bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Vivo Dynamics and Differential Microtubule-Binding Activities of MAP65 Proteins
Authors: Van Damme Daniël , Van Poucke Kris , Boutant Emmanuel , Ritzenthaler Christophe , Inzé Dirk , Geelen Danny 
Published: December 2004

Abstract
Plant cells produce different microtubule arrays that are essential for cell division and morphogenesis without equivalent in other eukaryotes. Microtubule-associated proteins influence the behavior of microtubules that is presumed to culminate into transitions from one array to another. We analyzed the microtubule-binding properties of three Arabidopsis (Arabidopsis thaliana) members, AtMAP65-1, AtMAP65-4, and AtMAP65-5, in live cells using laser scanning confocal microscopy. Depending on the overall organization of the cortical array, AtMAP65-1-GFP (green fluorescent protein) and AtMAP65-5-GFP associated with a subset of microtubules. In cells containing both coaligned and oblique microtubules, AtMAP65-1-GFP and AtMAP65-5-GFP tended to be associated with the coaligned microtubules. Cortical microtubules labeled with AtMAP65-1-GFP and AtMAP65-5-GFP appeared as thick bundles and showed more resistance to microtubule-destabilizing drugs. The polymerization rates of AtMAP65-1-GFP and AtMAP65-5-GFP microtubules were similar to those of tubulin-GFP marked microtubules but were different from AtEB1a-GFP, a microtubule plus-end-binding EB1-like protein that stimulated polymerization. By contrast, depolymerization rates of AtMAP65-1-GFP- and AtMAP65-5-GFP-labeled microtubules were reduced. AtMAP65-1-GFP associated with polymerizing microtubules within a bundle, and with fixed microtubule termini, suggesting that AtMAP65-1's function is to bundle and stabilize adjacent microtubules of the cortex. Polymerization within a bundle took place in either direction so that bundling occurred between parallel or antiparallel aligned microtubules. AtMAP65-4-GFP did not label cortical microtubules or the preprophase band, despite continuous expression driven by the 35S promoter, and its subcellular localization was restricted to microtubules that rearranged to form a spindle and the polar sides of the spindle proper. The expression of AtMAP65-4 peaked at mitosis, in agreement with a function related to spindle formation, whereas AtMAP65-1 and AtMAP65-5 were expressed throughout the cell cycle.
Plant-Specific Microtubule-Associated Protein SPIRAL2 Is Required for Anisotropic Growth in Arabidopsis
Authors: Shoji Tsubasa , Narita Noriyuki N. , Hayashi Kazunori , Asada Junko , Hamada Takahiro , Sonobe Seiji , Nakajima Keiji , Hashimoto Takashi 
Published: December 2004

Abstract
In diffusely growing plant cells, cortical microtubules play an important role in regulating the direction of cell expansion. Arabidopsis (Arabidopsis thaliana) spiral2 (spr2) mutant is defective in directional cell elongation and exhibits right-handed helical growth in longitudinally expanding organs such as root, hypocotyl, stem, petiole, and petal. The growth of spr2 roots is more sensitive to microtubule-interacting drugs than is wild-type root growth. The SPR2 gene encodes a plant-specific 94-kD protein containing HEAT-repeat motifs that are implicated in protein-protein interaction. When expressed constitutively, SPR2-green fluorescent protein fusion protein complemented the spr2 mutant phenotype and was localized to cortical microtubules as well as other mitotic microtubule arrays in transgenic plants. Recombinant SPR2 protein directly bound to taxol-stabilized microtubules in vitro. Furthermore, SPR2-specific antibody and mass spectrometry identified a tobacco (Nicotiana tabacum) SPR2 homolog in highly purified microtubule-associated protein fractions from tobacco BY-2 cell cultures. These results suggest that SPR2 is a novel microtubule-associated protein and is required for proper microtubule function involved in anisotropic growth.
Analysis in Vitro of the Enzyme CRTISO Establishes a Poly-cis-Carotenoid Biosynthesis Pathway in Plants
Authors: Isaacson Tal , Ohad Itzhak , Beyer Peter , Hirschberg Joseph 
Published: December 2004

Abstract
Most enzymes in the central pathway of carotenoid biosynthesis in plants have been identified and studied at the molecular level. However, the specificity and role of cis-trans-isomerization of carotenoids, which occurs in vivo during carotene biosynthesis, remained unresolved. We have previously cloned from tomato (Solanum lycopersicum) the CrtISO gene, which encodes a carotene cis-trans-isomerase. To study the biochemical properties of the enzyme, we developed an enzymatic in vitro assay in which a purified tomato CRTISO polypeptide overexpressed in Escherichia coli cells is active in the presence of an E. coli lysate that includes membranes. We show that CRTISO is an authentic carotene isomerase. Its catalytic activity of cis-to-trans isomerization requires redox-active components, suggesting that isomerization is achieved by a reversible redox reaction acting at specific double bonds. Our data demonstrate that CRTISO isomerizes adjacent cis-double bonds at C7 and C9 pairwise into the trans-configuration, but is incapable of isomerizing single cis-double bonds at C9 and C9′. We conclude that CRTISO functions in the carotenoid biosynthesis pathway in parallel with ζ-carotene desaturation, by converting 7,9,9′-tri-cis-neurosporene to 9′-cis-neurosporene and 7′9′-di-cis-lycopene into all-trans-lycopene. These results establish that in plants carotene desaturation to lycopene proceeds via cis-carotene intermediates.
Characterization of Plastidial Thioredoxins from Arabidopsis Belonging to the New y-Type
Authors: Collin Valérie , Lamkemeyer Petra , Miginiac-Maslow Myroslawa , Hirasawa Masakazu , Knaff David B. , Dietz Karl-Josef , Issakidis-Bourguet Emmanuelle 
Published: December 2004

Abstract
The plant plastidial thioredoxins (Trx) are involved in the light-dependent regulation of many enzymatic activities, owing to their thiol-disulfide interchange activity. Three different types of plastidial Trx have been identified and characterized so far: the m-, f-, and x-types. Recently, a new putative plastidial type, the y-type, was found. In this work the two isoforms of Trx y encoded by the nuclear genome of Arabidopsis (Arabidopsis thaliana) were characterized. The plastidial targeting of Trx y has been established by the expression of a Trx∷GFP fusion protein. Then both isoforms were produced as recombinant proteins in their putative mature forms and purified to characterize them by a biochemical approach. Their ability to activate two plastidial light-regulated enzymes, NADP-malate dehydrogenase (NADP-MDH) and fructose-1,6-bisphosphatase, was tested. Both Trx y were poor activators of fructose-1,6-bisphosphatase and NADP-MDH; however, a detailed study of the activation of NADP-MDH using site-directed mutants of its regulatory cysteines suggested that Trx y was able to reduce the less negative regulatory disulfide but not the more negative regulatory disulfide. This property probably results from the fact that Trx y has a less negative redox midpoint potential (−337 mV at pH 7.9) than thioredoxins f and m. The y-type Trxs were also the best substrate for the plastidial peroxiredoxin Q. Gene expression analysis showed that Trx y2 was mainly expressed in leaves and induced by light, whereas Trx y1 was mainly expressed in nonphotosynthetic organs, especially in seeds at a stage of major accumulation of storage lipids.
The Role of Plastocyanin in the Adjustment of the Photosynthetic Electron Transport to the Carbon Metabolism in Tobacco
Authors: Schöttler Mark Aurel , Kirchhoff Helmut , Weis Engelbert 
Published: December 2004

Abstract
We investigated adaptive responses of the photosynthetic electron transport to a decline in the carbon assimilation capacity. Leaves of different ages from wild-type tobacco (Nicotiana tabacum) L. var Samsun NN and young mature leaves of tobacco transformants with impaired photoassimilate export were used. The assimilation rate decreased from 280 in young mature wild-type leaves to below 50 mmol electrons mol chlorophyll−1 s−1 in older wild-type leaves or in transformants. The electron transport capacity, measured in thylakoids isolated from the different leaves, closely matched the leaf assimilation rate. The numbers of cytochrome (cyt)-bf complexes and plastocyanin (PC) decreased with the electron transport and assimilation capacity, while the numbers of photosystem I (PSI), photosystem II, and plastoquinone remained constant. The PC to PSI ratio decreased from five in leaves with high assimilation rates, to values below one in leaves with low assimilation rates, and the PC versus flux correlation was strictly proportional. Redox kinetics of cyt-f, PC, and P700 suggest that in leaves with low electron fluxes, PC is out of the equilibrium with P700 and cyt-f and the cyt-f reoxidation rate is restricted. It is concluded that the electron flux is sensitive to variations in the number of PC, relative to PSI and cyt-bf, and PC, in concert with cyt-bf, is a key component that adjusts to control the electron transport rate. PC dependent flux control may serve to adjust the electron transport rate under conditions where the carbon assimilation is diminished and thereby protects PSI against over-reduction and reactive oxygen production.
A Plant-Specific Kinesin Binds to Actin Microfilaments and Interacts with Cortical Microtubules in Cotton Fibers
Authors: Preuss Mary L. , Kovar David R. , Lee Y.-R. Julie , Staiger Christopher J. , Delmer Deborah P. , Liu Bo 
Published: December 2004

Abstract
A novel kinesin, GhKCH1, has been identified from cotton (Gossypium hirsutum) fibers. GhKCH1 has a centrally located kinesin catalytic core, a signature neck peptide of minus end-directed kinesins, and a unique calponin homology (CH) domain at its N terminus. GhKCH1 and other CH domain-containing kinesins (KCHs) belong to a distinct branch of the minus end-directed kinesin subfamily. To date the KCH kinesins have been found only in higher plants. Because the CH domain is often found in actin-binding proteins, we proposed that GhKCH1 might play a role in mediating dynamic interaction between microtubules and actin microfilaments in cotton fibers. In an in vitro actin-binding assay, GhKCH1's N-terminal region including the CH domain interacted directly with actin microfilaments. In cotton fibers, GhKCH1 decorated cortical microtubules in a punctate manner. Occasionally GhKCH1 was found to be associated with transverse-cortical actin microfilaments, but never with axial actin cables in cotton fibers. Localization of GhKCH1 on cortical microtubules was independent of the integrity of actin microfilaments. Thus, GhKCH1 may play a role in organizing the actin network in coordination with the cortical microtubule array. These data also suggest that flowering plants may employ unique KCHs to coordinate actin microfilaments and microtubules during cell growth.
The Biosynthesis of UDP-Galacturonic Acid in Plants. Functional Cloning and Characterization of Arabidopsis UDP-d-Glucuronic Acid 4-Epimerase
Authors: Gu Xiaogang , Bar-Peled Maor 
Published: December 2004

Abstract
UDP-GlcA 4-epimerase (UGlcAE) catalyzes the epimerization of UDP-α-d-glucuronic acid (UDP-GlcA) to UDP-α-d-galacturonic acid (UDP-GalA). UDP-GalA is a precursor for the synthesis of numerous cell-surface polysaccharides in bacteria and plants. Using a biochemical screen, a gene encoding AtUGlcAE1 in Arabidopsis (Arabidopsis thaliana) was identified and the recombinant enzyme biochemically characterized. The gene belongs to a small gene family composed of six isoforms. All members of the UGlcAE gene family encode a putative type-II membrane protein and have two domains: a variable N-terminal region approximately 120 amino acids long composed of a predicted cytosolic, transmembrane, and stem domain, followed by a large conserved C-terminal catalytic region approximately 300 amino acids long composed of a highly conserved catalytic domain found in a large protein family of epimerase/dehydratases. The recombinant epimerase has a predicted molecular mass of approximately 43 kD, although size-exclusion chromatography suggests that it may exist as a dimer (approximately 88 kD). AtUGlcAE1 forms UDP-GalA with an equilibrium constant value of approximately 1.9 and has an apparent Km value of 720 μm for UDP-GlcA. The enzyme has maximum activity at pH 7.5 and is active between 20°C and 55°C. Arabidopsis AtUGlcAE1 is not inhibited by UDP-Glc, UDP-Gal, or UMP. However, the enzyme is inhibited by UDP-Xyl and UDP-Ara, suggesting that these nucleotide sugars have a role in regulating the synthesis of pectin. The cloning of the AtUGlcAE1 gene will increase our ability to investigate the molecular factors that regulate pectin biosynthesis in plants. The availability of a functional recombinant UDP-GlcA 4-epimerase will be of considerable value for the facile generation of UDP-d-GalA in the amounts required for detailed studies of pectin biosynthesis.
Inactivation of the clpC1 Gene Encoding a Chloroplast Hsp100 Molecular Chaperone Causes Growth Retardation, Leaf Chlorosis, Lower Photosynthetic Activity, and a Specific Reduction in Photosystem Content
Authors: Sjögren Lars L.E. , MacDonald Tara M. , Sutinen Sirkka , Clarke Adrian K. 
Published: December 2004

Abstract
ClpC is a molecular chaperone of the Hsp100 family. In higher plants there are two chloroplast-localized paralogs (ClpC1 and ClpC2) that are approximately 93% similar in primary sequence. In this study, we have characterized two independent Arabidopsis (Arabidopsis thaliana) clpC1 T-DNA insertion mutants lacking on average 65% of total ClpC content. Both mutants display a retarded-growth phenotype, leaves with a homogenous chlorotic appearance throughout all developmental stages, and more perpendicular secondary influorescences. Photosynthetic performance was also impaired in both knockout lines, with relatively fewer photosystem I and photosystem II complexes, but no changes in ATPase and Rubisco content. However, despite the specific drop in photosystem I and photosystem II content, no changes in leaf cell anatomy or chloroplast ultrastructure were observed in the mutants compared to the wild type. Previously proposed functions for envelope-associated ClpC in chloroplast protein import and degradation of mistargeted precursors were examined and shown not to be significantly impaired in the clpC1 mutants. In the stroma, where the majority of ClpC protein is localized, marked increases of all ClpP paralogs were observed in the clpC1 mutants but less variation for the ClpR paralogs and a corresponding decrease in the other chloroplast-localized Hsp100 protein, ClpD. Increased amounts of other stromal molecular chaperones (Cpn60, Hsp70, and Hsp90) and several RNA-binding proteins were also observed. Our data suggest that overall ClpC as a stromal molecular chaperone plays a vital role in chloroplast function and leaf development and is likely involved in photosystem biogenesis.
Transfers Matter Most: How Changes in Transfer Systems of Canada and the United States Explain the Divergence in Household Poverty Levels from 1974-1994
Authors: Zuberi Daniyal 
Published: December 2004

From 1974 to 1994, Canada and the United States experienced quite substantial divergences in relative household poverty rates and inequality levels from similar starting points.Although several scholars have attempted to explain Canadian and U.S. differences in poverty and inequality levels at one point in time, none have satisfactorily explained the causes of these divergent trends. Utilizing high quality, comparable data from the Luxembourg Income Survey, my analysis of the household poverty rates demonstrates that differences in the policies and reforms of the two country’s transfer systems explains the divergence relative household poverty rates. The data also seriously cast doubt on other potential market, cultural, or tax system explanations. Further, by selectively removing the income from each specific category and then specific type of transfer income and recalculating the household poverty rate, my “sensitivity-type” analysis clearly demonstrates the predominant explanatory power for differences in the structure and reforms of social insurance transfers income and, more specifically, social retirement benefits. In Canada, the expansion of the Guaranteed Income Supplement (GIS) for low-income elderly families over this period provides the only plausible explanation for the dramatic reduction in the poverty rate of the elderly households relative to the United States and, perhaps somewhat surprisingly, explains most of the divergence in household poverty rates between the two countries from 1974 to 1994. As a large part of the divergence in inequality rates is also driven by reduction in household poverty rates in Canada relative to the United States, the expansion of the GIS benefits also provides a major explanation for the divergence in levels of household inequality over this period.
Women, Land-Struggles and Globalization: An International Perspective
Authors: Federici Silvia 
Published: December 2004

Despite a systematic attempt by colonial powers to destroy female systems of farming, across the planet women today constitute the bulk of agricultural workers and are in the forefront of the struggle for a non-capitalist use of natural resources (land, forests, waters). The article examines these struggles, arguing that by defending subsistence agriculture, communal access to land, and opposing land expropriation, women internationally are building the way to a new non-exploitative society, and one in which the threat of famines and ecological devastation will be dispelled. How can we ever get out of poverty if we can't get a piece of land to work? If we had land to plant, we wouldn't need to get food sent to us all the way from the United States. No. We'd have our own. But as long as the government refuses to give us the land and other resources we need, we'll continue to have foreigners running our country. —Elvia Alvarado (Benjamin 1987: 104)
An Economic Analysis of Agricultural Production in Senegal: A Case Study of the Thiès and Diourbel Regions
Authors: Cisse Aly , Bravo-Ureta Boris E. , Fuentes Paul , Thiam Abdourahmane 
Published: December 2004

Enterprise budgets and linear programming techniques are used to determine the profitability of individual crops and optimal cropping patterns for typical farms located in Diourbel and Thiès, two regions in the center of the Senegalese Peanut Basin. An intensification analysis through the introduction of La Fleur 11, which is a relatively new ground-nut seed variety, and operating capital constraints are also included in this study. Finally, farm income is compared with two poverty line measures. The profitability results show that groundnut exhibits the highest gross returns and net profits per hectare and millet the lowest net profits per hectare. Moreover, La Fleur 11 exhibits a higher yield when compared to traditional groundnut varieties such as 55-437. The results of the linear programming model suggest that groundnut production is the most profitable use of agricultural land in Diourbel, while in Thiès sorghum shows the highest profitability. Excess labor is found in all the cases examined while the opportunity cost of land ranges from FCFA 25,551 to FCFA 318,612 (US $39.31 to US $490.17, at an exchange rate of FCFA 650/US $1 for 1997). The farm income analysis indicates that the level of poverty is severe in the area of the study. In addition, large farms are not as poor as small farms, and non-farm income could contribute to poverty alleviation.
Insulin Sensitivity Among Obese Children and Adolescents, According to Degree of Weight Loss
Authors: Reinehr Thomas , Kiess Wieland , Kapellen Thomas , Andler Werner 
Published: December 2004

Objective. Insulin sensitivity is impaired among some obese children, reflecting an atherogenic risk factor profile for the affected subjects. This study was performed to examine the amount of weight reduction required to improve insulin sensitivity.Methods. We studied changes in insulin sensitivity indices (ISIs) for glucose metabolism (homeostasis model assessment and quantitative insulin sensitivity check index) and fat metabolism (free fatty acids) during a 1-year period among obese children who attended an obesity intervention program. The children were divided into 4 groups according to their changes in body mass index (BMI) SD score (SDS), as follows: group I, decrease in SDS-BMI of ≥0.5; group II, decrease in SDS-BMI of ≥0.25 to &lt;0.5; group III, decrease in SDS-BMI of &lt;0.25; group IV, increase in SDS-BMI.Results. Fifty-seven obese children (age range: 6–14 years; median age: 10 years; 46% boys) were included in the study. The 4 groups did not differ with respect to age, gender, degree of overweight (SDS-BMI), or ISI values at baseline. An increase in SDS-BMI (group IV, n = 12) was followed by a significant decrease in ISI values. The ISIs improved for group I (n = 9), whereas there were no significant changes in these parameters for group II (n = 21) and group III (n = 15).Conclusions. During a 1-year period, an increase in weight among obese children was associated with a decrease in insulin sensitivity. Weight loss was followed by significant improvement in insulin sensitivity for glucose and fat metabolism but only if the SDS-BMI decreased by ≥0.5 during the 1-year period.
Evaluation of a Staff-Only Hospitalist System in a Tertiary Care, Academic Children's Hospital
Authors: Dwight Prabo , MacArthur Colin , Friedman Jeremy N. , Parkin Patricia C. 
Published: December 2004

Objective.
The staff/housestaff hospitalist system has been evaluated in 2 pediatric centers in the United States. In Canada, fewer residents and duty hour restrictions led to the development of a staff-only hospitalist system. The objective of this study was to compare the staff-only pediatric hospitalist system and the staff/housestaff hospitalist system with respect to traditional outcome measures.

Design.
This cohort study (staff-only hospitalist system versus staff/housestaff system) used electronic health records data (July 1, 1996, to June 30, 1997) for all admissions (n = 3807) to the general pediatric inpatient unit of an urban, tertiary care, pediatric, teaching hospital in Toronto, Canada. Outcome measures included length of hospital stay, subspecialty consultations, readmission to the hospital, and death during the hospital stay.

Results.
The median length of hospital stay was reduced by 14% for patients admitted to the staff-only hospitalist system, compared with the staff/housestaff hospitalist system (2.5 and 2.9 days, respectively). This difference remained statistically significant after adjustment for age, gender, and comorbidity. There were no significant differences between the 2 models of care with respect to subspecialty consultation, hospital readmission, or mortality rates. A stratified analysis showed similar findings for the 10 most frequent diagnostic groups.

Conclusions.
The staff-only hospitalist system was associated with a significant reduction in the hospital length of stay, without evidence of adverse effects on mortality or readmission rates, compared with the staff/hospitalist system. In the context of recent restrictions on resident duty hours in the United States, these findings may be of interest to pediatric teaching hospitals considering the development of a similar staff-only hospitalist model.