bluuebunny/crossref_metadata_2025_split huggingface dataset:
Two Tomato Expansin Genes Show Divergent Expression and Localization in Embryos during Seed Development and Germination
Authors: Chen Feng , Dahal Peetambar , Bradford Kent J. 
Published: November 2008

Abstract
Expansins are plant proteins that can induce extension of isolated cell walls and are proposed to mediate cell expansion. Three expansin genes were expressed in germinating tomato (Lycopersicon esculentum Mill.) seeds, one of which (LeEXP4) was expressed specifically in the endosperm cap tissue enclosing the radicle tip. The other two genes (LeEXP8 andLeEXP10) were expressed in the embryo and are further characterized here. LeEXP8 mRNA was not detected in developing or mature seeds but accumulated specifically in the radicle cortex during and after germination. In contrast,LeEXP10 mRNA was abundant at an early stage of seed development corresponding to the period of rapid embryo expansion; it then decreased during seed maturation and increased again during germination. When gibberellin-deficient (gib-1) mutant seeds were imbibed in water, LeEXP8 mRNA was not detected, but a low level of LeEXP10 mRNA was present. Expression of both genes increased when gib-1 seeds were imbibed in gibberellin. Abscisic acid did not prevent the initial expression of LeEXP8 and LeEXP10, but mRNA abundance of both genes subsequently decreased during extended incubation. The initial increase in LeEXP8, but notLeEXP10, mRNA accumulation was blocked by low water potential, but LeEXP10 mRNA amounts fell after longer incubation. When seeds were transferred from abscisic acid or low water potential solutions to water, abundance of both LeEXP8and LeEXP10 mRNAs increased in association with germination. The tissue localization and expression patterns of bothLeEXP8 and LeEXP10 suggest developmentally specific roles during embryo and seedling growth.
High-Resolution Metabolic Phenotyping of Genetically and Environmentally Diverse Potato Tuber Systems. Identification of Phenocopies
Authors: Roessner Ute , Willmitzer Lothar , Fernie Alisdair R. 
Published: November 2008

Abstract
We conducted a comprehensive metabolic phenotyping of potato (Solanum tuberosum L. cv Desiree) tuber tissue that had been modified either by transgenesis or exposure to different environmental conditions using a recently developed gas chromatography-mass spectrometry profiling protocol. Applying this technique, we were able to identify and quantify the major constituent metabolites of the potato tuber within a single chromatographic run. The plant systems that we selected to profile were tuber discs incubated in varying concentrations of fructose, sucrose, and mannitol and transgenic plants impaired in their starch biosynthesis. The resultant profiles were then compared, first at the level of individual metabolites and then using the statistical tools hierarchical cluster analysis and principal component analysis. These tools allowed us to assign clusters to the individual plant systems and to determine relative distances between these clusters; furthermore, analyzing the loadings of these analyses enabled identification of the most important metabolites in the definition of these clusters. The metabolic profiles of the sugar-fed discs were dramatically different from the wild-type steady-state values. When these profiles were compared with one another and also with those we assessed in previous studies, however, we were able to evaluate potential phenocopies. These comparisons highlight the importance of such an approach in the functional and qualitative assessment of diverse systems to gain insights into important mediators of metabolism.
Characterization of Two cDNAs Encoding Mitochondrial Lipoamide Dehydrogenase from Arabidopsis
Authors: Lutziger Isabelle , Oliver David J. 
Published: November 2008

Abstract
In contrast to peas (Pisum sativum), where mitochondrial lipoamide dehydrogenase is encoded by a single gene and shared between the α-ketoacid dehydrogenase complexes and the Gly decarboxylase complex, Arabidopsis has two genes encoding for two mitochondrial lipoamide dehydrogenases. Northern-blot analysis revealed different levels of RNA expression for the two genes in different organs; mtLPD1 had higher RNA levels in green leaves compared with the much lower level in roots. The mRNA formtLPD2 shows the inverse pattern. The other organs examined showed nearly equal RNA expressions for both genes. Analysis of etiolated seedlings transferred to light showed a strong induction of RNA expression for mtLPD1 but only a moderate induction of mtLPD2. Based on the organ and light-dependent expression patterns, we hypothesize thatmtLPD1 encodes the protein most often associated with the Gly decarboxylase complex, and mtLPD2 encodes the protein incorporated into α-ketoacid dehydrogenase complexes. Due to the high level of sequence conservation between the two mtLPDs, we assume that the proteins, once in the mitochondrial matrix, are interchangeable among the different multienzyme complexes. If present at high levels, one mtLPD might substitute for the other. Supporting this hypothesis are results obtained with a T-DNA knockout mutant,mtlpd2, which shows no apparent phenotypic change under laboratory growth conditions. This indicates that mtLPD1 can substitute for mtLPD2 and associate with all these multienzyme complexes.
An Oligopeptide Transporter Gene Family in Arabidopsis
Authors: Koh Serry , Wiles Amy M. , Sharp Joshua S. , Naider Fred R. , Becker Jeffrey M. , Stacey Gary 
Published: November 2008

Abstract
We have identified nine oligopeptide transporter (OPT) orthologs (AtOPT1 to AtOPT9) in Arabidopsis. These proteins show significant sequence similarity to OPTs of Candida albicans (CaOpt1p),Schizosaccharomyces pombe (Isp4p), andSaccharomyces cerevisiae (Opt1p and Opt2p). Hydrophilicity plots of the OPTs suggest that they are integral membrane proteins with 12 to 14 transmembrane domains. Sequence comparisons showed that the AtOPTs form a distinct subfamily when compared with the fungal OPTs. Two highly conserved motifs (NPG and KIPPR) were found among all OPT members. The identification of multiple OPTs in Arabidopsis suggests that they may play different functional roles. This idea is supported by the fact that AtOPTs have a distinct, tissue-specific expression pattern. The cDNAs encoding seven of the AtOPTs were cloned into a yeast vector under the control of a constitutive promoter. AtOPT4 expressed in S. cerevisiae mediated the uptake of KLG-[3H]L. Similarly, expression of five of the seven AtOPT proteins expressed in yeast conferred the ability to uptake tetra- and pentapeptides as measured by growth. This study provides new evidence for multiple peptide transporter systems in Arabidopsis, suggesting an important physiological role for small peptides in plants.
Extracellular Protons Inhibit the Activity of Inward- Rectifying Potassium Channels in the Motor Cells ofSamanea samanPulvini
Authors: Yu Ling , Moshelion Menachem , Moran Nava 
Published: November 2008

AbstractThe intermittent influx of K+ into motor cells in motor organs (pulvini) is essential to the rhythmic movement of leaves and leaflets in various plants, but in contrast to the K+ influx channels in guard cells, those in pulvinar motor cells have not yet been characterized. We analyzed these channels in the plasma membrane of pulvinar cell protoplasts of the nyctinastic legume Samanea saman using the patch-clamp technique. Inward, hyperpolarization-activated currents were separated into two types: time dependent and instantaneous. These were attributed, respectively, to K+-selective and distinctly voltage-dependent KH channels and to cation-selective voltage-independent leak channels. The pulvinar KH channels were inhibited by external acidification (pH 7.8–5), in contrast to their acidification-promoted counterparts in guard cells. The inhibitory pH effect was resolved into a reversible decline of the maximum conductance and an irreversible shift of the voltage dependence of KH channel gating. The leak appeared acidification insensitive. External Cs (10 mm in 200 mmexternal K+) blocked both current types almost completely, but external tetraethylammonium (10 mm in 200 mm external K+) did not. Although these results do not link these two channel types unequivocally, both likely serve as K+ influx pathways into swelling pulvinar motor cells. Our results emphasize the importance of studying multiple model systems.
Long-Day Induction of Flowering in Lolium temulentumInvolves Sequential Increases in Specific Gibberellins at the Shoot Apex
Authors: King Rod W. , Moritz Thomas , Evans Lloyd T. , Junttila Olavi , Herlt Anthony J. 
Published: November 2008

Abstract
One challenge for plant biology has been to identify floral stimuli at the shoot apex. Using sensitive and specific gas chromatography-mass spectrometry techniques, we have followed changes in gibberellins (GAs) at the shoot apex during long day (LD)-regulated induction of flowering in the grass Lolium temulentum. Two separate roles of GAs in flowering are indicated. First, within 8 h of an inductive LD, i.e. at the time of floral evocation, the GA5 content of the shoot apex doubled to about 120 ng g−1 dry weight. The concentration of applied GA5 required for floral induction of excised apices (R.W. King, C. Blundell, L.T. Evans [1993] Aust J Plant Physiol 20: 337–348) was similar to that in the shoot apex. Leaf-applied [2H4] GA5 was transported intact from the leaf to the shoot apex, flowering being proportional to the amount of GA5 imported. Thus, GA5 could be part of the LD stimulus for floral evocation of L. temulentum or, alternatively, its increase at the shoot apex could follow import of a primary floral stimulus. Later, during inflorescence differentiation and especially after exposure to additional LD, a second GA action was apparent. The content of GA1 and GA4 in the apex increased greatly, whereas GA5 decreased by up to 75%. GA4 applied during inflorescence differentiation strongly promoted flowering and stem elongation, whereas it was ineffective for earlier floral evocation although it caused stem growth at all times of application. Thus, we conclude that GA1 and GA4are secondary, late-acting LD stimuli for inflorescence differentiation in L. temulentum.
Regulation of CAX1, an Arabidopsis Ca2+/H+ Antiporter. Identification of an N-Terminal Autoinhibitory Domain
Authors: Pittman Jon K. , Hirschi Kendal D. 
Published: November 2008

Abstract
Regulation of Ca2+ transport determines the duration of a Ca2+ signal, and hence, the nature of the biological response. Ca2+/H+ antiporters such as CAX1 (cation exchanger 1), play a key role in determining cytosolic Ca2+ levels. Analysis of a full-length CAX1 clone suggested that the CAX1 open reading frame contains an additional 36 amino acids at the N terminus that were not found in the original clone identified by suppression of yeast (Saccharomyces cerevisiae) vacuolar Ca2+ transport mutants. The long CAX1 (lCAX1) could not suppress the yeast Ca2+ transport defects despite localization to the yeast vacuole. Calmodulin could not stimulate lCAX1 Ca2+/H+ transport in yeast; however, minor alterations in the 36-amino acid region restored Ca2+/H+ transport. Sequence analysis suggests that a 36-amino acid N-terminal regulatory domain may be present in all Arabidopsis CAX-like genes. Together, these results suggest a structural feature involved in regulation of Ca2+/H+ antiport.
Sucrose Phosphate Synthase Activity Rises in Correlation with High-Rate Cellulose Synthesis in Three Heterotrophic Systems
Authors: Babb V. Michelle , Haigler Candace H. 
Published: November 2008

Abstract
Based on work with cotton fibers, a particulate form of sucrose (Suc) synthase was proposed to support secondary wall cellulose synthesis by degrading Suc to fructose and UDP-glucose. The model proposed that UDP-glucose was then channeled to cellulose synthase in the plasma membrane, and it implies that Suc availability in cellulose sink cells would affect the rate of cellulose synthesis. Therefore, if cellulose sink cells could synthesize Suc and/or had the capacity to recycle the fructose released by Suc synthase back to Suc, cellulose synthesis might be supported. The capacity of cellulose sink cells to synthesize Suc was tested by analyzing the Suc phosphate synthase (SPS) activity of three heterotrophic systems with cellulose-rich secondary walls. SPS is a primary regulator of the Suc synthesis rate in leaves and some Suc-storing, heterotrophic organs, but its activity has not been previously correlated with cellulose synthesis. Two systems analyzed, cultured mesophyll cells of Zinnia elegans L. var. Envy and etiolated hypocotyls of kidney beans (Phaseolus vulgaris), contained differentiating tracheary elements. Cotton (Gossypium hirsutum L. cv Acala SJ-1) fibers were also analyzed during primary and secondary wall synthesis. SPS activity rose in all three systems during periods of maximum cellulose deposition within secondary walls. The Z. elegans culture system was manipulated to establish a tight linkage between the timing of tracheary element differentiation and rising SPS activity and to show that SPS activity did not depend on the availability of starch for degradation. The significance of these findings in regard to directing metabolic flux toward cellulose will be discussed.
Arabidopsis RTM1 and RTM2 Genes Function in Phloem to Restrict Long-Distance Movement of Tobacco Etch Virus
Authors: Chisholm Stephen T. , Parra Michael A. , Anderberg Robert J. , Carrington James C. 
Published: November 2008

Abstract
Restriction of long-distance movement of tobacco etch virus (TEV) in Arabidopsis ecotype Col-0 plants requires the function of at least three genes: RTM1 (restricted TEV movement 1),RTM2, and RTM3. The mechanism of TEV movement restriction remains poorly understood, although it does not involve a hypersensitive response or systemic acquired resistance. A functional characterization of RTM1 andRTM2 was done. The RTM1 protein was found to be soluble with the potential to form self-interacting complexes. The regulatory regions of both the RTM1 and RTM2 genes were analyzed using reporter constructs. The regulatory sequences from both genes directed expression of β-glucuronidase exclusively in phloem-associated cells. Translational fusion proteins containing the green fluorescent protein and RTM1 or RTM2 localized to sieve elements when expressed from their native regulatory sequences. Thus, components of the RTM system may function within phloem, and sieve elements in particular, to restrict TEV long-distance movement.
Hydrogen Production. Green Algae as a Source of Energy
Authors: Melis Anastasios , Happe Thomas 
Published: November 2008

Abstract
Hydrogen gas is thought to be the ideal fuel for a world in which air pollution has been alleviated, global warming has been arrested, and the environment has been protected in an economically sustainable manner. Hydrogen and electricity could team to provide attractive options in transportation and power generation. Interconversion between these two forms of energy suggests on-site utilization of hydrogen to generate electricity, with the electrical power grid serving in energy transportation, distribution utilization, and hydrogen regeneration as needed. A challenging problem in establishing H2 as a source of energy for the future is the renewable and environmentally friendly generation of large quantities of H2 gas. Thus, processes that are presently conceptual in nature, or at a developmental stage in the laboratory, need to be encouraged, tested for feasibility, and otherwise applied toward commercialization.
AtFXG1, an Arabidopsis Gene Encoding α-l-Fucosidase Active against Fucosylated Xyloglucan Oligosaccharides
Authors: de la Torre Francisco , Sampedro Javier , Zarra Ignacio , Revilla Gloria 
Published: November 2008

AbstractAn α-l-fucosidase (EC 3.2.1.51) able to release the t-fucosyl residue from the side chain of xyloglucan oligosaccharides has been detected in the leaves of Arabidopsis plants. Moreover, an α-l-fucosidase with similar substrate specificity was purified from cabbage (Brassica oleracea) leaves to render a single band on SDS-PAGE. Two peptide sequences were obtained from this protein band, and they were used to identify an Arabidopsis gene coding for an α-fucosidase that we propose to call AtFXG1. In addition, an Arabidopsis gene with homology with known α-l-fucosidases has been also found, and we proposed to name it as AtFUC1. Both AtFXG1 andATFUC1 were heterologously expressed in Pichia pastoris cells and the α-l-fucosidase activities secreted to the culture medium. The α-l-fucosidase encoded by AtFXG1 was active against the oligosaccharides from xyloglucan XXFG as well as against 2′-fucosyl-lactitol but not againstp-nitrophenyl-α-l-fucopyranoside. However, the AtFUC1 heterologously expressed was active only against 2′-fucosyl-lactitol. Thus, the former must be related to xyloglucan metabolism.
Purification and Identification of a 42-Kilodalton Abscisic Acid-Specific-Binding Protein from Epidermis of Broad Bean Leaves
Authors: Zhang Da-Peng , Wu Zhong-Yi , Li Xi-Yan , Zhao Zhi-Xin 
Published: November 2008

AbstractPurification of abscisic acid (ABA)-binding proteins is considered to constitute a major step toward isolating ABA receptors. We report here that an ABA-binding protein was for the first time, to our knowledge, purified from the epidermis of broad bean (Vicia faba) leaves via affinity chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis, isoelectric focusing electrophoresis, and isoelectric focusing/sodium dodecyl sulfate-polyacrylamide gel electrophoresis two-dimensional electrophoresis of the purified ABA-binding protein all identified a single protein band with a molecular mass of 42 kD and an isoelectric point 4.86. The Scatchard plot for the purified protein showed a linear function with a maximum binding activity of 0.87 mol mol−1protein and an equilibrium dissociation constant of 21 nm, indicating that the purified protein may be a monomeric one, possessing one binding site. The ABA-binding protein was enriched more than 300-fold with a yield of 14%. (−)ABA and trans-ABA were substantially incapable of displacing 3H-(±)ABA bound to the ABA-binding protein, and (±)ABA was less effective than (+)ABA in the competition. These findings allow establishment of the stereospecificity of the 42-kD protein and suggest its ABA receptor nature. Pretreatment of the guard cell protoplasts of broad bean leaves with the monoclonal antibody raised against the 42-kD protein significantly decreased the ABA specific-induced phospholipase D activity in a dose-dependent manner. This physiological significance provides more clear evidence for the potential ABA-receptor nature of the 42-kD protein.
Phytochrome E Controls Light-Induced Germination of Arabidopsis
Authors: Hennig Lars , Stoddart Wendy M. , Dieterle Monika , Whitelam Garry C. , Schäfer Eberhard 
Published: November 2008

Abstract
Germination of Arabidopsis seeds is light dependent and under phytochrome control. Previously, phytochromes A and B and at least one additional, unspecified phytochrome were shown to be involved in this process. Here, we used a set of photoreceptor mutants to test whether phytochrome D and/or phytochrome E can control germination of Arabidopsis. The results show that only phytochromes B and E, but not phytochrome D, participate directly in red/far-red light (FR)-reversible germination. Unlike phytochromes B and D, phytochrome E did not inhibit phytochrome A-mediated germination. Surprisingly, phytochrome E was required for germination of Arabidopsis seeds in continuous FR. However, inhibition of hypocotyl elongation by FR, induction of cotyledon unfolding, and induction of agravitropic growth were not affected by loss of phytochrome E. Therefore, phytochrome E is not required per se for phytochrome A-mediated very low fluence responses and the high irradiance response. Immunoblotting revealed that the need of phytochrome E for germination in FR was not caused by altered phytochrome A levels. These results uncover a novel role of phytochrome E in plant development and demonstrate the considerable functional diversification of the closely related phytochromes B, D, and E.
Differential Effect of Jasmonic Acid and Abscisic Acid on Cell Cycle Progression in Tobacco BY-2 Cells
Authors: Świa̧tek Agnieszka , Lenjou Marc , Van Bockstaele Dirk , Inzé Dirk , Van Onckelen Harry 
Published: November 2008

Abstract
Environmental stress affects plant growth and development. Several plant hormones, such as salicylic acid, abscisic acid (ABA), jasmonic acid (JA), and ethylene play a crucial role in altering plant morphology in response to stress. Developmental regulation often has the cell cycle machinery among its targets. We analyzed the effect of JA and ABA on cell cycle progression in synchronized tobacco (Nicotiana tabacum) BY-2 cells. Both compounds were found to prevent DNA replication, keeping the cells in the G1 stage, when applied just before the G1/S transition. However, ABA did not have any effect on subsequent phases of the cell cycle when applied at a later stage, whereas JA effectively prevented mitosis on application during DNA synthesis. This demonstrates that JA treatment can freeze synchronized BY-2 cells in both the G1 and G2 stages of the cell cycle. Jasmonate administered after the S-phase was less effective in decreasing the mitotic index, suggesting that cell sensitivity toward JA is dependent on the cell cycle phase. In cultures detained in the G2-phase, we observed a reduced histone H1 kinase activity of kinases associated with the p13sucl protein.
Abscisic Acid Determines Basal Susceptibility of Tomato toBotrytis cinereaand Suppresses Salicylic Acid-Dependent Signaling Mechanisms
Authors: Audenaert Kris , De Meyer Geert B. , Höfte Monica M. 
Published: November 2008

AbstractAbscisic acid (ABA) is one of the plant hormones involved in the interaction between plants and pathogens. In this work, we show that tomato (Lycopersicon esculentum Mill. cv Moneymaker) mutants with reduced ABA levels (sitiens plants) are much more resistant to the necrotrophic fungus Botrytis cinerea than wild-type (WT) plants. Exogenous application of ABA restored susceptibility to B. cinerea insitiens plants and increased susceptibility in WT plants. These results indicate that ABA plays a major role in the susceptibility of tomato to B. cinerea. ABA appeared to interact with a functional plant defense response against B. cinerea. Experiments with transgenic NahG tomato plants and benzo(1,2,3)thiadiazole-7-carbothioic acid demonstrated the importance of salicylic acid in the tomato-B. cinereainteraction. In addition, upon infection with B. cinerea, sitiens plants showed a clear increase in phenylalanine ammonia lyase activity, which was not observed in infected WT plants, indicating that the ABA levels in healthy WT tomato plants partly repress phenylalanine ammonia lyase activity. In addition, sitiens plants became more sensitive to benzo(1,2,3)thiadiazole-7-carbothioic acid root treatment. The threshold values for PR1a gene expression declined with a factor 10 to 100 in sitiens compared with WT plants. Thus, ABA appears to negatively modulate the salicylic acid-dependent defense pathway in tomato, which may be one of the mechanisms by which ABA levels determine susceptibility to B. cinerea.