates the lz‐2 phenotype, phytochrome‐deficient lz‐2 plants were generated. Introduction of au alleles, which severely block chromophore biosynthesis, eliminated the reversal of hypocotyl gravitropism in continuous red and far‐red light. The fri1 and tri1 alleles were introduced to specifically deplete phytochromes A and B1, respectively. In dark‐grown seedlings, phytochrome A was necessary for response to high‐irradiance far‐red light, a complete response to low fluence red light, and also mediated the effects of blue light in a far‐red reversible manner. Loss of phytochrome B1 alone did not significantly affect the behaviour of lz‐2 plants under any light treatment tested. However, dark‐grown lz‐2 plants lacking both phytochrome A and B1 exhibited reduced responses to continuous red and were less responsive to low fluence red light and high fluence blue light than plants that were deficient for phytochrome A alone. In high light, full spectrum greenhouse conditions, lz‐2 plants grew downward regardless of the phytochrome deficiency. These results indicate that phytochromes A and B1 play significant roles in mediating the lz‐2 phenotype and that at least one additional phytochrome is involved in reversing shoot gravitropism in this mutant.
Evidence that amylose synthesis occurs within the matrix of the starch granule in potato tubers
Authors: TATGE H. , MARSHALL J. , MARTIN C. , EDWARDS E. A. , SMITH A. M.
Published: March 2003

Transgenic potatoes expressing reduced levels of granule‐bound starch synthase I (GBSSI) have been used to investigate whether the synthesis of amylose occurs at the surface of the starch granule or within the matrix formed by the synthesis and organization of amylopectin. Amylose in these potatoes is wholly or largely confined to a central region of the granule. Consequently this core region stains blue with iodine whereas the peripheral zone stains red. By making extensive measurements of the relative sizes of the granules and their blue‐staining cores in tubers over a range of stages of development, we have established that the blue core increases in size as the granule grows. The extent of the increase in size of the blue core is greater in potatoes with higher levels of GBSSI. These data show that amylose synthesis occurs within the matrix of the granule, and are consistent with the idea that the space available in the matrix may be an important determinant of the amylose content of storage starches.
Regulation by ABA of osmotic‐stress‐induced changes in protein synthesis in tomato roots
Authors: Jin S. , Chen C. C. S. , Plant A. L.
Published: March 2003

Polypeptide synthesis and accumulation were examined in the roots of tomato seedlings exposed to a polyethylene glycol‐imposed water deficit stress. In these roots, the synthesis of a number of polypeptides was induced, while that of several others was enhanced or repressed. To examine the role played by abscisic acid (ABA) in co‐ordinating the accumulation of these proteins, water‐deficit‐stress‐responsive polypeptide synthesis was investigated in the roots of the ABA‐deficient mutant flacca. In the roots of this mutant, the ability to accumulate a complete set of water‐deficit‐stress‐responsive polypeptides was impaired, indicating that ABA is required for their synthesis. The role of ABA was further examined by exposing the roots of both genotypes to exogenous ABA, which, with one exception, elicited the accumulation of all water‐deficit‐stress‐responsive proteins. Polyethylene glycol‐induced polypeptide accumulation was accompanied by a 1·6‐fold increase in the level of endogenous ABA in the roots of wild‐type plants and a 5‐fold increase in the roots of flc. Thus, although the absolute level was lower than that of the wild‐type, flc has the capacity to accumulate ABA in its roots. When fluridone was used to prevent the biosynthesis of ABA, the accumulation of several water‐deficit‐stress‐responsive polypeptides was reduced further. The synthesis of polypeptides was also examined in the roots of salt‐treated seedlings. Salt altered the accumulation of several polypeptides, all of which were previously observed in water‐deficit‐stressed roots, indicating that their synthesis was the result of the osmotic component of the salt stress. However, the accumulation of these polypeptides was not impaired in flc roots, indicating that the role played by ABA in regulating their accumulation in salt‐and polyethylene glycol‐treated roots differs. As such, salt‐ and water‐deficit‐stress‐induced changes in gene expression may be effected by different mechanisms, at least at the level of polypeptide accumulation.
Characterization and possible redox regulation of the purified calmodulin‐dependent NAD+ kinase from Lycopersicon pimpinellifolium
Authors: Delumeau O. , Renard M. , Montrichard F.
Published: March 2003

The soluble and calmodulin (CaM)‐dependent NAD+ kinase from Lycopersicon pimpinellifolium was previously shown to be largely inactivated in isolated cells exposed to a short‐term NaCl stress (Delumeau, Morère‐Le Paven, Montrichard, Laval‐Martin (2000) Plant Cell & Environment 23, 329–336). Nevertheless, the activity could be restored by adding a high dithiothreitol concentration to the protein extract, suggesting that the salt stress triggers an oxidation of the enzyme which leads to its inactivation. It was then interesting to investigate the effect of thiol‐modifying reagents and disulphide reductants on the activity of L. pimpinellifolium NAD+ kinase. A three‐step purification procedure was then established and allowed isolation of the enzyme which exists under two forms: a monomer and a dimer of a 56 kDa subunit, characterized, respectively, by pIs of 6·8 and 7·1. Isolated NAD+ kinase had a high affinity for CaM, half saturation being obtained for 7 ng mL−1 bovine CaM. The activity of NAD+ kinase was strongly inhibited by thiol‐modifying reagents and oxidized glutathione. NAD+ kinase was also found to be air‐inactivated, the residual activity being stimulated by disulphide reductants. The most efficient of them is reduced thioredoxin from Escherichia coli which induced a five‐fold increase in activity and restored 80% of the initial activity. These results which can be related to those previously observed in vivo suggest that the activity of the L. pimpinellifolium NAD+ kinase, besides its dependence on CaM, is also dependent on the reduction state of the protein which could be regulated by the thioredoxin h/NADP‐thioredoxin reductase system.
Cloning and characterization of an 18 kiloDalton protein in the roots of the perennial weed Taraxacum officinale Weber (Dandelion) which has allergen‐ and pathogenesis‐related protein properties
Authors: Xu X.‐Y. , Bewley J. D. , Greenwood J. S.
Published: March 2003

The root of the persistent weed, dandelion (Taraxacum officinale Weber), contains a predominant 18 kDa protein which undergoes small seasonal fluctuations in amount, increasing in the late autumn months, and declining in the spring. This protein has been purified and found to consist of two major isoforms of pI 5·56 and pI 5·49. A full‐length cDNA has been obtained, coding for the pI 5·56 isoform, and the 156‐amino‐acid sequence deduced. The protein shows homologies in amino acid composition to several allergen and intracellular pathogenesis‐related proteins. The deduced protein does not contain a signal peptide nor any known organelle‐targeting sequences, and thus is likely to be cytosolic. Expression of the 18 kDa protein gene is exclusive to the roots and stem tissues; transcripts accumulate during the late autumn months, and decline in the early spring. Changes in the amount of protein in the root are much less. The mRNA for the 18 kDa protein is not present in the dry seed, but appears in the roots within 16–18 h from the start of imbibition, and is expressed constitutively thereafter. Although it is the predominant protein in dandelion roots, its properties are different from those commonly associated with vegetative storage proteins.
Regulation of root hair density by phosphorus availability in Arabidopsis thaliana
Authors: Ma Z. , Bielenberg D. G. , Brown K. M. , Lynch J. P.
Published: March 2003

We characterized the response of root hair density to phosphorus (P) availability in Arabidopsis thaliana. Arabidopsis plants were grown aseptically in growth media with varied phosphorus concentrations, ranging from 1 mmol m−3 to 2000 mmol m−3 phosphorus. Root hair density (number of root hairs per mm of root length) was analysed starting at 7 d of growth. Root hair density was highly regulated by phosphorus availability, increasing significantly in roots exposed to low‐phosphorus availability. The initial root hairs produced by the radicle were not sensitive to phosphorus availability, but began to respond after 9 d of growth. Root hair density was about five times greater in low phosphorus (1 mmol m−3) than in high phosphorus (1000 mmol m−3) media. Root hair density decreased logarithmically in response to increasing phosphorus concentrations within that range. Root hair density also increased in response to deficiencies of several other nutrients, but not as strongly as to low phosphorus. Indoleacetic acid (IAA), the auxin transport inhibitor 2‐(p‐chlorophenoxy)‐2‐methylpropionic acid (CMPA), the ethylene precursor 1‐aminocyclopropane‐1‐carboxylic acid (ACC), and the ethylene synthesis inhibitor amino‐oxyacetic acid (AOA) all increased root hair density under high phosphorus but had very little effect under low phosphorus. Low phosphorus significantly changed root anatomy, causing a 9% increase in root diameter, a 31% decrease in the cross‐sectional area of individual trichoblasts, a 40% decrease in the cross‐sectional area of individual atrichoblasts, and 45% more cortical cells in cross‐section. The larger number of cortical cells and smaller epidermal cell size in low phosphorus roots increased the number of trichoblast files from eight to 12. Two‐thirds of increased root hair density in low phosphorus roots was caused by increased likelihood of trichoblasts to form hairs, and 33% of the increase was accounted for by changes in low phosphorus root anatomy resulting in an increased number of trichoblast files. These results show that phosphorus availability can fundamentally alter root anatomy, leading to changes in root hair density, which are presumably important for phosphorus acquisition.
Seasonal patterns of photosynthesis in Douglas fir seedlings during the third and fourth year of exposure to elevated CO2 and temperature
Authors: Lewis J. D. , Lucash M. , Olszyk D. , Tingey D. T.
Published: March 2003

The interactive effects of elevated atmospheric CO2 and temperature on seasonal patterns of photosynthesis in Douglas fir (Psuedotsuga menziesii (Mirb.) Franco) seedlings were examined. Seedlings were grown in sunlit chambers controlled to track either ambient (~400 p.p.m.) CO2 or ambient +200 p.p.m. CO2, and either ambient temperature or ambient +4 °C. Light‐saturated net photosynthetic rates were measured approximately monthly over a 21 month period. Elevated CO2 increased net photosynthetic rates by an average of 21% across temperature treatments during both the 1996 hydrologic year, the third year of exposure, and the 1997 hydrologic year. Elevated mean annual temperature increased net photosynthetic rates by an average of 33% across CO2 treatments during both years. Seasonal temperature changes also affected net photosynthetic rates. Across treatments, net photosynthetic rates were highest in the spring and autumn, and lowest in July, August and December–January. Seasonal increases in temperature were not correlated with increases in the relative photosynthetic response to elevated CO2. Seasonal shifts in the photosynthetic temperature optimum reduced temperature effects on the relative response to elevated CO2. These results suggest that the effects of elevated CO2 on net photosynthetic rates in Douglas fir are largely independent of temperature.
Co‐ordination of vapour and liquid phase water transport properties in plants
Authors: Meinzer F. C.
Published: March 2003

The pathway for water movement from the soil through plants to the atmosphere can be represented by a series of liquid and vapour phase resistances. Stomatal regulation of vapour phase resistance balances transpiration with the efficiency of water supply to the leaves, avoiding leaf desiccation at one extreme, and unnecessary restriction of carbon dioxide uptake at the other. In addition to maintaining a long‐term balance between vapour and liquid phase water transport resistances in plants, stomata are exquisitely sensitive to short‐term, dynamic perturbations of liquid water transport. In balancing vapour and liquid phase water transport, stomata do not seem to distinguish among potential sources of variation in the apparent efficiency of delivery of water per guard cell complex. Therefore, an apparent soil‐to‐leaf hydraulic conductance based on relationships between liquid water fluxes and driving forces in situ seems to be the most versatile for interpretation of stomatal regulatory behaviour that achieves relative homeostasis of leaf water status in intact plants. Components of dynamic variation in apparent hydraulic conductance in intact plants include, exchange of water between the transpiration stream and internal storage compartments via capacitive discharge and recharge, cavitation and its reversal, temperature‐induced changes in the viscosity of water, direct effects of xylem sap composition on xylem hydraulic properties, and endogenous and environmentally induced variation in the activity of membrane water channels in the hydraulic pathway. Stomatal responses to humidity must also be considered in interpreting co‐ordination of vapour and liquid phase water transport because homeostasis of bulk leaf water status can only be achieved through regulation of the actual transpirational flux. Results of studies conducted with multiple species point to considerable convergence with regard to co‐ordination of stomatal and hydraulic properties. Because stomata apparently sense and respond to integrated and dynamic soil‐to‐leaf water transport properties, studies involving intact plants under both natural and controlled conditions are likely to yield the most useful new insights concerning stomatal co‐ordination of transpiration with soil and plant hydraulic properties.
Leaf dispersion and light partitioning in three‐dimensionally digitized tall fescue–white clover mixtures
Authors: Sonohat G. , Sinoquet H. , Varlet‐Grancher C. , Rakocevic M. , Jacquet A. , Simon J.‐C. , Adam B.
Published: March 2003

A three‐dimensional digitizing method was used to assess the canopy structure of six Festuca arundinacea (FA)–Trifolium repens (TR) mixtures during the installation stage. Virtual canopy images were synthesized and used to derive light interception and partitioning between species. Computations from images were compared with a simple light model based on Beer’s law, in order to analyse within‐ and between‐species foliage dispersion. The total leaf area index of the mixtures ranged from 0·6 to 4·5. The fraction of FA foliage overtopping TR was 9–30%. The mean inclination of FA and TR was 66 and 57°, respectively. Within‐species dispersion parameters of FA and TR were about 0·8 and 1·0, namely clumped and random foliage dispersion, respectively. Although FA was sown in rows, between‐species dispersion was random. Lower leaf inclination and lesser clumping in TR compensated foliage overtopping by FA, so that light partitioning between FA and TR (about 80 and 20%, respectively) was similar to the species contribution to total canopy foliage. Since between‐species dispersion was random, a simple two‐layer light model based on Beer’s law provided correct estimations of light partitioning (RMSE = 0·05), although light interception by FA was slightly overestimated because of its clumped dispersion.
Inulin metabolism in dicots: chicory as a model system
Authors: Van Laere A. , Van Den Ende W.
Published: March 2003

Fructans are fructose‐based oligo‐ and polymers that serve as reserve carbohydrates in many plant species. The original Edelman and Jefford model for GFn inulin type fructan biosynthesis was confirmed by the de novo synthesis of fructans in vitro as well as by heterologous expression of the respective cDNAs in non‐fructan plants. Now the model can be extended for the biosynthesis of Fn inulin type fructans. Recent progress has now succeeded in elucidating the biochemistry and molecular biology of fructan biodegradation in chicory, an economically important species used for commercial inulin extraction. Unlike fructan biosynthetic genes that originated from vacuolar type invertase, plant fructan exohydrolases seem to have evolved from a cell wall invertase ancestor gene that later obtained a low iso‐electric point and a vacuolar targeting signal. Using chicory as a model system, expression analysis revealed that fructan enzymes are mainly controlled at the transcriptional level.
Membrane stabilization by abscisic acid under cold aids proline in alleviating chilling injury in maize (Zea mays L.) cultured cells
Authors: Chen W. P. , Li P. H.
Published: March 2003

Previous studies of maize suspension‐cultured cells showed that abscisic acid (ABA) treatment at warm temperatures improved the tolerance of cells to subsequent chilling. In the present study, it is shown that both ABA‐treated and untreated maize cells accumulated proline in response to chilling. However, ABA‐treated cells displayed less lipid peroxidation during chilling, and thus, unlike untreated cells, were able to retain the accumulated proline intracellularly. Proline application experiments indicate that an intracellular proline level higher than 2 µmole (g FW)−1 prior to chilling was needed to meaningfully reduce chilling‐enhanced lipid peroxidation and significantly improve chilling tolerance. The results suggest that total proline accumulation in ABA‐treated as well as untreated cells during chilling was enough to potentially improve chilling tolerance, but proline leakage rendered the control cells unable to benefit from the endogenous synthesis of proline in relation to the alleviation of chilling injury. Proline participated in chilling tolerance improvement in ABA‐treated maize cells, as evidenced by: (1) the inhibition of proline accumulation by l‐methionine‐d, l‐sulphoximine (MSO), an inhibitor of glutamine synthetase, reduced ABA‐improved chilling tolerance, and (2) the addition of glutamine into the medium prevented the MSO‐induced reduction in chilling tolerance. The revised relationship between proline accumulation and membrane stability at cold is discussed in the light of these current findings.
Diurnal variation in the stable isotope composition of water and dry matter in fruiting Lupinus angustifolius under field conditions
Authors: Cernusak L. A. , Pate J. S. , Farquhar G. D.
Published: March 2003

In this paper, we present an integrated account of the diurnal variation in the stable isotopes of water (δD and δ18O) and dry matter (δ15N, δ13C, and δ18O) in the long‐distance transport fluids (xylem sap and phloem sap), leaves, pod walls, and seeds of Lupinus angustifolius under field conditions in Western Australia. The δD and δ18O of leaf water showed a pronounced diurnal variation, ranging from early morning minima near 0‰ for both δD and δ18O to early afternoon maxima of 62 and 23‰, respectively. Xylem sap water showed no diurnal variation in isotopic composition and had mean values of −13·2 and −2·3‰ for δD and δ18O. Phloem sap water collected from pod tips was intermediate in isotopic composition between xylem sap and leaf water and exhibited only a moderate diurnal fluctuation. Isotopic compositions of pod wall and seed water were intermediate between those of phloem and xylem sap water. A model of average leaf water enrichment in the steady state (Craig & Gordon, pp. 9–130 in Proceedings of a Conference on Stable Isotopes in Oceanographic Studies and Palaeotemperatures, Lischi and Figli, Pisa, Italy, 1965; Dongmann et al., Radiation and Environmental Biophysics 11, 41–52, 1974; Farquhar & Lloyd, pp. 47–70 in Stable Isotopes and Plant Carbon–Water Relations, Academic Press, San Diego, CA, USA, 1993) agreed closely with observed leaf water enrichment in the morning and early afternoon, but poorly during the night. A modified model taking into account non‐steady‐state effects (Farquhar and Cernusak, unpublished) gave better predictions of observed leaf water enrichments over a full diurnal cycle. The δ15N, δ13C, and δ18O of dry matter varied appreciably among components. Dry matter δ15N was highest in xylem sap and lowest in leaves, whereas dry matter δ13C was lowest in leaves and highest in phloem sap and seeds, and dry matter δ18O was lowest in leaves and highest in pod walls. Phloem sap, leaf, and fruit dry matter δ18O varied diurnally, as did phloem sap dry matter δ13C. These results demonstrate the importance of considering the non‐steady‐state when modelling biological fractionation of stable isotopes in the natural environment.
Root respiration and associated costs in deciduous and evergreen species of Quercus
Authors: Martínez F. , Lazo Y. O. , Fernández‐Galiano J. M. , Merino J.
Published: March 2003

Root construction and maintenance costs were estimated in four evergreen and three deciduous Quercus species that are typical in the landscape of southern Spain. The cost quantification was based on analysis of the growth–­respiration ratio. Values observed for both construction cost (ranging from 1·17 to 1·29 g glucose g−1 dry weight) and maintenance   cost   (ranging   from   6·22   to   11·71 mg glucose g−1 dry weight d−1) were generally lower than those reported in other studies. The results showed non‐significant differences between deciduous and evergreen species. The lack of significant differences between species appeared to be due to the homogeneity of growth conditions. Hydroponic culture, with unrestricted nutrient and water supply, would lead to low tissue carbon content and low respiration rates, leading to the low costs observed. Furthermore, the fact that root organs are clearly importers of organic molecules inevitably entails some underestimation of the respiration associated with growth and, to a lesser extent, with maintenance respiration. This leads in turn to underestimation of the corresponding construction and maintenance costs. All this raises doubts as to the suitability of this method for studying root systems.
The role of cytoplasmic streaming in symplastic transport
Authors: PICKARD W. F.
Published: March 2003

The distributing of materials throughout a symplastic domain must involve at least two classes of transport steps: plasmodesmatal and cytoplasmic. To underpin the latter, the most obvious candidate mechanisms are cytoplasmic streaming and diffusion. The thesis will be here advanced that, although both candidates clearly do transport cytoplasmic entities, the cytoplasmic streaming per se is not of primary importance in symplastic transport but that its underlying molecular motor activity (of which the streaming is a readily visible consequence) is. Following brief tutorials on low Reynolds number flow, diffusion, and targeted intracytoplasmic transport, the hypothesis is broached that macromolecular and vesicular transport along actin trackways is both the cause of visible streaming and the essential metabolically driven cytoplasmic step in symplastic transport. The concluding discussion highlights four underdeveloped aspects of the active cytoplasmic step: (i) visualization of the real‐time transport of messages and metabolites; (ii) enumeration of the entities trafficked; (iii) elucidation of the routing of the messages and metabolites within the cytoplasm; and (iv) transference of the trafficked entities from cytoplasm into plasmodesmata.