bluuebunny/crossref_metadata_2025_split huggingface dataset:
ERECTA receptor‐like kinase and heterotrimeric G protein from Arabidopsis are required for resistance to the necrotrophic fungus Plectosphaerella cucumerina
Authors: Llorente Francisco , Alonso‐Blanco Carlos , Sánchez‐Rodriguez Clara , Jorda Lucía , Molina Antonio 
Published: July 2005

SummaryArabidopsis resistance to the necrotrophic fungus Plectosphaerella cucumerina is complex and depends on the ethylene, jasmonic acid and salicylic acid signaling pathways. A quantitative trait loci (QTL) analysis of resistance to this fungus was performed using two populations of recombinant inbred lines. Three loci QRP1‐QRP3 (for Quantitative Resistance to Plectosphaerella) were identified and mapped on chromosome 2 (QRP1 and QRP2) and 5 (QRP3). QRP1, the locus showing the strongest effect, was found to correspond to the ERECTA (ER) gene that encodes a receptor‐like‐kinase (RLK), which has been previously implicated in plant development, and resistance to the bacterium Ralstonia solanacearum. The leucine‐rich repeat and the kinase domains of ERECTA were specifically required for resistance to P. cucumerina, as er mutant alleles impaired in any of these domains showed enhanced susceptibility to this fungus, but not to other virulent pathogens. The involvement of the ER‐signaling pathway in resistance to P. cucumerina was supported by the fact that three mutants defective in this pathway, elk2, elk5 and elk4 (agb1‐1), which encodes the β‐subunit of Arabidopsis heterotrimeric G protein, were also impaired in their resistance to this fungus. The putative function of the Arabidopsis heterotrimeric G protein in resistance to P. cucumerina suggested by the enhanced susceptibility of agb1‐1 was corroborated by the demonstration that a null allele (gpa1‐4) of the G protein α‐subunit showed enhanced resistance to this pathogen. Deposition of β‐1,3‐glucan callose at infection sites was specifically impaired in er‐1 and agb1‐1 mutants upon P. cucumerina inoculation. Taken together, these data suggest a putative function of ERECTA and heterotrimeric G protein in P. cucumerina perception.
Altered microtubule dynamics by expression of modified α‐tubulin protein causes right‐handed helical growth in transgenic Arabidopsis plants
Authors: Abe Tatsuya , Hashimoto Takashi 
Published: July 2005

SummaryThe proper organization of cortical microtubule arrays is essential for anisotropic growth in plants but how distinct array patterns are formed is not understood. Here, we report a relationship between microtubule dynamics and array organization using transgenic plants expressing modified tubulins. When green fluorescent protein (GFP) or a hemaglutinin epitope tag was fused to the N‐terminus of tubulins and expressed in Arabidopsis plants, these tubulins were incorporated into microtubules along with endogenous tubulins. Plants expressing the modified β‐tubulins were phenotypically normal and possessed transversely oriented cortical arrays in the epidermal cells of the root elongation zone; however, the expression of modified α‐tubulins caused right‐handed helical growth, increased trichome branching, and a shallow left‐handed (S‐form) helical array organization. In cells expressing the modified α‐tubulins, microtubule dynamicity was suppressed and polymerization was promoted, and GFP‐EB1 (End Binding 1) labeled larger regions of the microtubule end more frequently, when compared with control cells. We propose that the N‐terminal appendage introduced into α‐tubulin inhibits GTP hydrolysis, thus producing polymerization‐prone microtubules with an extended GTP cap. Consistent with this interpretation, plants expressing an α‐tubulin mutated in the GTPase‐activating domain exhibited similar microtubule properties, with regard to dynamics and the localization of GFP‐EB1, and showed right‐handed helical growth.
Cell wall extension results in the coordinate separation of parallel microfibrils: evidence from scanning electron microscopy and atomic force microscopy
Authors: Marga Francoise , Grandbois Michel , Cosgrove Daniel J. , Baskin Tobias I. 
Published: July 2005

SummaryEnlargement of the cell wall requires separation of cellulose microfibrils, mediated by proteins such as expansin; according to the multi‐net growth hypothesis, enlargement passively reorients microfibrils. However, at the molecular scale, little is known about the specific movement of microfibrils. To find out, we examined directly changes in microfibril orientation when walls were extended slowly in vitro under constant load (creep). Frozen‐thawed cucumber hypocotyl segments were strained by 20–30% by incubation in pH 4.5 buffer or by incubation of heat‐inactivated segments in α‐expansin or a fungal endoglucanase (Cel12A). Subsequently, the innermost layer of the cell wall was imaged, with neither extraction nor homogenization, by field‐emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). AFM images revealed that sample preparation for FESEM did not appreciably alter cell wall ultrastructure. In both FESEM and AFM, images from extended and non‐extended samples appeared indistinguishable. To quantify orientational order, we used a novel algorithm to characterize the fast Fourier transform of the image as a function of spatial frequency. For both FESEM and AFM images, the transforms of non‐extended samples were indistinguishable from those of samples extended by α‐expansin or Cel12A, as were AFM images of samples extended by acidic buffer. We conclude that cell walls in vitro can extend slowly by a creep mechanism without passive reorientation of innermost microfibrils, implying that wall loosening agents act selectively on the cross‐linking polymers between parallel microfibrils, rather than more generally on the wall matrix.
Interaction of Arabidopsis BRASSINOSTEROID‐INSENSITIVE 1 receptor kinase with a homolog of mammalian TGF‐β receptor interacting protein
Authors: Ehsan Hashimul , Ray William Keith , Phinney Brett , Wang Xiaofeng , Huber Steven C. , Clouse Steven D. 
Published: July 2005

SummaryBrassinosteroids (BRs) regulate multiple aspects of plant growth and development and require an active BRASSINOSTEROID‐INSENSITIVE 1 (BRI1) receptor serine/threonine kinase for hormone perception and signal transduction. In mammals, the transforming growth factor‐beta (TGF‐β) family of polypeptides modulate numerous aspects of development and are perceived at the cell surface by a complex of type I and type II TGF‐β receptor serine/threonine kinases. TGF‐β receptor interacting protein (TRIP‐1) is a cytoplasmic substrate of the TGF‐β type II receptor kinase and plays a role in TGF‐β signaling. TRIP‐1 is a WD domain protein that also functions as an essential subunit of the eIF3 eukaryotic translation initiation factor in animals, yeast and plants. We previously cloned putative TRIP‐1 homologs from bean and Arabidopsis and found that transgenic Arabidopsis plants expressing antisense TRIP‐1 RNA exhibited a broad range of developmental defects including some morphological characteristics that resemble the phenotype of BR‐deficient and ‐insensitive mutants. We now show that the BRI1 kinase domain phosphorylates Arabidopsis TRIP‐1 on three specific sites in vitro (Thr‐14, Thr‐89 and either Thr‐197 or Ser‐198). Co‐immunoprecipitation experiments using antibodies against TRIP‐1, BRI1 and various fusion proteins strongly suggest that TRIP‐1 and BRI1 also interact directly in vivo. These findings support a role for TRIP‐1 in the molecular mechanisms of BR‐regulated plant growth and development, possibly as a cytoplasmic substrate of the BRI1 receptor kinase.
Heat shock protein 90 and its co‐chaperone protein phosphatase 5 interact with distinct regions of the tomato I‐2 disease resistance protein
Authors: De La Fuente Bentem van Sergio , Vossen Jack H. , de Vries Klaas Jan , van Wees Saskia , Tameling Wladimir I.L. , Dekker Henk L. , de Koster Chris G. , Haring Michel A. , Takken Frank L.W. , Cornelissen Ben J.C. 
Published: July 2005

SummaryRecent data suggest that plant disease resistance (R) proteins are present in multi‐protein complexes. Tomato R protein I‐2 confers resistance against the fungal pathogen Fusarium oxysporum. To identify components of the I‐2 complex, we performed yeast two‐hybrid screens using the I‐2 leucine‐rich repeat (LRR) domain as bait, and identified protein phosphatase 5 (PP5) as an I‐2 interactor. Subsequent screens revealed two members of the cytosolic heat shock protein 90 (HSP90) family as interactors of PP5. By performing in vitro protein–protein interaction analysis using recombinant proteins, we were able to show a direct interaction between I‐2 and PP5, and between I‐2 and HSP90. The N‐terminal part of the LRR domain was found to interact with HSP90, whereas the C‐terminal part bound to PP5. The specific binding of HSP90 to the N‐terminal region of the I‐2 LRR domain was confirmed by co‐purifying HSP90 from tomato lysate using recombinant proteins. Similarly, the interaction between PP5 and HSP90 was established. To investigate the role of PP5 and HSP90 for I‐2 function, virus‐induced gene silencing was performed in Nicotiana benthamiana. Silencing of HSP90 but not of PP5 completely blocked cell death triggered by I‐2, showing that HSP90 is required for I‐2 function. Together these data suggest that R proteins require, like steroid hormone receptors in animal systems, an HSP90/PP5 complex for their folding and functioning.
Siderophore‐mediated upregulation of Arabidopsis ferritin expression in response to Erwinia chrysanthemi infection
Authors: Dellagi Alia , Rigault Martine , Segond Diego , Roux Camille , Kraepiel Yvan , Cellier Françoise , Briat Jean‐François , Gaymard Frédéric , Expert Dominique 
Published: July 2005

SummaryFerritins are multimeric iron storage proteins encoded by a four‐member gene family in Arabidopsis (AtFer1–4). To investigate whether iron sequestration in ferritins is a part of an iron‐withholding defense system induced in response to bacterial invasion, we used Arabidopsis thaliana as a susceptible host for the pathogenic bacterium Erwinia chrysanthemi. In this study, we used a T‐DNA insertion mutant line to show that the lack of a functional AtFer1 gene resulted in an enhanced susceptibility of Arabidopsis plants to E. chrysanthemi. We found that the AtFer1 gene is upregulated during infection, with a biphasic accumulation of the transcript at critical time points 0.5 and 24 h post‐infection (p.i.). The activation of AtFer1 expression observed at 24 h p.i. was independent of the iron‐dependent regulatory sequence (IDRS) known to mediate the transcriptional response of the AtFer1 gene to iron excess and to nitric oxide. Upregulation of AtFer1 gene expression was compromised after inoculation with an E. chrysanthemi siderophore null mutant. Infiltration of the purified siderophores chrysobactin and desferrioxamine strongly increased AtFer1 transcript abundance and it did not occur with the iron‐loaded forms of these siderophores. We found that neither oxidative stress nor nitric oxide was involved in the plant response to chrysobactin. Our data show that ferritin accumulation during infection of Arabidopsis by E. chrysanthemi is a basal defense mechanism which is mainly activated by bacterial siderophores. The potential role of siderophores in this process is discussed.
Disruption of the cellulose synthase gene, AtCesA8/IRX1, enhances drought and osmotic stress tolerance in Arabidopsis
Authors: Chen Zhizhong , Hong Xuhui , Zhang Hairong , Wang Youqun , Li Xia , Zhu Jian‐Kang , Gong Zhizhong 
Published: July 2005

SummaryTwo allelic Arabidopsis mutants, leaf wilting 2‐1 and leaf wilting 2‐2 (lew2‐1 and lew2‐2 ), were isolated in a screen for plants with altered drought stress responses. The mutants were more tolerant to drought stress as well as to NaCl, mannitol and other osmotic stresses. lew2 mutant plants accumulated more abscisic acid (ABA), proline and soluble sugars than the wild type. The expression of a stress‐inducible marker gene RD29A, a proline synthesis‐related gene P5CS (pyrroline‐5‐carboxylate synthase) and an ABA synthesis‐related gene SDR1 (alcohol dehydrogenase/reductase) was higher in lew2 than in the wild type. Map‐based cloning revealed that the lew2 mutants are new alleles of the AtCesA8/IRX1 gene which encodes a subunit of a cellulose synthesis complex. Our results suggest that cellulose synthesis is important for drought and osmotic stress responses including drought induction of gene expression.
Potential impacts of climate change on the distributions of several common and rare freshwater fishes in Canada
Authors: Chu Cindy , Mandrak Nicholas E. , Minns Charles K. 
Published: July 2005

ABSTRACTClimate change will ultimately affect the supply and quality of freshwater lakes and rivers throughout the world. This study examines the potential impacts of climate change on freshwater fish distributions in Canada. Climate normals data (means from 1961 to 1990) from Environment Canada were used to map current climate found throughout the tertiary watersheds of Canada. Logistic regressions based on these climate data were used to develop predictive presence‐absence equations for (a) common commercially and recreationally important species and (b) an Arctic freshwater species and a freshwater fish species of conservation significance listed by the Committee on the Status of Endangered Wildlife (COSEWIC). The Canadian Centre for Climate Modelling and Analysis Global Coupled Model 2(IS92a) provided forecasts of Canada's climate in 2020 and 2050. The data from this scenario and the logistic regressions provided a ready framework for predicting the potential distributions of the fishes. Physical and ecological barriers would have to be overcome for the distribution of these species to actually change in response to climate change. Generally, coldwater species may be extirpated from much of their present range while cool and warm‐water species may expand northward. Species that are limited to the most southern regions of the country may expand northwards. A conceptual framework for assessing potential climate change impacts on fishes and the variety of management strategies required to deal with these impacts are discussed. Our forecasts demonstrate the need for climate change assessments in species at risk as well as for common species.
Dispersal and establishment: spatial patterns and species–area relationships
Authors: Hovestadt Thomas , Poethke Hans Joachim 
Published: July 2005

ABSTRACTAccording to the equilibrium theory of island biogeography, high colonization ability of species is associated with low exponents (z) of the species–area relationship (SAR) and weak spatial patterns in species number and dissimilarity. However, the relationship betweenzand the strength of these spatial patterns has not been investigated systematically. We used a multispecies metapopulation model to investigate these relationships in an archipelago of islands. We conclude that this relationship can only be predicted if either the dispersal ability or the power of establishment of species is known. With species richness limited by establishment, we generated highz‐values associated with weak spatial patterns in species number and dissimilarity. If species richness was constrained by the dispersal ability of species, we observed low to mediumz‐values but strong spatial patterns. If the dispersal ability and the abilities of species to establish were both high,z‐values and spatial pattern tend to be low and species numbers were limited by the size of the regional species pool.
Invasive alien plant species in China: regional distribution patterns
Authors: Liu Jian , Liang Shi‐Chu , Liu Feng‐Hong , Wang Ren‐Qing , Dong Ming 
Published: July 2005

ABSTRACTPlant invasions have been attracting increasing attention from ecologists because of their worldwide environmental impacts and huge economic costs. Research on the characteristics of the recipient regions is essential for understanding the process of plant invasion. However, few previous studies on invasibility of habitats include social factors, although human activities are critical in the process of plant invasion. China is a vast country with high plant species diversity and a long history of introduction of exotic plant species and is particularly vulnerable to invasive plant species. Alien plant species are widespread in the country. Therefore, the study of invasive plants in China is urgent in practice and theoretically important for developing invasion ecology. For the present study, 126 species were selected to represent the major invasive plant species in China. We then collected data on their species richness in 31 provincial administrative units of China and performed Spearman rank correlations between species richness and possible natural and socio‐economic factors. We found that socio‐economic factors, such as human density and GDP, correlated positively with the species richness of invasive plants in China. In conjunction with the natural and socio‐economic correlations in the study of regional distribution pattern of the major invasive plants, we discussed the factors influencing the regional distribution pattern of the major invasive plants in China. We suggest that native plant species richness was mainly determined by the natural conditions of the regions, while invasive species richness was influenced by natural conditions and human disturbance together.
Profiling invasive fish species: the importance of phylogeny and human use
Authors: Alcaraz Carles , Vila‐Gispert Anna , García‐Berthou Emili 
Published: July 2005

ABSTRACTUnderstanding the ecological differences between native and invasive species is of considerable scientific and practical interest. We examined such differences between native and invasive inland fish species from the Iberian Peninsula in order to analyse the importance of phylogenetic correction and variability (in addition to central tendency). We collected 26 quantitative and qualitative variables on the ecology, life‐history traits and human use of the 69 inland fish species of the Iberian Peninsula, including native, invasive and migratory species. The taxonomic distribution of invasive fish species deviated significantly from world freshwater richness and in contrast to native species, invasive fish belongs to only five taxonomic orders but to a wide spectrum of families not native to the Iberian Peninsula. Because the life‐history traits were highly dependent on taxonomy, the results, with or without applying phylogenetic methods, differed and after accounting for phylogeny, invasive species displayed higher and wider latitude in general and a different reproductive season mainly among salmonids and cyprinids. Human use was also significantly different between native and invasive fish species and produced more variability in life‐history traits of invasive species and uneven taxonomic distribution because of the high diversity of species introduced. We show that accounting for taxonomy and studying variability in addition to central tendency is important in the comparison of life‐history traits between native and invasive species.
Borosilicate‐ and phengite‐bearing veins from the Grenville Province of Labrador: evidence for rapid uplift
Authors: KORHONEN F. J. , STOUT J. H. 
Published: July 2005

AbstractQuartzo‐feldspathic veins emplaced within a migmatite terrane near Wilson Lake in the Grenville Province of central Labrador record a metamorphic event not evident in the host rocks. The discordant veins are undeformed and have undisturbed primary igneous/hydrothermal textures. Most of the veins contain euhedral kyanite, as well as aggregates of kyanite, K‐feldspar, phlogopite and minor dumortierite which are likely pseudomorphs after primary phengite. The reconstructed phengite compositions range from 3.1 to 3.2 Si per 11 oxygen formula unit. The pseudomorph assemblage is interpreted as the product of phengite + quartz melting under H2O‐undersaturated conditions, which brackets P–T conditions of formation to about 9–16 kbar and 775–875 °C. A parallel vein that is likely of the same generation contains the borosilicate phases, dumortierite, prismatine and grandidierite, but no kyanite. The borosilicate assemblages constrain the P–T conditions of vein crystallization to ≥10 kbar and c. 750–850 °C. Vein emplacement is constrained to T ≤ 875 °C at the same pressures, which is well within the kyanite zone.Because the host rocks and veins must have experienced the same P–T history following vein emplacement, the presence of unreacted sillimanite in the host migmatites implies insufficient time for host rock equilibration. Slow reaction rates because of anhydrous conditions are not a likely explanation given the abundance of biotite and hornblende in the host rocks. The ductility implied by the breakdown of a hydrous phase (phengite) and the production of an H2O‐undersaturated melt in the veins contrasts with the apparently brittle behaviour of the host rocks. The absence of deformation since the time of vein emplacement, even at temperatures above 750 °C, suggests that the deep crust in this part of Labrador had a very short residence time under conditions of the kyanite zone. Rapid decompression from those conditions is consistent with quartz + phengite melting and accounts for the relatively brittle behaviour of the terrane as it was uplifted.
Progress of actinolite‐forming reactions in mafic schists during retrograde metamorphism: an example from the Sanbagawa metamorphic belt in central Shikoku, Japan
Authors: OKAMOTO A. , TORIUMI M. 
Published: July 2005

AbstractHydration reactions are direct evidence of fluid–rock interaction during regional metamorphism. In this study, hydration reactions to produce retrograde actinolite in mafic schists are investigated to evaluate the controlling factors on the reaction progress. Mafic schists in the Sanbagawa belt contain amphibole coexisting with epidote, chlorite, plagioclase and quartz. Amphibole typically shows two types of compositional zoning from core to rim: barroisite → hornblende → actinolite in the high‐grade zone, and winchite → actinolite in the low‐grade zone. Both types indicate that amphibole grew during the exhumation stage of the metamorphic belt. Microstructures of amphibole zoning and mass‐balance relations suggest that: (1) the actinolite‐forming reactions proceeded at the expense of the preexisting amphibole; and (2) the breakdown reaction of hornblende consumed more H2O fluid than that of winchite, when one mole of preexisting amphibole was reacted. Reaction progress is indicated by the volume fraction of actinolite to total amphibole, Yact, with the following details: (1) reaction proceeded homogeneously in each mafic layer; (2) the extent of the hornblende breakdown reaction is commonly low (Yact < 0.5), but it increases drastically in the high‐grade part of the garnet zone (Yact > 0.7); and (3) the extent of the winchite breakdown reaction is commonly high (Yact > 0.7). Many microcracks are observed within hornblende, and the extent of hornblende breakdown reaction is correlated with the size reduction of the hornblende core. Brittle fracturing of hornblende may have enhanced retrograde reaction progress by increasing of influx of H2O and the surface area of hornblende. In contrast to high‐grade rocks, the winchite breakdown reaction is well advanced in the low‐grade rocks, where reaction progress is not associated with brittle fracturing of winchite. The high extent of the reaction in the low‐grade rocks may be due to small size of winchite before the reaction.