bluuebunny/crossref_metadata_2025_split huggingface dataset:
Side chains of pectic polysaccharides are regulated in relation to cell proliferation and cell differentiation
Authors: Willats William G. T. , Steele‐King Clare G. , Marcus Sue E. , Knox J. Paul 
Published: March 2003

SummaryThe occurrence and function of the side chains occurring in the rhamnogalacturonan I domain of pectic poly‐ saccharides have been investigated during carrot cell development using monoclonal antibodies to defined epitopes of (1→4)‐β‐D‐galactan and (1→5)‐α‐L‐arabinan. Immunolocalization studies of carrot root apices indicated that cell walls in the central region of the meristem contained higher levels of (1→5)‐α‐arabinan than the cell walls of surrounding cells. In contrast (1→4)‐β‐galactan was absent from the cell walls of the central meristematic cells but appeared abundantly at a certain point during root cap cell differentiation and also appeared in cell walls of differentiating stele and cortical cells. This developmental pattern of epitope occurrence was also reflected in a suspension‐cultured carrot cell line that can be induced to switch from proliferation to elongation by altered culture conditions. (1→4)‐β‐galactan occurred at a low level in cell walls of proliferating cells but accumulated rapidly in cell walls following induction, before any visible cell elongation, while (1→5)‐α‐arabinan was present in cell walls of proliferating cells but was absent from cell walls of elongated cells. Immunochemical assays of the cultured cells confirmed the early appearance of (1→4)‐β‐galactan during the switch from cell proliferation to cell elongation. Anion‐exchange chromatography confirmed that (1→4)‐β‐galactan was attached to acidic pectic domains and also indicated that it was separate from a distinct homogalacturonan‐rich component. These results indicate that the neutral components of pectic polysaccharides may have important roles in plant cell development.
Reversible binding of the starch‐related R1 protein to the surface of transitory starch granules
Authors: Ritte Gerhard , Lorberth Ruth , Steup Martin 
Published: March 2003

SummaryIntact starch granules were isolated from leaves of Solanum tuberosum L. (and from Pisum sativum L.), and the patterns of starch‐associated proteins were determined by SDS–PAGE. Depending on the pretreatment of the leaves the protein patterns varied: a 160 kDa compound was present in the starch‐associated protein fraction when the leaves were darkened and performed net starch degradation. However, following illumination (i.e. during net starch biosynthesis) the 160 kDa protein was recovered almost exclusively in a soluble state. The 160 kDa protein was identified to be the recently described starch‐related R1 protein. In in vitro assays recombinant R1 did bind to starch granules isolated from either illuminated or darkened leaves. However, binding to the latter was more effective. It is concluded that, depending upon the metabolic state of the cells, the starch granule surface changes and thereby affects binding of the R1 protein.
Stability determinants in the chloroplast psbB/T/H mRNAs of Chlamydomonas reinhardtii
Authors: Vaistij Fabián E. , Goldschmidt‐Clermont Michel , Wostrikoff Katia , Rochaix Jean‐David 
Published: March 2003

SummaryThe chloroplast gene psbB encodes the chlorophyll‐a binding protein P5 (CP47), one of the core subunits of photosystem II (PSII). The psbB mRNA and the downstream psbT and psbH transcripts fail to accumulate in the Chlamydomonas reinhardtii nuclear mutant 222E affected in the Mbb1 gene (
Monod et al. 1992
, Mol. Gen. Genet. 231, 449–459). By introducing chimeric genes consisting of sequences from psbB and the reporter gene aadA into the chloroplast, the target site of Mbb1 was mapped in the psbB 5′ untranslated region (UTR). Primer extension analysis indicates that the psbB RNA exists in a less abundant long form and a more abundant short form, with 5′ ends at positions −147 and −35 relative to the AUG initiation codon, respectively. The longer transcript is present both in the wild type (WT) and 222E mutant, but the shorter one accumulates only in the WT. Two putative stem‐loop structures in the longer 5′ UTR can be deleted individually without affecting psbB mRNA accumulation. Insertion of a poly G cassette in the long leader stabilizes a chimeric psbB transcript in the 222E mutant, suggesting the involvement of a 5′‐3′ exonuclease. We also show that psbH and psbT are transcribed from the upstream psbB gene promoter, and that the psbH mRNA has its own target sequence for Mbb1 function. We discuss the role of this nucleus‐encoded factor, required for specific chloroplast gene expression, in the assembly of the multi‐protein PSII complex.
Tissue‐specific induction of the mRNA for an extracellular invertase isoenzyme of tomato by brassinosteroids suggests a role for steroid hormones in assimilate partitioning
Authors: Goetz Marc , Godt Dietmute E. , Roitsch Thomas 
Published: March 2003

SummaryBrassinosteroids (BRs) induce various growth responses when applied exogenously to plant tissues, and the analysis of biosynthetic mutants reveals an essential role for plant growth and development. Only a few BR‐regulated genes have been identified so far, and the corresponding gene products are assumed to be involved in cell elongation. The present study shows that BR growth responses are linked to the regulation of carbohydrate metabolism by induction of the mRNA for the key enzyme of an apoplastic phloem‐unloading pathway. Addition of BRs to autotrophic tomato suspension culture cells specifically elevates the activity of cell‐wall‐bound invertase, whereas the intracellular invertase activities were not affected. This enhanced enzyme activity was shown to correlate with the induction of the mRNA of extracellular invertase Lin6, whereas the mRNA levels of the other three extracellular invertase isoenzymes were not affected. The induction level induced by different BRs correlates with their growth‐promoting activity. The physiological significance of this regulation is further supported by the low concentrations and short incubation times required to induce Lin6 mRNA. This regulatory mechanism results in an elevated uptake of sucrose via the hexose monomers, and thus an increased supply of carbohydrates to the BR‐treated cells. Experiments with tomato seedlings showed that the localized BR‐dependent growth response of the hypocotyl elongation zone was accompanied by a specific induction of Lin6 mRNA that is restricted to the corresponding tissues. This study demonstrates a role of BRs in tissue‐specific source/sink regulation.
A plant virus vector for systemic expression of foreign genes in cereals
Authors: Choi Il‐Ryong , Stenger Drake C. , Morris T. Jack , French Roy 
Published: March 2003

SummaryInserts bearing the coding sequences of NPT II and β‐glucuronidase (GUS) were placed between the nuclear inclusion b (NIb) and coat protein (CP) domains of the wheat streak mosaic virus (WSMV) polyprotein ORF. The WSMV NIb‐CP junction containing the nuclear inclusion a (NIa) protease cleavage site was duplicated, permitting excision of foreign protein domains from the viral polyprotein. Wheat, barley, oat and maize seedlings supported systemic infection of WSMV bearing NPT II. The NPT II insert was stable for at least 18–30 days post‐inoculation and had little effect on WSMV CP accumulation. Histochemical assays indicated the presence of functional GUS protein in systemically infected wheat and barley plants inoculated with WSMV bearing GUS. The GUS constructs had greatly reduced virulence on both oat and maize. RT–PCR indicated that the GUS insert was subject to deletion, particularly when expressed as a GUS–NIb protein fusion. Both reporter genes were expressed in wheat roots at levels comparable to those observed in leaves. These results clearly demonstrate the utility of WSMV as a transient gene expression vector for grass species, including two important grain crops, wheat and maize. The results further indicate that both host species and the nature of inserted sequences affect the stability and expression of foreign genes delivered by engineered virus genomes.
Specific HR‐associated recognition of secreted proteins from Cladosporium fulvum occurs in both host and non‐host plants
Authors: Laugé Richard , Goodwin Paul H. , De Wit Pierre J. G. M. , Joosten Matthieu H. A. J. 
Published: March 2003

SummaryThe resistance of tomato (Lycopersicon esculentum) to the pathogenic fungus Cladosporium fulvum complies with the gene‐for‐gene concept. Host resistance is based on specific recognition of extracellular fungal proteins, resulting in a hypersensitive response (HR). Five proteins secreted by C. fulvum were purified and the encoding cDNA clone was obtained from two novel ones among them. Various tomato breeding lines and accessions of Lycopersicon pimpinellifolium were tested for their recognitional specificity by injection of the purified proteins or potato virus X‐based expression of the cDNA. We found that HR‐associated recognition of one or more of these proteins, in addition to recognition of the race‐specific elicitors AVR4 and AVR9 of C. fulvum, occurs among Lycopersicon species. Studies on the inheritance of this recognition confirmed that single dominant genes are involved. Furthermore, one of the extracellular proteins of C. fulvum is specifically recognized by Nicotiana paniculata, which is not a host for C. fulvum. These results indicate that plants have a highly effective surveillance system for the presence of ‘foreign’ proteins, which, together with the high mutation rate of pathogens, can explain the complex gene‐for‐gene relationships frequently observed in pathosystems.
Evidence that endo‐1,4‐β‐glucanases act on cellulose in suspension‐cultured poplar cells
Authors: Ohmiya Yasunori , Samejima Masahiro , Shiroishi Masahiro , Amano Yoshihiko , Kanda Takahisa , Sakai Fukumi , Hayashi Takahisa 
Published: March 2003

SummarySuspension‐cultured poplar (Populus alba) cells produce two distinct endo‐1,4‐β‐glucanases, one of which is released in the extracellular culture medium and the other localized in their walls. Two cDNA clones, PopCel1 and PopCel2, isolated from a poplar cDNA library, encode the extracellular and the wall‐bound endo‐1,4‐β‐glucanases, respectively, based upon deduced amino acid sequences. The products of these two genes contained domains conserved in endo‐1,4‐β‐glucanase (family 9) and showed 91.5% amino acid identity. The levels of both PopCel1 and PopCel2 mRNAs increased during the lag phase of growth and decreased rapidly during the linear phase. After the levels had decreased, they were again increased by addition of sucrose to the culture medium and further enhanced by the addition of 2,4‐dichlorophenoxyacetic acid (2,4‐D) in the presence of sucrose. The accumulation of the mRNAs was correlated with the solubilization of cello‐oligosaccharides. Cello‐oligosaccharides and xyloglucan were also solubilized from the wall preparations of poplar cells incubated with enzyme preparations from the extracellular culture medium and walls. An antibody against both PopCel proteins reduced the production of cello‐oligosaccharides by the extracellular enzyme by 90% and that by the wall‐bound enzyme by 55%, and also prevented xyloglucan solubilization. The results show that the accumulation of poplar endo‐1,4‐β‐glucanases is regulated indirectly by auxin in the presence of sucrose and can act on cellulose in suspension‐cultured poplar cells.
Various abiotic stresses rapidly activate Arabidopsis MAP kinases ATMPK4 and ATMPK6
Authors: Ichimura Kazuya , Mizoguchi Tsuyoshi , Yoshida Riichiro , Yuasa Takashi , Shinozaki Kazuo 
Published: March 2003

SummaryMitogen‐activated protein kinase (MAP kinase, MAPK) cascades play pivotal roles in signal transduction of extracellular stimuli, such as environmental stresses and growth regulators, in various organisms. Arabidopsis thaliana MAP kinases constitute a gene family, but stimulatory signals for each MAP kinase have not been elucidated. Here we show that environmental stresses such as low temperature, low humidity, hyper‐osmolarity, touch and wounding induce rapid and transient activation of the Arabidopsis MAP kinases ATMPK4 and ATMPK6. Activation of ATMPK4 and ATMPK6 was associated with tyrosine phosphorylation but not with the amounts of mRNA or protein. Kinetics during activation differ between these two MAP kinases. These results suggest that ATMPK4 and ATMPK6 are involved in distinct signal transduction pathways responding to these environmental stresses.
Genetic dissection of blue‐light sensing in tomato using mutants deficient in cryptochrome 1 and phytochromes A, B1 and B2
Authors: Weller James L. , Perrotta Gaetano , Schreuder Mariëlle E.L. , Van Tuinen Ageeth , Koornneef Maarten , Giuliano Giovanni , Kendrick Richard E. 
Published: March 2003

SummarySeveral novel allelic groups of tomato (Solanum lycopersicum L.) mutants with impaired photomorphogenesis have been identified after γ‐ray mutagenesis of phyA phyB1 double‐mutant seed. Recessive mutants in one allelic group are characterized by retarded hook opening, increased hypocotyl elongation and reduced hypocotyl chlorophyll content under white light (WL). These mutants showed a specific impairment in response to blue light (BL) resulting from lesions in the gene encoding the BL receptor cryptochrome 1 (cry1). Phytochrome A and cry1 are identified as the major photoreceptors mediating BL‐induced de‐etiolation in tomato, and act under low and high irradiances, respectively. Phytochromes B1 and B2 also contribute to BL sensing, and the relative contribution of each of these four photoreceptors differs according to the light conditions and the specific process examined. Development of the phyA phyB1 phyB2 cry1 quadruple mutant under WL is severely impaired, and seedlings die before flowering. The quadruple mutant is essentially blind to BL, but experiments employing simultaneous irradiation with BL and red light suggest that an additional non‐phytochrome photoreceptor may be active under short daily BL exposures. In addition to effects on de‐etiolation, cry1 is active in older, WL‐grown plants, and influences stem elongation, apical dominance, and the chlorophyll content of leaves and fruit. These results provide the first mutant‐based characterization of cry1 in a plant species other than Arabidopsis.
A recessive mutation in the Arabidopsis SSI2 gene confers SA‐ and NPR1‐independent expression of PR genes and resistance against bacterial and oomycete pathogens
Authors: Shah Jyoti , Kachroo Pradeep , Nandi Ashis , Klessig Daniel F. 
Published: March 2003

SummaryThe Arabidopsis thaliana NPR1 gene is required for salicylic acid (SA)‐induced expression of pathogenesis‐related (PR) genes and systemic acquired resistance. However, loss‐of‐function mutations in NPR1 do not confer complete loss of PR gene expression or disease resistance. Thus these responses also can be activated via an NPR1‐independent pathway that currently remain to be elucidated. The ssi2‐1 mutant, identified in a genetic screen for suppressors of npr1‐5, affects signaling through the NPR1‐independent defense pathway(s). In comparison with the wild‐type (SSI2 NPR1) plants and the npr1‐5 mutant (SSI2 npr1‐5), the ssi2‐1 npr1‐5 double mutant and the ssi2‐1 NPR1 single mutant constitutively express PR genes [PR‐1, BGL2 (PR‐2) and PR‐5]; accumulate elevated levels of SA; spontaneously develop lesions; and possess enhanced resistance to a virulent strain of Peronospora parasitica. The ssi2‐1 mutation also confers enhanced resistance to Pseudomonas syringae pv. tomato (Pst); however, this is accomplished primarily via an NPR1‐dependent pathway. Analysis of ssi2‐1 NPR1 nahG and ssi2‐1 npr1‐5 nahG plants revealed that elevated SA levels were not essential for the ssi2‐1‐conferred phenotypes. However, expression of the nahG transgene did reduce the intensity of some ssi2‐1‐conferred phenotypes, including PR‐1 expression, and disease resistance. Based on these results, SSI2 or an SSI2‐generated signal appears to modulate signaling of an SA‐dependent, NPR1‐independent defense pathway, or an SA‐ and NPR1‐independent defense pathway.
Gastrodianin‐like mannose‐binding proteins: a novel class of plant proteins with antifungal properties
Authors: Wang Xiaochen , Bauw Guy , Van Damme Els J.M. , Peumans Willy J. , Chen Zhang‐Liang , Van Montagu Marc , Angenon Geert , Dillen Willy 
Published: March 2003

SummaryThe orchid Gastrodia elata depends on the fungus Armillaria mellea to complete its life cycle. In the interaction, fungal hyphae penetrate older, nutritive corms but not newly formed corms. From these corms, a protein fraction with in vitro activity against plant‐pathogenic fungi has previously been purified. Here, the sequence of gastrodianin, the main constituent of the antifungal fraction, is reported. Four isoforms that encoded two different mature proteins were identified at the cDNA level. Another isoform was detected in sequenced peptides. Because the antifungal activity of gastrodianins produced in and purified from Escherichia coli and Nicotiana tabacum was comparable to that of gastrodianin purified from the orchid, gastrodianins are the active component of the antifungal fractions. Gastrodianin accumulation is probably an important part of the mechanism by which the orchid controls Armillaria penetration. Gastrodianin was found to be homologous to monomeric mannose‐binding proteins of other orchids, of which at least one (Epipactis helleborine mannose‐binding protein) also displayed in vitro antifungal activity. This establishes the gastrodianin‐like proteins (GLIPs) as a novel class of antifungal proteins.
Arabidopsis UVH3 gene is a homolog of the Saccharomyces cerevisiae RAD2 and human XPG DNA repair genes
Authors: Liu Zongrang , Hall Jennifer D. , Mount David W. 
Published: March 2003

SummaryTo identify mechanisms of DNA repair in Arabidopsis thaliana, we have analyzed a mutant (uvh3) which exhibits increased sensitivity to ultraviolet (UV) light, H2O2 and ionizing radiation and displays a premature senescence phenotype. The uvh3 locus was mapped within chromosome III to the GL1 locus. A cosmid contig of the GL1 region was constructed, and individual cosmids were used to transform uvh3 mutant plants. Cosmid N9 was found to confer UV‐resistance, H2O2‐resistance and a normal senescence phenotype following transformation, indicating that the UVH3 gene is located on this cosmid and that all three phenotypes are due to the same mutation. Analysis of cosmid N9 sequences identified a gene showing strong similarity to two homologous repair genes, RAD2 (Saccharomyces cerevisiae) and XPG (human), which encode an endonuclease required for nucleotide excision repair of UV‐damage. The uvh3 mutant was shown to carry a nonsense mutation in the coding region of the AtRAD2/XPG gene, thus revealing that the UVH3 gene encodes the AtRAD2/XPG gene product. In humans, the homologous XPG protein is also involved in removal of oxygen‐damaged nucleotides by base excision repair. We discuss the possibility that the increased sensitivity of the uvh3 mutant to H2O2 and the premature senescence phenotype might result from failure to repair oxygen damage in plant tissues. Finally, we show that the AtRAD2/XPG gene is expressed at moderate levels in all plant tissues.
In vitro interactions between barley TALE homeodomain proteins suggest a role for protein–protein associations in the regulation of Knox gene function
Authors: Müller Judith , Wang Yamei , Franzen Rainer , Santi Luca , Salamini Francesco , Rohde Wolfgang 
Published: March 2003

SummaryThis paper describes two‐hybrid interactions amongst barley homeodomain proteins encoded by the Three Amino acid Loop Extension (TALE) superfamily. The class I KNOX protein BKN3 is shown to homodimerise and to associate with proteins encoded by the class I and II Knox genes BKn‐1 and BKn‐7. Furthermore, JUBEL1 and JUBEL2, two BELL1 homologous proteins, are identified and characterised as interacting partners of BKN3. Differences in the requirements of BKN3 derivatives for interactions with KNOX and JUBEL proteins imply the involvement of overlapping but slightly different domains. This set of results is an example for interactions amongst different classes of plant TALE homeodomain proteins, as previously described for related animal proteins. Apparently identical spatial and temporal expression patterns of BKn‐1, BKn‐3, BKn‐7, JuBel1 and JuBel2, as determined by in situ hybridisation, are compatible with possible interactions of their protein products in planta. Contradictory to the common model, that the transcriptional down‐regulation of certain class 1 Knox‐genes is the prerequisite for organ differentiation, transcripts of all five genes were, similar to Tkn1 and Tkn2/LeT6 of tomato, detected in incipient and immature leaves as well as in meristematic tissues. A characteristic phenotype is induced by the overexpression of JuBel2 in transgenic tobacco plants.
Chloroplast lysates support directed mutagenesis via modified DNA and chimeric RNA/DNA oligonucleotides
Authors: Kmiec Eric B. , Johnson Christina , May Gregory D. 
Published: March 2003

SummaryChimeric RNA/DNA and modified DNA oligonucleotides have been shown to direct gene‐conversion events in vitro through a process involving proteins from several DNA‐repair pathways. Recent experiments have extended the utility of these molecules to plants, and we previously demonstrated that plant cell‐free extracts are competent to support oligonucleotide‐directed genetic repair. Using this system, we are studying Arabidopsis DNA‐repair mutants and the role of plant proteins in the DNA‐repair process. Here we describe a method for investigating mechanisms of plastid DNA‐repair pathways. Using a genetic readout system in bacteria and chimeric or modified DNA oligonucleotides designed to direct the conversion of mutations in antibiotic resistance genes, we have developed an assay for genetic repair of mutations in a spinach chloroplast lysate system. We report genetic repair of point and frameshift mutations directed by both types of modified oligonucleotides. This system enables the mechanistic study of plastid gene repair and facilitates the direct comparison between plant nuclear and organelle DNA‐repair pathways.
Constitutive over‐expression of AtGSK1 induces NaCl stress responses in the absence of NaCl stress and results in enhanced NaCl tolerance in Arabidopsis
Authors: Piao Hai Lan , Lim Jeong Hwa , Kim Soo Jin , Cheong Gang‐Won , Hwang Inhwan 
Published: March 2003

SummaryGSK3/shaggy‐like protein kinases have been shown to play diverse roles in development and signal transduction pathways in various organisms. An Arabidopsis homologue of GSK3/shaggy‐like kinase, AtGSK1, has been shown to be involved in NaCl stress responses. In order to further clarify the role of AtGSK1 in NaCl stress responses in plants, we generated transgenic Arabidopsis plants that over‐expressed AtGSK1 mRNA. These plants showed enhanced resistance to NaCl stress when assayed either as whole plants or by measurement of root growth on NaCl plates. In addition, AtGSK1 transgenic plants in the absence of NaCl stress showed phenotypic changes, such as accumulation of anthocyanin, that were similar to those observed in wild‐type plants under NaCl stress. Transgenic plants accumulated 30–50% more Na+ than did wild‐type plants when subjected to NaCl stress, and Ca2+ content was increased by 15–30% in the transgenic plants regardless of the NaCl stress level. Northern blotting revealed that AtGSK1 over‐expression induced expression of the NaCl stress‐responsive genes AtCP1, RD29A and CHS1 in the absence of NaCl stress. In addition, AtCBL1 and AtCP1 were super‐induced in the NaCl‐stressed transgenic plants. Taken together, these results suggest that AtGSK1 is involved in the signal transduction pathway(s) of NaCl stress responses in Arabidopsis.