bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Arabidopsis gene encoding a chloroplast‐targeted β‐amylase
Authors: Lao Nga T. , Schoneveld Onard , Mould Ruth M. , Hibberd Julian M. , Gray John C. , Kavanagh Tony A. 
Published: March 2003

Summaryβ‐Amylase is one of the most abundant starch degrading activities found in leaves and other plant organs. Despite its abundance, most if not all of this activity has been reported to be extrachloroplastic and for this reason, it has been assumed that β‐amylases are not involved in the metabolism of chloroplast‐localized transitory leaf starch. However, we have identified a novel β‐amylase gene, designated ct‐Bmy, which is located on chromosome IV of Arabidopsis thaliana. Ct‐Bmy encodes a precursor protein which contains a typical N‐terminal chloroplast import signal and is highly similar at the amino acid level to extrachloroplastic β‐amylases of higher plants. Expression of the ct‐Bmy cDNA in E. coli confirmed that the encoded protein possesses β‐amylase activity. CT‐BMY protein, synthesized in vitro, was efficiently imported by isolated pea chloroplasts and shown to be located in the stroma. In addition, fusions between the predicted CT‐BMY transit peptide and jellyfish green fluorescent protein (GFP) or the entire CT‐BMY protein and GFP showed accumulation in vivo in chloroplasts of Arabidopsis. Expression of the GUS gene fused to ct‐Bmy promoter sequences was investigated in transgenic tobacco plants. GUS activity was most strongly expressed in the palisade cell layer in the leaf blade and in chlorenchyma cells associated with the vascular strands in petioles and stems. Histochemical staining of whole seedlings showed that GUS activity was largely confined to the cotyledons during the first 2 weeks of growth and appeared in the first true leaves at approximately 4 weeks.
Elicitor‐responsive, ethylene‐independent activation of GCC box‐mediated transcription that is regulated by both protein phosphorylation and dephosphorylation in cultured tobacco cells
Authors: Yamamoto Sumiko , Suzuki Kaoru , Shinshi Hideaki 
Published: March 2003

SummaryIn cultured XD6S tobacco cells, xylanase from Trichoderma viride (TvX) induced the expression of a luciferase reporter gene that was under the control of a GCC box, which is an 11 bp sequence (TAAGAGCCGCC) that is found in the 5′‐upstream region of pathogen‐responsive defence genes that include genes for class I basic chitinase. TvX‐induced biosynthesis of ethylene was not required for the TvX‐activated transcription. The TvX‐induced, GCC box‐mediated transcription of the reporter gene was completely blocked not only by staurosporine, an inhibitor of serine/threonine protein kinases, at 1 μM, but also by calyculin A, an inhibitor of protein phosphatases 1 and 2A, at 0.2 μM. It appeared also that protein synthesis de novo was required for the GCC box‐mediated transcription of the reporter gene. Accumulation of mRNAs for various ERFs (ethylene‐responsive transcription factors), which have been shown to bind specifically to the GCC box, was also induced by TvX prior to increases in the level of mRNA for a class I basic chitinase. In particular, the level of mRNA for EFR2 reached a maximum from 3 to 6 h, whereas levels of mRNAs for ERF3 and ERF4 were highest 0.5 h after the start of treatment of TvX and decreased thereafter. Moreover, induction of accumulation of the mRNA for ERF2 was inhibited by staurosporine and calyculin A. These results suggest that ERF2 might play a major role in TvX‐induced, GCC box‐mediated transcription of genes and that both protein kinase(s) and protein phosphatase(s) might be involved, as positive regulators, in the signal transduction pathway that leads to expression of ERF2 and subsequent GCC box‐mediated transcription of genes.
FALSIFLORA, the tomato orthologue of FLORICAULA and LEAFY, controls flowering time and floral meristem identity
Authors: Molinero‐Rosales Nuria , Jamilena Manuel , Zurita Sergio , Gómez Pedro , Capel Juan , Lozano Rafael 
Published: March 2003

SummaryCharacterization of the tomato falsiflora mutant shows that fa mutation mainly alters the development of the inflorescence resulting in the replacement of flowers by secondary shoots, but also produces a late‐flowering phenotype with an increased number of leaves below first and successive inflorescences. This pattern suggests that the FALSIFLORA (FA) locus regulates both floral meristem identity and flowering time in tomato in a similar way to the floral identity genes FLORICAULA (FLO) of Antirrhinum and LEAFY (LFY) of Arabidopsis. To analyse whether the fa phenotype is the result of a mutation in the tomato FLO/LFY gene, we have cloned and analysed the tomato FLO/LFY homologue (TOFL) in both wild‐type and fa plants following a candidate gene strategy. The wild‐type gene is predicted to encode a protein sharing 90% identity with NFL1 and ALF, the FLO/LFY‐like proteins in Nicotiana and Petunia, and about 80 and 70% identity with either FLO or LFY. In the fa mutant, however, the gene showed a 16 bp deletion that results in a frameshift mutation and in a truncated protein. The co‐segregation of this deletion with the fa phenotype in a total of 240 F2 plants analysed supports the idea that FA is the tomato orthologue to FLO and LFY. The gene is expressed in both vegetative and floral meristems, in leaf primordia and leaves, and in the four floral organs. The function of this gene in comparison with other FLO/LFY orthologues is analysed in tomato, a plant with a sympodial growth habit and a cymose inflorescence development.
Allene oxide synthases of barley (Hordeum vulgare cv. Salome): tissue specific regulation in seedling development
Authors: Maucher Helmut , Hause Bettina , Feussner Ivo , Ziegler Jörg , Wasternack Claus 
Published: March 2003

SummaryAllene oxide synthase (AOS) is the first enzyme in the lipoxygenase (LOX) pathway which leads to formation of jasmonic acid (JA). Two full‐length cDNAs of AOS designated as AOS1 and AOS2, respectively, were isolated from barley (H. vulgare cv. Salome) leaves, which represent the first AOS clones from a monocotyledonous species. For AOS1, the open reading frame encompasses 1461 bp encoding a polypeptide of 487 amino acids with calculated molecular mass of 53.4 kDa and an isoelectric point of 9.3, whereas the corresponding data of AOS2 are 1443 bp, 480 amino acids, 52.7 kDa and 7.9. Southern blot analysis revealed at least two genes. Despite the lack of a putative chloroplast signal peptide in both sequences, the protein co‐purified with chloroplasts and was localized within chloroplasts by immunocytochemical analysis. The barley AOSs, expressed in bacteria as active enzymes, catalyze the dehydration of LOX‐derived 9‐ as well as 13‐hydroperoxides of polyenoic fatty acids to the unstable allene oxides. In leaves, AOS mRNA accumulated upon treatment with jasmonates, octadecanoids and metabolizable carbohydrates, but not upon floating on abscisic acid, NaCl, Na‐salicylate or infection with powdery mildew. In developing seedlings, AOS mRNA strongly accumulated in the scutellar nodule, but less in the leaf base. Both tissues exhibited elevated JA levels. In situ hybridizations revealed the preferential occurrence of AOS mRNA in parenchymatic cells surrounding the vascular bundles of the scutellar nodule and in the young convoluted leaves as well as within the first internode. The properties of both barley AOSs, their up‐regulation of their mRNAs and their tissue specific expression suggest a role during seedling development and jasmonate biosynthesis.
Axillary meristem development in Arabidopsis thaliana
Authors: Grbić Vojislava , Bleecker Anthony B. 
Published: March 2003

SummaryAxillary shoot apical meristems initiate post‐embryonically in the axils of leaves. Their developmental fate is a main determinant of the final plant body plan. In Arabidopsis, usually a single axillary meristem initiates in the leaf axil even though there is developmental potential for formation of multiple branches. While the wild‐type plants rarely form multiple branches in the leaf axil, tfl1‐2 plants regularly develop two or more branches in the axils of the rosette leaves. Axillary meristem formation in Arabidopsis occurs in two waves: an acropetal wave forms during plant vegetative development, and a basipetal wave forms during plant reproductive development. We report here the morphological and anatomical changes, and the STM expression pattern associated with the formation of axillary and accessory meristems during Arabidopsis vegetative development.
Cloning and functional expression of the gene encoding the key enzyme for chlorophyll b biosynthesis (CAO) from Arabidopsis thaliana
Authors: Oster Ulrike , Tanaka Ryouichi , Tanaka Ayumi , Rüdiger Wolfhart 
Published: March 2003

SummaryChlorophyll (Chl) biosynthesis and degradation are the only biochemical processes on Earth that can be directly observed from satellites or other planets. The bulk of the Chls is found in the light‐harvesting antenna complexes of photosynthetic organisms. Surprisingly little is known about the biosynthesis of Chl b, which is the second most abundant Chl pigment after Chl a. We describe here the expression and properties of the chlorophyllide a oxygenase gene (CAO) from Arabidopsis thaliana, which is apparently the key enzyme in Chl b biosynthesis. The recombinant enzyme produced in Escherichia coli catalyses an unusual two‐step oxygenase reaction that is the ‘missing link’ in the chlorophyll cycle of higher plants.
Dof1 and Dof2 transcription factors are associated with expression of multiple genes involved in carbon metabolism in maize
Authors: Yanagisawa Shuichi 
Published: March 2003

SummaryDof proteins are transcription factors that appear to be unique to plants. Maize Dof1 has been suggested to be a regulator for C4 photosynthetic phosphoenolpyruvate carboxylase (C4PEPC) gene expression. The present study demonstrates that Dof1 also enhances transcription from the promoters of both cytosolic orthophosphate dikinase (cyPPDK) genes and a non‐photosynthetic PEPC gene, which are not present in animals. Expression of Dof1‐specific antisense RNA or the DNA‐binding domain of Dof1 alone reduced the activities of these promoters in maize leaf protoplasts. Electrophoretic mobility shift assays revealed several Dof1‐binding sites in these promoters. The cyppdk1 promoter contained two Dof1‐binding sites, one of which was linked to the binding site of a plant bZIP protein. By using deleted or mutated cyppdk1 promoters, both Dof1‐binding sites were shown to be functional. Furthermore, Dof1 elevated the activities of the cyppdk and pepc promoters more strongly in greening protoplasts than in etiolated protoplasts, in accordance with the different activities of these promoters in two types of protoplasts. Another Dof protein of maize, Dof2, suppressed the activity of the C4pepc promoter but was able to activate certain other promoters. These results suggest that Dof proteins may play regulatory roles in multiple gene expressions associated with the plant‐specific pathway for carbon metabolism in maize. In addition, the primary characteristic of Dof proteins, i.e. different activities in distinct types of cells and opposite actions on promoters in different contexts, suggests the potential of Dof proteins to differentially regulate diverse promoters in a variety of plant tissues. Speculation raised by these results concerning the evolution of the C4pepc gene is also discussed.
Sucrose transport into barley seeds: molecular characterization of two transporters and implications for seed development and starch accumulation
Authors: Weschke Winfriede , Panitz Reinhard , Sauer Norbert , Wang Qing , Neubohn Birgit , Weber Hans , Wobus Ulrich 
Published: March 2003

SummaryIn order to understand sucrose transport in developing seeds of cereals at the molecular level, we cloned from a caryopses library two cDNAs encoding sucrose transporters, designated HvSUT1 and HvSUT2. Sucrose uptake activity was confirmed by heterologous expression in yeast. Both transporter genes are expressed in maternal as well as filial tissues. In a series of in situ hybridizations we analysed the cell type‐specific expression in developing seeds. HvSUT1 is preferentially expressed in caryopses in the cells of the nucellar projection and the endospermal transfer layer, which represent the sites of sucrose exchange between the maternal and the filial generation and are characterized by transfer cell formation. HvSUT2 is expressed in all sink and source tissues analysed and may have a general housekeeping role. The rapid induction of HvSUT1 gene expression in caryopses at approximately 5–6 days after fertilization coincides with increasing levels of sucrose as well as sucrose synthase mRNA and activity, and occurs immediately before the onset of rapid starch accumulation within the endosperm. Starch biosynthesis requires sucrose to be imported into the endosperm, as direct precursor for starch synthesis and to promote storage‐associated processes. We discuss the possible role of HvSUT1 as a control element for the endospermal sucrose concentration.
Functional, c‐myc‐tagged Cf‐9 resistance gene products are plasma‐membrane localized and glycosylated
Authors: Piedras Pedro , Rivas Susana , Dröge Swenja , Hillmer Stephan , Jones Jonathan D. G. 
Published: March 2003

SummaryThe Cf‐9 resistance gene from tomato confers resistance to races of the fungal pathogen Cladosporium fulvum that express the corresponding avirulence gene, Avr9. Avr9 encodes a secreted peptide. To investigate Cf‐9 function, we tagged the Cf‐9 protein with a triple myc epitope at either the amino‐ or carboxy‐terminus of the mature protein. Tobacco plants carrying these constructs activate a defence response to Avr9 peptide. The Cf‐9 sequence predicts a protein of 94 kDa, with 22 glycosylation sites. Using c‐myc antibodies, c‐myc : Cf‐9 protein was detected as a unique band with a molecular size of 160 kDa. The band shifted to approximately 105 kDa after glucosidase treatment, indicating that Cf‐9 protein is highly glycosylated. Plasma membranes were isolated using two‐phase partitioning, and c‐myc : Cf‐9 was enriched in these fractions, indicating that Cf‐9 is a plasma membrane protein. This was confirmed by silver‐enhanced immunogold labelling of tobacco protoplasts carrying the amino‐terminal c‐myc tag; a higher labelling density was observed on the surface of protoplasts derived from c‐myc : Cf‐9 tobacco compared to untransformed control. The presence of Cf‐9 in the plasma membrane is consistent with its role in conferring recognition of the extracellular Avr9 peptide.
A new type of mutation in the plant photoreceptor phytochrome B causes loss of photoreversibility and an extremely enhanced light sensitivity
Authors: Kretsch Thomas , Poppe Christoph , Schäfer Eberhard 
Published: March 2003

SummaryPhotoreversibility, reversion of the inductive effect of a brief red light pulse by a subsequent far‐red light pulse, is a property of photoresponses regulated by the plant photoreceptor phytochrome B (phyB). We screened for mutants with impaired photoreversibility to gain better insight into the phyB‐specific signalling cascade. The phenotype of the mutant described is caused by a single amino acid exchange in a phyB subdomain that is highly conserved in all phytochromes but whose functional significance was unknown. The mutated phyB showed a slower dark reversion but no major alterations in its spectral properties. In addition to its loss of photoreversibility, the mutant also exhibited a hypersensitivity towards continuous red‐light irradiation and an altered phenotype of adult plants under short‐day conditions.
Diverse effects of overexpression of LEAFY and PTLF, a poplar (Populus) homolog of LEAFY/FLORICAULA, in transgenic poplar and Arabidopsis
Authors: Rottmann William H. , Meilan Richard , Sheppard Lorraine A. , Brunner Amy M. , Skinner Jeffrey S. , Ma Caiping , Cheng Shuping , Jouanin Lise , Pilate Gilles , Strauss Steven H. 
Published: March 2003

SummaryPTLF, thePopulus trichocarpahomolog ofLEAFY(LFY) andFLORICAULA, was cloned to assess its function in a dioecious tree species.In situhybridization studies showed that the gene was expressed most strongly in developing inflorescences. Expression was also seen in leaf primordia and very young leaves, most notably in apical vegetative buds near inflorescences, but also in seedlings. Although ectopic expression of thePTLFcDNA inArabidopsisaccelerated flowering, only one of the many tested transgenic lines ofPopulusflowered precociously. The majority of trees within a population of 3‐year‐old transgenic hybridPopuluslines with PTLF constitutively expressed showed few differences when compared to controls. However, phenotypic effects on growth rate and crown development, but not flowering, were seen in some trees with strong PTLF expression and became manifest only as the trees aged. Competence to respond to overexpression of LFY varied widely amongPopulusgenotypes, giving consistent early flowering in only a single maleP. tremula × P. tremuloideshybrid and causing gender change in another hybrid genotype. PTLF activity appears to be subject to regulation that does not affect heterologously expressed LFY, and is dependent upon tree maturation. Both genes provide tools for probing the mechanisms of delayed competence to flower in woody plants.
Mutations in the Arabidopsis VAR2 locus cause leaf variegation due to the loss of a chloroplast FtsH protease
Authors: Chen Meng , Choi YangDo , Voytas Daniel F. , Rodermel Steve 
Published: March 2003

SummaryVariegated plants have green‐ and white‐sectored leaves. Cells in the green sectors contain morphologically normal chloroplasts, whereas cells in the white sectors contain non‐pigmented plastids that lack organized lamellar structures. Many variegations are caused by mutations in nuclear genes that affect plastid function, yet in only a few cases have the responsible genes been cloned. We show that mutations in the nuclear VAR2 locus of Arabidopsis cause variegation due to loss of a chloroplast thylakoid membrane protein that bears similarity to the FtsH family of AAA proteins (ATPases associated with diverse cellular activities). Escherichia coli FtsH is a chaperone metalloprotease that functions in a number of diverse membrane‐associated events. Although FtsH homologs have been identified in multicellular organisms, their functions and activities are largely unknown; we provide genetic in vivo evidence that VAR2 functions in thylakoid membrane biogenesis. We have isolated four var2 alleles and they have allowed us to define domains of the protein that are required for activity. These include two putative ATP‐binding sites. VAR2 protein amounts generally correlate with the severity of the var2 mutant phenotype. One allele lacks detectable VAR2 protein, suggesting that the mechanism of var2 variegation involves the action of a redundant activity in the green sectors. We conclude that redundant activities may be a general mechanism to explain nuclear gene‐induced plant variegations.
Expression of a bacterial serine acetyltransferase in transgenic potato plants leads to increased levels of cysteine and glutathione
Authors: Harms Karsten , Von Ballmoos Peter , Brunold Christian , Höfgen Rainer , Hesse Holger 
Published: March 2003

SummaryThe coding sequence of the wild‐type, cys‐sensitive, cysE gene from Escherichia coli, which encodes an enzyme of the cysteine biosynthetic pathway, namely serine acetyltransferase (SAT, EC 2.3.1.30), was introduced into the genome of potato plants under the control of the cauliflower mosaic virus 35S promoter. In order to target the protein into the chloroplast, cysE was translationally fused to the 5′‐signal sequence of rbcS from Arabidopsis thaliana. Transgenic plants showed a high accumulation of the cysE mRNA. The chloroplastic localisation of the E. coli SAT protein was demonstrated by determination of enzymatic activities in enriched organelle fractions. Crude leaf extracts of these plants exhibited up to 20‐fold higher SAT activity than those prepared from wild‐type plants. The transgenic potato plants expressing the E. coli gene showed not only increased levels of enzyme activity but also exhibited elevated levels of cysteine and glutathione in leaves. Both were up to twofold higher than in control plants. However, the thiol content in tubers of transgenic lines was unaffected. The alterations observed in leaf tissue had no effect on the expression of O‐acetylserine(thiol)‐lyase, the enzyme which converts O‐acetylserine, the product of SAT, to cysteine. Only a minor effect on its enzymatic activity was observed. In conclusion, the results presented here demonstrate the importance of SAT in plant cysteine biosynthesis and show that production of cysteine and related sulfur‐containing compounds can be enhanced by metabolic engineering.
Transgenic tobacco plants co‐expressing Agrobacterium iaa and ipt genes have wild‐type hormone levels but display both auxin‐ and cytokinin‐overproducing phenotypes
Authors: Eklöf Staffan , Åstot Crister , Sitbon Folke , Moritz Thomas , Olsson Olof , Sandberg Göran 
Published: March 2003

SummaryTransgenic tobacco lines simultaneously expressing the Agrobacterium iaaM, iaaH and ipt genes, obtained by crossing lines expressing ipt with lines expressing iaaM and iaaH, were used to study in planta interactions between auxin and cytokinins. All phenotypic traits of the respective parental lines characteristic of cytokinin and auxin overproduction were present in the cross. Indole‐3‐acetic acid (IAA) and combined zeatin riboside (ZR) and zeatin riboside‐5′‐monophosphate (ZRMP) contents were analysed by mass spectrometry in young, developing leaves from the cross, the parental lines and the wild type. Unexpectedly, hormone levels in the cross were very similar to wild‐type levels. Thus IAA levels in the cross were much lower throughout vegetative development than in the parental IAA overproducing line, although expression of the bacterial IAA biosynthesis genes was not reduced. The results suggest that effects on apical dominance, adventitious root formation, leaf morphology and other traits commonly ± associated with IAA and cytokinin overproduction, and observed in the iaaËipt cross, cannot be explained solely by analysis of auxin and cytokinin contents in individual organs. As traits associated with both hormones are expressed in close spatial and temporal proximity, it is likely that cellular resolution of hormone contents is essential to explain physiological responses to auxins and cytokinins.
Proton extrusion is an essential signalling component in the HR of epidermal single cells in the barley–powdery mildew interaction
Authors: Zhou Fasong , Andersen Claus H. , Burhenne Kim , Fischer Pernille Hertz , Collinge David B. , Thordal‐Christensen Hans 
Published: March 2003

SummaryWe propose a model for activation of the epidermal cell hypersensitive response (HR) in the barley/powdery mildew interaction. The model suggests that the plasma membrane proton pump (H+‐ATPase) of epidermal cells is activated following penetration by an avirulent powdery mildew fungus. This will cause an acidification of the apoplast towards the mesophyll cells, thereby activating generation of H2O2 from the mesophyll, which subsequently triggers the epidermal cell to undergo HR. The model is supported by the following data: (1) the earliest HR‐related H2O2 is found in the attachment zones between the epidermal cell and underlying mesophyll cells; (2) scavenger treatment reduces HR; (3) treatment of leaves with low‐pH (3.5) citrate and succinate buffers causes more cells to undergo HR in the compatible interaction, while treatment with the same buffers at pH 5.5 reduces the number of HR‐cells in the incompatible interaction; (4) race‐specific proton extrusion is observed underneath epidermal tissue detached from leaves inoculated 15 h earlier; and (5) treatment of leaves with fusicoccin, an activator of the plasma membrane H+‐ATPase, increases the number of HR‐cells in the compatible interaction.