bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of boron starvation on boron compartmentation, and possibly hormone‐mediated elongation growth and apical dominance of pea (Pisum sativum) plants
Authors: Li Chunjian , Pfeffer Heidrun , Dannel Frank , Römheld Volker , Bangerth Fritz
Published: March 2003

Two experiments were carried out to study the effects of boron (B) deficiency on 7‐day‐old pea plants for 6 or 9 days under controlled growth chamber conditions. Growth and apical dominance (AD) of the plants and their B concentration and compartmentation were followed throughout the starvation period. Additionally, auxin (indoleacetic acid, IAA) concentration in the shoot apex and polar transport from it were measured along with the cytokinin (CK) concentration in the shoot apex and the roots. The results demonstrate that during a 6‐day B‐deficiency period, B concentration in the water‐insoluble residue of the roots was very stable and could not easily be reduced. In contrast, B concentration in the cell sap fraction was very sensitive to external B supply. Twelve hours after transferring the plants from B‐sufficient to B‐deficient solutions, the B concentration in root cell sap declined to half the concentration of the control plants. In addition, B concentration in the new aerial plant parts, which developed after the onset of the B‐deficiency treatment, was extremely low. A decline in elongation growth could be observed as soon as about 4 days after the imposition of B deficiency. This preceded the first measurable growth of lateral buds (release from AD). Before the onset of these morphological changes, there was a considerable decline in CK concentration, accompanied by a dramatic decrease in IAA export out of the shoot apex, a decline in IAA concentration in the shoot apex and the roots and a reduced capacity for polar IAA‐transport. These changes are discussed as possible reasons for the observed reduction in elongation growth and AD. These hormonal changes themselves are possibly the result of the decreased symplasmic B concentration, which in turn may be responsible for the reduced concentration in apical CKs. A sequence of events, which may be causally related, is suggested to explain the effects of B deficiency on the growth and AD of pea plants.
The role of sucrose during maturation of black spruce (Picea mariana) and white spruce (Picea glauca) somatic embryos
Authors: Iraqi Driss , Tremblay Francine M.
Published: March 2003

The present study was conducted to understand the role of sucrose in the medium on the maturation of black spruce and white spruce somatic embryos. A maturation medium containing 6% sucrose, which hydrolyzed into glucose and fructose, gave significantly more embryos than a medium containing 3.16% of each glucose and fructose. Preventing the complete sucrose hydrolysis by a daily transfer of the tissues onto fresh medium significantly decreased the yield of somatic embryos compared to when sucrose was allowed to complete its hydrolysis. This reduction was not due to the manipulation of the tissues during the transfer, since a daily in situ transfer did not affect embryo production. To verify if the better embryo production observed on a medium containing 6% sucrose was due to the increasing osmotic pressure of the medium, this increasing osmotic pressure was simulated with a sequence of media containing different concentrations of glucose and fructose. Unexpectedly and for both species, this simulation did not improve somatic embryo production, which stayed similar to the one obtained on constant osmotic pressure. To understand these results, embryos produced on the different treatments were analyzed in terms of sucrose, glucose, fructose and starch levels and protein contents. The embryo carbohydrate content was independent from the carbohydrate used in the maturation medium. However, embryos matured on 6% sucrose allowed to hydrolyze during the maturation period contained significantly more soluble and insoluble proteins than embryos matured on any other treatment. Furthermore, embryos with a higher protein content also exhibited a higher epicotyl appearance frequency. The role of sucrose as a regulatory factor during the maturation of spruce somatic embryos is discussed.
Subcellular localization of β‐glucosidase in rye, maize and wheat seedlings
Authors: Nikus Jeanette , Daniel Geoffrey , Jonsson Lisbeth M. V.
Published: March 2003

The subcellular compartmentation of β‐glucosidase was studied in rye, maize and wheat seedlings by immunocytochemical methods. For detection, we used a 10 nm gold‐labeled secondary antibody, and results were observed using transmission electron microscopy. In all three species, β‐glucosidase was found in plastids, cytoplasm and cell walls. In rye, gold particles were seen on cell walls and cytoplasm in epidermal cells of the root tip and shoot, in bundle sheath cells of the shoot and in all cells, except the vascular bundle cells of the coleoptile. Gold labeling was also observed in plastids of the bundle sheath cells of rye shoot tips and in cortical cells of root tips. In wheat, gold labeling was observed on cell walls and cytoplasm of epidermal cells in the shoot base and coleoptile, and on cell walls and plastids in epidermal cells of the root tip. In maize, gold labeling was mainly found in plastids or proplastids in vascular bundle cells and bundle sheath cells of the shoot, in bundle sheath cells of the coleoptile and in epidermal cells of the root. Some gold particles were also found in cell walls and cytoplasm of stomatal guard cells of the shoot base and vascular bundle cells of the shoot tip and in the cell walls of bundle sheath cells of the shoot tip and root tip epidermal cells. Results are discussed in relation to the role of β‐glucosidase in hydroxamic acid release and overall defense mechanism of monocotyledons.
Winter rye antifreeze activity increases in response to cold and drought, but not abscisic acid
Authors: Yu Xiao‐Ming , Griffith Marilyn
Published: March 2003

Antifreeze activity increases in winter rye (Secale cereale L.) during cold acclimation as the plants accumulate antifreeze proteins (AFPs) that are similar to glucanases, chitinases and thaumatin‐like proteins (TLPs) in the leaf apoplast. In the present work, experiments were conducted to assess the role of drought and abscisic acid (ABA) in the regulation of antifreeze activity and accumulation of AFPs. Antifreeze activity was detected as early as 24 h of drought treatment at 20°C and increased as the level of apoplastic proteins increased. Apoplastic proteins accumulated rapidly under water stress and reached a level within 8 days that was equivalent to the level of apoplastic proteins accumulated when plants were acclimated to cold temperature for 7 weeks. These drought‐induced apoplastic proteins had molecular masses ranging from 11 to 35 kDa and were identified as two glucanases, two chitinases, and two TLPs, by using antisera raised against cold‐induced rye glucanase, chitinase, and TLP, respectively. Apoplastic extracts obtained from plants treated with ABA lacked the ability to modify the growth of ice crystals, even though ABA induced the accumulation of apoplastic proteins within 4 days to a level similar to that obtained when plants were either drought‐stressed for 8 days or cold‐acclimated for 7 weeks. These ABA‐induced apoplastic proteins were identified immunologically as two glucanases and two TLPs. Moreover, the ABA biosynthesis inhibitor fluridone did not prevent the accumulation of AFPs in the leaves of cold‐acclimated rye plants. Our results show that cold acclimation and drought both induce antifreeze activity in winter rye plants and that the pathway regulating AFP production is independent of ABA.
Cloning, characterization and functional expression of a phospholipase Dα cDNA from tomato fruit
Authors: Whitaker Bruce D. , Smith David L. , Green Karen C.
Published: March 2003

Phospholipase D (PLD; EC 3.1.4.4) initiates phospholipid (PL) catabolism in plant cells and is also involved in signal transduction and retailoring of membrane PL. Phosphatidic acid (PA), the product of PLD hydrolysis of PL, increases in pericarp tissue during ripening of tomato (Lycopersicon esculentum Mill.) fruit, suggesting that increased PLD activity may be involved in loss of membrane function associated with ripening. However, a recent report showed a decline in soluble PLD activity in both normal and nonripening mutant fruit over the span that encompasses full ripening. To directly assess the role of PLD in tomato ripening, we have initiated a molecular genetic approach. Using a PLDα cDNA from castor bean as a probe, a PLDα cDNA (LEPLD2) was isolated from a tomato fruit library. It has an open reading frame of 2 421 nucleotides, predicted to encode a polypeptide of 807 amino acids, with a molecular mass of 91.9 kDa. These values are close to those of PLDαs from 11 plant species and LEPLD2 has ≥73% nucleotide sequence identity with PLDα cDNAs from castor bean and tobacco, as well as another tomato cDNA. LEPLD2 transcript was detected in all tissues of the tomato plant by RNA gel‐blot analysis. Levels were very low in roots, low in stems, moderate in leaves, high in flowers and increased in fruit during development and ripening. Expression of LEPLD2 in Escherichia coli yielded phosphatidylcholine‐hydrolyzing enzyme, and cells transformed with a pFLAG‐MAC vector construct produced a FLAG‐PLDα fusion protein that migrated close to the calculated 94 kDa on sodium dodecyl sulfate‐polyacrylamide gel electrophoresis.
The last step of the ethylene biosynthesis pathway in turnip tops (Brassica rapa) seeds: Alterations related to development and germination and its inhibition during desiccation
Authors: Rodriguez‐Gacio María del Carmen , Matilla Angel Jesús
Published: March 2003

The involvement of ethylene in zygotic embryogenesis is a little known aspect of the growth and development in higher plants. In the present work, we study the alterations of the last step of the ethylene biosynthesis pathway during the formation period of turnip tops (Brassica rapa cv. Rapa) seeds and its repercussions in the germination process and post‐germinative growth. For this, we chose 11 different phases of silique development, the first being the recently fertilized pistil and the last being the silique just prior to its dehiscence (ca. 2 months post‐anthesis). In the 11 phases, ethylene production was detected in both whole silique (with or without seeds) and in the seeds enclosed by the silique wall. The levels of ACC, ACO and ethylene production proved high in seeds belonging to: (1) the pod in the very early phases, when the seeds were growing but without photosynthetic competence; (2) the silique at maximum growth, in which the seeds will initiate desiccation and loss of photosynthetic activity. During the phases prior to dehiscence, there was a marked inhibition in the last step of the ethylene biosynthesis pathway. In viable dry seeds, no ACO activity was detected and the ACC levels were 4‐fold lower than at the onset of the silique senescence. Germination brings about a net synthesis of ACC with respect of the stores dry seed. This fact, together with other results presented in this work, point towards, as in other seeds, a dependence of ethylene synthesis for radicle emergence. The possible role played by the silique wall in the control of ethylene biosynthesis during zygotic embryogenesis, as well as the participation of ethylene as a hormonal signal in the triggering of seed desiccation in Brassica rapa cv. Rapa, are discussed in depth.
Characterisation and expression studies of a root cDNA encoding for ferredoxin‐nitrite reductase fromLotus japonicus
Authors: Orea Alicia , Pajuelo Purificación , Pajuelo Eloísa , Márquez Antonio J. , Romero José M.
Published: March 2003

A full‐length cDNA encoding for ferredoxin‐nitrite reductase (NiR, EC 1.7.7.1), has been isolated from a root cDNA library from the legumeLotus japonicusand characterised. The NiR gene (Nii) is present as a single copy in this plant, and encodes a protein of 582 amino acids. TheLotusNiR protein is synthesised as a precursor with an amino‐terminal transit peptide consisting of 25 amino acid residues. Sequence comparisons with leaf NiRs from different plant species and with other related redox proteins identified in the root NiR the same highly conserved residues involved in the cofactor binding than previously reported for leaves. Besides, a putative binding site for ferredoxin was also found in the N‐terminal region of the protein. The NiR gene is expressed in roots and leaves, although the level of expression is much higher in roots, in accordance with the fact thatL. japonicusassimilates nitrate mainly in roots. NiR mRNA, protein and activity are induced by nitrate in roots and leaves, while ammonium‐grown plants only showed basal levels. No oscillations of NiR mRNA, protein and activity were observed during the day/night cycle, neither in roots nor leaves, making an interesting difference with rhythms observed in other plant species.
Characterization of an ethylene‐induced esterase gene isolated from Citrus sinensis by competitive hybridization
Authors: Zhong Guang Yan , Goren Raphael , Riov Joseph , Sisler Edward C. , Holland Doron
Published: March 2003

A simple new method, competitive hybridization, for identification of differentially regulated genes was used to isolate novel genes induced by ethylene in citrus (Citrus sinensis [L.] Osbeck cv. Shamouti) leaves. One of the isolated genes, an ethylene‐induced esterase gene (EIE), was further characterized. The deduced protein sequence of this gene shows a similarity to those of several plant α/β hydrolase gene family members, which are known to be involved in secondary metabolism. Northern blot analysis demonstrated that EIE mRNA was induced by ethylene within 4 h and accumulated to a very high level 24 h after the initiation of ethylene treatment. Induction of EIE by ethylene could be counteracted by 1‐methylcyclopropene, a potent ethylene perception inhibitor, indicating that the expression of EIE is ethylene‐dependent. The bacterially expressed protein of EIE was recognized by antiserum against Pir7b, a naphthol AS esterase induced in rice by the non‐host pathogen, Pseudomonas syringae pv. syringae. The EIE protein was identified in ethylene‐treated leaves using anti‐Pir7b antibodies. An α‐naphthyl acetate esterase accumulated concomitantly with the increase in EIE protein in ethylene‐treated citrus leaves. An enzyme activity assay followed by western analysis confirmed that the esterase was EIE.
Apoplastic accumulation of iron in the epidermis of maize (Zea mays) roots grown in calcareous soil
Authors: Kosegarten Harald , Koyro Hans‐Werner
Published: March 2003

High concentrations of Fe in the roots of plants grown in calcareous soil have been found in a variety of plants, which, nevertheless, show Fe deficiency symptoms. In the present work, energy dispersive X‐ray (EDX) analysis at the cellular level has been used to characterize high root Fe concentrations in maize (Zea mays L.) grown in a calcareous soil in comparison with low root Fe concentrations under acidic soil conditions. Roots were thoroughly washed to remove adhering soil particles from the root surface as far as possible. To avoid any interference with possibly still present soil particles, the excitation beam was focused on radial walls of neighboring cells as well as on the symplast. Under alkaline conditions, high Fe concentrations in the mM range and higher accumulated in the epidermal root apoplast. Symplastic Fe was not detectable. Only traces of Fe were detectable in the apoplast of the cortex parenchyma. Under acidic conditions, apoplastic root Fe concentrations were clearly lower than under alkaline conditions, and no Fe was detectable in the root apoplast by use of EDX analysis. We conclude that, under alkaline conditions, high amounts of Fe are trapped in the epidermal root apoplast (apoplastic Fe inactivation), probably because of a high apoplastic pH and thus restricted translocation towards the root stele and to the upper plant parts. In contrast, on acidic soils Fe translocation towards the root stele and thus Fe supply to the upper plant parts was not impaired. Our findings imply that Fe deficiency on calcareous soils is not caused by restricted acquisition of Fe from the soil.
Requirement for far‐red light to maintain secondary needle extension growth in northern but not southern populations of Pinus sylvestris (Scots pine)
Authors: Clapham David H. , Ekberg Inger , Eriksson Gösta , Norell Lennart , Vince‐Prue Daphne
Published: March 2003

Extension growth of secondary needles is under photoperiodic control in Pinus sylvestris. To test for the effects of far‐red light on maintaining this extension growth, seedlings of six populations originating from latitudes between 57° and 67°N were raised for 11 weeks in continuous incandescent (metal halogen) light at 300 µmol m−2 s−1 and 20°C and then transferred at the same temperature to a daily regime of 8 h incandescent light (230 µmol m−2 s−1) followed by a 16 h day extension with cool white fluorescent light (40 µmol m−2 s−1, R/FR ratio 7.5) or with incandescent lamps (20 µmol m−2 s−1, R/FR ratio 2.0). For the seedlings from the three populations north of 64°, needle extension growth over 42 days in the FR‐poor day extension treatment was lower by up to 40% than in the FR‐rich day extension treatment, whereas for the seedlings from the three southern populations the needle extension growth was similar in both day extension treatments. The requirement for FR in day extensions is characteristic of ‘light‐dominant’ photoperiodic control mechanisms. It appears that P. sylvestris changes from dark‐dominant night timekeeping to light‐dominant day timekeeping with increasing latitude, as with the photoperiodic control of budset in Picea abies.
Lignification and lignin heterogeneity for various age classes of bamboo (Phyllostachys pubescens) stems
Authors: Lin Jinxing , He Xinqiang , Hu Yuxi , Kuang Tingyun , Ceulemans R.
Published: March 2003

The lignification process and lignin heterogeneity of fibre, vessel and parenchyma cell walls for various age classes of bamboo stems of Phyllostachys pubescens Mazel were investigated. It was shown that protoxylem vessels lignified in the early stage of vascular bundle differentiation, metaxylem vessel and fibre walls initiated lignification from the middle lamella and cell corners after the completion of vascular bundle differentiation. Most of the parenchyma cell walls lignified after the stem reached its full height, while a few parenchyma cells remained non‐lignified even in the mature culm. The cell walls of fibres and most parenchyma cells thickened further during the stem growth to form polylamellate structure and the lignification process of these cells may last even up to 7 years. The fibre walls were rich in guaiacyl lignin in the early stage of lignification, and lignin rich in syringyl units were deposited in the later stage. Vessel walls mainly contained guaiacyl lignin, while both guaiacyl and syringyl lignin were present in the fibre and parenchyma cell walls.
Developmental regulation of H+‐ATPase‐dependent auxin responses in the diageotropica mutant of tomato (Lycopersicon esculentum)
Authors: Coenen Catharina , Bierfreund Nicole , Lüthen Hartwig , Neuhaus Gunther
Published: March 2003

Rapid auxin effects on H+ pumping across the plasma membrane precede auxin‐induced elongation growth of hypocotyls and swelling of guard cells, as well as auxin inhibition of root growth. To investigate whether auxin‐signalling mechanisms in such diverse cell types are similar, we characterized these responses in various tissues of the diageotropica (dgt) mutant of tomato (Lycopersicon esculentum Mill.). Abraded hypocotyl segments of 4‐day‐old, etiolated dgt seedlings showed an impaired H+ secretion response to applied auxin. mRNA levels for two PM H+‐ATPase isoforms, LHA2 and LHA4, were not reduced in dgt hypocotyl segments as compared to wild‐type segments, suggesting that the dgt mutation does not affect H+ secretion by reducing the transcription of major PM H+‐ATPase genes. The dgt mutation also disrupted auxin inhibition of growth and H+ secretion in roots of 4‐day‐old dgt seedlings. However, immediately after germination, dgt seedling roots responded to auxin with a near‐normal inhibition of growth. In addition, stomata in epidermal peels from 2‐week‐old dgt cotyledons demonstrated normal auxin‐induced opening. We conclude that an intact DGT gene product is required for auxin‐induced H+ secretion in tomato hypocotyl segments and for auxin inhibition of H+ secretion in roots of older seedlings, but that a DGT‐independent pathway for auxin responses exists in young root tips and in guard cells. A developmentally controlled switch from DGT‐independent to DGT‐dependent auxin signalling appears to take place in root tips within 2 days after germination.
Salt‐ and glyphosate‐induced increase in glyoxalase I activity in cell lines of groundnut (Arachis hypogaea)
Authors: Jain Mukesh , Choudhary Dharamainder , Kale Raosaheb K , Bhalla‐Sarin Neera
Published: March 2003

Glyoxalase I (EC 4.4.1.5) activity has long been associated with rapid cell proliferation, but experimental evidence is forthcoming, linking its role to stress tolerance as well. Proliferative callus cultures of groundnut (Arachis hypogaea L. cv. JL24) showed a 3.3‐fold increase in glyoxalase I activity during the logarithmic growth phase, correlating well with the data on FW gain and mitotic index. Inhibition of cell division decreased glyoxalase I activity and vice versa, thus further corroborating its role as a cell division marker enzyme. Cell lines of A. hypogaea selected in the presence of high salt (NaCl) and herbicide (glyphosate) concentrations, yielded 4.2‐ to 4.5‐fold and 3.9‐ to 4.6‐fold elevated glyoxalase I activity, respectively, in a dose dependent manner reflective of the level of stress tolerance. The stress‐induced increase in enzyme activity was also accompanied by an increase in the glutathione content. Exogenous supplementation of glutathione could partially alleviate the growth inhibition of callus cultures induced by methylglyoxal and d‐isoascorbic acid, but failed to recover the loss in glyoxalase I activity due to d‐isoascorbic acid. The adaptive significance of elevated glyoxalase I activity in maintaining glutathione homeostasis has been discussed in view of our understanding on the role of glutathione in the integration of cellular processes with plant growth and development under stress conditions.
Regulation of the catalytic behaviour of L‐form starch phosphorylase from sweet potato roots by proteolysis
Authors: Chen Han‐Min , Chang Shih‐Chung , Wu Chi‐Chen , Cuo Ting‐Shen , Wu Jiann‐Shing , Juang Rong‐Huay
Published: March 2003

Starch phosphorylase (SP) is an enzyme used for the reversible phosphorolysis of the α‐glucan in plant cells. When compared to its isoform in an animal cell, glycogen phosphorylase, a peptide containing 78 amino acids (L78) is inserted in the centre of the low‐affinity type starch phosphorylase (L‐SP). We found that the amino acid sequence of L78 had several interesting features including the presence of a PEST region, which serves as a signal for rapid degradation. Indeed, most L‐SP molecules isolated from mature sweet potato roots were nicked in the middle of a molecule, but still retained their tertiary or quaternary structures, as well as full catalytic activity. The nicking sites on the L78 were identified by amino acid sequencing of these peptides, which also enabled us to propose a proteolytic process for L‐SP. Enzyme kinetic studies of L‐SP in the direction of starch synthesis indicated that the Km decreased during the proteolytic process when starch was used as the limiting substrate, but the Km for the other substrate (Glc‐1‐P) increased. On the other hand, the maximum velocities (Vmax) increased for both substrates. Mobility of the nicked L‐SP was retarded on a native polyacrylamide gel containing soluble starch, indicating the increased affinity for starch. Results in this study suggested that L78 and its proteolytic modifications might play a regulatory role on the catalytic behaviour of L‐SP in starch biosynthesis.
Solubilization of galactosyltransferase that synthesizes 1,4‐β‐galactan side chains in pectic rhamnogalacturonan I
Authors: Geshi Naomi , Pauly Markus , Ulvskov Peter
Published: March 2003

β‐1,4‐Galactan galactosyltransferase (GT) activity was solubilized from potato microsomal membranes in the presence of 78 mM 3‐[(3‐cholamidopropyl)dimethylammonio]‐1‐propanesulphonic acid. The solubilized GT activity transferred 14[C]galactose from UDP‐14[C]galactose onto the acceptor‐substrates composed of rhamnogalacturonan (RG) with short galactan chains (RG‐A, approximately 1.2 MDa, mol% Gal/Rha = 0.7; RG‐B, approximately 21 kDa, mol% Gal/Rha = 1.2). However, shorter RG containing short galactan chains (approximately 2 kDa and 1.2 kDa), RG oligomers without galactosyl‐residues, galactan, and galactooligomers did not act as acceptor‐substrates. Optimal pH for 14[C] incorporation onto RG‐A and RG‐B was around 5.6 and 7.5, respectively. The 14[C]‐labelled products synthesized upon RG‐A and RG‐B could be digested with a RG specific lyase into smaller RG fragments. 1,4‐β‐Endogalactanase could not digest the former product, whereas the latter product was digested to 14[C]galactobiose and 14[C]galactose. This demonstrates that at least two GT activities were solubilized from potato microsomal membranes. One had optimal pH around 5.6 to transfer galactosyl residues onto RG‐A, whereas the other had optimal pH around 7.5 to transfer galactosyl residues onto RG‐B. Both synthesized galactan attached to the RG backbone of RG‐A and RG‐B, and the galactan synthesized onto the RG‐B acceptor was 1,4‐β‐linked.
A relationship between seed development, Arabinogalactan‐proteins (AGPs) and the AGP mediated promotion of somatic embryogenesis
Authors: Van Hengel Arjon J. , Van Kammen Ab , De Vries Sacco C.
Published: March 2003

Arabinogalactan‐protein (AGP) epitopes are known to display developmentally regulated patterns of expression in several plant tissues. Therefore, AGPs have been suggested to play a role in plant development. Somatic embryogenesis is regulated by AGPs as well as by EP3 endochitinases. Using four different methods we have analysed the composition of AGPs in immature carrot seeds. The results obtained show that: (1) the native electrophoretic mobility of such AGPs changes during development; (2) AGP epitopes in immature seeds are developmentally regulated; (3) enzymatically released fragments of AGPs show that the composition of these molecules changes as a function of development; and (4) the biological activity of AGPs on the formation of somatic embryos changes depending on the age of the seeds. Our results suggest that degradation of maternally derived AGPs occurs after fertilization, while cellularization of the endosperm leads to synthesis of a new set of AGPs. The presence of an endochitinase cleavage site as well as the capacity to increase somatic embryogenesis only occurred in AGPs that were isolated from seeds in which the endosperm had been cellularized. Apparently, both EP3 endochitinases and somatic embryogenesis‐promoting AGPs are developmentally regulated in immature carrot seeds.
Abscisic acid‐ and cold‐induced thaumatin‐like protein in winter wheat has an antifungal activity against snow mould, Microdochium nivale
Authors: Kuwabara Chikako , Takezawa Daisuke , Shimada Takiko , Hamada Tatsurou , Fujikawa Seizo , Arakawa Keita
Published: March 2003

Cold acclimation of winter wheat (Triticum aestivum L.) seedlings induces accumulation in the apoplast of taTLPs that are similar to thaumatin‐like proteins (TLPs), which are pathogenesis‐related proteins. We characterized a cDNA of WAS‐3a encoding the major isoform of taTLPs from winter wheat cells and showed that WAS‐3a transcripts were markedly increased by treatment with ABA and by treatment with elicitors (chitosan, β‐glucan and cell wall fractions of Fusarium oxysporum and Microdochium nivale) in wheat cells. To analyse the function of WAS‐3a, a highly efficient expression system using wheat cells was established, and a large amount of recombinant WAS‐3a protein (rWAS‐3a) was obtained with near homogeneity. Antifungal assays using various fungi grown on agar plates revealed that rWAS‐3a inhibits hyphal growth of pink snow mould, Microdochium nivale, at a low temperature. The results suggest that cold‐induced taTLPs that accumulate in the apoplast contribute to snow mould resistance of winter wheat.
Electrophysiological characterization of tomato hypocotyl putative action potentials induced by cotyledon heating
Authors: Rousset Mathieu , De Roo Mathias , Le Guennec Jean‐Yves , Pichon Olivier
Published: March 2003

Young tomato plants (Lycopersicon esculentum, 8 days old) were given a heat‐wound to a cotyledon. The resulting electrical activity at the hypocotyl level was monitored with intracellular microelectrodes. We observed an original pattern of slow wave potentials (SWPs), consisting of 2–3 slow waves, with associated spikes. The electrophysiological study of the SWPs confirms previous conclusions that the SWPs are due to the inhibition of an active component of the membrane potential. The electrophysiological study of the spikes shows that they fit particularities of putative action potentials (APs). They seem to be triggered by the depolarization accompanying the SWPs and thus can appear late during the SWP. An ionic characterization of the spikes by using different extracellular ionic concentrations and channel blockers suggests that anionic channels might be involved, carrying SO42– ions. The channels activity might be down regulated by the calcium released by the vacuole during the SWPs and APs. A better characterization of the nature of these APs could permit the understanding of the information transmission mechanisms in higher plants.
From common signalling components to cell specific responses: insights from the cereal aleurone
Authors: Ritchie Sian M. , Swanson Sarah J. , Gilroy Simon
Published: March 2003

Studies into the molecules underlying plant signal transduction events continue to reveal the involvement of highly conserved factors such as Ca2+, calmodulin, cyclic GMP and phospholipases in a remarkably diverse array of physiological processes. The hormonal response systems in the aleurone cells of the cereal grain and in the stomatal guard cell are beginning to reveal how diversity of response can be hard wired into these cells despite the use of these common signalling intermediates. In both the aleurone and the guard cell ABA signalling operates through the action of phospholipase D and alterations in a Ca2+‐dependent signalling system. The role of phospholipase D is highly analogous in these two divergent cell types, perhaps reflecting the closeness of this enzyme to a conserved ABA receptor. However, specificity in response becomes evident in elements downstream from PLD, such as in the Ca2+ signalling system. For example, ABA has opposite effects on cytoplasmic Ca2+ in the aleurone and guard cell. Combining the Ca2+‐dependent signalling activities in networks with parallel regulatory activities such as cyclic GMP appears to underlie the flexible regulatory systems that are the hallmark of plant cell function.
Isolation and identification of a potent allelopathic substance in rice root exudates
Authors: Kato‐Noguchi Hisashi , Ino Takeshi , Sata Noriko , Yamamura Shosuke
Published: March 2003

A search for growth inhibitors in rice root exudates was undertaken in order to clarify the allelopathic system in rice (Oryza sativa L.). Rice seedlings inhibited the growth of cress (Lepidium sativum L.) and lettuce (Lactuca sativa L.) seedlings when the cress and lettuce were grown with rice seedlings. The putative compound causing the inhibitory effect of rice seedlings was isolated from their culture solution, and the chemical structure of the inhibitor was determined by spectral data as momilactone B. Momilactone B inhibited the growth of cress and lettuce seedlings at concentrations greater than 3 and 30 µM, respectively. The concentration of momilactone B was 3.4 and 1.1 nmol per seedling in the culture solutions of husked and non‐husked rice seedlings, respectively. These results suggest that rice seedlings may release momilactone B into the environment and the stress caused by the husk‐treatment may increase the amount of momilactone B released. Thus, momilactone B may play an important role in rice allelopathy.
Carbon allocation to the insoluble fraction, respiration and triose‐phosphate cycling in the sugarcane culm
Authors: Bindon Keren A. , Botha Frederick C.
Published: March 2003

The changes in carbon allocation to non‐sucrose metabolic pathways were investigated in developing internodes of sugarcane. Radiolabelling studies were done on internode 3, 6 and 9 tissues, representing three stages of increasing maturity. Carbon partitioning into sucrose increased from 34% of total 14C uptake in internode 3, to 66% in internodes 9. In immature tissue, the protein and fibre components were the dominant competing sinks with sucrose for incoming carbon, to which 14 and 16% of carbon was allocated. Increased carbon allocation to sucrose with tissue maturity coincided with a decrease in partitioning to fibre and total respiration. Between internodes 3 and 9 carbon allocation to total respiration decreased by 9%, and to fibre by 14%. Carbon cycling between the triose‐ and hexose phosphate pools was evident in all internodes. More than 90% of carbon entering triose‐phosphates was returned to hexose in internode 3 tissue, and this flux decreased with tissue maturity.
Drought regulation of GST8, encoding the Arabidopsis homologue of ParC/Nt107 glutathione transferase/peroxidase
Authors: Bianchi Michele W. , Roux Camille , Vartanian Nicole
Published: March 2003

Glutathione transferases (GST; EC 2.5.1.18) have been involved in many biotic and abiotic interactions of plants with their environment, but very little information is available on their regulation and possible role in drought tolerance. The GST8 gene of Arabidopsis thaliana encodes, as assessed by phylogenetic analysis, the homologue of an extremely conserved subgroup of Tau GSTs. During rapid dehydration of seedlings and progressive drought stress of mature plants, GST8 transcript levels increased following slower kinetics than RNAs for dehydration responsive genes RD29A and B, and strictly paralleled, in a mostly ABA independent manner, expression of oxidative stress marker PRX. GST8 RNA levels were also consistently increased by oxidative stress, high doses of auxin or cytokinin, and to a lesser extent, by wounding. RNA levels of ERD13, a previously described rapid dehydration responsive GST of the Phi class, were not co‐regulated with those of GST8. Our results suggest that a drought‐associated oxidative stress induces accumulation of GST8, whose function could be to counteract the effect of higher ROS production in stressed plants
Bean class IV chitinase promoter is modulated during plant development and under abiotic stress
Authors: Lima Viviane M. , Magioli Cláudia , B. de A. Gerhardt Liliane , Tarré Erica , Menezes Rosa M.G. , Sachetto‐Martins Gilberto , Margis‐Pinheiro Márcia
Published: March 2003

To investigate howPvChi4promoter regulates gene expression during plant development and in response to stress, we have introduced promoter‐GUS transcriptional fusion constructs in transgenicArabidopsis thalianaand tobacco plants. GUS activity was not detected in aerial vegetative organs of transgenic plants carrying the 2189 bp promoter. However,gusexpression was activated at the parenchyma and epidermis of leaves and stem, when these transgenic tobacco plants were submitted to heat shock and UV irradiation. The non‐stressed plants showed promoter activity in the meristematic region of lateral roots and in reproductive organs. In both species, the promoter was active in pollen grains and ovaries. In tobacco anthers,gusexpression was observed in the middle layer. In transgenic plants harbouring promoters of 1445 bp, 1199 bp, 501 bp and 416 bp, GUS activity has been detected, in addition to the meristematic region of lateral roots, at the apical meristem, and in the phloem and epidermic tissues of leaves, stems and petioles. These analyses suggest that allcis‐acting elements controlling the tissue expression ofPvChi4promoter are located 416 bp upstream of the gene. A putative negative regulatory element that is inactivated during heat shock or UV treatments was also identified between 2189 and 1445 bp. GUS activity was not detected in globular embryos, but is present in the radicle region at the heart‐shaped stage. During transition from heart‐shaped to torpedo, the activity was extended until the hypocotyl. This expression pattern was maintained until embryo maturity, when staining was detected in the whole embryo, with lower intensity in the cotyledon region. These results corroborate the current idea that this class of chitinase may have some functional role on plant development in addition to the stress response.
Cuticle characteristics and volatile emissions of petals in Antirrhinum majus
Authors: Goodwin S. Mark , Kolosova Natalia , Kish Christine M. , Wood Karl V. , Dudareva Natalia , Jenks Matthew A.
Published: March 2003

Floral volatiles, which are small and generally water‐insoluble, must move from their intracellular sites of synthesis through the outermost cuticle membrane before release from the flower surface. To determine whether petal cuticle might influence volatile emissions, we performed the first analysis of petal cuticle development and its association with the emission of flower volatiles using Antirrhinum majus L. (snapdragon) as a model system. Petal cuticular wax amount and composition, cuticle thickness and ultrastructure, and the amounts of internal and emitted methylbenzoate (the major snapdragon floral scent compound) were examined during 12 days, from flower opening to senescence. Normal (n‐) alkanes were found to be the major wax class of snapdragon petals (29.0% to 34.3%) throughout the 12 days examined. Besides n‐alkanes, snapdragon petals possessed significant amounts of methyl branched alkanes (23.6–27.8%) and hydroxy esters (12.0–14.0%). Hydroxy esters have not been previously reported in plants. Changes in amount of methylbenzoate inside the petals followed closely with levels of methylbenzoate emission, suggesting that snapdragon petal cuticle may provide little diffusive resistance to volatile emissions. Moreover, clear associations did not exist between methylbenzoate emission and the cuticle properties examined during development. Nevertheless, the unique wax composition of snapdragon petal cuticles shows similarities with those of other highly permeable cuticles, suggesting an adaptation that could permit rapid volatile emission by scented flowers.
Economic impact of cytomegalovirus in solid organ transplantation
Authors: Paya C.V.
Published: March 2003

Cytomegalovirus (CMV) infection has a direct effect on morbidity in solid organ transplantation patients, and indirect effects related to the development of opportunistic infections, allograft rejection, and patient mortality. Although intuitively it follows that costs attributable to CMV infections would be increased, direct proof has remained elusive. Accumulating evidence suggests, however, that CMV infection has a significant impact on the costs to transplantation programs, particularly in seronegative recipients of seropositive allografts (D+/R–), and additional costs may be incurred through the effects on CMV potentiating the risks of various opportunistic infections leading to graft rejection.
Disseminated toxoplasmosis after bone marrow transplantation: report of 9 cases
Authors: De Medeiros B.C. , De Medeiros C.R. , Werner B. , Loddo G. , Pasquini R. , Bleggi‐Torres L.F.
Published: March 2003

Abstract: Toxoplasma infection following bone marrow transplantation (BMT) is infrequently reported. We report 9 cases of disseminated Toxoplasma gondii infection in BMT recipients documented during an 11‐year period at our institution. The incidence of T. gondii infection in our institution (1.14 per 100 allogeneic BMT) is higher than previously reported. The most frequently affected sites were the brain, lungs, and heart. Findings common to most patients who developed toxoplasmosis were positive pre‐transplant serology, allogeneic transplant and graft‐versus‐host disease and its treatment, as well as BMT from matched unrelated donors. All 9 patients died and 8 were diagnosed only after autopsy. Heightened awareness of the occurrence of toxoplasmosis in marrow recipients, especially in highly endemic areas, and early diagnosis and therapy are needed for a better outcome.
The Epstein–Barr virus and post‐transplant lymphoproliferative disease: interplay of immunosuppression, EBV, and the immune system in disease pathogenesis
Authors: Tanner J.E. , Alfieri C.
Published: March 2003

Abstract: Transplant patients are at particular risk for developing post‐transplant lymphoproliferative disease (PTLD) following administration of immunosuppressive therapy. In many cases the PTLD lesions express Epstein–Barr virus (EBV) latent and lytic genes as well as elevated levels of host cytokines. An outline of the potential contributions of EBV, host cytokines and T cells, and the immunosuppressives cyclosporine A, tacrolimus, and anti‐CD3 antibody in the mechanism and pathogenesis of this disease is presented and discussed.
Failure of anti‐Forssman antibodies to induce rejection of mouse heart xenografts
Authors: Wu Guo‐Du , Fujii Gary , Johnson Ehrin , Swensson Joyce , Oakley Ova , Cramer Donald V.
Published: March 2003

The Forssman antigen has been proposed to be a target for the xenograft reaction in selected species combinations, including the rat and mouse, which are Forssman‐negative and ‐positive species respectively. The mouse represents an important experimental model for a variety of immune‐mediated disease processes, and the availability of a simple, inexpensive target antigen could provide an important tool for studying a selected portion of the immunologic basis for the rejection of xenografts. We have examined the potential that antibodies directed against mouse Forssman antigen could cause the hyperacute rejection of mouse heart xenografts in naive rat recipients. The Forssman antibodies tested included rat anti‐mouse (R‐anti‐M) antiserum, R‐anti‐M antiserum depleted of anti‐Forssman (anti‐F) antibodies, rat anti‐sheep red blood cell (SRBC) antiserum containing anti‐F antibodies and a rat monoclonal anti‐F IgM antibody. Our results demonstrate that the R‐anti‐M antiserum at day 4 post transplantation displayed significant titers (1:512–4096) of hemagglutinating antibodies for SRBC and mild to moderate levels of IgM that specifically binds to Forssman glycolipid (GalNAcαl–3GalNAcβl–3Galαl–4Galβ1–4Glcβ1–1ceramide) as measured by an enzyme‐linked immunosorbent assay (ELISA). Passive transfer of the R‐anti‐M serum to rats receiving mouse cardiac grafts immediately after transplantation caused hyperacute rejection of the xenografts. Sequential immunoabsorption of R‐anti‐M sera with SRBCs resulted in total removal of the anti‐Forssman activity (as defined by negative hemagglutination titer and minimal binding to Forssman glycolipid in ELISA). The anti‐F Ab‐depleted R‐anti‐M antisera, however, retained the capacity to induce hyperacute rejection of the mouse hearts [n = 6, median survival time (MST) 13 min] when passively transferred to rat recipients. Anti‐Forssman antibodies induced by immunization of LEW rats with SRBCs or a rat anti‐Forssman monoclonal antibody, mAb M.1.22.25, exhibited substantial anti‐Forssman activity (hemagglutinating titer 1: 512–4096 and moderate‐to‐strong binding to Forssman glycolipid in ELISA respectively). These antibodies also failed, however, to trigger hyperacute rejection of mouse cardiac xenografts. In conclusion, our results suggest that the rat anti‐Forssman antibodies, including those stimulated by mouse cardiac xenografts, do not appear to play a role in the immediate (hyperacute) rejection of mouse heart xenografts.
Inhibition of platelet aggregation in baboons: therapeutic implications for xenotransplantation
Authors: Alwayn Ian P. J. , Appel James Z. , Goepfert Christian , Buhler Leo , Cooper David K. C. , Robson Simon C.
Published: March 2003

Methods: Drugs tested in these experiments were aurintricarboxylic acid (ATA, von Willebrand Factor‐GPIb inhibitor), fucoidin (a selectin‐inhibitor), 1‐benzylimidazole (1‐BI, thromboxane synthase antagonist), prostacyclin (PGI2, endothelial stabilizer), heparin (thrombin antagonist), nitroprusside sodium or nicotinamide (NPN or NA, both NO‐donors), and eptifibatide (EFT, GPIIb/IIIa receptor antagonist). These were infused intravenously to nine baboons. Coagulation parameters and platelet counts were monitored and baboons were observed for adverse side‐effects. The efficacy of these agents in inhibiting platelet aggregation was assayed in a platelet aggregometer.

Results: Treatment with ATA and fucoidin resulted in complete inhibition of platelet aggregation but also in major perturbation of coagulation parameters. 1‐BI and PGI2 had no effect when administered alone, but in combination resulted in moderate inhibition of aggregation without disturbance in PT or PTT. NPN and NA had no substantive effects on platelet aggregation. Heparin resulted in specific inhibition of thrombin‐induced platelet aggregation and, as anticipated, was associated with moderate prolongation of PTT. Importantly, EFT caused complete inhibition of platelet aggregation without changes in coagulation. Platelet counts, fibrinogen levels, and fibrinogen degradation products remained within the normal ranges in all experiments.

Conclusions: Although excellent inhibition of platelet activation was obtained with ATA and fucoidin, clinical use may be precluded by concomitant disturbances of coagulation. Combinations of heparin and EFT may prove beneficial in preventing the thrombotic disorders associated with xenograft rejection while maintaining adequate hemostatic responses. These agents are to be evaluated in our pig‐to‐primate xenotransplantation models.