bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ecdysone agonist‐inducible expression of a coat protein gene from tobacco mosaic virus confers viral resistance in transgenic Arabidopsis
Authors: Koo Ja Choon , Asurmendi Sebastian , Bick Jennifer , Woodford‐Thomas Terry , Beachy Roger N. 
Published: January 2004

SummaryConstitutive expression of a gene encoding tobacco mosaic virus (TMV) coat protein (CP) in transgenic plants confers resistance to infection by TMV and related tobamoviruses. Here, we examined resistance to TMV by temporal and quantitative control of TMV Cg CP (CgCP) gene expression using a simple, methoxyfenozide‐inducible system in Arabidopsis plants. By soil drenching with a commercial ecdysone agonist (Intrepid‐2F/methoxyfenozide), most transgenic lines were induced from undetectable levels of gene expression to protein levels from 0.05 to 0.8% (w/w) of CgCP. This corresponds to up to four times the amount of CP produced by the constitutive cauliflower mosaic virus (CaMV) double 35S promoter. CgCP transcripts were induced by 700‐fold, without changing the expression patterns of pathogenesis‐related (PR) genes. The high level of accumulation of CgCP was sufficient to produce large amounts of virus‐like particles that accumulate in large aggregates throughout the cells. In virus challenge assays, treatment with Intrepid‐2F prior to TMV infection resulted in high levels of viral resistance, while no treatment or treatment with the inducer following infection did not confer resistance. This report demonstrates chemically controlled disease resistance and confirms the utility of the ecdysone agonist‐inducible system under greenhouse conditions.
HvDRF1 is involved in abscisic acid‐mediated gene regulation in barley and produces two forms of AP2 transcriptional activators, interacting preferably with a CT‐rich element
Authors: Xue Gang‐Ping , Loveridge Carl W. 
Published: January 2004

SummaryApetala2/ethylene‐responsive factor (AP2/ERF) proteins are AP2 domain‐containing transcription factors and form the second largest transcription factor family in plants. Biological functions of many of these AP2 proteins are still unknown. Here, we report the characterisation of a novel member of the AP2/ERF superfamily, dehydration‐responsive factor 1 (HvDRF1) from barley, and its role in abscisic acid (ABA)‐mediated gene regulation. The expression of HvDRF1 was upregulated in barley leaves and roots under drought, salt or ABA treatment, and in embryos during seed maturation. Three forms of HvDRF1 transcripts were produced through alternative splicing, two of which encoded AP2 proteins. This alternative splicing pattern was also observed in a wheat homologue gene, TaDRF1. Both of HvDRF1 AP2 proteins acted as transcriptional activators, capable of activating the promoter activity of an ABA‐inducible HVA1s in barley. In vitro DNA‐binding analysis using synthetic oligonucleotides revealed that HvDRF1 AP2 protein bound preferably to a CT‐rich element (T(T/A)ACCGCCTT). HvDRF1 activity on the activation of HVA1s expression in barley leaves was markedly enhanced by HvABI5 (a bZIP transcription factor), ABA or drought treatment. These results indicate that the HvDRF1 transcriptional activator co‐operates with other ABA‐responsive factors in the upregulation of stress gene expression through an ABA‐dependent pathway.
Arabidopsis ALF4 encodes a nuclear‐localized protein required for lateral root formation
Authors: DiDonato Raymond J. , Arbuckle Erin , Buker Shane , Sheets Jill , Tobar José , Totong Ronald , Grisafi Paula , Fink Gerald R. , Celenza John L. 
Published: January 2004

SummaryLateral root formation, the primary way plants increase their root mass, displays developmental plasticity in response to environmental changes. The aberrant lateral root formation (alf)4‐1 mutation blocks the initiation of lateral roots, thus greatly altering root system architecture. We have positionally cloned the ALF4 gene and have further characterized its phenotype. The encoded ALF4 protein is conserved among plants and has no similarities to proteins from other kingdoms. The gene is present in a single copy in Arabidopsis. Using translational reporters for ALF4 gene expression, we have determined that the ALF4 protein is nuclear localized and that the gene is expressed in most plant tissues; however, ALF4 expression and ALF4's subcellular location are not regulated by auxin. These findings taken together with further genetic and phenotypic characterization of the alf4‐1 mutant suggest that ALF4 functions independent from auxin signaling and instead functions in maintaining the pericycle in the mitotically competent state needed for lateral root formation. Our results provide genetic evidence that the pericycle shares properties with meristems and that this tissue plays a central role in creating the developmental plasticity needed for root system development.
Development of a luciferase reporter gene, luxCt, for Chlamydomonas reinhardtii chloroplast
Authors: Mayfield Stephen P. , Schultz Jason 
Published: January 2004

SummaryLuciferase reporter genes have been successfully used in a variety of organisms to examine gene expression in living cells, but are yet to be successfully developed for use in chloroplast. Green fluorescent protein (gfp) has been used as a reporter of chloroplast gene expression, but because of high auto‐fluorescence, very high levels of GFP accumulation are required for visualization in vivo. We have developed a luciferase reporter for chloroplast by synthesizing the two‐subunit bacterial luciferase (lux)AB, as a single fusion protein in Chlamydomonas reinhardtii chloroplast codon bias. We expressed a chloroplast luciferase gene, luxCt, in C. reinhardtii chloroplasts under the control of the ATPase alpha subunit (atpA) or psbA promoter and 5′ untranslated regions (UTRs) and the rubisco large subunit (rbcL) 3′ UTR. We show that luxCt is a sensitive reporter of chloroplast gene expression, and that luciferase activity can be measured in vivo using a charge coupled device (CCD) camera or in vitro using a luminometer. We further demonstrate that luxCt protein accumulation, as measured by Western blot analysis, is proportional to luminescence, as determined both in vivo and in vitro, and that luxCt is capable of reporting changes in chloroplast gene expression during a dark to light shift. These data demonstrate the utility of the luxCt gene as a versatile and sensitive reporter of chloroplast gene expression in living cells.
Organelle inheritance in plant cell division: the actin cytoskeleton is required for unbiased inheritance of chloroplasts, mitochondria and endoplasmic reticulum in dividing protoplasts
Authors: Sheahan Michael B. , Rose Ray J. , McCurdy David W. 
Published: January 2004

SummaryNuclear inheritance is highly ordered, ensuring stringent, unbiased partitioning of chromosomes before cell division. In plants, however, little is known about the analogous cellular processes that might ensure unbiased inheritance of non‐nuclear organelles, either in meristematic cell divisions or those induced during the acquisition of totipotency. We have investigated organelle redistribution and inheritance mechanisms during cell division in cultured tobacco mesophyll protoplasts. Quantitative analysis of organelle repositioning observed by autofluorescence of chloroplasts or green fluorescent protein (GFP), targeted to mitochondria or endoplasmic reticulum (ER), demonstrated that these organelles redistribute in an ordered manner before division. Treating protoplasts with cytoskeleton‐disrupting drugs showed that redistribution depended on actin filaments (AFs), but not on microtubules (MTs), and furthermore, that an intact actin cytoskeleton was required to achieve unbiased organelle inheritance. Labelling the actin cytoskeleton with a novel GFP‐fusion protein revealed a highly dynamic actin network, with local reorganisation of this network itself, appearing to contribute substantially to repositioning of chloroplasts and mitochondria. Our observations show that each organelle exploits a different strategy of redistribution to ensure unbiased partitioning. We conclude that inheritance of chloroplasts, mitochondria and ER in totipotent plant cells is an ordered process, requiring complex interactions with the actin cytoskeleton.
Papain protects papaya trees from herbivorous insects: role of cysteine proteases in latex
Authors: Konno Kotaro , Hirayama Chikara , Nakamura Masatoshi , Tateishi Ken , Tamura Yasumori , Hattori Makoto , Kohno Katsuyuki 
Published: January 2004

SummaryMany plants contain latex that exudes when leaves are damaged, and a number of proteins and enzymes have been found in it. The roles of those latex proteins and enzymes are as yet poorly understood. We found that papain, a cysteine protease in latex of the Papaya tree (Carica papaya, Caricaceae), is a crucial factor in the defense of the papaya tree against lepidopteran larvae such as oligophagous Samia ricini (Saturniidae) and two notorious polyphagous pests, Mamestra brassicae (Noctuidae) and Spodoptera litura (Noctuidae). Leaves of a number of laticiferous plants, including papaya and a wild fig, Ficus virgata (Moraceae), showed strong toxicity and growth inhibition against lepidopteran larvae, though no apparent toxic factors from these species have been reported. When the latex was washed off, the leaves of these lactiferous plants lost toxicity. Latexes of both papaya and the wild fig were rich in cysteine‐protease activity. E‐64, a cysteine protease‐specific inhibitor, completely deprived the leaves of toxicity when painted on the surface of papaya and fig leaves. Cysteine proteases, such as papain, ficin, and bromelain, all showed toxicity. The results suggest that plant latex and the proteins in it, cysteine proteases in particular, provide plants with a general defense mechanism against herbivorous insects.
A GFP‐based assay reveals a role for RHD3 in transport between the endoplasmic reticulum and Golgi apparatus
Authors: Zheng Huanquan , Kunst Ljerka , Hawes Chris , Moore Ian 
Published: January 2004

SummaryWe describe the use of a secreted form ofAequoria victoriagreen fluorescent protein (secGFP) in a non‐invasive live cell assay of membrane traffic inArabidopsis thaliana. We show that in comparison to GFP‐HDEL, which accumulates in the endoplasmic reticulum (ER), secGFP generates a weak fluorescence signal when transported to the apoplast. The fluorescence of secGFP in the apoplast can be increased by growth of seedlings on culture medium buffered at pH 8.1, suggesting that apoplastic pH is responsible, at least in part, for the low fluorescence intensity of seedlings expressing secGFP. Inhibition of secGFP transport between the ER and plasma membrane (PM), either by Brefeldin A (BFA) treatment or by genetic intervention results in increased intracellular secGFP accumulation accompanied by an increase in the secGFP fluorescence intensity. secGFP thus provides a valuable tool for forward and reverse genetic analysis of membrane traffic and endomembrane organisation inArabidopsis. Using this assay for quantitative sublethal perturbation of secGFP transport, we identify a role for root hair defective 3 (RHD3) in transport of secreted and Golgi markers between the ER and the Golgi apparatus.
Trafficking of the plant potassium inward rectifier KAT1 in guard cell protoplasts of Vicia faba
Authors: Hurst Annette C. , Meckel Tobias , Tayefeh Sascha , Thiel Gerhard , Homann Ulrike 
Published: January 2004

SummaryTrafficking of K+ inward (Kin+) rectifying channels was analyzed in guard cells of Vicia faba transfected with the Kin+ rectifier from Arabidopsis thaliana KAT1 fused to the green fluorescent protein (GFP). Confocal images and whole‐cell patch‐clamp measurements confirmed the incorporation of active KAT1 channels into the plasma membrane of transfected guard cell protoplasts. The Kin+ rectifier current density of the plasma membrane was much larger in transfected protoplasts than in wild‐type (wt) protoplasts. This shows a coupling between K+ channel synthesis and incorporation of the channel into the plasma membrane. Pressure‐driven increase and decrease in surface area led to the incorporation and removal of vesicular membrane carrying active Kin+ rectifier in wt and transfected protoplasts. These vesicular membranes revealed a higher channel density than the plasma membrane, suggesting that Kin+ rectifier remains in clusters during trafficking to and from the plasma membrane. The observed results can be explained by a model illustrating that vesicles of a pre‐plasma membrane pool carry K+ channels preferentially in clusters during constitutive and pressure‐driven exo‐ and endocytosis.
Photosynthetic Responses of a Temperate Liana to Xylella fastidiosa Infection and Water Stress
Authors: McElrone A. J. , Forseth I. N. 
Published: January 2004

Abstract Xylella fastidiosa is a xylem‐limited bacterial plant pathogen that causes bacterial leaf scorch in its hosts. Our previous work showed that water stress enhances leaf scorch symptom severity and progression along the stem of a liana, Parthenocissus quinquefolia, infected by X. fastidiosa. This paper explores the photosynthetic gas exchange responses of P. quinquefolia, with the aim to elucidate mechanisms behind disease expression and its interaction with water stress. We used a 2 × 2‐complete factorial design, repeated over two growing seasons, with high and low soil moisture levels and infected and non‐infected plants. In both years, low soil moisture levels reduced leaf water potentials, net photosynthesis and stomatal conductance at all leaf positions, while X. fastidiosa‐infection reduced these parameters at basally located leaves only. Intercellular CO2 concentrations were reduced in apical leaves, but increased at the most basal leaf location, implicating a non‐stomatal reduction of photosynthesis in leaves showing the greatest disease development. This result was supported by measured reductions in photosynthetic rates of basal leaves at high CO2 concentrations, where stomatal limitation was eliminated. Repeated measurements over the summer of 2000 showed that the effects of water stress and infection were progressive over time, reaching their greatest extent in September. By reducing stomatal conductances at moderate levels of water stress, P. quinquefolia maintained relatively high leaf water potentials and delayed the onset of photosynthetic damage due to pathogen and drought‐induced water stress. In addition, chlorophyll fluorescence measurements showed that P. quinquefolia has an efficient means of dissipating excess light energy that protects the photosynthetic machinery of leaves from irreversible photoinhibitory damage that may occur during stress‐induced stomatal limitation of photosynthesis. However, severe stress induced by disease and drought eventually led to non‐stomatal decreases in photosynthesis associated with leaf senescence.
Bacterial Stem Rot in Greenhouse Pepper (Capsicum annuum L.) in Sardinia (Italy): Occurrence of Erwinia carotovora subsp. carotovora
Authors: Fiori M. , Schiaffino A. 
Published: January 2004

AbstractAn unusual bacterial disease was observed in pepper plants during research carried out in greenhouses in central‐north Sardinia. The characteristics were: the presence of lesions and exudates on stems, soft rot of the pith, and a brownish‐black colour in the petioles and leaf‐veins. Only two isolates of 21 were pathogens. One was obtained from exudate present on the stem and the other from pith. Experimental infections revealed that the bacterial isolates were particularly aggressive in the stems and fruit of pepper and tomato. Biochemical, physiological and serological tests in conjunction with fatty acid profile analysis confirmed that they were Erwinia carotovora subsp. carotovora (Jones) Bergey et al. The product of 434 bp polymerase chain reaction (PCR) enabled a preliminary identification of isolates to be made. Restriction fragment length polymorphism (RFLP) analysis of amplification products showed that the isolates DPP 23ef and DPP 24m, strain type CFBP 2046 and DPP 281, isolated from pepper fruit, belonged to the RFLP group 12, whereas DPP 29, also isolated from pepper fruit, was included in RFLP group 1. Measures to prevent and control this recently introduced disease are suggested in the conclusion of this paper.
Induction of Resistance in Melon to Didymella bryoniae and Sclerotinia sclerotiorum by Seed Treatments with Acibenzolar‐S‐methyl and Methyl Jasmonate but not with Salicylic Acid
Authors: Buzi A. , Chilosi G. , De Sillo D. , Magro P. 
Published: January 2004

AbstractThe plant resistance activator acibenzolar‐S‐methyl (BTH), the signalling molecules salicylic acid (SA) and methyl jasmonate (MeJA) were tested by seed treatment for their ability to protect melon seedlings from gummy stem blight and white mould disease caused by the soil‐borne fungal pathogens Didymella bryoniae and Sclerotinia sclerotiorum, respectively. Didymella bryoniae infection on melon seedlings was completely suppressed by MeJA treatment. Necrotic lesions akin hypersensitive response occurred on all inoculated seedlings and prevented pathogen diffusion into healthy tissues. Didymella bryoniae infection was restricted following BTH seed treatment as well, although the percentage of necrotic lesions in comparison with the water soaked lesions was significantly lower than that from MeJA‐induced seedlings. BTH protected melon seedlings against S. sclerotiorum by the occurrence of a high percentage of necrotic lesions. A lower level of resistance was also achieved by MeJA seed treatment. The augmented level of resistance of tissues from BTH and MeJA‐treated seeds was associated with rapid increases in the activity of the pathogenesis‐related proteins chitinase and peroxidase. MeJA also determined a rapid and transient accumulation of lipoxygenase. Moreover, BTH and MeJA treatments determined the differential induction of particular de novo synthesized isoenzymes of these proteins. Results indicate that BTH and MeJA applied to melon seeds may activate on seedlings diverse metabolic pathways leading to the enhancement of resistance against distinct pathogens.
Systemic Resistance in Tomato Induced by Biocontrol Bacteria Against the Root‐Knot Nematode, Meloidogyne javanica is Independent of Salicylic Acid Production
Authors: Siddiqui I. A. , Shaukat S. S. 
Published: January 2004

AbstractSalicylic acid (SA)‐mediated induction of systemic resistance by Pseudomonas aeruginosa strain 7NSK2 and P. fluorescens strain CHA0 against soil‐borne fungi and viruses have been reported. The role of SA biosynthesis in the enhancement of defence mechanism against plant‐parasitic nematodes by these bacterial strains in tomato is not known. To better understand the importance of SA in rhizobacteria‐mediated suppression of root‐knot nematodes, biocontrol potential of SA‐negative or SA‐overproducing mutants against Meloidogyne javanica was evaluated with their respective wild type counter parts. Culture supernatant of 7NSK2, CHA0 and their respective mutants caused significant mortality of M. javanica juveniles in vitro. SA deletion in 7NSK2 and SA overproduction in CHA0 did not influence bacterial efficacy to cause nematode deaths. Similarly, culture supernatants resulting from King's B liquid medium amended with FeCl3 did not influence nematicidal activity of the bacterial strains. Strain CHA0 induced juvenile deaths more than 7NSK2 did. In pot experiments, the bacterial strains applied in unsterilized sandy loam soil markedly reduced final nematode population densities in roots and subsequent root‐knot infection in tomato seedlings. SA‐negative or overproducing derivatives prevented tomato roots in kinetics similar to those with their respective wild types. When soil iron concentration was lowered by the addition of ethylenediamine di(o‐hydroxyphenylacetic acid), nematode biocontrol by the bacterial strains (both wild type and mutants) remained unaltered. To understand the mechanism involved in rhizobacteria‐mediated suppression of root‐knot nematode in tomato, bacterial performance was assessed in a split root trial in which one‐half of the root system was treated with bacterium while the other inoculated with nematode. Compared with the controls, application of the bacterial cell suspension to one‐half of the root system lowered the populations of root‐knot nematode in non‐bacterized nematode‐treated sections indicating enhanced defence in the non‐bacterized half. With respect to nematode infection, mutants induced systemic resistance to a similar extent as that caused by the wild types in both wild type tomato and NahG tomato plants. It is concluded that fluorescent pseudomonads induce systemic resistance against root‐knot nematode via a signal transduction pathway, which is independent of SA accumulation in roots.
Allelism Tests between the Rust Resistance Gene Present in Common Bean Cultivar Ouro Negro and Genes Ur‐5 and Ur‐11
Authors: Alzate‐Marin A. L. , de Souza T. L. P. O. , Ragagnin V. A. , Moreira M. A. , de Barros E. G. 
Published: January 2004

AbstractThe pathogenic variability of the fungus Uromyces appendiculatus is an obstacle for the creation of rust‐resistant common bean (Phaseolus vulgaris L.) varieties. Gene pyramiding is an alternative strategy for the development of varieties with durable resistance. However, to reach this goal it is important to identify different genes with ample resistance spectra. Cultivars Ouro Negro, Mexico 309 and Belmidak RR‐3 have been shown to be resistant to several rust races identified in the state of Minas Gerais, Brazil. Ouro Negro is the only rust resistance source being used in the BIOAGRO/Universidade Federal de Viçosa (UFV) breeding programme, which aims at pyramiding resistance genes in the ‘carioca‐type’ cultivar Rudá. It would be also interesting to use Mexico 309 (Ur‐5) and Belmidak RR‐3 (Ur‐11) in the breeding programme. However, there is no available information on the possible allelic relationships between the Ouro Negro resistance gene and Ur‐5 and Ur‐11. This work aimed at: (1) determining the allelic relationship between the Ouro Negro resistance gene and Ur‐5 and Ur‐11; and (2) evaluating a random amplified polymorphic DNA (RAPD) marker previously reported as being linked to Ur‐11, in populations from crosses between Belmidak RR‐3 and Rudá. The allelism tests confirmed that the Ouro Negro rust resistance gene is distinct from Ur‐5 and Ur‐11 and the molecular analyses confirmed that the RAPD marker can be used in our breeding programme to develop ‘carioca‐type’ cultivars with the Ur‐11 gene.