bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seasonal variations in nitrate reductase activity and internal N pools in intertidal brown algae are correlated with ambient nitrate concentrations
Authors: YOUNG ERICA B. , DRING MATTHEW J. , SAVIDGE GRAHAM , BIRKETT DARYL A. , BERGES JOHN A. 
Published: May 2007

ABSTRACTNitrogen metabolism was examined in the intertidal seaweeds Fucus vesiculosus, Fucus serratus, Fucus spiralis and Laminaria digitata in a temperate Irish sea lough. Internal NO3‐ storage, total N content and nitrate reductase activity (NRA) were most affected by ambient NO3‐, with highest values in winter, when ambient NO3‐ was maximum, and declined with NO3‐ during summer. In all species, NRA was six times higher in winter than in summer, and was markedly higher in Fucus species (e.g. 256 ± 33 nmol NO3‐ min−1 g−1 in F. vesiculosus versus 55 ± 17 nmol NO3‐ min−1 g−1 in L. digitata). Temperature and light were less important factors for N metabolism, but influenced in situ photosynthesis and respiration rates. NO3‐ assimilating capacity (calculated from NRA) exceeded N demand (calculated from net photosynthesis rates and C : N ratios) by a factor of 0.7–50.0, yet seaweeds stored significant NO3‐ (up to 40–86 µmol g−1). C : N ratio also increased with height in the intertidal zone (lowest in L. digitata and highest in F. spiralis), indicating that tidal emersion also significantly constrained N metabolism. These results suggest that, in contrast to the tight relationship between N and C metabolism in many microalgae, N and C metabolism could be uncoupled in marine macroalgae, which might be an important adaptation to the intertidal environment.
Evaluation of a rapid diagnostic field test kit for identification of Phytophthora species, including P. ramorum and P. kernoviae at the point of inspection
Authors: Lane C. R. , Hobden E. , Walker L. , Barton V. C. , Inman A. J. , Hughes K. J. D. , Swan H. , Colyer A. , Barker I. 
Published: May 2007

Plant health regulations to prevent the introduction and spread of Phytophthora ramorum and P. kernoviae require rapid, cost effective diagnostic methods for screening large numbers of plant samples at the time of inspection. Current on‐site techniques require expensive equipment, considerable expertise and are not suited for plant health inspectors. Therefore, an extensive evaluation of a commercially available lateral flow device (LFD) for Phytophthora species was performed involving four separate trials and 634 samples. The assay proved simple to use, provided results in a few minutes and on every occasion a control line reacted positively confirming the validity of the test. LFD results were compared with those from testing a parallel sample, using laboratory methods (isolation and real‐time PCR). The diagnostic sensitivity of the LFD (87·6%) compared favourably with the standard laboratory methods although the diagnostic specificity was not as stringent (82·9%). There were a small number (n = 28) of false negatives, but for statutory purposes where all positive samples must be identified to species level by laboratory testing, overall efficiency was 95·6% as compared with visual assessment of symptoms of between 20‐30% for P. ramorum and P. kernoviae. This work demonstrates the value of the LFD for diagnosing Phytophthora species at the time of inspection and as a useful primary screen for selecting samples for laboratory testing to determine the species identification.
Variation in virus populations and growth characteristics of two sugarcane cultivars naturally infected by Sugarcane yellow leaf virus in different geographical locations
Authors: Abu Ahmad Y. , Girard J.‐C. , Fernandez E. , Pauquet J. , Lockhart B. E. L. , Letourmy P. , Rott P. 
Published: May 2007

Two sugarcane cultivars (R570 and SP71‐6163) naturally infected by Sugarcane yellow leaf virus (SCYLV) were each imported from several geographical locations into a sugarcane yellow leaf‐free environment (Montpellier, France). Plants were grown as plant cane for 5–6 months and the experiment was repeated for three consecutive years (2003–2005) in a greenhouse. Several sugarcane‐growth and disease characteristics were monitored to identify variation in pathogenicity of SCYLV. Depending on their geographical origin, sugarcane cvs R570 and SP71‐6163 were infected by SCYLV genotypes BRA‐PER or REU, or a mixture of the two. Severity of symptoms did not vary between plants of cv. R570, but variation in disease severity between plants of cv. SP71‐6163 from different geographical locations suggested the occurrence of pathogenic variants of SCYLV. For each sugarcane cultivar, differences in stalk length, number of stalk internodes, virus titre in the top visible dewlap leaf, and percentage of infection of leaf and stalk phloem vessels were also found between plants from different geographical origins. However, these differences were not always reproducible from one year to another, suggesting occurrence of different plant responses to SCYLV isolates under varying environmental conditions.
Histamine in Rheumatoid Arthritis
Authors: Adlesic M. , Verdrengh M. , Bokarewa M. , Dahlberg L. , Foster S. J. , Tarkowski A. 
Published: May 2007

AbstractRheumatoid arthritis (RA) is an autoimmune disease characterized by a persistent inflammation of the synovium, leading to the erosion of articular cartilage and bone. Synovial mast cells and their effector molecule, histamine, receive increased attention as mediators of joint inflammation. The aim of our study was to analyse levels of free histamine in serum and joint fluid of RA patients and to evaluate the potential inflammatogenic properties of histamine in vivo and in vitro. Histamine levels were measured by an ELISA in synovial fluid and sera of RA patients and of healthy controls. Histamine levels were also assessed in plasma of RA patients undergoing anti‐TNF‐α treatment. In the murine part of the study, histamine was injected intra‐articularly in the knee joint of mice and the joints were subsequently analysed with respect to induction of inflammation. RA patients displayed significantly lower levels of histamine in circulation (0.93 ± 0.16 ng/ml) compared with the healthy controls (1.89 ± 0.45 ng/ml, P < 0.001). Locally, in synovial fluid the levels of histamine were even lower (0.37 ± 0.16 ng/ml, P < 0.0006). Long‐term anti‐TNF‐α treatment significantly increased circulating levels of histamine in RA patients. Our experiments on animals show that histamine on its own neither induces inflammation in the joint cavity nor influences the course of HMGB1 and peptidoglycan‐induced joint inflammation. Based on our experimental and clinical studies we suggest that histamine lacks harmful properties in RA.
Patterns of In vitro Lymphoproliferative Responses Among HTLV‐1‐infected Subjects: Upregulation by HTLV‐1 During HIV‐1 Co‐infection
Authors: Olah I. , Fukumori L. M. I. , Montanheiro P. , Vergara M. P. , Smid J. , Duarte A. J. S. , Penalva de Oliveira A. C. , Casseb J. 
Published: May 2007

AbstractThe present study evaluated the in vitro response to different mitogens and a candidin antigen (CMA) in Human T‐cell lymphotropic virus type 1 (HTLV‐1) and co‐infected HIV‐1/HTLV‐1 patients, to identify if this co‐infection may modify the spontaneous lymph proliferative response. Peripheral blood mononuclear cells from 72 healthy seronegative controls, 75 asymptomatic HTLV‐1‐infected carriers, 42 HAM/TSP cases, 33 solely HIV‐1‐infected subjects and 24 HIV‐1/HTLV‐1 patients were assayed in the presence and absence of mitogens (PHA, PWM and OKT3) and CMA. The HAM/TSP group had the highest proliferation rate at 3 and 6 days after culture. HAM/TSP cases showed decreased response to PHA, compared with asymptomatic HTLV‐1 subjects, and most important, the co‐infected HIV‐1/HTLV‐1 cases presented a similar response to HTLV‐1‐infected subjects after 3 days of culture. The singles HIV‐1‐infected group had decreased in vitro response. It appears that during co‐infection, the HTLV‐1 regulatory proteins overwhelm the action of HIV‐1 regulatory proteins.
SHA1, a novel RING finger protein, functions in shoot apical meristem maintenance in Arabidopsis
Authors: Sonoda Yutaka , Yao Shan‐Guo , Sako Kaori , Sato Takeo , Kato Wataru , Ohto Masa‐aki , Ichikawa Takanari , Matsui Minami , Yamaguchi Junji , Ikeda Akira 
Published: May 2007

SummaryPost‐embryonic plant growth is dependent on a functional shoot apical meristem (SAM) that provides cells for continuous development of new aerial organs. However, how the SAM is dynamically maintained during vegetative development remains largely unclear. We report here the characterization of a new SAM maintenance mutant, sha1‐1 (shoot apical meristem arrest 1‐1), that shows a primary SAM‐deficient phenotype at the adult stage. The SHA1 gene encodes a novel RING finger protein, and is expressed most intensely in the shoot apex. We show that, in the sha1‐1 mutant, the primary SAM develops normally during the juvenile vegetative stage, but cell layer structure becomes disorganized after entering the adult vegetative stage, resulting in a dysfunctional SAM that cannot initiate floral primordia. The sha1‐1 SAM terminates completely at the stage when the wild‐type begins to bolt, producing adult plants with a primary inflorescence‐deficient phenotype. These observations indicate that SHA1, a putative E3 ligase, is required for post‐embryonic SAM maintenance by controlling proper cellular organization.
Self‐incompatibility of Prunus tenella and evidence that reproductively isolated species of Prunus have different SFB alleles coupled with an identical S‐RNase allele
Authors: Šurbanovski Nada , Tobutt Kenneth R. , Konstantinović Miroslav , Maksimović Vesna , Sargent Daniel J. , Stevanović Vladimir , Ortega Encarnación , Bošković Radovan I. 
Published: May 2007

SummaryMany species of Prunus display an S‐RNase‐based gametophytic self‐incompatibility (SI), controlled by a single highly polymorphic multigene complex termed the S‐locus. This comprises tightly linked stylar‐ and pollen‐expressed genes that determine the specificity of the SI response. We investigated SI of Prunus tenella, a wild species found in small, isolated populations on the Balkan peninsula, initially by pollination experiments and identifying stylar‐expressed RNase alleles. Nine P. tenella S‐RNase alleles (S1–S9) were cloned; their sequence analysis showed a very high ratio of non‐synonymous to synonymous nucleotide substitutions (Ka/Ks) and revealed that S‐RNase alleles of P. tenella, unlike those of Prunus dulcis, show positive selection in all regions except the conserved regions and that between C2 and RHV. Remarkably, S8‐RNase, was found to be identical to S1‐RNase from Prunus avium, a species that does not interbreed with P. tenella and, except for just one amino acid, to S11 of P. dulcis. However, the corresponding introns and S‐RNase–SFB intergenic regions showed considerable differences. Moreover, protein sequences of the pollen‐expressed SFB alleles were not identical, harbouring 12 amino‐acid replacements between those of P. tenella SFB8 and P. avium SFB1. Implications of this finding for hypotheses about the evolution of new S‐specificities are discussed.
Light‐regulated large‐scale reorganization of chromatin during the floral transition in Arabidopsis
Authors: Tessadori Federico , Schulkes Roeland Kees , Driel Roel van , Fransz Paul 
Published: May 2007

SummaryThe floral transition marks the switch from vegetative to reproductive growth, and is controlled by different pathways responsive to endogenous and exogenous cues. The developmental switch is accompanied by local changes in chromatin such as histone modifications. In this study we demonstrate large‐scale reorganization of chromatin in rosette leaves during the floral transition. An extensive reduction in chromocenters prior to bolting is followed by a recovery of the heterochromatin domains after elongation of the floral stem. The transient reduction in chromocenters is a result of relocation away from chromocenters of methylated DNA sequences, 5S rDNA and interspersed pericentromeric repeats, but not of 45S rDNA or the 180‐bp centromere tandem repeats. Moreover, fluorescence in situ hybridization analysis revealed decondensation of chromatin in gene‐rich regions. A mutant analysis indicated that the blue‐light photoreceptor CRYPTOCHROME 2 is involved in triggering chromatin decondensation, suggesting a light‐signaling pathway towards large‐scale chromatin modulation.
The Arabidopsis ABA‐deficient mutant aba4 demonstrates that the major route for stress‐induced ABA accumulation is via neoxanthin isomers
Authors: North Helen M. , Almeida Aurélie De , Boutin Jean‐Pierre , Frey Anne , To Alexandra , Botran Lucy , Sotta Bruno , Marion‐Poll Annie 
Published: May 2007

SummaryA novel abscisic acid (ABA)‐deficient mutant, aba4, was identified in a screen for paclobutrazol‐resistant germination. Compared with wild‐type, the mutant showed reduced endogenous ABA levels in both dehydrated rosettes and seeds. Carotenoid composition analysis demonstrated that the defective locus affects neoxanthin synthesis. The ABA4 gene was identified by map‐based cloning, and found to be a unique gene in the Arabidopsis genome. The predicted protein has four putative helical transmembrane domains and shows significant similarity to predicted proteins from tomato, rice and cyanobacteria. Constitutive expression of the ABA4 gene in Arabidopsis transgenic plants led to increased accumulation of trans‐neoxanthin, indicating that the ABA4 protein has a direct role in neoxanthin synthesis. aba4 mutant phenotypes were mild compared with previously identified ABA‐deficient mutants that exhibit vegetative tissue phenotypes. Indeed, ABA levels in seeds of aba4 mutants were higher than those of aba1 mutants. As aba1 mutants are also affected in a unique gene, this suggests that ABA can be produced in the aba4 mutant by an alternative pathway using violaxanthin as a substrate. It appears, therefore, that in Arabidopsis both violaxanthin and neoxanthin are in vivo substrates for 9‐cis‐epoxycarotenoid dioxygenases. Furthermore, significantly reduced levels of ABA were synthesized in the aba4 mutant on dehydration, demonstrating that ABA biosynthesis in response to stress must occur mainly via neoxanthin isomer precursors.
The KNOX gene SHOOT MERISTEMLESS is required for the development of reproductive meristematic tissues in Arabidopsis
Authors: Scofield Simon , Dewitte Walter , Murray James A.H. 
Published: May 2007

SummaryIn Arabidopsis, the central stem cells of the shoot apical meristem (SAM) are indefinitely maintained, whereas those in floral meristems differentiate into female gametophyte‐bearing organs termed carpels. The class 1 KNOX genes encode homeodomain transcription factors that function variously in the establishment and maintenance of the SAM, and have also been implicated in carpel development. Here we show that the KNOX gene SHOOT MERISTEMLESS (STM) induces carpel formation and promotes homeotic conversion of ovules to carpels when ectopically expressed in flowers, as previously reported for the related gene KNAT2. In contrast to KNAT2, loss of which confers no phenotype, we show using inducible RNA interference and mutational analysis that progressive loss of STM causes floral phenotypes ranging from reduced formation of placental tissues and inhibited carpel fusion to complete loss of carpel development. These effects result neither from failure to establish the central stem cell niche nor from reduced floral homeotic gene expression, but rather indicate a specific requirement for STM in carpel initiation, as further supported by the loss of leafy carpelloid features in stm leafy double mutants. Activation of carpel development by STM is independent of LEAFY and WUSCHEL, but requires the function of AGAMOUS. The essential role for STM in carpel development, together with its previous reported role in the SAM, shows that, despite the existence of several partially redundant paralogous genes, STM provides the critical KNOX function in the development of both vegetative and reproductive meristematic tissues.
Arabidopsis Ovate Family Protein 1 is a transcriptional repressor that suppresses cell elongation
Authors: Wang Shucai , Chang Ying , Guo Jianjun , Chen Jin‐Gui 
Published: May 2007

SummaryTranscription factors regulate multiple aspects of plant growth and development. Here we report the identification and functional analysis of a plant‐specific, novel transcription factor in Arabidopsis. We isolated a dominant, gain‐of‐function mutant that displays reduced lengths in all aerial organs including hypocotyl, rosette leaf, cauline leaf, inflorescence stem, floral organs and silique. Molecular cloning revealed that these phenotypes are caused by elevated expression of the Arabidopsis thaliana Ovate Family Protein 1 (AtOFP1). This mutant was designated as Atofp1‐1D. We show that the altered morphology of Atofp1‐1D mutant is caused by reduced cell length resulting from reduced cell elongation, and demonstrate that a mutant harboring a transposon insertion that disrupts the OVATE domain of AtOFP1 is indistinguishable from wild‐type plants. Plants overexpressing other closely related AtOFP genes phenocopy plants overexpressing AtOFP1, implying a possible overlapping function among members of the AtOFP gene family. We found that AtOFP1 localizes in the nucleus, and that AtOFP1 functions as an active transcriptional repressor. Chromatin immunoprecipitation results indicated that AtGA20ox1, a gene encoding the key enzyme in GA biosynthesis, is a target gene regulated by AtOFP1. Consistent with this, exogenous gibberellic acid can partially restore defects in cell elongation in plants overexpressing AtOFP1, suggesting that such a reduced cell elongation is caused, in part, by the deficiency in gibberellin biosynthesis. Taken together, our results indicate that AtOFP1 is an active transcriptional repressor that has a role in regulating cell elongation in plants.
Patterns of gene duplication in the plant SKP1 gene family in angiosperms: evidence for multiple mechanisms of rapid gene birth
Authors: Kong Hongzhi , Landherr Lena L. , Frohlich Michael W. , Leebens‐Mack Jim , Ma Hong , DePamphilis Claude W. 
Published: May 2007

SummaryGene duplication plays important roles in organismal evolution, because duplicate genes provide raw materials for the evolution of mechanisms controlling physiological and/or morphological novelties. Gene duplication can occur via several mechanisms, including segmental duplication, tandem duplication and retroposition. Although segmental and tandem duplications have been found to be important for the expansion of a number of multigene families, the contribution of retroposition is not clear. Here we show that plant SKP1 genes have evolved by multiple duplication events from a single ancestral copy in the most recent common ancestor (MRCA) of eudicots and monocots, resulting in 19 ASK (Arabidopsis SKP1‐like) and 28 OSK (Oryza SKP1‐like) genes. The estimated birth rates are more than ten times the average rate of gene duplication, and are even higher than that of other rapidly duplicating plant genes, such as type I MADS box genes, R genes, and genes encoding receptor‐like kinases. Further analyses suggest that a relatively large proportion of the duplication events may be explained by tandem duplication, but few, if any, are likely to be due to segmental duplication. In addition, by mapping the gain/loss of a specific intron on gene phylogenies, and by searching for the features that characterize retrogenes/retrosequences, we show that retroposition is an important mechanism for expansion of the plant SKP1 gene family. Specifically, we propose that two and three ancient retroposition events occurred in lineages leading to Arabidopsis and rice, respectively, followed by repeated tandem duplications and chromosome rearrangements. Our study represents a thorough investigation showing that retroposition can play an important role in the evolution of a plant gene family whose members do not encode mobile elements.
Transcript and metabolite profiling during cold acclimation of Arabidopsis reveals an intricate relationship of cold‐regulated gene expression with modifications in metabolite content
Authors: Kaplan Fatma , Kopka Joachim , Sung Dong Yul , Zhao Wei , Popp Mick , Porat Ron , Guy Charles L. 
Published: May 2007

SummaryExposure of Arabidopsis to low temperatures results in cold acclimation where freezing tolerance is enhanced. To achieve a wider view of the role of transcriptome to biochemical changes that occur during cold acclimation, analyses of concurrent transcript and metabolite changes during cold acclimation was performed revealing the dynamics of selected gene–metabolite relationships. Exposure to low temperature resulted in broad transcriptional and metabolite responses. Principal component analysis revealed sequentially progressive, global changes in both gene expression and metabolite profiles during cold acclimation. Changes in transcript abundance for many metabolic processes, including protein amino acid biosynthetic pathways and soluble carbohydrates, during cold acclimation were observed. For some metabolic processes, changes in transcript abundance temporally correlated with changes in metabolite levels. For other metabolic processes, changes in transcript levels were not correlated with changes in metabolite levels. The present findings demonstrate that regulatory processes independent of transcript abundance represent a key part of the metabolic adjustments that occur during cold acclimation.
Identification of a flavin‐monooxygenase as the S‐oxygenating enzyme in aliphatic glucosinolate biosynthesis in Arabidopsis
Authors: Hansen Bjarne G. , Kliebenstein Daniel J. , Halkier Barbara A. 
Published: May 2007

SummaryThe cancer‐preventive activity of cruciferous vegetables is commonly attributed to isothiocyanates resulting from the breakdown of the natural products glucosinolates (GSLs). Sulforaphane, the isothiocyanate derived from 4‐methylsulfinylbutyl GSL, is thought to be the major agent conferring cancer‐preventive properties, whereas the isothiocyanate of 4‐methylthiobutyl GSL does not have the same activity. We report the identification of an Arabidopsis flavin‐monooxygenase (FMO) enzyme, FMOGS‐OX1, which catalyzes the conversion of methylthioalkyl GSLs into methylsulfinylalkyl GSLs. This is evidenced by biochemical characterization of the recombinant protein, and analyses of the GSL content in FMOGS‐OX1 overexpression lines and an FMOGS‐OX1 knock‐out mutant of Arabidopsis. The FMOGS‐OX1 overexpression lines show almost complete conversion of methylthioalkyl into methylsulfinylalkyl GSLs, with an approximately fivefold increase in 4‐methylsulfinylbutyl GSL in seeds. Identification of FMOGS‐OX1 provides a molecular tool for breeding of Brassica vegetable crops with increased levels of this important GSL, which has implications for production of functional foods enriched with the cancer‐preventive sulforaphane.