bluuebunny/crossref_metadata_2025 huggingface dataset:
Ethylene regulation of an ERS1 homolog in mung bean seedlings
Authors: Kim Joo Hee , Lee Jae Hyeok , Joo Sunjoo , Kim Woo Taek
Published: March 2003

ETR1 (ethylene resistant) and ERS1 (ethylene response sensor) have been shown to act as a receptor for ethylene in Arabidopsis. We isolated a full length cDNA clone (VR‐ERS1) encoding the ERS1 homolog from mung bean hypocotyls by screening a cDNA library with a partial cDNA fragment obtained by the reverse transcriptase‐polymerase chain reaction (RT‐PCR) method. VR‐ERS1 is
2 477 bp long and contains a single open reading frame encoding 636 amino acids (Mr=70.9 kDa). The predicted amino acid sequence shares a high degree of identity (72–78%) with other ERS1 homologs from Arabidopsis, tomato and Rumex palustris, and is 39% identical to Arabidopsis ERS2. Genomic Southern blot analysis using a gene‐specific probe suggests the existence of one copy of the VR‐ERS1 gene in the mung bean genome. Northern hybridization indicates that the level of VR‐ERS1 transcript varies in different parts of dark‐ and light‐grown mung bean seedlings, with the greatest amount of the transcript being detected in apical hooks. Results showed that the abundance of the message was highly inducible by ethylene in all tissues examined. However, the magnitudes of ethylene‐induction of VR‐ERS1 were significantly different in each part of mung bean seedlings, with the leaf tissue being most sensitive to ethylene and there being an 8‐fold increase in mRNA level after 6 h ethylene treatment. These results suggest that ethylene positively modulates the expression of its receptor gene in the vegetative tissues of mung bean plants.
Differential ethylene sensitivity of epidermal cells is involved in the establishment of cell pattern in theArabidopsisroot
Authors: Cao Xiao Feng , Linstead Paul , Berger Fred , Kieber Joe , Dolan Liam
Published: March 2003

Root hairs ofArabidopsisroots develop on trichoblasts located over the anticlinal (radial) walls of underlying cortical cells. Non‐hair cells, on the other hand, develop on atrichoblasts overlying the periclinal (tangential) walls of cortical cells. Dark‐grown wild‐type seedlings, which produce little ethylene, are largely root hairless. Exogenous treatment of dark‐grown plants with either ethylene or 1‐aminocyclopropane‐1‐carboxylic acid (ACC) restores the development of root hairs in cells overlying the anticlinal cortical cell walls, indicating that cells in this position are more sensitive to ethylene than atrichoblasts. We used mutations in genes that overproduce ethylene (eto1,eto2,eto3andeto4) to illustrate the positive regulatory role of ethylene. The preferential development of root hairs on epidermal cells overlying the cortical anticlinal cell walls in these mutants also illustrates that trichoblasts are more sensitive to ethylene than atrichoblasts.CTR1is a negative regulator of the ethylene response and might, therefore, be a candidate regulator of differential sensitivity.CTR1mRNA is expressed in all cell types in the root, suggesting that its transcriptional pattern alone cannot account for the differential sensitivity of epidermal cells to ethylene. Cellular mapping of wild‐type and mutant roots supports previous findings indicating that ethylene acts after, and perhaps independently, ofTTGduring the establishment of cell fate in the root epidermis.
Genotypic variation within Zea mays for susceptibility to and rate of recovery from chill‐induced photoinhibition of photosynthesis
Authors: Aguilera C. , Stirling C. M. , Long S. P.
Published: March 2003

Six genotypes of Zea mays L. were grown in pots inside a glasshouse at a mean temperature of 22±2°C and a minimum photosynthetic photon flux density (Q) during the daylight period of 400 μmol m−2 s−1. Chilling‐dependent photoinhibition was induced by exposing plants to a temperature of 7°C and a Q of 1 000 μmol m−2 s−1 for 6 h. Recovery from photoinhibition was then followed at a temperature of 25°C and a Q of 200 μmol m−2 s−1. Leaf gas exchange and chlorophyll fluorescence were measured on attached leaves at room temperature prior to the photoinhibitory treatments and at 6 sampling intervals from 0 to 24 h during the recovery period. The relative water content (RWC) was also measured during the recovery period. The results showed a significant genotypic variation in the susceptibility to and rate of recovery from chilling‐dependent photoinhibition of photosynthesis in Zea mays seedlings. The Highland Pool 1a from highland sites in Mexico was the least susceptible to chill‐induced photoinhibition, but had the slowest rate of recovery. The hybrid variety LG11 showed the highest rate of recovery, whilst the inbred line ZPF307 was the most susceptible to chill‐induced photoinhibition. Susceptibility to photoinhibition and subsequent recovery were at least partially independent, suggesting that selection for improved genotypes will require independent selection for both tolerance and capacity for recovery. Although chlorophyll fluorescence provided a more rapid method of assessing the occurrence of photoinhibition, it was not as effective as direct gas‐exchange measurements of the maximum quantum yield of photosynthesis (φ) in separating genotypes with respect to their susceptibility to photoinhibition, especially in the most vulnerable genotypes such as ZPF307. Water stress induced by chilling and high Q treatments appeared to impair the recovery processes. Decreases in stomatal conductance (gs) produce a significant decrease in intercellular CO2 concentration (Ci), although this decrease was never so extreme that it limited photosynthetic rates at the light intensities used to determine φ. Nevertheless, closure of stomata in patches, producing local restriction of CO2 supply, would explain the poor correlation between chlorophyll fluorescence and quantum yield measurements in some genotypes immediately after photoinhibitory treatments.
Molecular and functional properties of highly purified transcriptionally active chromosomes from spinach chloroplasts
Authors: Krause Kirsten , Krupinska Karin
Published: March 2003

In the present work we describe the preparation of highly purified, transcriptionally active chromosomes (TACs) from spinach chloroplasts by refinement and improvement of the method commonly used so far. The plastid DNA‐bound TAC‐RNA polymerase and soluble plastid RNA polymerase were efficiently separated from each other with a single gel filtration step that is preceded by protamine sulfate precipitation and treatment with heparin. Removal of all detergents from the extraction buffer in a further purification step drastically increases the specific transcriptional activity and yields a 23 000‐fold purification compared to the crude chloroplast extract. The purified TAC extract reveals 10 highly enriched proteins among 30‐40 identifiable polypeptides. The rpoA gene product encoded by the plastid DNA was copurified with the transcriptional activity through all purification steps, confirming its functional integrity in the TAC complex. The transcript patterns of crude and highly purified TAC extracts are identical for 10 selected chloroplast genes, indicating no influence of the purification steps on transcriptional selectivity. The reported method provides a basis for the identification and analysis of the components of the TAC fraction in general and of the TAC‐associated RNA polymerase in particular.
Effects of ultraviolet‐B radiation on leaf elongation, production and phenylpropanoid concentrations of Deschampsia antarctica and Colobanthus quitensis in Antarctica
Authors: Ruhland Christopher T. , Day Thomas A.
Published: March 2003

Stratospheric ozone depletion by anthropogenic chlorofluorocarbons has lead to increases in ultraviolet‐B radiation (UV‐B; 280–320 nm) along the Antarctic Peninsula during the austral spring. We manipulated UV‐B levels around plants of Antarctic hair grass (Deschampsia antarctica; Poaceae) and Antarctic pearlwort (Colobanthus quitensis; Caryophyllaceae) for one field season near Palmer Station along the west coast of the Antarctic Peninsula. Treatments involved placing frames over naturally growing plants that either (1) held filters that absorbed most biologically effective radiation (UV‐BBE; ‘reduced UV‐B’, 22% of ambient UV‐BBE levels), (2) held filters that transmitted most UV‐BBE (‘near‐ambient UV‐B’, 87% of ambient UV‐BBE levels), or (3) lacked filters (‘ambient UV‐B’). Leaves on D. antarctica exposed to near‐ambient and ambient UV‐B were 16–17% shorter than those exposed to reduced UV‐B, and this was associated with shorter epidermal cells at the leaf base and tip. Leaves on C. quitensis exposed to near‐ambient and ambient UV‐B tended to be shorter (P=0.18) and epidermal cells at the leaf base tended to be smaller than those under reduced UV‐B (P<0.10). In order to further explain reductions in leaf length, we examined leaf concentrations of insoluble (cell‐wall bound) phenylpropanoids, since it has been proposed that wall‐bound phenylpropanoids such as ferulic acid may constrain cell expansion and leaf elongation. In both species, HPLC analysis revealed that ferulic and p‐coumaric acid were major components of both insoluble and soluble phenylpropanoids. Although there were no significant differences in concentrations between UV‐B treatments, concentrations of insoluble ferulic acid in D. antarctica tended to be higher under ambient and near‐ambient UV‐B than under reduced UV‐B (P=0.17). We also examined bulk‐leaf concentrations of soluble (methanol extractable) UV‐B‐absorbing compounds and found that concentrations were higher in plants exposed to near‐ambient and ambient UV‐B than in plants exposed to reduced UV‐B. We also assessed the UV‐B‐screening effectiveness of leaves that had developed on plants at the field site with a fiber‐optic microprobe. Leaf epidermal transmittance of 300‐nm UV‐B was 4.0 and 0.6% for D. antarctica and C. quitensis, respectively, which is low compared to grasses and herbaceous dicotyledonous plants found in more temperate climates. While the leaves of Antarctic vascular plants are relatively effective at screening UV‐B, levels of UV‐B in Antarctica are sufficient to reduce leaf epidermal cell size and leaf elongation in these species, although the mechanisms for these reductions remain unclear.
Uptake of 13C‐glucose by cell suspensions of carrot (Daucus carota) measured by in vivo NMR: Cycling of triose‐, pentose‐ and hexose‐phosphates
Authors: Krook Janhendrik , Vreugdenhil Dick , Dijkema Cor , Van Der Plas Linus H.W.
Published: March 2003

After a lag phase of 2 days, batch‐grown cells of carrot (Daucus carota L.) cv. Flakkese entered the exponential growth phase and started to accumulate sucrose and hexoses. Short‐term feeding 13C‐glucose in this period resulted in only minor labelling of sucrose or fructose. CO2 production from [1‐13C]‐ and [6‐13C]‐glucose revealed, that at least 40% of the added glucose passed through the oxidative pentose phosphate pathway (OPPP), up to 40% through glycolysis leaving only minor 13C‐glucose for incorporation in various cell components in the exponential growth phase. After about 11 days of culture, the medium sugars were exhausted, cells entered the stationary growth phase and consumed stored sugar. Both neutral and acid invertase (EC 3.2.1.26) and sucrose synthase (EC 2.4.1.13) increased 50% from day 0 to days 11–13; thereafter their levels decreased again. Labelling with 13C‐glucose resulted in the accumulation of labelled sucrose and fructose during the stationary growth phase. Sucrose labelling was transient, i.e. after 6 h its level started to decrease again. Labelled fructose, however, evolved slower and increased even after 8 h. In sucrose and fructose up to 20% of the 13C‐label was exchanged from C‐1 to C‐6 carbons, indicating intensive cycling of at least 40% of the carbon between hexoses and triose phosphates. In the stationary phase only 10% of the labelled glucose passed through the OPPP and about 30% passed through the respiratory pathway; the remaining 60% was incorporated in cell constituents and sugars. Comparing the various cycles revealed that the regulation of the OPPP operated relatively independently from the cytosolic cycling of hexose phosphates through sucrose and from the cycling between hexose phosphates and triose phosphates.
Formation of a hexokinase complex is associated with changes in energy utilization in celery organs and cells
Authors: Yamamoto Yuri T. , Prata Rogerio T. N. , Williamson John D. , Weddington Megan , Pharr D. Mason
Published: March 2003

We previously presented evidence that the hexose‐regulated repression of the mannitol catabolic enzyme mannitol dehydrogenase (MTD) in celery (Apium graveolens L.) may be mediated by hexokinase (EC 2.7.1.1) (HK) [Prata et al. (1997) Plant Physiol 114: 307–314]. To see if differential regulation of HK forms might be involved in the sugar‐regulated repression of MTD we characterized two forms of HK with respect to their expression in various plant organs as well as in celery suspension cell cultures. We found that the vast majority of HK activity was membrane‐associated, whereas fructokinase (EC 2.7.1.4) was found largely in the soluble cell fraction. Gel filtration chromatography further revealed the differential expression of two molecular size classes of HK. One HK (HK‐L) chromatographed at 68 kDa, a typical size for a plant HK, while the second (HK‐H) chromatographed at 280 kDa. This unique 280 kDa HK was shown to be composed of a 50 kDa HK protein, possibly complexed with other, as yet unidentified, components. The HK‐L was present in all cells and organs analyzed, and thus may be a likely candidate for mediation of sugar repression. In contrast, the presence of the HK‐H complex was specific to certain organs and cells grown under certain conditions. Our analyses here showed no correlation between the presence of the HK‐H and MTD repression or derepression in celery cells. Instead, the HK‐H complex was present exclusively in rapidly growing organs and cells, but not in non‐growing celery storage tissues or in carbon‐depleted celery suspension‐cultured cells. Furthermore, the HK‐H complex was present when Glc in the growth media was replaced with 2‐deoxy Glc, a HK substrate that does not provide energy for growth and metabolism. These results imply that the HK‐H complex may have a potentially unique role in the metabolism of rapidly growing celery cells, in particular, in hexose phosphorylation. We also found that mitochondria prepared from Glc‐grown celery suspension‐cultured cells contained substantial HK activity, and that oxygen uptake of these mitochondria was stimulated by Glc. These results are consistent with the hypothesis that mitochondrial localization of celery HK may play a role in rapid recycling of adenylate.
Difference in zeaxanthin formation in nitrate‐ and ammonium‐grown Phaseolus vulgaris
Authors: Bendixen Roy , Gerendás Joska , Schinner Katrin , Sattelmacher Burkhard , Hansen Ulf Peter
Published: March 2003

Absorption at 505 nm and high‐performance liquid chromatography showed that light‐induced conversion of violaxanthin to antheraxanthin and zeaxanthin was much stronger in leaves of nitrate‐ than in leaves of ammonium‐grown Phaseolus vulgaris. Feeding ascorbate via the petiole increased zeaxanthin formation in ammonium‐grown plants. However, there was no difference in energy quenching, qE, or photoinhibition (measured as FV/FM), as determined by chlorophyll fluorescence in nitrate‐ and ammonium‐grown plants. Dithiothreitol decreased the light‐induced stimulation of zeaxanthin formation and increased photoinhibition in nitrate‐grown plants, suggesting that these plants utilize zeaxanthin for the protection of photosystem II (PSII). Ammonium‐grown plants seem to have established an alternative way to protect PSII.
Dark‐inducible genes from Arabidopsisthaliana are associated with leaf senescence and repressed by sugars
Authors: Fujiki Yuki , Yoshikawa Yoko , Sato Tokuyuki , Inada Noriko , Ito Masaki , Nishida Ikuo , Watanabe Akira
Published: March 2003

We have isolated 5 cDNA clones (din2,din6, din9, din10 and din11) corresponding to genes, the transcripts of which accumulated in leaves of Arabidopsisthaliana kept in the dark. These cDNA clones encode proteins similar to β‐glucosidase (EC 3.2.1.21, din2), asparagine synthetase (EC 6.3.5.4, din6), phosphomannose isomerase (EC 5.3.1.8, din9), seed imbibition protein (din10) and 2‐oxoacid‐dependent dioxygenases (din11). Accumulation of the transcripts from din6 and din10 occurred within 3 h after plants were transferred to darkness. The transcripts from din2,din9 and din11 were only detected after 24 h of dark treatment. We also observed the accumulation of the din transcripts in senescing leaves. Application of a photosynthesis inhibitor, 3‐(3,4‐dichlorophenyl)‐1‐1‐dimethyl‐urea, induced the expression of the din genes under illumination. Application of sucrose to detached leaves suppressed the accumulation of the din transcripts in the dark. These results indicate that expression of these genes partly depends on cellular sugar level. The sugar‐modulated expression of the din genes suggests that dark‐induced expression of these genes might be related to sugar starvation occurring in leaf cells in the dark, when the photosynthesis is hindered.
Is the infiltration‐centrifugation technique appropriate for the isolation of apoplastic fluid? A critical evaluation with different plant species
Authors: Lohaus Gertrud , Pennewiss Kerstin , Sattelmacher Burkhard , Hussmann Melanie , Hermann Muehling Karl
Published: March 2003

The suitability of the infiltration‐centrifugation method for collection of apoplastic fluid from intact leaves was evaluated for different plant species. Large differences with respect to infiltrability of the leaves, which correlated inversely with stomatal and mesophyll resistance, became apparent. Osmolality of infiltration medium (deionised water, 0.2 mM CaCl2, 10 mM KCl, 180 mM 2‐[N‐morpholino]ethane‐sulphonic acid) and incubation time, time passed between onset of infiltration and end of centrifugation, revealed relatively little influence on the composition of the apoplastic washing fluid (AWF). In contrast, the pH of the infiltrated solution highly influenced the concentration of sucrose and hexoses. With increasing centrifugation force, hexosephosphate isomerase (HPI) activity in the AWF, which was taken as an indication for cytoplasmic contamination, increased. At the same time, Ca2+ concentration in the AWF increased even more. Since Ca2+ cannot originate from the cytoplasm, the suitability of HPI as marker for cytoplasmic contamination is questioned. From the composition of the AWF, it is concluded that, if centrifugation force does not exceed 1

 000 g, cytoplasmic contamination is negligible and that the infiltration‐centrifugation technique reveals an easy and inexpensive way to study apoplastic solutes. The infiltration‐centrifugation method was also suitable to determine apoplastic air volume (Vair) and apoplastic water volume (Vwater), which are necessary for the calculation of the ion concentration in the leaf apoplast. It could be shown that the leaves of different species and the apical and basal leaves of single plants differ in Vair and Vwater.
Effects of cytokinin on ethylene production and nodulation in pea (Pisumsativum) cv. Sparkle
Authors: Lorteau Marie‐Agathe , Ferguson Brett James , Guinel Frédérique Catherine
Published: March 2003

In this study, we were interested in learning if cytokinins play a role in the developmental process that leads to nodulation in the pea cv. Sparkle. We demonstrate that the application of the synthetic cytokinin BAP (6‐benzyl‐amino‐purine) results in a number of nodulation‐related changes. BAP stimulates the production of ethylene, a known inhibitor of nodulation. At low levels (up to 1 μM), BAP also stimulates nodulation but as its concentration is increased (up to 25 μM), nodule number decreases. In BAP‐treated roots, the infection threads are abnormal; they are twisted, very knotty, and generally grow in a direction parallel to the root surface. In addition, the centers of cell division in the inner cortex are very few. Thus, BAP‐treated Sparkle appears to phenocopy the low‐nodulating pea mutant R50 [Guinel FC, Sloetjes LL (2000) Ethylene is involved in the nodulation phenotype of Pisum sativum R50 (sym 16), a pleiotropic mutant that nodulates poorly and has pale green leaves. J Exp Bot 51: 885–894]. However, it appears doubtful that there is a direct correlation between the actions of cytokinin and ethylene in causing a reduction in nodule organogenesis because nodulation is not restored by treating BAP‐treated Sparkle with ethylene inhibitors.
Ethylene‐triggered abscisic acid: A principle in plant growth regulation?
Authors: Grossmann Klaus , Hansen Hauke
Published: March 2003

The application of auxins to sensitive plant species or their overproduction in transgenic plants stimulates ethylene biosynthesis via induction of 1‐aminocyclopropane‐1‐carboxylic acid (ACC) synthase. Recent studies with auxin herbicides and indole‐3‐acetic acid (IAA) have revealed that auxin‐stimulated ethylene triggers an increase in the biosynthesis of abscisic acid (ABA), which then functions as a second messenger, leading to growth inhibition and senescence. This raises the question of whether ethylene‐triggered ABA is restricted to the action of auxin herbicides or whether it is a widespread phenomenon in the normal plant growth regulation. Our own results and a reappraisal of the literature indicate that ethylene‐induced ABA may, indeed, play a role in natural physiological phenomena, such as root gravireaction and suppression of lateral bud growth in apical dominance. In addition, it would be worthwhile to investigate whether ethylene‐triggered ABA is involved in other processes which coincide with a strong stimulation of ethylene biosynthesis, such as growth inhibition induced by cytokinins and senescence elicited under stress conditions.
Photoperiodic control of dormancy in Sedum telephium and some other herbaceous perennial plants
Authors: Heide O. M.
Published: March 2003

The environmental control of dormancy and flowering of the herbaceous perennial Sedum telephium was studied in controlled environments. Short photoperiods induced growth cessation and the formation of resting buds in both seedlings and mature plants, whereas long photoperiods resulted in immediate growth activation of dormant buds. No chilling was required for dormancy release, even in plants induced to dormancy and maintained at high temperature (21°C) for more than 3 months. The critical photoperiod for dormancy release was about 15 h, a minimum of four long‐day (LD) cycles (24 h) being required. The true photoperiodic nature of this response was ascertained by night interruption experiments. Flowering of S. telephium was found to have an obligatory LD requirement, with no requirement for vernalization. The critical photoperiod and minimum number of inductive cycles for floral induction were the same as for dormancy release. Dormancy release by long days was also obtained in preliminary experiments with three other herbaceous perennials. The eco‐physiological significance of photoperiodic control of dormancy is discussed, and it is concluded that the mechanism ensures stability of winter dormancy, even under conditions of climatic warming.
Ascorbate transport from the apoplast to the symplast in intact leaves
Authors: Kollist Hannes , Moldau Heino , Oksanen Elina , Vapaavuori Elina
Published: March 2003

Infiltration of reduced ascorbate (ASC) into the leaves of Betula pendula Roth and subsequent measurement of its loss therein after incubation allowed us to follow ascorbate transport from apoplast to symplast in intact leaves. All of the ascorbate extracted from the native apoplast was in fully oxidized form, dehydroascorbate (DHA). When 5 mM of ASC was infiltrated into the leaves, its intense decay occurred, but only 55% of ASC lost was recovered in apoplast as DHA. When ASC was added to the freshly extracted intercellular washing fluid (IWF), ASC oxidation occurred as well. However, all oxidized ASC was recovered as DHA, indicating that further decomposition of DHA did not occur. Similarly, all of the ASC infiltrated into the leaves was found therein either as ASC or DHA after incubation of leaves for up to 60 min. On this base the ascorbate infiltrated into the leaves and not recovered in the IWF was interpreted as ascorbate taken up into the symplast. The calculated uptake rates of ascorbate at different ASC concentrations followed saturation kinetics with the maximum uptake rate of 300 nmol m−2 plasma membrane (PM) area min−1 and Michaelis constant of 12.8 mM. The uptake of ascorbate was significantly inhibited by the addition of dithiothreitol or by PM H+ ATPase inhibitor erythrosin B. Thus, our results support the previous observations that DHA is preferably transported from the apoplastic to the cytoplasmic side of the membrane and show that this process is dependent upon PM proton gradient.
Susceptibility to low‐temperature photoinhibition and the acquisition of freezing tolerance in winter and spring wheat: The role of growth temperature and irradiance
Authors: Pocock Tessa H. , Hurry Vaughan , Savitch Leonid V. , Huner Norman P. A.
Published: March 2003

Five winter and five spring wheat (Triticum aestivum L.) cultivars were grown under either control conditions (20°C/250 photosynthetic photon flux density (PPFD) [μmol m−2 s−1]), high irradiance (20°C/800 PPFD) or at low temperature (either 5°C/250 PPFD or 5°C/50 PPFD). To eliminate any potential bias, the wheat cultivars were arbitrarily chosen without any previous knowledge of their freezing tolerance or photosynthetic competence. We show that the differential susceptibilities to photoinhibition exhibited between spring and winter wheat cultivars, as assessed by chlorophyll fluorescence cannot be explained on the basis of either growth irradiance or low growth temperature per se. The role of excitation pressure is discussed. We assessed the correlation between susceptibility to low‐temperature photoinhibition, maximum ribulose 1,5‐bisphosphate carboxylase‐oxygenase (EC 4.1.1.39) and NADP‐dependent malate dehydrogenase (EC 1.1.1.82) activities, chlorophyll and protein concentrations and freezing tolerance determined by electrolyte leakage. Susceptibility to photoinhibition is the only parameter examined that is strongly and negatively correlated with freezing tolerance. We suggest that the assessment of susceptibility to photoinhibition may be a useful predictor of freezing tolerance and field survival of cereals.
Induction by pathogen, salt and drought of a basic class II chitinase mRNA and its in situ localization in pepper (Capsicum annuum)
Authors: Hong Jeum Kyu , Hwang Byung Kook
Published: March 2003

Northern blot and in situ hybridization analyses revealed that a pepper basic class II chitinase gene (CAChi2) is constitutively expressed in floral organs and root endodermis, but not in leaf, stem and fruit of pepper. Resistance of pepper leaves to Colletotrichum coccodes infection at a late growth stage was correlated with induction of β−1,3‐glucanase and PR‐1 mRNA, but not of chitinase (CAChi2) mRNA. Transcriptional activation of the CAChi2 gene in pepper leaves occurred during anthracnose development. The CAChi2 transcripts were mainly localized in phloem cells of vascular tissues of pepper leaves infected with C. coccodes. The CAChi2 gene was also differentially induced in leaf and stem tissue by treatment with abscisic acid (ABA), sodium chloride or drought. Strong accumulation of the CAChi2 transcripts occurred in pepper stem tissues due to high salt and drought, and also due to treatment with ABA. These results suggest involvement of the chitinase gene in protection of pepper plants against the pathogen, but also document cross talk with stress signals mediated by ABA, high salinity and drought.
The tomato ethylene receptor gene family: Form and function
Authors: Klee Harry , Tieman Denise
Published: March 2003

Phytohormones are essential for integrating many aspects of plant development and responses to the environment. Regulation of hormonally controlled events occurs at multiple levels: synthesis, catabolism and perception (Trewavas 1983, Bradford and Trewavas 1994). At the level of perception, sensitivity to hormones can be regulated both spatially and temporally during the life cycle. An example of spatial regulation is the differential response to a hormone that occurs during organ abscission. Temporally, sensitivity of an organ to a hormone may change during maturation, as occurs during fruit ripening. In this review, we will focus on the initial event in recognition of one hormone, ethylene. The ethylene receptor was the first plant hormone receptor to be unambiguously identified. Over the last few years, great progress has been made in elucidating the genes involved in ethylene action. Nonetheless, the mechanisms of signal transduction remain to be established. Here, we will address the status of the tomato receptor gene family and the evidence that regulation of receptor gene expression can influence the response of the plant to the hormone.
Characterization of mutants with reduced seed dormancy  at two novel rdo loci and a further characterization of rdo1 and rdo2 in Arabidopsis
Authors: Peeters Anton J. M. , Blankestijn‐de Vries Hetty , Hanhart Corrie J. , Léon‐Kloosterziel Karen M. , Zeevaart Jan A. D. , Koornneef Maarten
Published: March 2003

Seed dormancy and germination are complex traits that are controlled by many genes. Four mutants in Arabidopsis thaliana exhibiting a reduced dormancy phenotype, designated rdo1, rdo2, rdo3, and rdo4, have been characterized, both genetically and physiologically. Two of these mutants, rdo1 and rdo2, have been described before, the other two represent novel loci. The mutants mapped on chromosome 1 (rdo3), chromosome 2 (rdo2 and rdo4), and chromosome 3 (rdo1). None of these loci has been related to dormancy before. All four mutants show pleiotropic effects in the adult plant stage, which are different for each mutant. None of the mutants is deficient in ABA. Compared to Ler (wild‐type), ABA sensitivity is not altered either, thereby excluding the possibility that ABA is involved in causing the reduced dormancy phenotype. The GA requirement was studied by using the GA biosynthesis inhibitor paclobutrazol, and genetically by generating double mutants with the GA‐deficient mutant ga1‐3. The results obtained by these two methods were comparable for all but one mutant: rdo1. In a GA‐deficient background, rdo1, rdo2 and rdo3, all show sensitivity to GA between that of ga1‐3 and ga1‐3 aba1. However, when using paclobutrazol rdo1 exhibited the same sensitivity as rdo4 and wild‐type. Analysis of double mutants among the rdo mutants revealed a very complex and inconsistent pattern.
Allelochemical stress produced by the aqueous leachate of Callicarpa acuminata: effects on roots of bean, maize, and tomato
Authors: Cruz‐Ortega Rocío , Ayala‐Cordero Gabriela , Anaya Ana Luisa
Published: March 2003

The in vitro effects of an aqueous leachate (1%) of Callicarpa acuminata Kunth. (Verbenaceae) on radicle growth, protein expression, catalase activity, free radical production and membrane lipid peroxidation in roots of bean, maize, and tomato were examined. Aqueous extract of C. acuminata inhibited the radicle growth of tomato by 47%, but had no effect on root growth of maize and beans. 2D‐PAGE and densitometry analysis showed that C. acuminata aqueous leachate modified the expression of various proteins in the roots of all treated plants. In treated bean roots, microsequencing analysis of an 11.3‐kDa protein, whose expression was enhanced by leachate treatment, revealed a 99% similarity with subunits of α‐amylase inhibitor of other beans. A 27.5‐kDa protein induced in treated tomato showed 69–95% similarity to glutathione‐S‐transferases (GST) of other Solanaceae. Spectrophotometric analysis and native gels revealed that catalase activity was increased by 2.2‐fold in tomato roots and 1.4‐fold in bean roots. No significant changes were observed in treated maize roots. Luminol chemiluminescence levels, a measure of free radicals, increased 3.8‐fold in treated tomato roots and 2.1‐fold in treated bean roots. Oxidative membrane damage in treated roots was measured by lipid peroxidation rates. In tomato we observed a 2.4‐fold increase in peroxidation, however, no effect was observed in maize or beans.
Methods and approaches to study plant mitochondrial alternative oxidase
Authors: McDonald Allison E. , Sieger Stephen M. , Vanlerberghe Greg C.
Published: March 2003

The alternative oxidase is a non‐proton motive ‘alternative’ to electron transport through the cytochrome pathway. Despite its wasteful nature in terms of energy conservation, the pathway is likely present throughout the plant kingdom and appears to be expressed in most plant tissues. A small alternative oxidase gene family exists, the members of which are differentially expressed in response to environmental, developmental and other cell signals. The alternative oxidase enzyme possesses tight biochemical regulatory properties that determine its ability to compete with the cytochrome pathway for electrons. Studies show that alternative oxidase can be a prominent component of total respiration in important crop species. All these characteristics suggest this pathway plays an important role in metabolism and/or other aspects of cell physiology. This brief review is an introduction to experimental methods and approaches applicable to different areas of alternative oxidase research. We hope it provides a framework for further investigation of this fascinating component of primary plant metabolism.
Spatial expression pattern of SAG12:GUS transgene in tobacco (Nicotiana tabacum)
Authors: Grbić Vojislava
Published: March 2003

Senescence syndrome is characterized by the breakdown of nutrients in senescing organs and their remobilization to the other parts of the plant. While proteases, nucleases, and proteins involved in nitrogen and lipid metabolism have been identified as cDNAs showing senescence‐specific or senescence‐preferred expression in many plant species, little is known about their spatial expression pattern that leads to the co‐ordinated senescence of the whole organ. In order to elucidate the spatial regulation of SAGs, we have examined the expression pattern of SAG12:GUS in transgenic tobacco plants (Nicotiana tabacum cv. Wisconsin 38). The SAG12 promoter was ubiquitously active in senescing leaves, however, specific SAG12 expression domains were found in senescing flowers.
Aquaporin functionality in relation to H+‐ATPase activity in root cells of Capsicum annuum grown under salinity
Authors: Martínez‐Ballesta M. Carmen , Martínez Vicente , Carvajal Micaela
Published: March 2003

As water and nutrient uptake should be related in the response of plants to salinity, the aim of this paper is to establish whether or not aquaporin functionality is related to H+‐ATPase activity in root cells of pepper (Capsicum annuum L.) plants. Thus, H+‐ATPase activity was measured in plasma membrane vesicles isolated from roots and aquaporin functionality was measured using a cell pressure probe in intact roots. Salinity was applied as 60 mM NaCl or 60 mM KCl, to determine which ion (Na+, K+ or Cl−) is producing the effects. We also investigated whether the effects of both salts were ameliorated by Ca2+. Similar results were obtained for cell hydraulic conductivity, Lpc, and H+‐ATPase activity, large reductions in the presence at NaCl or KCl and an ameliorative effect of Ca2+. However, fusicoccin (an activator of H+‐ATPase) did not alter osmotic water permeability of protoplasts isolated from roots. Addition of Hg2+ inhibited both ATPase and aquaporins, but ATPase also contains Hg‐binding sites. Therefore, the results indicate that H+‐ATPase and aquaporin activities may not be related in pepper plants.
Fungal infections in patients undergoing blood and marrow transplantation
Authors: Marr K.A. , Bowden R.A.
Published: March 2003

Fungal infections are currently a leading cause of infectious morbidity and mortality in patients undergoing allogeneic blood and marrow transplantation (BMT). Although the introduction of azole antifungals for prophylaxis has had a significant impact on the incidence of candidal infections (especially those caused by C. albicans and C. tropicalis), invasive aspergillosis has increased in incidence in many centers worldwide. Given the long risk period corresponding with graft‐versus‐host disease, and the toxicities of currently available mold‐active antifungals, the development of a prevention strategy for these angioinvasive molds remains a challenge. The introduction of new antifungal drugs and adjunctive therapy to improve immune function may be beneficial in decreasing mortality associated with these infections in the future. Most importantly, a greater understanding of the pathogenesis of fungal disease and specific host risks is necessary to impact this increasingly important infection in immunocompromised hosts.
Cidofovir treatment of human polyomavirus‐associated acute haemorrhagic cystitis
Authors: González‐Fraile M.I. , Cañizo C. , Caballero D. , Hernández R. , Vázquez L. , López C. , Izarra A. , Arroyo J.L. , De La Loma A. , Otero M.J. , San Miguel J.F.
Published: March 2003

Abstract: We report the case of an 18‐year‐old patient who received an allogeneic bone marrow transplant from an HLA‐identical unrelated donor for a Ph+ acute lymphoblastic leukemia, in his third complete remission. Cyclophosphamide and busulfan were used as conditioning treatment. Acute graft‐versus‐host disease developed on day +9, and the response to adequate treatment (steroids) was favourable. On day +45 the patient developed an acute severe haemorhragic cystitis, and BK polyomavirus was demonstrated in urine samples using electron microscopy and polymerase chain reaction. Urinary symptoms did not improve in spite of palliative treatment, but a response was evident after 2 weeks of cidofovir treatment.
Immunopathogenesis of hepatitis C virus in the immunosuppressed host
Authors: Einav S. , Koziel M.J. , Einav Koziel S., M.J.
Published: March 2003

The prevalence of chronic hepatitis C virus (HCV) infection among various groups of immunosuppressed patients is high. These groups include patients co‐infected with human immunodeficiency virus (HIV), recipients of organ transplants, and those with hypogammaglobulinemia. The liver disease in the immunosuppressed host is typically severe with an unusually rapid progression to cirrhosis. This is somewhat paradoxical, as the classical model for HCV‐induced liver disease assumes that cell‐mediated immune responses induce liver injury. It is likely that a combination of viral‐related factors and host‐related factors plays a role in this accelerated natural history of HCV. Data are accumulating in immunocompromised hosts that address the immunopathogenesis of liver injury, although there are still fundamental gaps in our understanding of this process. In this review, we will focus on our current understanding of the mechanisms of liver injury and how it relates to the accelerated liver disease progression in immunocompromised hosts.
Intravenous synthetic αgal saccharides delay hyperacute rejection following pig‐to‐baboon heart transplantation
Authors: Romano Egidio , Neethling Francisca A. , Nilsson Kurt , Kosanke Stanley , Shimizu Akira , Magnusson Stefan , Svensson Lola , Samuelsson Bo , Cooper David K. C.
Published: March 2003

Romano E, Neethling FA, Nilsson K, Kosanke S, Shimizu A, Magnusson S, Svensson L, Samuelsson B, Cooper DKC Intravenous synthetic αgal saccharides delay hyperacure rejection following pig‐to‐baboon heart transplantation. Xenotransplantation 1999; 6: 00‐00

Several oligosaccharides containing the terminal structure Galα1–3Gal (αGal) and different side chains were tested in vitro for their ability to block natural antiαGal antibodies. A di‐and a trisaccharide (diαGal and triαGal) were selected. A blood group B baboon, having IgG and IgM natural antipig titers of 1 : 256 and 1 : 1024 and a hemolytic titer (to pig red blood cells, RBCs) of 1 : 8, was chosen to measure pharmacokinetic parameters of the saccharides and to assess the extent of in vivo neutralization of the antibodies. Three grams each of the diαGal and the triαGal dissolved in saline were administered by bolus intravenous (i.v.) injection. Blood samples were collected at various times and urine was collected at 8 and 24 h. Plasma and urine concentrations of the αGal saccharides were estimated by an ELISA specially developed for this study. A fast distribution phase followed by equilibrium and excretion phases were observed, indicating a T1/2 in the order of 1 h. Fifty‐eight per cent of the saccharides were recovered in the urine within 24 h. Determination of antipig antibody binding by FACS analysis and of serum cytotoxicity titers for pig endothelial cells demonstrated that a 70% reduction in binding and cytotoxicity could be achieved with plasma saccharide levels of 300–400 µg/ml. Six months later, a pig heart was transplanted heterotopically into the baboon. A 3‐g bolus of the saccharide mixture (1.5 g of each saccharide) was given i.v. before allowing blood reperfusion of the transplanted heart, followed by an i.v. infusion of 1 g/hr for 1 hr and 0.5 g/hr for the 3 succeeding hours. Blood concentrations of the saccharides, CH50, hematology and cytotoxicity for PK15 cells were estimated in blood samples taken at various times. Heart function was observed to be satisfactory for 8 h, but was found to have ceased at 18 h. Myocardial biopsies taken at 3 and 5 h showed congestion only, suggestive of minimal vascular rejection, but by 18 h demonstrated severe vascular rejection. In conclusion, αGal saccharide therapy given for a period of 4 h delayed, but did not totally prevent, the development of vascular rejection in the pig‐to‐baboon heart transplant model. αGal saccharide therapy may be one of several useful approaches for the prevention of hyperacute rejection in pig‐to‐primate organ transplantation.
Venular thrombosis is the key event in the pathogenesis of antibody‐mediated cardiac rejection
Authors: Rose Alan G. , Cooper David K. C.
Published: March 2003

Abstract: A review of the histopathologic features of serial biopsies and excised grafts of 117 experimental and clinical cardiac allografts and xenografts revealed a common sequence in the development of histopathologic changes in grafts showing antibody‐mediated (hyperacute and acute vascular) rejection. Based on these observations, we propose the new concept that thrombosis of cardiac veins and venules is the initial key event in antibody‐mediated rejection. This is followed by the development of congestion in the subtended venules and capillaries accompanied by interfascicular and, later, intermyocyte edema. Subsequently, focal or diffuse interstitial hemorrhage affecting the subendocardium, extending sometimes to involve the inner half of the ventricular myocardium, is observed. Antibody‐mediated rejection therefore appears to be analogous to incomplete venous infarction of the heart. The observed histopathology (in which venular thrombosis plays a key role) favors a thrombogenic basis for the classical features of antibody‐mediated rejection, namely edema, vascular thrombi and interstitial hemorrhage. A key role for venular thrombosis would explain the non‐uniform distribution of the changes and may suggest new ways of preventing antibody‐mediated xenograft rejection.
C1‐Inhibitor for treatment of acute vascular xenograft rejection in cynomolgus recipients of h‐DAF transgenic porcine kidneys
Authors: Vangerow Burkhard , Hecker Jens M. , Lorenz Ralf , Loss Martin , Przemeck Michael , Appiah Richard , Schmidtko Jan , Jalali Arman , Rueckoldt Horst , Winkler Michael
Published: March 2003

Abstract: At present, the major barrier to successful discordant xenotransplantation of unmodified or complement regulator transgenic porcine xenografts is acute vascular xenograft rejection (AVR). AVR is associated with the intragraft deposition of induced recipient xenoreactive antibodies and subsequent complement activation. In a life‐supporting pig to primate kidney xenotransplantation setting using h‐DAF transgenic donor organs and postoperative immunosuppression, episodes of AVR were either treated with boluses of cyclophosphamide and steroids or with the same regimen supplemented by a three‐day course of C1‐Inhibitor, a multifunctional complement regulator. In 8 out of 10 animals stable initial graft function was achieved; in all animals one or more episodes of AVR were observed. When, in 4 animals, C1‐Inhibitor was added to the standard anti‐rejection treatment regimen, AVR was successfully reversed in 6 out of 7 episodes, while in another group of 4 animals receiving the standard anti‐rejection treatment 0 out of 4 episodes of AVR responded to treatment. Response to anti‐rejection treatment was associated with a significant increase in recipient survival time. We conclude that AVR of h‐DAF transgenic porcine kidneys can be successfully treated by additional short‐term fluid phase complement inhibition.
Protection of hDAF‐transgenic porcine endothelial cells against activation by human complement: role of the membrane attack complex
Authors: Fecke Wolfgang , Long Joanna , Richards Andrew , Harrison Richard
Published: March 2003

Xenograft rejection in the discordant pig‐to‐primate model is dependent on binding of natural antibodies to gal‐α [1–3]‐gal epitopes on the porcine endothelial cell (EC). This leads to complement activation and deposition of activation products onto the membrane and results in perturbation of EC function and thrombus formation. Here we investigated the ability of human complement activation products to directly induce activation of porcine EC, with subsequent upregulation of adhesion and pro‐coagulant molecules. Porcine aortic EC were isolated from wild‐type and hDAF‐transgenic pigs and incubated with human serum, either in the presence or absence of the soluble complement inhibitor TP10 (sCR1). Recombinant C5a, C1q‐IgG immune complexes, C6‐deficient human serum and serum containing anti‐C9 Ab were used to identify EC activating complement products. Heat‐inactivated human serum was used as a negative control. Cells were stained with antibodies against human C3, the MAC or with antibodies cross‐reactive for porcine E‐Selectin, VCAM‐1 or Tissue Factor, and analyzed by flow cytometry. We found upregulation of E‐Selectin and Tissue Factor on wild‐type EC after incubation with human serum. This effect coincided with the deposition of C3 and MAC on the membrane of these cells. The addition of TP10 inhibited EC activation by up to 95%. In contrast, greatly reduced C3 and MAC deposition was detected on hDAF transgenic cells, and no complement‐mediated EC activation was seen. Experiments with C6‐deficient serum and incubation with anti‐C9 Ab indicate a major role of the MAC in serum‐mediated EC activation, whereas neither C5a nor C1q‐IgG caused activation of EC. These data provide further explanation of the protective role of human DAF in the pig‐to‐primate xenotransplantation model.