bluuebunny/crossref_metadata_2025 huggingface dataset:
Antigenicity and immunogenicity of phage library‐selected peptide mimics of the major surface proteophosphoglycan antigens of Entamoeba histolytica
Authors: Melzer Helen , Fortugno Paola , Mansouri Erfan , Felici Franco , Marinets Alexandra , Wiedermann Gerhard , Kollaritsch Herwig , Von Specht Bernd‐Ulrich , Duchêne Michael
Published: March 2003

Entamoeba histolytica is the protozoan parasite responsible for intestinal amoebiasis and amoebic liver abscess, which cause significant morbidity and mortality in many countries of the world. Proteophosphoglycans (PPGs, also known as lipophosphoglycans, LPGs, or lipopeptidophosphoglycans, LPPGs) represent dominant surface components of E. histolytica. Passive immunization with a monoclonal antibody (EH5) directed against these components protected SCID mice from amoebic liver abscess, so PPGs might be regarded as vaccine candidates; however, their structure is very complex and only known in part. They are glycosylphosphatidylinositol‐linked polypeptides of unknown sequence carrying glycan side‐chains linked to serine residues via phosphodiester bonds. In order to identify peptide mimics of the E. histolytica PPG antigens, we screened six different phage‐displayed random peptide libraries with the antibody EH5. Various peptide mimics of different length were identified and, in all the peptides, a distinct consensus sequence Gly‐Thr‐His‐Pro‐X‐Leu could be identified. The phages strongly bound to the antibody, and the natural antigen inhibited binding of the phages to antibody EH5. In addition, several of the phages induced a significant immunoglobulin G response against amoebic antigens in immunized mice.
Role of colour and shape stimuli in host‐enhanced oogenesis in the walnut fly, Rhagoletis juglandis
Authors: ALONSO‐PIMENTEL HENAR , KORER JAMIE , NUFIO CESAR , PAPAJ DANIEL
Published: March 2003

This study aimed to quantify effects of the host plant on oogenesis in the walnut‐husk‐infesting fly, Rhagoletis juglandis Cresson (Diptera: Tephritidae), and to assess the role of physical cues in those effects.

In laboratory assays, the presence of fruit was manipulated independently of the presence of foliage for newly emerged females. After eight days, in each of two trials, females with fruit were found to have significantly higher egg loads than females without fruit. Foliage presence had little effect.

In a second experiment, females held with fruit or a fruit model (plastic yellow sphere of a size similar to fruit) had significantly higher egg loads than females held with neither fruit nor model. Egg loads of females with fruit were not significantly different from those of females with models.

In a third experiment, females were held with spheres of various colours or no sphere at all. Females with yellow or green spheres (similar to the colour of walnut fruit) had significantly higher egg loads than females with black, blue or red spheres of other colours or females without spheres.

In a fourth experiment, females held with spheres had significantly higher egg loads than females held with cubes of equivalent surface area or females held without a model.

Finally, cohorts of newly emerged females held with yellow spheres or without spheres were sampled periodically. In the sphere treatment, mean egg load increased sharply from negligible levels between days 8 and 10. The pattern was similar in the no‐sphere treatment, although the increase in egg load appeared to occur a day later.

From these experiments, we conclude that physical host fruit stimuli known to be important in host selection in Rhagoletis flies, including colour and shape, also enhance oogenesis in the first egg maturation cycle, and that enhancement of oogenesis via these stimuli requires neither nutritional input from the fruit nor prior egg deposition.
Survival of Heleomyza borealis (Diptera, Heleomyzidae) larvae down to − 60°C
Authors: Worland M. Roger , Block W.I.lliam , Grubor‐Lajsic G.O.rdana
Published: March 2003

Heleomyza borealis Boh. (Diptera, Heleomyzidae) overwinters as larvae in Arctic habitats, where they may experience winter temperatures below − 15°C. The larvae freeze at c.− 7°C but in acclimation experiments 80% survived when exposed to − 60°C. Of the larvae exposed to between − 4 and − 15°C, only 3% pupated. However, when cooled to − 20°C this increased to 44%, with 4% emerging as adults. Larvae maintained at 5°C contained low levels of glycerol, sorbitol and trehalose, which did not increase with acclimation to low temperatures. However, levels of fructose increased from 6.1 μg mg−1 fw in control animals to 17 μg mg−1 fw when exposed to − 2°C for 1 week. Larval body water (2.2 ± 0.1 g/g dw, mean ± SD, n = 100) and lipid content (0.22 ± 0.002 g/g fw, mean ± SE) showed no significant change during acclimation to low temperatures. Larvae maintained at a constant 5°C survived for over 18 months with little loss of body mass (from 7.5 ± 1.2 to 7.0 ± 1.2 mg fw, mean ± SD, n = 20), but none pupated. Heleomyza borealis larvae appear to feed and grow until they reach a body mass of about 7.5 mg and then become dormant. They remain in this state until they experience a low temperature stimulus (< − 15°C) followed by a warm period (≈ 5°C). This ensures that the larvae pupate and adults emerge in early summer, allowing the maximum growing period before the following winter. Heleomyza borealis are adapted to survive long winters in a dormant larval state. They have a low metabolic rate, can conserve body water even at subzero temperatures but do not synthesize large quantities of cryoprotectants.
Patterns of respiration in Locusta migratoria nymphs when feeding
Authors: Gouveia Scott M. , Simpson S.T.ephen J. , Raubenheimer David , Zanotto Flavia P.
Published: March 2003

Flow‐through respirometry was used to investigate patterns of respiration of fifth‐instar Locusta migratoria L. nymphs fed a chemically defined, synthetic food. Each animal was recorded for up to 2.7 h, during which they had access to food and water ad libitum, and at least one meal was taken. The start of feeding was coincident with a sudden and rapid rise in respiration. Both carbon dioxide (CO2) production and oxygen (O2) consumption rose, the traces for the two gasses showing a high degree of alignment. The end of a meal correlated with a sudden and rapid decrease in respiratory rate towards resting levels. When feeding was interrupted by an intra‐meal pause, respiratory rate tended to drop marginally and then stabilize, before rising rapidly upon the resumption of feeding within the meal. Maximal rates of respiration during feeding represented a 3–4‐fold increase over those at rest. Walking and climbing within the chamber were not associated with any noticeable change in respiratory rate above baseline. When locusts were quiescent between feeding episodes, respiration was steady and continuous, rather than discontinuous. Possible causes for large changes in respiration during feeding are discussed.
The effect of host acceptability on oviposition and egg accumulation by the small white butterfly, Pieris rapae
Authors: Hopkins Richard J. , Van Loon Joop J. A.
Published: March 2003

The influence of host‐plant acceptability on oviposition rate, egg load, internal fat storage and longevity was studied in the small white butterfly, Pieris rapae L. (Lepidoptera: Pieridae). Newly emerged females and males were presented with either cabbage (Brassica oleracea L. var. gemmifera), which is a highly acceptable host for the small white, or wallflower (Cheiranthus cheiri L.), which is much less acceptable for oviposition. Individuals were dissected when 3, 6 and 9‐days‐old. Females kept on cabbage contained fewer mature eggs than those kept on wallflower and there was no change in the load of mature eggs over the time course studied. The number of immature eggs carried did not vary with host plant species, but did fall significantly between days 6 and 9. The body fat content of individuals declined with increasing age, but the decline was slower for individuals kept on the host of low acceptability. Individuals that were allowed to spend their natural lifespan on cabbage showed similar oviposition patterns over time, where the oviposition rate started high and gradually reduced until death. However, considerable differences in oviposition pattern were found in individuals kept on wallflower, varying from that found on cabbage to no oviposition at all. The implications of these findings are discussed in the light of existing oviposition theories. This leads to the conclusion that in one species the premises of existing theories on optimization of oviposition are not mutually exclusive but rather play in concert.
Effects of larval diet on development rates and reproductive maturation of male and female Mediterranean fruit flies
Authors: Kaspi R. , Mossinson S. , Drezner T. , Kamensky B. , Yuval B.
Published: March 2003

Abstract Mediterranean fruit fly Ceratitis capitata (Diptera: Tephritidae) larvae are capable of developing in one of many hosts that may vary greatly in quality. We hypothesized that they will respond to the larval environment in a manner beneficial to their subsequent reproductive performance. Accordingly, we investigated the effects of various larval diets (varying in the amount of protein and sugar they contain) on the size, development time, nutritional status and reproductive maturation (ovarian development and onset of sexual behaviour) of females and males. We found that flies which undergo larval development in artificial host fruit that contain sugar and protein (‘protein‐fed’) were larger, developed faster and emerged with more nutritional reserves than flies that were protein‐deprived as larvae. Protein‐fed males, regardless of their size, became sexually active before males that developed in hosts with no protein. Protein‐fed females produced more mature eggs than protein‐deprived ones. Moreover, protein‐fed females tended to copulate sooner than females that developed in hosts with no protein. In addition, regardless of female larval diet, females with more mature eggs tended to copulate sooner than females with less mature eggs. In light of these results, the importance of the larval environment for adult reproductive success is discussed.
CanInachis iodetect nectar amino acids at low concentrations?
Authors: Mevi‐Schütz J. , Erhardt A.
Published: March 2003

AbstractThis study testedInachis ioL. butterflies' preference for nectar amino acids using a dilution series (100, 75, 50, 25 and 0%) of the amino acid concentration ofLantana camarato determine how sensitive the insects are to low concentrations of amino acids, such as those found in the flowers of many plant species. Female butterflies clearly detected and preferred nectar amino acids even at the lowest concentration offered, whereas males did not. These results further support the hypothesis that female butterflies detect and select for nectar with amino acids at levels found in the field.
Behavioural response of aphids to the alarm pheromone component (E )‐β‐farnesene in the field
Authors: Jing‐Gong Xiangyu , Feng Zhang , Yu‐Ling Fang , Wei Kan , Guang‐Xue Zhang , Zhong‐Ning Zhang
Published: March 2003

The alarm response of aphids to (E)‐β‐farnesene was examined for 59 species in the subfamilies Aphididae, Callaphididae, Chaitophoridae and Lachnidae, in the field. Forty‐one aphid species responded to (E)‐β‐farnesene at a dosage of 1 ng and/or 10 ng; however, 18 species did not. Myrmecophilous aphids did not react as extensively or strongly as non‐myrmecophilous aphids. The response of aphids to (E)‐β‐farnesene was related to host‐plant species.
Spaceflight reduces somatic embryogenesis in orchardgrass (Poaceae)
Authors: Conger B. V. , Tomaszewski Jr Z. , Mcdaniel J. K. , Vasilenko A.
Published: March 2003

Somatic embryos initiate and develop from single mesophyll cells in in vitro cultured leaf segments of orchardgrass (Dactylis glomerata L.). Segments were plated at time periods ranging from 21 to 0·9 d (21 h) prior to launch on an 11 d spaceflight (STS‐64). Using a paired t‐test, there was no significant difference in embryogenesis from preplating periods of 14 d and 21 d. However, embryogenesis was reduced by 70% in segments plated 21 h before launch and this treatment was significant at P = 0·0001. The initial cell divisions leading to embryo formation would be taking place during flight in this treatment. A higher ratio of anticlinal:periclinal first cell divisions observed in the flight compared to the control tissue suggests that microgravity affects axis determination and embryo polarity at a very early stage. A similar reduction in zygotic embryogenesis would reduce seed formation and have important implications for long‐term space flight or colonization where seeds would be needed either for direct consumption or to grow another generation of plants.
Altered resource allocation during seed development in Arabidopsis caused by the abi3 mutation
Authors: ROBINSON C. K , HILL S. A.
Published: March 2003

The regulation of whole‐plant resource allocation during seed development in Arabidopsis thaliana was investigated by examining growth rate and partitioning of 14CO2 in wild‐type plants and those carrying the abi3 mutation. Plants carrying the abi3 mutation partitioned more resources into seed development than the wild type. The extra resources were available as a result of delayed senescence of the cauline leaves in the mutant. After supply of 14CO2 at later stages of reproductive development differences in patterns of 14C distribution between mutant and wild type were consistent with long‐term changes in growth and allocation. The role of long‐distance signals in the regulation of seed yield in Arabidopsis is discussed.
Ammonium can stimulate nitrate and nitrite reductase in the absence of nitrate in Clematis vitalba
Authors: Bungard R. A. , Wingler A. , Morton J. D. , Andrews M. , Press M. C. , Scholes J. D.
Published: March 2003

Nitrogen assimilation was studied in the deciduous, perennial climber Clematis vitalba. When solely supplied with NO3– in a hydroponic system, growth and N‐assimilation characteristics were similar to those reported for a range of other species. When solely supplied with NH4+, however, nitrate reductase (NR) activity dramatically increased in shoot tissue, and particularly leaf tissue, to up to three times the maximum level achieved in NO3– supplied plants. NO3– was not detected in plant material that had been solely supplied with NH4+, there was no NO3– contamination of the hydroponic system, and the NH4+‐induced activity did not occur in tobacco or barley grown under similar conditions. Western Blot analysis revealed that the induction of NR activity, either by NO3– or NH4+, was matched by NR and nitrite reductase protein synthesis, but this was not the case for the ammonium assimilation enzyme glutamine synthetase. Exposure of leaf disks to N revealed that NO3– assimilation was induced in leaves directly by NO3– and NH4+ but not glutamine. Our results suggest that the NH4+‐induced potential for NO3– assimilation occurs when externally sourced NH4+ is assimilated in the absence of any NO3– assimilation. These data show that the potential for nitrate assimilation in C. vitalba is induced by a nitrogenous compound in the absence of its substrate and suggest that NO3– assimilation in C. vitalba may have a significant role beyond the supply of reduced N for growth.
Stable isotopic composition of carbon and nitrogen and nitrogen content in vascular epiphytes along an altitudinal transect*
Authors: Hietz P. , Wanek W. , Popp M.
Published: March 2003

The foliar content of nitrogen and the relative abundances of 13C and 15N were analysed in vascular epiphytes collected from six sites along an altitudinal gradient from tropical dry forests to humid montane forests in eastern Mexico. The proportion of epiphyte species showing crassulacean acid metabolism (CAM) (atmospheric bromeliads, thick‐leaved orchids, Cactaceae, and Crassulaceae) decreased with increasing elevation and precipitation from 58 to 6%. Atmospheric bromeliads, almost all of which had δ13C values indicating CAM, were more depleted in 15N (x=−10·9‰± 2·11) than the C3 bromeliads which form water‐storing tanks (−6·05‰± 2·26). As there was no difference in δ15N values between C3 and CAM orchids, the difference in bromeliads was not related to photosynthetic pathways but to different nitrogen sources. While epiphytes with strong 15N depletion appear to obtain their nitrogen mainly from direct atmospheric deposition, others have access to nitrogen in intercepted water and from organic matter decomposing on branches and in their phytotelmata. Bromeliads and succulent orchids had a lower foliar nitrogen content than thin‐leaved orchids, ferns and Piperaceae. Ground‐rooted hemi‐epiphytes exhibited the highest nitrogen contents and δ15N values.
Utilization of O2 in the metabolic optimization of C4 photosynthesis
Authors: Maroco J. P. , Edwards M. S. B. Ku & G. E. , Edwards G. E.
Published: March 2003

The combined effects of O2 on net rates of photosynthesis, photosystem II activity, steady‐state pool size of key metabolites of photosynthetic metabolism in the C4 pathway, C3 pathway and C2 photorespiratory cycle and on growth were evaluated in the C4 species Amaranthus edulis and the C3 species Flaveria pringlei. Increasing O2 reduced net CO2 assimilation in F. pringlei due to an increased flux of C through the photorespiratory pathway. However, in A. edulis increasing O2 up to 5–10% stimulated photosynthesis. Analysis of the pool size of key metabolites in A. edulis suggests that while there is some O2 dependent photorespiration, O2 is required for maximizing C4 cycle activity to concentrate CO2 in bundle sheath cells. Therefore, the response of net photosynthesis to O2 in C4 plants may result from the balance of these two opposing effects. Under 21 versus 5% O2, growth of A. edulis was stimulated about 30% whereas that of F. pringlei was inhibited about 40%.
Incomplete 13C labelling of α‐pinene content of Quercus ilex leaves and appearance of unlabelled C in α‐pinene emission in the dark
Authors: Loreto F. , Ciccioli P. , Brancaleoni E. , Frattoni M. , Delfine S.
Published: March 2003

α‐Pinene is formed in and emitted by Quercus ilex leaves. The carbon emitted as α‐pinene is rapidly and totally labelled by 13C in CO2 in air, but α‐pinene contained in the leaf shows a fraction of completely unlabelled carbon even after long exposures to air containing only 13CO2. When the labelled leaf is darkened, α‐pinene emission drops but is still measurable for about 10 h, and carbon becomes partially unlabelled. After an 11 h darkening the α‐pinene content is still as high as in the light but the carbon is mostly unlabelled. If the leaf is re‐illuminated but photosynthesis is inhibited by removing CO2 and lowering O2, a burst of emission occurs and the content of α‐pinene is depleted. Our experiments suggest that a pool of α‐pinene which is not directly generated by photosynthesis intermediates exists. Since this pool does not contribute relevantly to the emission in the light, we hypothesize that it is inhibited in the light and spatially located in a different compartment from chloroplasts. As we discuss, glycolysis in the cytoplasm and leucine catabolism in the mitochondria are both possible extra‐chloroplasts sources of carbon for isoprenoids.
The isolation of genes from the resurrection grass Sporobolus stapfianus which are induced during severe drought stress
Authors: Neale A. D. , Blomstedt C. K. , Bronson P. , Le T.‐N. , Guthridge K. , Evans J. , Gaff D. F. , Hamill J. D.
Published: March 2003

A modification of the ‘cold plaque’ screening technique (Hodge et al., Plant Journal1992, 2, 257–260) was used to screen a cDNA library constructed from drought‐stressed leaf tissue of the desiccation tolerant (‘resurrection’) grass Sporobolus stapfianus. This technique allowed a large number of clones representing genes expressed at low abundance to be isolated. An examination of expression profiles revealed that several of these genes are induced in desiccation‐tolerant tissue experiencing severe drought stress. Further characterization indicated that the gene products encoded include an eIF1 protein translation initiation factor and a glycine‐ and proline‐rich protein which have not previously been associated with drought stress. In addition, genes encoding a serine/threonine phosphatase type 2C, a tonoplast‐intrinsic protein (TIP) and an early light‐inducible protein (ELIP) were isolated. A number of these genes are expressed differentially in desiccation‐tolerant and desiccation‐sensitive tissues, suggesting that they may be associated with the desiccation tolerance response of S. stapfianus. The results indicate that there may be unique gene regulation processes occurring during induction of desiccation tolerance in resurrection plants which allow different drought‐responsive genes to be selectively expressed at successive levels of water loss.
Late‐stage canopy tree species with extremely low δ13C and high stomatal sensitivity to seasonal soil drought in the tropical rainforest of French Guiana
Authors: Bonal D. , Barigah T. S. , Granier A. , Guehl J. M.
Published: March 2003

We assessed the daily time‐courses of CO2 assimilation rate (A), leaf transpiration rate (E), stomatal conductance for water vapour (gs), leaf water potential (Ψw) and tree transpiration in a wet and a dry season for three late‐stage canopy rainforest tree species in French Guiana differing in leaf carbon isotope composition (δ13C). The lower sunlit leaf δ13C values found in Virola surinamensis (− 29·9‰) and in Diplotropis purpurea (− 30·9‰), two light‐demanding species, as compared to Eperua falcata (− 28·6‰), a shade‐semi‐tolerant species, were clearly associated with higher maximum gs values of sunlit leaves in the two former species. These two species were also characterized by a high sensitivity of gs, sap flow density (Ju) and canopy conductance (gc) to seasonal soil drought, allowing maintenance of high midday Ψw values in the dry season. The data for Diplotropis provided an original picture of increasing midday Ψw with increasing soil drought. In Virola, stomata were extremely sensitive to seasonal soil drought, leading to a dramatic decrease in leaf and tree transpiration in the dry season, whereas midday Ψw remained close to − 0·3 MPa. The mechanisms underlying such an extremely high sensitivity of stomata to soil drought remain unknown. In Eperua, gs of sunlit leaves was non‐responsive to seasonal drought, whereas Ju and gc were lower in the dry season. This suggests a higher stomatal sensitivity to seasonal drought in shaded leaves than in sunlit ones in this species.
The fate of [14C]glutamate and [14C]malate in birch roots is strongly modified under inoculation with Paxillus involutus
Authors: Blaudez D. , Botton B. , Dizengremel P. , Chalot M.
Published: March 2003

The impact of inoculation with Paxillus involutus on the utilization of organic carbon compounds by birch roots was studied by feeding [14C]Glu or [14C]malate to the partners of the symbiosis, separately or in association, and by monitoring the subsequent distribution of 14C. Inoculation increased [14C]Glu and [14C]malate absorption capacities by up to eight and 17 times, respectively. Six‐ and 15‐d‐old mycorrhizal roots showed about four‐fold higher [14C]Glu and [14C]malate absorption capacities compared with 60‐d‐old mycorrhizal roots, suggesting that the early stages of mycorrhiza formation induced higher requirements for C skeletons. Moreover, the results demonstrated that inoculation strongly modified the fate of [14C]Glu and [14C]malate. It was demonstrated that exogenously supplied Glu and malate might serve as C skeletons for amino acid synthesis in mycorrhizal birch roots and in the free‐living fungus. Gln was the major 14C‐sink in mycorrhizal roots and in the free‐living P. involutus. In contrast, citrulline and insoluble compounds were the major 14C sinks in non‐mycorrhizal roots, whatever the 14C source. It was concluded that mycorrhiza formation leads to a profound alteration of the metabolic fate of exogenously supplied C compounds. The ecological significance of amino acid and organic acid utilization by mycorrhizal plants is further discussed.
Expressing the yeast HAL1 gene in tomato increases fruit yield and enhances K+/Na+ selectivity under salt stress
Authors: Rus A. M. , Estañ M. T. , Gisbert C. , Garcia‐Sogo B. , Serrano R. , Caro M. , Moreno V. , Bolarín M. C.
Published: March 2003

The yeast HAL1 gene facilitates K+/Na+ selectivity and salt tolerance of cells. Ectopic expression of HAL1 in transgenic tomato (Lycopersicon esculentum Mill.) plants minimized the reduction in fruit production caused by salt stress. Maintenance of fruit production by transgenic plants was correlated with enhanced growth under salt stress of calli derived from the plants. The HAL1 transgene enhanced water and K+ contents in both leaf calli and leaves in the presence of salt, which indicates that HAL1 functions in plants using a similar mechanism to that in yeast, namely by facilitating K+/Na+ selectivity under salt stress.
Plant water relations at elevated CO2– implications for water‐limited environments
Authors: Wullschleger S. D. , Tschaplinski T. J. , Norby R. J.
Published: March 2003

Long‐term exposure of plants to elevated [CO2] leads to a number of growth and physiological effects, many of which are interpreted in the context of ameliorating the negative impacts of drought. However, despite considerable study, a clear picture in terms of the influence of elevated [CO2] on plant water relations and the role that these effects play in determining the response of plants to elevated [CO2] under water‐limited conditions has been slow to emerge. In this paper, four areas of research are examined that represent critical, yet uncertain, themes related to the response of plants to elevated [CO2] and drought. These include (1) fine‐root proliferation and implications for whole‐plant water uptake; (2) enhanced water‐use efficiency and consequences for drought tolerance; (3) reductions in stomatal conductance and impacts on leaf water potential; and (4) solute accumulation, osmotic adjustment and dehydration tolerance of leaves. A survey of the literature indicates that the growth of plants at elevated [CO2] can lead to conditions whereby plants maintain higher (less negative) leaf water potentials. The mechanisms that contribute to this effect are not fully known, although CO2‐induced reductions in stomatal conductance, increases in whole‐plant hydraulic conductance and osmotic adjustment may be important. Less understood are the interactive effects of elevated [CO2] and drought on fine‐root production and water‐use efficiency, and the contribution of these processes to plant growth in water‐limited environments. Increases in water‐use efficiency and reductions in water use can contribute to enhanced soil water content under elevated [CO2]. Herbaceous crops and grasslands are most responsive in this regard. The conservation of soil water at elevated [CO2] in other systems has been less studied, but in terms of maintaining growth or carbon gain during drought, the benefits of CO2‐induced improvements in soil water content appear relatively minor. Nonetheless, because even small effects of elevated [CO2] on plant and soil water relations can have important implications for ecosystems, we conclude that this area of research deserves continued investigation. Future studies that focus on cellular mechanisms of plant response to elevated [CO2] and drought are needed, as are whole‐plant investigations that emphasize the integration of processes throughout the soil–plant–atmosphere continuum. We suggest that the hydraulic principles that govern water transport provide an integrating framework that would allow CO2‐induced changes in stomatal conductance, leaf water potential, root growth and other processes to be uniquely evaluated within the context of whole‐plant hydraulic conductance and water transport efficiency.
Expression analysis of putative high‐affinity phosphate transporters in Chinese winter wheats
Authors: Davies T. G. E. , Ying J. , Xu Q. , Li Z. S. , Li J. , Gordon‐Weeks R.
Published: March 2003

China's soils tend to be phosphate deficient. Application of phosphorus fertilisers to the soil is yield and cost ineffective as much of the phosphate applied is rapidly locked‐in and is inaccessible to the crop. Chinese Institutes have established intensive wheat breeding programmes to generate wheat varieties that produce adequate yields and grain quality in such soils. Three such wheat cultivars have been identified with good performance characteristics in the field. These three cultivars are thought to harbour chromosome translocations that may confer enhanced phosphate scavenging abilities to the plants. The isolation and study of the expression of high‐affinity phosphate transporters in tissues of these wheats, in two of the donor wheatgrasses and in another widely planted Chinese wheat variety is presented and the first full‐length sequence of a wheat phosphate transporter and partial clones of several other putative phosphate transporters are reported. Relative quantitative reverse‐transcription – polymerase chain‐reaction was used to demonstrate that different phosphate transporters have different expression patterns within a given variety and respond differently to phosphate deprivation. The significance of the genetic background for these findings and for the different phosphate acquisition properties of the wheats under study is discussed.
Stomatal responses of Douglas‐fir seedlings to elevated carbon dioxide and temperature during the third and fourth years of exposure
Authors: Lewis J. D. , Lucash M. , Olszyk D. M. , Tingey D. T.
Published: March 2003

Two major components of climate change, increasing atmospheric [CO2] and increasing temperature, may substantially alter the effects of water availability to plants through effects on the rate of water loss from leaves. We examined the interactive effects of elevated [CO2] and temperature on seasonal patterns of stomatal conductance (gs), transpiration (E) and instantaneous transpiration efficiency (ITE) in Douglas‐fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings. Seedlings were grown in sunlit chambers at either ambient CO2 (AC) or ambient + 180 µmol mol−1 CO2 (EC), and at ambient temperature (AT) or ambient + 3·5 °C (ET) in a full‐factorial design. Needle gas exchange at the target growth conditions was measured approximately monthly over 21 months. Across the study period and across temperature treatments, growth in elevated [CO2] decreased E by an average of 12% and increased ITE by an average of 46%. The absolute reduction of E associated with elevated [CO2] significantly increased with seasonal increases in the needle‐to‐air vapour pressure deficit (D). Across CO2 treatments, growth in elevated temperature increased E an average of 37%, and did not affect ITE. Combined, growth in elevated [CO2] and elevated temperature increased E an average of 19% compared with the ACAT treatment. The CO2 supply and growth temperature did not significantly affect stomatal sensitivity to D or the relationship between gs and net photosynthetic rates. This study suggests that elevated [CO2] may not completely ameliorate the effect of elevated temperature on E, and that climate change may substantially alter needle‐level water loss and water use efficiency of Douglas‐fir seedlings.
Calcium oxalate and sulphate‐containing structures on the thallial surface of the lichenRamalina lacera: response to polluted air and simulated acid rain
Authors: GARTY J. , KUNIN P. , DELAREA J. , WEINER S.
Published: March 2003

The formation of calcium‐containing structures on the thallial surface of the lichenRamalina lacera(With.) J.R. Laund. in response to air pollution and to simulated acid rain, was studied inin situand transplanted thalli.In situthalli were collected from an unpolluted site and transplanted to heavily polluted and less polluted sites for a 10 month period. Additional thalli were treated either with double distilled water or with simulated acid rain. Scanning electron microscopy and infrared spectrometry revealed that thallial surfaces ofin situ R. lacerasamples collected in unpolluted sites were covered with two kinds of calcium oxalate crystals: whewellite and weddellite. These aggregates of calcium oxalate crystals appear to disintegrate and provide a crystal layer on the thallial surface. Infrared spectroscopy of powder scraped from thallial surfaces of transplants, retrieved from non‐polluted sites, showed the presence of whewellite and weddellite, whereas powders obtained from thalli retrieved from polluted sites contained whewellite, weddellite and gypsum. It is suggested that a certain fraction of the gypsum detected in crater‐like structures in transplants from polluted sites and in thalli treated with simulated acid rain is endogenous and should be considered a biomineral.
Xylem in early tracheophytes
Authors: EDWARDS D.
Published: March 2003

The architecture of the presumed water‐conducting cells of the major lineages of early tracheophytes recorded in Silurian and Devonian rocks is reviewed, together with descriptions of further diverse types whose derivation remains uncertain. Evidence has been obtained from a wide gamut of fossils including coalified compressions, silicified, pyritized and calcium carbonate perimineralizations. Most of the cells, only a few having been unequivocally demonstrated to be tracheidal, have walls with two layers, the inner sometimes broadly similar to annular, spiral and scalariform secondary thickenings of extant xylem. There are, however, very few cases of identical construction and the fossil representatives show greater complexity and variety. Their walls are presumed to have been lignified, but the polymer has not yet been directly identified in the fossils. The implications of these wall architectures on the functioning of the cells in water conduction are briefly considered, as is their relevance to hypotheses on inter‐relationships of early tracheophytes and on tracheid ontogeny.
Formation of oospores of Phytophthora infestans in cultivars of potato with different levels of race‐nonspecific resistance
Authors: Hanson K. , Shattock R. C.
Published: March 2003

Leaf discs in vitro, whole plants growing in a walk‐in plastic tunnel, and field plots of up to 10 cultivars of potato were inoculated with an A1 and an A2 isolate of Phytophthora infestans of recent UK origin. Numbers of oospores produced varied between repeated experiments involving leaf discs of four cultivars but ranking was unchanged 20 days after inoculation. Maximum mean numbers of oospores (approximately 20 000 per cm2 of leaf) were formed in the highly susceptible cv. Home Guard, with progressively fewer in Maris Piper, Cara, and the fewest in leaf discs of the highly resistant cv. Stirling. In Stirling, the number of oospores increased from approximately 1000–16 000 per cm2 of leaf between 11 and 30 days post‐inoculation. When leaf discs of 10 cultivars were inoculated, numbers of oospores were highest in cultivars with medium levels of race‐nonspecific resistance such as Desiree and Record. On Maris Piper and Cara, but not Home Guard and Stirling, asexual sporulation was significantly (P < 0.05) lower following dual inoculation with A1 and A2 isolates than following inoculation with either isolate alone. The highly susceptible cultivars Home Guard and Bintje were rapidly destroyed after inoculation of field and tunnel‐grown whole plants, and oospores were not observed. Oospores occurred in leaflets of various cultivars with medium levels of resistance to late‐blight, and in stems of all cultivars except Stirling. Twenty‐five isolates from single blight lesions from leaflets, and 16 from blighted tubers from the plastic tunnel‐grown plants, were characterized for mitochondrial and nuclear DNA polymorphisms. All but one were identical to parental isolates or confirmed as contaminants from an adjacent late‐blight‐affected tuber dump. One isolate, however, obtained from cv. Pimpernel 20 days after inoculation, may have been a recombinant between the A1 and A2 parental isolates, or alternatively a product of selfing or somatic recombination of the A1 parent.
Production of monoclonal antibodies to potato virus YNTN strain and their use for strain differentiation
Authors: Čeřovská N.
Published: March 2003

Four mouse monoclonal antibodies (MAbs) against potato virus Y (PVY) were produced. MAb 4C1 reacted with four isolates of PVYNTN and only very weakly with one isolate of the necrotic strain of PVY (PVYN). It did not react with other isolates of the ordinary strain of PVY tested. MAb 2C9 reacted with all isolates tested and can be used to produce a specific diagnostic kit for routine PVY detection. Other MAbs had different specificities and reacted with isolates of various strains of PVY. MAbs did not react with seven other members of the Potyvirus group including potato virus A. A MAb‐based ELISA, using MAb 4C1, was devised and shown to detect PVYNTN specifically.
Pathogenicity and histopathology of Pratylenchus thornei populations on selected chickpea genotypes
Authors: Castillo P. , Vovlas N. , Jiménez‐Díaz R. M.
Published: March 2003

Four populations of Pratylenchus thornei from different locations were tested for reproductive fitness in axenic carrot disc cultures and for pathogenicity to chickpea cultivars JG 62 and UC 27 and lines K 850 and ILC 1929. Parasitism and histopathology on selected chickpea genotypes (JG 62, UC 27 and lines ILC 482, ICC 11324 and ICC 12237) were also investigated. Reproductive fitness, assessed as the ratio of the final number of nematodes per carrot disc to the number of nematodes inoculated, was similar among the populations tested and the four populations reproduced to a similar extent in a given chickpea genotype. However, the extent of reproduction was significantly affected by the chickpea genotype, JG 62 and UC 27 being the best and poorest hosts, respectively. Pathogenicity to chickpea genotypes was assessed by the difference in fresh root and dry shoot weights between infected and uninfected plants 90 days after inoculation. Plant growth was significantly reduced by the four nematode populations in all chickpea genotypes, with the exception of cv. JG 62, which was tolerant of P. thornei. Severity of root necrosis caused by nematode infection was similar for all populations. Histopathological studies of chickpea genotypes infected by P. thornei showed that all were suitable hosts according to nematode reproduction and host reaction. P. thornei always migrated through epidermal and cortical cells by breaking down cell walls along the nematode pathway. In the most susceptible lines (ILC 482 and JG 62), damage to endodermal cells adjacent to nematode feeding sites was occasionally observed.
Temporary partial breakdown of mlo‐resistance in spring barley by sudden relief of soil water‐stress under field conditions: the effects of genetic background and mlo allele
Authors: Baker S. J. , Newton A. C. , Crabb D. , Guy D. C. , Jefferies R. A. , Mackerron D. K. L. , Thomas W. T. B. , Gurr S. J.
Published: March 2003

This study, carried out under field conditions, assessed the extent to which temporary breakdown of mlo‐resistance, following relief of water‐stress, was determined by genetic background and mlo allele. Commercial barley cultivars expressing the mlo gene for resistance to powdery mildew (Erysiphe graminis (Blumeria graminis) f.sp. hordei) were tested as well as doubled haploid progeny from spring barley genotypes, a proportion of which were sown in the field in two successive years. Plants were protected from natural rain by a mobile rain shelter and either watered by trickle‐irrigation or allowed to dry. Percentage mildew infection resulting from natural inoculum was recorded and the doubled haploid genotypes were classified as resistant, intermediate or susceptible on the basis of their control (watered) treatment scores. In each of the three designated classes, particular genotypes developed infection levels, following relief of water‐stress, that were higher than those observed on the well‐watered controls. This was found not to be related to the mlo allele as there was no significant difference between the increases observed on resistant plants carrying mlo9 and resistant plants carrying mlo11. Differences in the degree of breakdown of resistance were attributed to genetic background rather than to the specific mlo allele.
Increased susceptibility to bacterial wilt in tomatoes by nematode galling and the role of the Mi gene in resistance to nematodes and bacterial wilt
Authors: Deberdt  , Quénéhervé  , Darrasse  , Prior
Published: March 2003

The soil‐borne bacterial pathogen Ralstonia solanacearum commonly coexists with polyspecific nematode populations in tropical and subtropical areas. The wounding of roots by nematodes is usually invoked to explain the correlation between nematode infection and bacterial wilt, since this wounding increases the number of sites for bacterial entry. Bacterial wilt development on tomato was investigated in a controlled environment on the susceptible tomato cultivar Floradel and the polygenically wilt‐resistant cultivar Caraïbo. The bacterial isolate GMI 8217 and two different sedentary plant parasitic nematodes, the endoparasitic root‐knot nematode, Meloidogyne incognita, and semi‐endoparasitic reniform nematode, Rotylenchulus reniformis, were cross‐infected. At low temperatures (22–27°C), the bacterium GMI 8217 was slightly pathogenic on all tomato lines, except on Floradel coinfected by root‐knot nematode. At high temperatures (27–32°C), the root‐knot nematode greatly increased wilt severity in susceptible Floradel and resistant Caraïbo, but the reniform nematode had no such effect regardless of temperature × cultivar combination. This showed that infection of tomato roots by root‐knot nematodes reduced genetic resistance to bacterial wilt. The effects of combining bacterial wilt resistance with the Mi gene for resistance to root‐knot nematode (Mi, resistant; Mi+, susceptible) was investigated using the near‐isogenic lines Caraïbo (Mi+/ Mi+)/Carmido (Mi/Mi) and CRA 66 (Mi+/Mi+)/Cranita (Mi/Mi), which differ by the size of the segment of L. peruvianum DNA carrying the Mi gene. The presence of the Mi gene was associated with a marked decrease in bacterial wilt resistance. It is suggested that at least one gene governing part of the bacterial wilt resistance is closely linked or allelic to the Mi gene in the tomato lines used in this experiment.
Effects of temperature on the latent period of the rose powdery mildew pathogen, Sphaerotheca pannosa
Authors: Xu
Published: March 2003

The effects of temperature on the length of the latent period of rose powdery mildew, caused by Sphaerotheca pannosa var. rosae, were studied. At constant temperatures over the range of 10–28°C, the length of the latent period ranged from 4 to 10 days. The relationship between temperature and the rate of fungal development during the latent period (expressed as the reciprocal of the latent period) was described by a nonlinear (thermodynamic) model. The resulting curve was asymmetrically bell‐shaped with an optimum temperature of about 22°C. The latent period was further subdivided into two periods: incubation period (from inoculation to visible colonies) and postincubation period (from visible colonies to the first sign of conidiophores). The relationship between temperature and the rate of fungal development during the incubation period (expressed as the reciprocal of the incubation period) was also well described by a thermodynamic model. In contrast, the relationship between temperature and the rate of fungal development during the postincubation period (expressed as the reciprocal of the postincubation period) was approximately linear. The latent period under fluctuating temperatures was predicted using a two‐stage integration scheme at a step of 24 min by first integrating the incubation rate and then the postincubation rate. The predicted length of the latent period agreed well with the observed values.
Variation in cultural characteristics, pathogenicity, vegetative compatibility and electrophoretic karyotype within field populations of Stagonospora nodorum
Authors: Caten C.E. , Newton A.C.
Published: March 2003

Isolates of Stagonospora nodorum, the cause of septoria leaf and glume blotch of wheat, were sampled intensively from single fields in two consecutive years and compared for growth rate, colony morphology, pathogenicity, vegetative compatibility and electrophoretic karyotype. The two populations were highly variable for all characters, even though the isolates in each population originated from a small geographical area. Studies of vegetative compatibility within each population indicated the presence of many genotypes and suggested that clonal spread was very limited. Individual lesions contained a single genotype and therefore, presumably, originated from a single unit of inoculum. However, adjacent lesions, even on the same leaf, frequently contained different genotypes. Ten isolates from population II possessed six different karyotypes, demonstrating that polymorphism for this fundamental feature of the genome occurs within field populations. The population structure revealed by these studies supports the hypothesis that ascospores play a major role in the epidemiology of the disease. On this basis, the observed variation in all the characters, including karyotype, can be explained by recombination during sexual reproduction.
Effect of various crop establishment methods practised by Asian farmers on epidemics of rice sheath blight caused by Rhizoctonia solani
Authors: Willocquet L. , Fernandez L. , Savary S.
Published: March 2003

Establishment methods for rice crops in tropical Asia are very diverse, leading to variation in the structure of rice canopies. Differences in canopy structure can in turn affect the spread of the rice sheath blight pathogen, Rhizoctonia solani. Rice sheath blight epidemics were compared during two seasons in crops established by different methods: direct broadcasting of pregerminated rice seeds, and transplanting of rice seedlings at spacings of 20 × 20 cm, 13 × 25 cm and 25 × 25 cm between hills (i.e. along and between rows, respectively). In both years, the apparent infection rate based on incidence data and the terminal severity of sheath blight were lower in the direct‐seeded crops than in any of the transplanted ones, regardless of spacing. The frequency of leaf‐to‐leaf contacts (CF) between hills (or plants) was highest in direct‐seeded rice, and lowest in rice transplanted at a spacing of 25 × 25 cm. Larger CF is known to favour rice sheath blight epidemics. The apparent contradiction between higher incidence and lower CF in the transplanted stands than in the direct‐seeded stands is interpreted in terms of accessibility of healthy host tissues to the spread of the pathogen in the canopy, and accounts for within‐host (rice hill or plant) and between‐host (hill or plant) disease spread. The analysis of incidence‐severity relationships indicated a less aggregated distribution of the disease in direct‐seeded rice, which was related to the spatial distribution of the tillers. These findings have direct implications for the management of the disease.