bluuebunny/crossref_metadata_2025 huggingface dataset:
Antibody responses to Lucilia cuprina in sheep selected for resistance or susceptibility to L. cuprina
Authors: O'MEARA T.J. , NESA M. , SANDEMAN R.M.
Published: November 2003

Sheep bred for resistance (R) or susceptibility (S) to fleece rot and myiasis (blowfly strike) have been shown to differ in inflammatory response to intradermal administration of blowfly (Lucilia cuprina) antigens and artificial challenge. The current paper describes analysis of antibody responses to L. cuprina antigens in the R and S animals. Serum antibody titres and specificities to larval antigens were examined and the specificity of wound exudate antibodies was also investigated in animals artificially challenged with L. cuprina. Titres of L. cuprina specific serum IgA, IgM, IgG2 and IgG1 were measured by ELISA, while specificities were examined on two‐dimensional immunoblots of larval homogenates. Exposure to L. cuprina stimulated the production of specific antibody in both R and S animals, however antibody titres did not differ between the R and S animals. There was large variation in antibody specificity between individual animals and some L. cuprina proteins appear to be more frequently recognized by sera from either resistant or susceptible animals, however the recognition of a specific protein could not be solely attributed to the resistance status of the animal. It appears that resistance in these animals may be independent of serum antibody and is likely to be an innate response. Despite high levels of IgG in wound exudates, this antibody recognized few antigens in comparison with serum from the same animal, suggesting that exudate contains little functional antibody in comparison to serum.
Follow‐up of Gambian children recruited to a pilot safety and immunogenicity study of the malaria vaccine SPf66
Authors: BOJANG KALIFA A. , OBARO STEPHEN K. , LEACH AMANDA , D'ALESSANDRO UMBERTO , BENNETT STEPHEN , METZGER WOLFRAM , BALLOU W.RIPLEY , TARGETT GEOFFREY A.T. , GREENWOOD BRIAN M.
Published: November 2003

A pilot safety and immunogenicity trial of the malaria vaccine SPf66 was undertaken in The Gambia in 1993. One hundred and fifty infants aged 6–11 months were immunized with either 0.5 mg or 1.0 mg of SPf66 produced either in Colombia or in the USA or with a control vaccine. Children who received SPf66 experienced more clinical attacks of malaria than did children in the control group during the first period of surveillance and the difference in incidence between children who had received high dose Colombian vaccine and the control children was statistically significant at the 5% level. During the 1995 malaria transmission season, 127 children from the original cohort of 150 were observed. During 18 weeks of intensive surveillance, the incidence of clinical malaria was again higher among children who had received SPf66 than among children who had received inactivated polio vaccine (6.23 vs 4.89 clinical attacks per 1000 days at risk), the effect being most marked among children who were in the high dose groups, but differences between groups were now no longer statistically significant.
Cross‐reactive cellular immune response to circumsporozoite proteins of Plasmodium vivax and P. falciparum in malaria‐exposed individuals
Authors: CARVALHO L.H. , FONTES C.J.F. , FERNANDES A.A.M. , MARINUZZI H.C. , KRETTLI A.U.
Published: November 2003

Acquired immunity against the recombinant circumsporozoite protein of P. falciparum (rPfCS) or P. vivax (rPvCS) was studied in two malarious areas of the Brazilian Amazon. Cellular responsiveness, evaluated by proliferative assays, was detected in about 45% of individuals who had recovered from recent acute malaria infections. Peripheral blood mononuclear cells of individuals whose last malaria infection was by P. vivax responded more to the rCS proteins than those who had P. falciparum. Since in P. vivax infections hypnozoites in the liver retain CS antigen, this stage may have contributed to the increased cellular response. The unexpected result was that in primoinfections by P. falciparum or P. vivax the proliferative response did not correspond to the rPfCS and rPvCS, respectively. Furthermore, among the malaria‐exposed individuals, there was a positive correlation between the intensity of the responses to the two rCS proteins. Our results suggest that cross‐reactive epitopes exist in the CS protein of P. falciparum and P. vivax. In the areas studied, the frequency of antibodies against rPvCS and/or rPfCS ranged from 43% to 11%. Species‐specific antibodies against the CS protein were detected in the primoinfected individuals. Some individuals living in the endemic area but with no clinical history of malaria were positive by serology (8%) or by in vitro proliferation (21%). However, antibodies and cellular responses against rCS were detected only in malaria‐exposed individuals, since those living outside the endemic area were all negative.
Antibodies against Echinococcus multilocularis alkaline phosphatase as markers for the specific diagnosis and the serological monitoring of Alveolar echinococcosis
Authors: SARCIRON ELISABETH M. , BRESSON‐HADNI SOLANGE , MERCIER MARIETTE , LAWTON PHILIPPE , DURANTON CHRISTELLE , LENYS DANIELE , PETAVY ANNE F. , VUITTON DOMINIQUE A.
Published: November 2003

The immunological properties of the purified alkaline phosphatase (pAP) of Echinococcus multilocularis metacestodes have been investigated using alveolar echinococcosis (AE) patient sera in ELISA tests. A comparative study was done with EmC‐Ag (crude antigen) and pAP‐Ag (purified antigen). When the parasite purified enzyme pAP was used as antigen, the specificity of the ELISA was markedly increased since it reached 100% without any decrease of its sensitivity (100%). The serologic follow‐up of AE patients was conducted during several months with these two antigens in three categories of patients: cured, stabilized and aggravated. There was a good correlation between clinical and serologic data when the pAP was used as antigen in ELISA tests. The anti‐pAP antibodies titres did change more rapidly than anti‐EmC antibodies titres when a recurrence occurred. Modifications of the anti‐pAP antibodies levels were also observed during the patient’s therapy: mebendazole, albendazole and Isoprinosine®. These results suggest that pAP‐Ag should be used for the diagnosis and the follow‐up of AE patients.
Prolonged Th1‐like response generated by a Plasmodium yoeli‐specific T cell clone allows complete clearance of infection in reconstituted mice
Authors: AMANTE FIONA H. , GOOD MICHAEL F.
Published: November 2003

In the present study, we report the ability of in vitro cultured CD4+ T cells, generated following immunization with dead blood stage P. yoelii parasites, to mediate protection against homologous challenge infection in reconstituted nude mice. P. yoelii‐specific T cell line cells produced IFN‐γ after in vitro stimulation with specific antigen, and were protective when adoptively transferred into athymic nude mice. Following transfer of P. yoelii‐specific T cell lines into nude and SCID mice, elevated levels of nitric oxide (NO) were detected during the first week of infection at a time when parasitaemias were suppressed. However, in vivo blocking of NO production through administration of L‐NMMA, an inhibitor of NO synthase, increased mortality, but did not alter the course of primary parasitaemia in P. yoelii‐specific T cell line‐reconstituted nude mice. In addition, a P. yoelii‐specific CD4+ T cell clone, which produced IFN‐γin vitro, afforded sterile protection via mechanisms other than NO. By ELISA, antibodies were undetectable on all but one day (day 79) post T cell clone transfer and parasite challenge, where very low levels of antibodies were detected, with some evidence of recognition of malaria proteins by Western blot. Collectively, our data suggest that T cell effector functions, independent of NO production and in the absence of high levels of parasite‐specific antibodies, can contribute to sterile immunity to P. yoelii.
Peripheral blood lymphocytes from Eimeria tenella infected chickens produce gamma‐interferon after stimulation in vitro
Authors: Breed Dominique G.J. , Dorrestein Jan , Schetters Theo P.M. , Waart Leo v.d. , Rijke Eric , Vermeulen Arno N.
Published: November 2003

Protective immunity to infection by Eimeria parasites has been demonstrated to be dependent on T‐cell mediated immune responses and may be associated with the release of cytokines. We have previously shown that the proportion of CD8‐expressing T‐cells in the peripheral blood of chickens increases transiently at 8 days after a primary infection with Eimeria tenella oocysts. The increase in the CD8+ population coincided with an increased proliferative lymphocyte response upon stimulation with E. tenella sporozoite antigen in vitro. In this study, we further investigated the functional activity of these peripheral blood leucocytes (PBL) by determining both the potential to proliferate and to produce IFN upon stimulation with E. tenella sporozoite antigens and mitogens. Enhanced proliferative responses to parasite antigen were accompanied by reduced responses to T‐cell mitogens around 1 week of infection. The IFN activity in the supernatants of the stimulated PBL was measured by the ability to inhibit Semliki Forest Virus (SFV) replication in chicken embryo fibroblasts (CEF) and to activate macrophages, as measured by nitric oxide production. At eight days after infection the highest levels of virus inhibition and NO‐production were detected upon stimulation with both E.tenella sporozoite antigen and mitogen. A strong correlation between the individual data of the two methods was found at this timepoint indicating that the produced cytokine was indeed IFN‐γ. These results suggest that around eight days after a primary E. tenella infection a parasite specific T‐cell subset with the capacity to produce IFN(‐γ) is circulating which could be involved in the induction of protective immunity against Eimeria tenella.
Immunomodulation by hydatid cyst fluid toxin (Echinococcus granulosus)
Authors: JANSSEN D. , RUEDA M.C. , DE RYCKE P.H. , OSUNA A.
Published: November 2003

Since the experimental infection by hydatid cysts (Echinococcus granulosus) in mice causes immunomodulation of the host, the effects of hydatid fluid (HF) and fractions of HF were compared in vitro and in vivo. Fractions of HF were obtained using ammonium sulphate precipitation, chloroform/methanol extraction and thin‐layer chromatography (TLC). HF proved to be toxic to murine peritoneal macrophages in vitro, and when macrophages were incubated with the different fractions of HF, most toxicity was found in a single TLC‐purified fraction with an adjuvant‐like effect on the production of specific antibodies against bovine albumin and human red blood cells in mice. Treatment of mice with the toxin caused a drop in the percentage of peripheral blood lymphocytes. Flow‐cytometric analysis showed that T‐cells from toxin‐treated mice had lower membrane‐CD3, CD4 and CD8 density, and had higher percentages of CD8+ splenocytes and CD4+ thymocytes expressing CD25. The toxin caused a down‐regulation of CD4 and CD8 expression on thymocytes in vitro, that was dependent on the presence of macrophages. The results may attribute to these toxins a role in the host‐parasite relationship of hydatidosis.
Intranasal administration of Schistosoma mansoni adult worm antigen in combination with cholera toxin induces a Th2 cell response
Authors: AKHIANI A.A. , NILSSON L.‐Å. , OUCHTERLONY Ö.
Published: November 2003

Mice immunized with soluble adult worm antigen (SWAP) in combination with cholera toxin (CT) displayed significantly larger numbers of IgG1, IgM and IgA secreting cells in the spleen and in the lungs as compared to mice which had received SWAP only. The ratio of SWAP‐specific IgG1 to IgG2a antibody‐secreting spleen cells was also significantly higher in the SWAP‐CT group. Analysis of cytokine responses revealed that SWAP‐stimulated spleen and lung cells from the SWAP‐CT group produced lower levels of IFN‐γ but higher levels of IL‐4 and IL‐5 as compared to cells from the SWAP group. These findings indicate that intranasal administration of SWAP‐CT induces a Th2 cell response in the spleen and in the lungs. Our findings also suggest that CT was responsible for induction of this Th2 cell response, since intranasal administration of SWAP alone induced a Th1 type response in the spleen and in the lungs.
Intranasal immunization of mice with Echinococcus granulosus surface antigens Iscoms evokes a strong immune response, biased towards glucidic epitopes
Authors: CAROL HERNÁN , NIETO ALBERTO , VILLACRES‐ERIKSSON MARIA , MOREIN BROR
Published: November 2003

The present work describes the preparation and characterization of iscoms from tegumental antigens of Echinococcus granulosus protoscoleces, and their use as immunogens in mice by intranasal and subcutaneous routes. Iscoms given at 10 mg doses evoke a significant antibody response when administered i.n. and a strong and long lasting antibody response by s.c. route. The Ag administered i.n. in a non‐adjuvanted form as a booster was not immunogenic. The i.n. route of immunization induced higher IgA serum titre in relation to IgG than the s.c. route and antisera of slightly higher avidity. Also, ten fold lower IgG2a/IgG1 and ten fold higher IgG3/IgG1 ratios were observed for the i.n. protocol compared to the s.c. one. Moreover, the mucosal route of immunization induced more efficiently antibodies of both isotypes directed to carbohydrate epitopes. The differences between immune response generated by i.n. and parenteral immunizations should be taken into consideration, particularly in those cases in which protective antigens are glycosylated.
Cellular immunity to merozoite surface protein 2 (FC27 and 3D7) in Papua New Guinean children. Temporal variation and relation to clinical and parasitological status
Authors: AL‐YAMAN F. , GENTON B. , TARAIKA J. , ANDERS R. , ALPERS M.P.
Published: November 2003

A prospective study in 207 children aged 0.5–15 years was carried out in a highly endemic area of Papua New Guinea to examine the relationship between cellular responses to Plasmodium falciparum merozoite surface protein 2 (MSP2) and malaria infection and morbidity. In vitro proliferation, IFN‐γ and IL‐4 induction were measured against two recombinant proteins of MSP2, FC27 and 3D7 as well as against a form of the 3D7 MSP2 lacking the central repetitive sequences (d3D7). The prevalence of proliferative response was generally low, 6% for FC27, 9% for 3D7 and 11% for d3D7. A higher prevalence of IL‐4 response was obtained being 27% for FC27, 34% for 3D7 and 30% for d3D7 while the prevalence of IFN‐γ response was 13%, 15% and 18%, respectively. There was no correlation between age and proliferative responses; in contrast cytokine production increased with age for all three antigens. When proliferation or stimulation of either cytokine was used to assess T‐cell activation the frequency of responders increased to 39%, 47% and 46% for FC27, 3D7 and d3D7 respectively. Analysis of the relation of T cell responses to concurrent infection and morbidity showed that lymphoproliferative response only to d3D7 was significantly associated with parasitaemia; while lymphoproliferative responses to all 3 MSP2 antigens were highest in the group of clinical malaria cases. There was no significant correlation between proliferation or cytokine production to MSP2 and concurrent or subsequent malaria morbidity.
Identification of a surrogate TSL‐1 antigen of Trichinella spiralis from a phage library of random peptides
Authors: LIM PAK LEONG , TAM FRANKIE C.H. , CHUI YIU LOON , NG LAWRENCE W.K.
Published: November 2003

We sought to find a peptide analogue of an important antigen (TSL‐1) of Trichinella spiralis which is recognized by the 7C2C5 antibody. A phage library which displays a short (15‐mer) randomly‐generated peptide at the filament of the minor coat protein of the virion was used for selection by the 7C2C5 antibody. A peptide thus identified, ICDASGLGCWCWSLSP, was found to be a true surrogate since its binding to the antibody could be blocked by the native antigen and, conversely, an antiserum made to the peptide could recognize the native antigen. In addition, the peptide appeared to detect T. spiralis‐infected pigs although it was less discriminatory than the native antigen.
Association between cellular response (IL‐4) to RESA/Pf155 and protection from clinical malaria among Papua New Guinean children living in a malaria endemic area
Authors: AL‐YAMAN F. , GENTON B. , TARAIKA J. , ANDERS R. , ALPERS M.P.
Published: November 2003

A prospective study in 207 children aged 0.5–15 years was carried out to examine the relationship between cellular responses to Plasmodium falciparum ring‐infected erythrocyte surface antigen (RESA) and malaria infection and morbidity. The prevalence of lymphoproliferative response to RESA was 13%, IFN‐γ prevalence was 40% and IL‐4 prevalence was 22%. Only the IFN‐γ, response to RESA increased significantly with age. When proliferation or stimulation of either cytokine was used to assess T‐cell activation the overall frequency of responders increased to 55%. The proliferative and IFN‐γ response to RESA were positively associated. Although there was no association between any of the CMI responses to RESA and concurrent morbidity the prevalence of IL‐4 response to RESA was significantly lower in children who experienced clinical malaria in the following year. These results coupled with our earlier data showing a negative relationship between humoral responses to RESA and malaria morbidity support the inclusion of RESA in a subunit vaccine against malaria.
Allograft responses can interfere with the development of immunity against Theileria annulata following vaccination with parasite infected cell lines
Authors: NICHANI A.K. , BROWN C.G.D. , CAMPBELL J.D.M. , MAXWELL M.H. , WADDINGTON D. , SPOONER R.L.
Published: November 2003

Theileria annulata macroschizont‐infected cell lines are successfully used as vaccines in several countries. The inoculated animals produce a strong allogeneic response against the MHC antigens of the immunizing cell line followed by an anti‐parasite response. Immunity against the parasite wanes in the absence of challenge and re‐immunization is sometimes recommended. However, it is not known if allogeneic responses generated by the first immunization with a T. annulata infected cell line will interfere with the boosting of immunity against the parasite at the time of re‐immunization with the same cell line. Animals were primed against MHC antigens by skin grafting, followed by immunization with a T. annulata infected cell line prepared from the skin donor. A strong anti‐MHC response was produced. This interfered with parasite transfer and the development of an anti‐parasite immune response; the effect was more marked when a low vaccine cell dose was used. There was a negative correlation between the ease of isolating infected cells from the animals after cell line immunization, and the subsequent response to challenge. Where no cell lines could be isolated, the animals were fully susceptible to sporozoite challenge. These observations are of immediate importance in endemic areas where cell lines of T. annulata schizonts are being used as vaccines to control the disease.
Eosinophilic interleukin 5 (IL‐5) transgenic mice: eosinophil activity and impaired clearance of Schistosoma mansoni
Authors: DENT LINDSAY A. , MUNRO GRANT H. , PIPER KAREN P. , SANDERSON COLIN J. , FINLAY DAVID A. , DEMPSTER RACHEL K. , BIGNOLD LEON P. , HARKIN DAMIEN G. , HAGAN PAUL
Published: November 2003

Eosinophilia is a feature common to many invasive helminth infections and eosinophils are often considered to be effector cells in immunity to helminths. This study examined the possible influence of constituitive eosinophilia on the clearance of Schistosoma mansoni infections in mice. Eosinophils from interleukin‐5 transgenic mice exhibit normal ultrastructure and function with regard to phagocytosis and killing of bacteria and responses to chemotactic stimuli. IL‐5 transgenics and non‐transgenic littermates were immunized once or four (hyperimmunization) times with irradiated cercariae of S. mansoni. Animals were challenged percutaneously with unirradiated cercariae one month after their last exposure to irradiated parasites. One month after challenge transgenic animals, whether unimmunized, vaccinated or hypervaccinated, carried significantly more liver‐stage parasites than non‐transgenic animals. These results suggest that although eosinophils from IL‐5 transgenic mice are functional for a number of key parameters, large numbers of eosinophils and/or high levels of IL‐5 may in some way impair clearance of S. mansoni. A re‐evaluation of the roles of eosinophils and IL‐5 in infections with this and other parasites may therefore be warranted.
Blastogenic responses, interleukin‐2 production and interleukin‐2 receptor expression on CD4+ and CD8+ lymphocytes in rhesus monkeys experimentally inoculated with Loa loa
Authors: DENNIS VIDA A. , OSAE‐ADDO GLORIA , LOWRIE ROBERT C
Published: November 2003

To better understand cellular responses in loiasis infection, in vitro blastogenesis of peripheral blood mononuclear cells (PBMC) to filarial antigen was assessed in 12 Loa loa‐inoculated rhesus monkeys over a two‐year period. Cellular reactivity to antigen was observed between 10–35 weeks postinoculation (WPI), but had declined by week 50. The roles of interleukin‐2 (IL‐2) and IL‐2 receptor (IL‐2R) expression on CD4+ and CD8+ T cells in regulating the response to antigen were examined during the initial (57 WPI) and late (92 WPI) time points of the observed diminished reactivity to antigen. The levels of IL‐2 in antigen cultures at both time points were not significantly different from those in unstimulated cultures. Also, exogenous IL‐2 partially reversed the PBMC response to antigen. The percentages of CD4+ and CD8+ T cells expressing IL‐2R in antigen cultures at 57 WPI were not different from those of control animals. Likewise at 92 WPI, the percentage of CD4+ T cells expressing IL‐2R in antigen cultures, were not increased above those of control animals. In contrast, the percentage of CD8+ T cells expressing IL‐2R in antigen cultures were significantly increased above those of control animals (P < 0.0001), coinciding with an increase in CD8+ T cell numbers in these cultures. The data show that factors besides IL‐2, and probably an imbalance in the percentages of CD4+ and CD8+ T cells bearing IL‐2R in antigen cultures, may contribute to the diminished reactivity to antigen in L. loa‐inoculated rhesus monkeys.
Expression of acquired immunity to the hookworm Ancylostoma ceylanicum in hamsters
Authors: BEHNKE JERZY M. , GUEST JOSEPHINE , ROSE RICHARD
Published: November 2003

Four experiments are described in which hamsters, initially exposed to primary infection with Ancylostoma ceylanicum, were given a homologous challenge and components of the secondary response were quantified and compared to relevant control groups. The initial establishment of the L3 larvae was not prevented in immunized hamsters but their growth was slowed and virtually all larvae were lost within a week of challenge, when the majority were still at the L4 stage of development. The loss of worms was associated with an accelerated mucosal mastocytosis and increased systemic antibody. Thus acquired immunity to hookworm larvae in this system acted on L3 and L4 stages, thereby preventing larvae from maturing in immunized animals. In contrast to primary infections, immunized hamsters responding to a challenge infection did not lose weight nor did they experience significant anaemia, because of the lack of adult worms. The secondary immune responses therefore prevented manifestation of hookworm disease among immunized‐challenged animals.
In vitro infection with Theileria parva is associated with IL10 expression in all bovine lymphocyte lineages
Authors: MCKEEVER DECLAN J. , NYANJUI JOHN K. , BALLINGALL KEITH T.
Published: November 2003

The protozoan parasite Theileria parva infects and transforms bovine lymphocytes, giving rise to a fatal lymphoproliferative condition known as East Coast fever. Although immune cattle mount strong cytolytic T lymphocyte responses to the parasite, naive animals appear unable to respond and develop severe immunopathological lesions. We have investigated the patterns of cytokine mRNA expressed by 19 bulk and cloned parasite‐infected lymphoblast cell lines using a multiplex PCR system. Considerable variation was observed in the cytokine profiles of these lines and only IL10 was universally expressed. Investigation of cloned lines representing the major bovine lymphocyte populations failed to reveal a lineage‐specific pattern of cytokine mRNA expression that could be associated with infection. Nonetheless, analysis of a CD4+ T cell clone before and after transformation with the parasite indicated that infection does alter the pattern of cytokine expression, with apparent upregulation of IL10. These observations raise the possibility that IL10 derived from infected cells may influence the immune responses of naive cattle to challenge.
The course of Plasmodium chabaudi chabaudi infections in interferon‐gamma receptor deficient mice
Authors: FAVRE NICOLAS , RYFFEL BERNHARD , BORDMANN GÉRARD , RUDIN WERNER
Published: November 2003

Interferon‐gamma receptor (IFN‐γR) deficient mice parasitized with blood‐stage Plasmodium chabaudi chabaudi were used to assess the anti‐malarial activity of interferon‐gamma (IFN‐γ). There was no significant difference in the parasitaemia between the two types of mice during the first peak of parasitaemia. However, IFN‐γR deficient mice displayed an increased leucocytosis and a high mortality rate, whereas all of the wild type mice survived. IFN‐γR deficient mice, unlike wild type mice, developed a pronounced second parasitaemia peak, 9 to 11 days after the first one, with a parasitaemia of up to 65% associated with mortality. Furthermore, increased serum levels of nitric oxide (NO) were only found in wild type mice at the peak of parasitaemia, whereas it remained at background levels in IFN‐γR deficient mice. Parasite‐specific antibody production was not significantly different in IFN‐γR deficient mice, as compared to wild type mice. In addition, both wild type and IFN‐γR deficient mice were equally protected upon reinfection. These results indicate a delayed development of protective immunity and imply a crucial function for the IFN‐γR in the control of blood stage malaria during the initial three weeks of infection.
Will elevated CO2 concentrations protect the yield of wheat from O3 damage?
Authors: MCKEE I. F. , BULLIMORE J. F. , LONG S. P.
Published: November 2003

This study investigated the interacting effects of carbon dioxide and ozone concentrations on the growth and yield of spring whet (Triticum aestivum L. cv. Wembley). Plants were exposed from time of sowing to harvest to reciprocal combinations of two carbon dioxide and two ozone treatments: [CO2] at 350 or 700 μmol mol−1, and [O3] at < 5 or 60 nmol mol−1. Records of leaf emergence, leaf duration and tillering were taken throughout leaf development. At harvest, biomass, yield and partitioning were analysed. Our data showed that elevated [CO2] fully protected against the detrimental effect of elevated [O3] on biomass, but not yield.
Effects of elevated CO2 and temperature on photosynthesis and Rubisco in rice and soybean
Authors: VU J. C. V. , ALLEN L. H. , BOOTE K. J. , BOWES G.
Published: November 2003

Rice (Oryza sativa L. cv. IR‐72) and soybean (Glycine max L. Merr. cv. Bragg), which have been reported to differ in acclimation to elevated CO2, were grown for a season in sunlight at ambient and twice‐ambient [CO2], and under daytime temperature regimes ranging from 28 to 40°C. The objectives of the study were to test whether CO2 enrichment could compensate for adverse effects of high growth temperatures on photosynthesis, and whether these two C3 species differed in this regard. Leaf photosynthetic assimilation rates (A) of both species, when measured at the growth [CO2], were increased by CO2 enrichment, but decreased by supraoptimal temperatures. However, CO2 enrichment more than compensated for the temperature‐induced decline in A. For soybean, this CO2 enhancement of A increased in a linear manner by 32–95% with increasing growth temperatures from 28 to 40°C, whereas with rice the degree of enhancement was relatively constant at about 60%, from 32 to 38°C. Both elevated CO2 and temperature exerted coarse control on the Rubisco protein content, but the two species differed in the degree of responsiveness. CO2 enrichment and high growth temperatures reduced the Rubisco content of rice by 22 and 23%, respectively, but only by 8 and 17% for soybean. The maximum degree of Rubisco down‐regulation appeared to be limited, as in rice the substantial individual effects of these two variables, when combined, were less than additive. Fine control of Rubisco activation was also influenced by both elevated [CO2] and temperature. In rice, total activity and activation were reduced, but in soybean only activation was lowered. The apparent catalytic turnover rate (Kcat) of rice Rubisco was unaffected by these variables, but in soybean elevated [CO2] and temperature increased the apparent Kcat by 8 and 22%, respectively. Post‐sunset declines in Rubisco activities were accelerated by elevated [CO2] in rice, but by high temperature in soybean, suggesting that [CO2] and growth temperature influenced the metabolism of 2‐carboxyarabinitol‐1‐phosphate, and that the effects might be species‐specific. The greater capacity of soybean for CO2 enhancement of A at supraoptimal temperatures was probably not due to changes in stomatal conductance, but may be partially attributed to less down‐regulation of Rubisco by elevated [CO2] in soybean than in rice. However, unidentified species differences in the temperature optimum for photosynthesis also appeared to be important. The responses of photosynthesis and Rubisco in rice and soybean suggest that among C3 plants species‐specific differences will be encountered as a result of future increases in global [CO2] and air temperatures.
The shade avoidance syndrome: multiple responses mediated by multiple phytochromes
Authors: SMITH H. , WHITELAM G. C.
Published: November 2003

In recent years, the concept of shade avoidance has provided a functional meaning to the role of the phytochrome photoreceptor family in mature plants in their natural environment, and the question of which of these phytochromes is responsible for shade avoidance reactions has inevitably been raised. Unfortunately, a misconception has arisen that phytochrome B is solely responsible for detecting the environmental signal that initiates the shade avoidance syndrome. This view is too simplistic, and is based upon a selective interpretation of the available evidence. In this short Commentary, we review the concept of the shade avoidance syndrome, show how the misconception arose, and emphasize the plurality of perception and response that is crucial to successful competition for light.
UV and blue light signal transduction in Arabidopsis
Authors: JENKINS G. I.
Published: November 2003

The application of genetic and biochemical approaches in Arabidopsis has generated new insights into the photoreceptors and signal transduction processes that mediate the effects of UV and blue light on gene expression and development. Biochemical studies with an Arabidopsis cell culture have provided information on the signal transduction events that couple UV‐B and UV‐A/blue light perception to transcription of the chalcone synthase (CHS) gene. Interactions between UV‐B and both UV‐A and blue light signalling pathways enhance the level of CHS transcription. Mutants which identify negative regulators of CHS transcription in response to UV and blue light have been isolated. The integration of biochemical and genetic approaches will further advance understanding of UV and blue light perception and signal transduction.
Fundamental and biotechnological applications of phytochrome transgenes
Authors: ROBSON P. R. H. , SMITH H.
Published: November 2003

Individual phytochrome genes share regions of high homology which have facilitated the isolation of many phytochrome sequences from both higher and lower plants. Transgenes have been used to study the transcriptional control of phytochrome gene expression, and to create phytochrome‐deficient lines in polyploid species. Transgenically produced phytochrome apoproteins assemble with endogenous chromophore to become photoactive, and in most cases confer predictable light responses on the transgenic plants. The biological activity of transgenically produced phytochromes has been used to investigate the functions of domains within the phytochrome molecule. Physiological analysis of plants expressing phytochrome transgenes has revealed the potential of transgenic approaches to modifying the architecture of crop plants. Tobacco plants expressing to moderate levels an oat PHYA transgene exhibit proximity‐conditional dwarfing which leads to up to 20% improvement in harvest index in the field. These results provide prospects for a new genetic engineering approach to crop plant improvement.
Stomatal responses to jasmonic acid, linolenic acid and abscisic acid in wild‐type and ABA‐deficient tomato plants
Authors: HERDE O. , PEÑA‐CORTÉS H. , WILLMITZER L. , FISAHN J.
Published: November 2003

Wild‐type and abscisic acid (ABA) ‐deficient (sitiens) tomato plants were used to analyse the effects of abscisic acid (ABA), butyric acid (BA), jasmonic acid (JA) and linolenic acid (LA) on assimilation and transpiration rates in detached leaves taking up those substances into the transpiration stream. BA did not affect assimilation and transpiration rates. ABA decreased assimilation and transpiration in both wild‐type and ABA‐deficient mutants. JA reduced the assimilation rate in both lines but induced a significant reduction of transpiration in the wild type only. The response to LA in both lines was slower than that to JA.
Photomorphogenesis and phyfohormones
Authors: KRAEPIEL Y. , MIGINIAC E.
Published: November 2003

There are numerous reports of interactions between light and phytohormones. However, the exact nature of this interaction is not well understood. This article considers the possible roles played in the light signal transduction chain by four phytohormones (auxin, abscisic acid, gibberellins and cytokinins). As the involvement of phytohormones in this signalling mechanism is controversial, the major arguments in the debate are reported, including recently published results based on genetic, biochemical and physiological approaches.
Foraging for light: photosensory ecology and agricultural implications
Authors: BALLARÉ C. L. , SCOPEL A. L. , SÁNCHEZ R. A.
Published: November 2003

This mini‐review is concerned with one of the facets of the sensory physiology of plants that, in the last decade, has been intensively studied using genetically altered plants and eco‐physiological techniques – the perception of the proximity of neighbouring plants through specific informational photoreceptors. We focus on the signalling mechanisms that allow individual shoots to ‘forage’ for light in patchy and highly dynamic canopy environments. We present evidence from recent experiments suggesting that the fitness of each individual plant in the population, the growth of the population as a whole, and the degree of growth inequality among neighbours are all strongly dependent on the timing and precision of foraging mechanisms controlled, at least partially, by phytochrome‐B‐like phytochromes. This evidence is discussed in the context of potential impacts on yield of agricultural crops resulting from the artificial alteration of plant sensitivity to proximity photo‐signals. Directed overexpression of phytochrome genes appears to be an interesting avenue to explore in order to alter the photomorphogenesis of specific organs (or developmental stages) without affecting the overall ability of the plants to forage for light.
Phytochrome gene diversity
Authors: MATHEWS S. , SHARROCK R. A.
Published: November 2003

The structures and functions of the phytochrome apoprotein genes (the PHY genes), their diversity across the plant kingdom, and their evolution are central concerns in the study of red‐light sensing in plants. We summarize here recent advances in two areas relating to these topics: (1) the characteristics of the PHY gene family in Arabidopsis thaliana, the higher plant species for which the most extensive information on these genes is available, and (2) the similarity relationships, phylogeny, and evolutionary implications of PHY gene sequences and partial sequences which have been described from various plants. Together, these two areas of study, one directed at understanding in detail the phytochromes present in a single species and the other directed at a much broader understanding of PHY gene relatedness and distribution, are producing an increasingly clear picture of the diversity and evolution of plant red‐light photoreceptors. Moreover, they suggest that the complexity of the phytochrome family has increased as land plants have evolved novel morphologies.
Gravity, light and plant form
Authors: HANGARTER R. P.
Published: November 2003

Plants have evolved highly sensitive and selective mechanisms that detect and respond to various aspects of their environment. As a plant develops, it integrates the environmental information perceived by all of its sensory systems and adapts its growth to the prevailing environmental conditions. Light is of critical importance because plants depend on it for energy and, thus, survival. The quantity, quality and direction of light are perceived by several different photosensory systems that together regulate nearly all stages of plant development, presumably in order to maintain photosynthetic efficiency. Gravity provides an almost constant stimulus that is the source of critical spatial information about its surroundings and provides important cues for orientating plant growth. Gravity plays a particularly important role during the early stages of seedling growth by stimulating a negative gravitropic response in the primary shoot that orientates it towards the source of light, and a positive gravitropic response in the primary root that causes it to grow down into the soil, providing support and nutrient acquisition. Gravity also influences plant form during later stages of development through its effect on lateral organs and supporting structures. Thus, the final form of a plant depends on the cumulative effects of light, gravity and other environmental sensory inputs on endogenous developmental programs. This article is focused on developmental interactions modulated by light and gravity.
Effects of elevated CO2 on leaf gas exchange in beech and oak at two levels of nutrient supply: consequences for sensitivity to drought in beech
Authors: HEATH J. , KERSTIENS G.
Published: November 2003

Beech (Fagus sylvatica L.) and pedunculate oak (Quercus robur L.) were grown from seed for two whole seasons at two CO2 concentrations (ambient and ambient + 250 μmol mol−1) with two levels of soil nutrient supply. Measurements of net leaf photosynthetic rate (A) and stomatal conductance (gs) of well‐watered plants were taken over both seasons; a drought treatment was applied in the middle of the second growing season to a separate sample of beech drawn from the same population. The net leaf photosynthetic rate of well‐watered plants was stimulated in elevated CO2 by an average of 75% in beech and 33% in oak; the effect continued through both growing seasons at both nutrient levels. There were no interactive effects of CO2 concentration and nutrient level on A or gs in beech or oak. Stomatal conductance was reduced in elevated CO2 by an average of 34% in oak, but in beech there were no significant reductions in gs except under cloudy conditions (–22% in elevated CO2). During drought, there was no effect of CO2 concentration on gs in beech grown with high nutrients, but for beech grown with low nutrients, gs was significantly higher in elevated CO2, causing more rapid soil drying. With high nutrient supply, soil drying was more rapid at elevated CO2 due to increased leaf area. It appears that beech may substantially increase whole‐plant water consumption in elevated CO2, especially under conditions of high temperature and irradiance when damage due to high evaporative demand is most likely to occur, thereby putting itself at risk during periods of drought.
Interactions among stomata in response to perturbations in humidity
Authors: MOTT K. A. , DENNE F. , POWELL J.
Published: November 2003

The existence of patchy stomatal closure suggests interactions among neighbouring stomata that synchronize stomatal movements in small areas of a leaf. To test for such interactions, water vapour partial pressure (ewv) for a small group of stomata was controlled independently of that for the surrounding stomata using gas flow from a small needle. The ewv for the surrounding stomata was controlled with a larger gas flow, termed the primary flow. The spatial pattern of ewv isobars caused by the needle flow was assessed experimentally and theoretically. Stomatal apertures were monitored following perturbations in ewv of the primary flow and the needle flow. When ewv of the primary flow was perturbed and that of the needle flow held constant, stomata for which there was little or no perturbation in ewv responded similarly to stomata experiencing the perturbation. When the ewv of the needle flow was perturbed and that of the primary flow held constant, many stomata experiencing little or no perturbation responded similarly to those experiencing a large perturbation. The results are discussed in relation to a mechanism for stomatal interactions that has been proposed in a previous study [Haefner, Buckley & Mott (1997) Plant, Cell and Environment 20, 1087–1097, this issue].
Atmospheric CO2 enrichment increases growth and photosynthesis of Pinus taeda: a 4 year experiment in the field
Authors: TISSUE D. T. , THOMAS R. B. , STRAIN B. R.
Published: November 2003

Forest trees are major components of the terrestrial biome and their response to rising atmospheric CO2 plays a prominent role in the global carbon cycle. In this study, loblolly pine seedlings were planted in the field in recently disturbed soil of high fertility, and CO2 partial pressures were maintained at ambient CO2 (Amb) and elevated CO2 (Amb + 30 Pa) for 4 years. The objective of the study was to measure seasonal and long‐term responses in growth and photosynthesis of loblolly pine exposed to elevated CO2 under ambient field conditions of precipitation, light, temperature and nutrient availability. Loblolly pine trees grown in elevated CO2 produced 90% more biomass after four growing seasons than did trees grown in ambient CO2. This large increase in final biomass was primarily due to a 217% increase in leaf area in the first growing season which resulted in much higher relative growth rates for trees grown in elevated CO2. Although there was not a sustained effect of elevated CO2 on relative growth rate after the first growing season, absolute production of biomass continued to increase each year in trees grown in elevated CO2 as a consequence of the compound interest effect of increased leaf area on the production of more new leaf area and more biomass. Allometric analyses of biomass allocation patterns demonstrated size‐dependent shifts in allocation, but no direct effects of elevated CO2 on partitioning of biomass. Leaf photosynthetic rates were always higher in trees grown in elevated CO2, but these differences were greater in the summer (60–130% increase) than in the winter (14–44% increase), reflecting strong seasonal effects of temperature on photosynthesis. Our results suggest that seasonal variation in the relative photosynthetic response to elevated CO2 will occur in natural ecosystems, but total non‐structural carbohydrate (TNC) levels in leaves indicate that this variation may not always be related to sink activity. Despite indications of canopy‐level adjustments in carbon assimilation, enhanced levels of leaf photosynthesis coupled with increased total leaf area indicate that net carbon assimilation for the whole tree was greater for trees grown under elevated CO2 compared with ambient CO2. If the large growth enhancement observed in loblolly pine were maintained after canopy closure, then these trees could be a large sink for fossil carbon emitted to the atmosphere and produce a negative feedback on atmospheric CO2.
Mannitol inhibits growth of intact cucumber but not pea seedlings by mechanically collapsing the root pressure
Authors: STAHLBERG R. , COSGROVE D. J.
Published: November 2003

The positive xylem pressure (Px) in cucumber hypocotyls is a direct extension of root pressure and therefore depends on the root environment. Solutions of the electrolyte KCl (0.10 osm) reduced the hypocotyl Px transiently (biphasic response), while the Px reduction by mannitol solutions was sustained. The amplitudes of the induced Px reduction depended directly, and the degree of Px restoration after stress release depended indirectly, on the size of the initial positive Px, indicating that mannitol released the root pressure by a mechanical rather than osmotic mechanism. Mannitol treatment and other means of root pressure reduction revealed two separate growth responses in the affected cucumber hypocotyls. Only steep Px drops (following root excision or root pressure release in mannitol) directly cause a rapid, transient drop in growth rate (GR). Both rapid and slow (after root incubation in KCN or NEM) decreases in root pressure, however, led to a sustained growth inhibition of cucumber hypocotyls after about 30 min. This delay characterizes the growth response as an indirect consequence of the Px change. Pea seedlings, which lacked root pressure and had a negative Px throughout, showed extremely small changes in epicotyl Px and GR after root incubation in mannitol. It is apparent that the higher sensitivity of cucumber growth to mannitol depended on the presence and release of root pressure.
Impact of gas transport through rice cultivars on methane emission from rice paddy fields
Authors: BUTTERBACH‐BAHL K. , PAPEN H. , RENNENBERG H.
Published: November 2003

Two Italian rice (Oryza sativa var. japonica) cultivars, Lido and Roma, were tested in the field for methane production, oxidation and emission. In two consecutive years, fields planted with the rice cultivar Lido showed methane emissions 24–31% lower than fields planted with the cultivar Roma. This difference was observed irrespective of fertilizer treatment. In contrast to methane emissions, differences in methane production or oxidation were not observed between fields planted with the two cultivars. Plant‐mediated transport of methane from the sediment to the atmosphere was the dominating pathway of methane emission. During the entire vegetation period, the contribution of this pathway to total methane emission amounted to c. 90%, whereas the contribution of gas bubble release and of diffusion through the water column to total methane emission was of minor significance. Results obtained from transport studies of tracer gas through the aerenchyma system of rice plants demonstrated that the root–shoot transition zone is the main site of resistance to plant‐mediated gas exchange between the soil and the atmosphere. The cultivar Lido, showing relatively low methane emissions in the field, had a significantly lower gas transport capacity through the aerenchyma system than the cultivar Roma. Thus, the observed differences in methane emissions in the field between the cultivars Lido and Roma can be explained by different gas transport capacities. Apparently, these differences in gas transport capacities are a consequence of differences in morphology of the aerenchyma systems, especially in the root–shoot transition zone. It is, therefore, concluded that identification and use of high‐yielding rice cultivars which have a low gas transport capacity represent an economically feasible, environmentally sound and promising approach to mitigating methane emissons from rice paddy fields.