bluuebunny/crossref_metadata_2025_split huggingface dataset:
Zinc‐dependent intermembrane space proteins stimulate import of carrier proteins into plant mitochondria
Authors: Lister Ryan , Mowday Brett , Whelan James , Millar A. Harvey 
Published: March 2003

SummaryMitochondrial inner membrane carrier proteins are imported into mitochondria from yeast, fungi and mammals by specific machinery, some components of which are distinct from those utilized by other proteins. Import of two different carriers into plant mitochondria showed that one contains a cleavable presequence which was processed during import, while the other imported in a valinomycin‐sensitive manner without processing. Mild osmotic shock of mitochondria released intermembrane space (IMS) components and impaired carrier protein import. Adding back the released IMS proteins as a concentrate in the presence of micromolar ZnCl2 stimulated carrier import into IMS‐depleted mitochondria, but did not stimulate import of a non‐carrier control precursor protein, the alternative oxidase. Anion‐exchange separation of IMS components before addition to IMS‐depleted mitochondria revealed a correlation between several 9–10 kDa proteins and stimulation of carrier import. MS/MS sequencing of these proteins identified them as plant homologues of the yeast zinc‐finger carrier import components Tim9 and Tim10. Stimulation of import was dependent on either Zn2+ or Cd2+ and inhibited by both N‐ethylmalamide (NEM) and a divalent cation chelator, consistent with a functional requirement for a zinc finger protein. This represents direct functional evidence for a distinct carrier import pathway in plant mitochondria, and provides a tool for determining the potential function of other IMS proteins associated with protein import.
Phytochrome signalling modulates the SA‐perceptive pathway in Arabidopsis
Authors: Genoud Thierry , Buchala Antony J. , Chua Nam‐Hai , Métraux Jean‐Pierre 
Published: March 2003

SummaryThe interaction of phytochrome signalling with the SA signal transduction pathway has been investigated in Arabidopsis using single and multiple mutants affected in light perception (phyA and phyB deficient) and light‐signal processing (psi2, phytochrome signalling). The induction of PR1 by SA and functional analogues has been found to strictly correlate with the activity of the signalling pathway controlled by both phyA and phyB photoreceptors. In darkness as well as dim light, and independently of a carbohydrate source, SA‐induced PR gene expression as well as the hypersensitive response to pathogens (HR) are strongly reduced. Moreover, the initiation of HR also exhibits a strict dependence upon both the presence and the amplitude of a phytochrome‐elicited signal. The growth of an incompatible strain of bacterial a pathogen (Pseudomonas syringae pv. tomato) was enhanced in phyA‐phyB and decreased in psi2 mutants. While functional chloroplasts were found necessary for the development of an HR, the induction of PRs was strictly dependent on light, but independent of functional chloroplasts. Taken together, these data demonstrate that the light‐induced signalling pathway interacts with the pathogen/SA‐mediated signal transduction route. These results are summarized in a formalism that allows qualitative computer simulation.
CpR18, a novel SAP‐domain plant transcription factor, binds to a promoter region necessary for ABA mediated expression of the CDeT27‐45 gene from the resurrection plant Craterostigma plantagineum Hochst
Authors: Hilbricht Tobias , Salamini Francesco , Bartels Dorothea 
Published: March 2003

SummaryCDeT27‐45 is a lea‐like gene from the resurrection plant Craterostigma plantagineum (Scrophulariaceae) which is strongly expressed in vegetative tissues in response to dehydration or treatment with abscisic acid (ABA). Expression of the gene is correlated with the acquisition of desiccation tolerance. Nuclear proteins bind to a 29‐bp cis‐regulatory region of the promoter which is essential for transcriptional activation of the CDeT27‐45 gene by ABA. Using a yeast one‐hybrid screen, the cDNA clone CpR18 was isolated, which encodes a protein with specific binding activity for the cis‐regulatory element in the CDeT27‐45 promoter. The protein contains an acidic region, a SAP‐domain, a zinc finger of the C3H‐type, and two motifs which are conserved in proteins from several plant species. One of the conserved regions is rich in basic residues and is predicted to form a helix‐loop‐helix structure. The R18 gene shows high similarities to genomic sequences and ESTs from other plant species. The tissue‐specific expression pattern of the rare R18 mRNA and the distribution of nuclear protein binding activity for the CDeT27‐45 promoter fragment are compared. The R18 protein is indeed localized in the nucleus, and activates transcription of CDeT27‐45 promoter‐GUS fusion constructs in tobacco protoplasts. DNA blot analysis and isolation of genomic clones reveal that two copies of R18 are present in the C. plantagineum genome.
Arf1 GTPase plays roles in the protein traffic between the endoplasmic reticulum and the Golgi apparatus in tobacco and Arabidopsis cultured cells
Authors: Takeuchi Masaki , Ueda Takashi , Yahara Natsuko , Nakano Akihiko 
Published: March 2003

SummaryArf GTPases are known to be key regulators of vesicle budding in various steps of membrane traffic in yeast and animal cells. We cloned the Arabidopsis Arf1 homologue, AtArf1, and examined its function. AtArf1 complements yeast arf1 arf2 mutants and its GFP‐fusion is localized to the Golgi apparatus in plant cells like its animal counterpart. The expression of dominant negative mutants of AtArf1 in tobacco and Arabidopsis cultured cells affected the localization of co‐expressed GFP‐tagged proteins in a variety of ways. AtArf1 Q71L and AtArf1 T31N, GTP‐ and GDP‐fixed mutants, respectively, changed the localization of a cis‐Golgi marker, AtErd2‐GFP, from the Golgi apparatus to the endoplasmic reticulum but not that of GFP‐AtRer1B or GFP‐AtSed5. GFP‐AtRer1B and GFP‐AtSed5 were accumulated in aberrant structures of the Golgi by AtArf1 Q71L. A soluble vacuolar protein, sporamin‐GFP, was also located to the ER by AtArf1 Q71L. These results indicate that AtArf1 play roles in the vesicular transport between the ER and the Golgi and in the maintenance of the normal Golgi organization in plant cells.
Five years of Bt cotton in China – the benefits continue
Authors: Pray Carl E. , Huang Jikun , Hu Ruifa , Rozelle Scott 
Published: March 2003

SummaryBt cotton is spreading very rapidly in China, in response to demand from farmers for technology that will reduce both the cost of pesticide applications and exposure to pesticides, and will free up time for other tasks. Based on surveys of hundreds of farmers in the Yellow River cotton‐growing region in northern China in 1999, 2000 and 2001, over 4 million smallholders have been able to increase yield per hectare, and reduce pesticide costs, time spent spraying dangerous pesticides, and illnesses due to pesticide poisoning. The expansion of this cost‐saving technology is increasing the supply of cotton and pushing down the price, but prices are still sufficiently high for adopters of Bt cotton to make substantial gains in net income.
A delayed leaf senescence mutant is defective in arginyl‐tRNA:protein arginyltransferase, a component of the N‐end rule pathway in Arabidopsis
Authors: Yoshida Satoko , Ito Masaki , Callis Judy , Nishida Ikuo , Watanabe Akira 
Published: March 2003

SummaryWe have isolated a delayed‐leaf‐senescence mutant, designated dls1, from an Arabidopsis T‐DNA line. Leaf senescence progresses more slowly in the dls1 mutant than in the wild‐type plant in both age‐dependent and dark‐induced senescence. Genetic analysis revealed that the dls1 is a monogenic recessive mutation that cosegregated with the T‐DNA insertion. Isolation of DNA flanking the T‐DNA revealed that the T‐DNA was inserted into the fourth intron of the AtATE1 gene, which encodes arginyl‐tRNA:protein arginyltransferase (EC. 2.3.2.8, R‐transferase), a component of the N‐end rule proteolytic pathway in yeast and mammals that transfers arginine to the N‐terminus of proteins with N‐terminal glutamyl or aspartyl residues. AtATE1 transcripts were not detectable in the dls1 mutant by RT‐PCR analysis. Introduction of a wild‐type AtATE1 gene into the dls1 mutant complemented the dls1 phenotype. We also showed using a transient expression assay system, that the dls1 mutation results in a decreased degradation of proteins with Asp or Glu at their N‐termini, and that the introduction of the wild‐type AtATE1 gene reverses this deficiency. These results suggest that the normal progression of leaf senescence requires R‐transferase activity, and that proteolysis by the N‐end rule pathway has an important physiological function in the progress of leaf senescence in plants.
COI1 links jasmonate signalling and fertility to the SCF ubiquitin–ligase complex in Arabidopsis
Authors: Devoto Alessandra , Nieto‐Rostro Manuela , Xie Daoxin , Ellis Christine , Harmston Rebecca , Patrick Elaine , Davis Jackie , Sherratt Leigh , Coleman Mark , Turner John G. 
Published: March 2003

SummaryJasmonates (JAs) regulate Arabidopsis thaliana wound and defence responses, pollen development, and stress‐related growth inhibition. Significantly, each of these responses requires COI1, an F‐box protein. Other F‐box proteins interact with SKP1 and cullin proteins to form SCF complexes that selectively recruit regulatory proteins targeted for ubiquitination. To determine whether COI1 also functions in an SCF complex, we have characterized Arabidopsis proteins that bind to COI1. An Arabidopsis cDNA expression library was screened in yeast for clones that produce proteins which can bind to COI1. We recovered two SKP1 homologues and a histone deacetylase. The Arabidopsis F‐box protein TIR1 interacted with SKP1 proteins, but not with the histone deacetylase. Mutant COI1 proteins revealed that the F‐box is required for interaction with SKP1s, but that sequences in leucine‐rich repeat domains are required for interaction with the histone deacetylase. Epitope‐tagged COI1 was introduced into Arabidopsis plants and cell cultures. Co‐immunoprecipitation experiments confirmed the interaction in planta of COI1 with SKP1‐like proteins and histone deacetylase, and also indicated that COI1 interacted with cullin. These results suggest that COI1 forms an SCFCOI1 complex in vivo. COI1 is therefore expected to form a functional E3‐type ubiquitin ligase in plants and to regulate expression of jasmonate responsive genes, possibly by targeted ubiquitination of a histone deacetylase.
RCY1, an Arabidopsis thaliana RPP8/HRT family resistance gene, conferring resistance to cucumber mosaic virus requires salicylic acid, ethylene and a novel signal transduction mechanism
Authors: Takahashi Hideki , Miller Jennifer , Nozaki Yukine ,   Sukamto, Takeda Megumi , Shah Jyoti , Hase Shu , Ikegami Masato , Ehara Yoshio , Dinesh‐Kumar S. P. 
Published: March 2003

SummaryThe dominant locus, RCY1, in the Arabidopsis thaliana ecotype C24 confers resistance to the yellow strain of cucumber mosaic virus (CMV‐Y). The RCY1 locus was mapped to a 150‐kb region on chromosome 5. Sequence comparison of this region from C24 and a CMV‐Y‐susceptible C24 mutant predicts that the RCY1 gene encodes a 104‐kDa CC‐NBS‐LRR‐type protein. The RCY1 gene from C24, when expressed in the susceptible ecotype Wassilewskija (Ws), restricted the systemic spread of virus. RCY1 is allelic to the resistance genes RPP8 from the ecotype Landsberg erecta and HRT from the ecotype Dijon‐17, which confer resistance to Peronospora parasitica biotype Emco5 and turnip crinkle virus (TCV), respectively. Examination of RCY1 plants defective in salicylic acid (SA), jasmonic acid (JA) and ethylene signaling revealed a requirement for SA and ethylene signaling in mounting a resistance response to CMV‐Y. The RCY1 nahG etr1 double mutants exhibited an intermediate level of susceptibility to CMV‐Y, compared to the resistant ecotype C24 and the susceptible ecotypes Columbia and Nossen. This suggests that in addition to SA and ethylene, a novel signaling mechanism is associated with the induction of resistance in CMV‐Y‐infected C24 plants. Moreover, our results suggest that the signaling pathways downstream of the RPP8, HRT, and RCY1 have evolved independently.
Tobacco plants were transformed by Agrobacterium rhizogenes infection during their evolution
Authors: Suzuki Kenji , Yamashita Ichiro , Tanaka Nobukazu 
Published: March 2003

SummaryWe discovered that the origin of cT‐DNA in the genome of wild‐type Nicotiana glauca is the T‐DNA of the mikimopine‐type Ri plasmid (pRi) harbored in Agrobacterium rhizogenes. The cT‐DNA was inserted into the genomic DNA of N. glauca from the position corresponding to the right border of mikimopine‐type pRi. The cT‐DNA contained two mikimopine synthase gene (mis) homologs, NgmisL and NgmisR, both of which were transcribed at low level in all N. glauca organs. NgMisR protein expressed in Escherichia coli has preserved Mis activity, which converts l‐histidine and α‐ketoglutaric acid to mikimopine. The mis homolog was also found in the genome of three other Nicotiana species: N. tomentosa, N. tomentosiformis, and N. tabacum; however, the site of insertion differed from that in N. glauca, suggesting that A. rhizogenes harboring mikimopine‐type pRi independently infected the ancestors of some Nicotiana plants. This is the first clear evidence of a host–parasite relationship during the early evolution of Nicotiana plants. We propose that a new phylogenetic approach using opine type cT‐DNA is applicable for presuming divergence in the genus Nicotiana.
Overexpression of a kinase‐deficient form of the EDR1 gene enhances powdery mildew resistance and ethylene‐induced senescence in Arabidopsis
Authors: Tang Dingzhong , Innes Roger W. 
Published: March 2003

SummaryThe EDR1 gene of Arabidopsis has previously been reported to encode a Raf‐like mitogen‐activated protein kinase kinase (MAPKK) kinase, and to function as a negative regulator of disease resistance. A phylogenetic analysis of plant and animal protein kinases revealed, however, that plant Raf‐like kinases are more closely related to animal mixed lineage kinases (MLKs) than Raf‐like kinases, and are deeply divergent from both classes of animal kinases, making inferences of substrate specificity questionable. We, therefore, assayed the kinase activity of recombinant EDR1 protein in vitro. The EDR1 kinase domain displayed autophosphorylation activity and phosphorylated the common MAP kinase substrate myelin basic protein. The EDR1 kinase domain also phosphorylated a kinase‐deficient EDR1 protein, indicating that EDR1 autophosphorylation can occur via an intermolecular mechanism. Overexpression of a kinase‐deficient full‐length EDR1 gene (35S::dnEDR1) in wild‐type Arabidopsis plants caused a dominant negative phenotype, conferring resistance to powdery mildew (Erysiphe cichoracearum) and enhancing ethylene‐induced senescence. RNA‐gel blot analyses showed that the 35S::dnEDR1 transgene was highly transcribed in transgenic plants. Western blot analysis, however, revealed that neither the wild‐type nor mutant EDR1 protein could be detected in these lines, indicating that the dominant negative phenotype may be caused by a translational inhibition mechanism rather than by a protein level effect. Overexpression of orthologous dnEDR1 constructs may provide a novel strategy for controlling powdery mildew disease in crops.
Susceptible to intolerance – a range of hormonal actions in a susceptible Arabidopsis pathogen response
Authors: O'Donnell Philip J. , Schmelz Eric A. , Moussatche Patricia , Lund Steven T. , Jones Jeffery B. , Klee Harry J. 
Published: March 2003

SummaryEthylene and salicylic acid (SA) are key intermediates in a host's response to pathogens. Previously, we have shown using a tomato compatible interaction that ethylene and SA act sequentially and are essential for disease symptom production. Here, we have examined the relationship between the two signals in the Arabidopsis–Xanthomonas campestris pv. campestris (Xcc) compatible interaction. Preventing SA accumulation by expression of the nahG gene reduced subsequent ethylene production and altered the development of disease symptoms, with plants showing no visible chlorosis. The ethylene insensitive lines, etr1‐1 and etr2‐1, on the other hand, accumulated SA and exhibited normal but precocious symptom development. Therefore, Arabidopsis, like tomato, was found to exhibit co‐operative ethylene and SA action for the production of disease symptoms. However, in Arabidopsis, SA was found to act upstream of ethylene. Jasmonic acid and indole‐3‐acetic acid levels were also found to increase in response to Xcc. In contrast to ethylene, accumulation of these hormones was not found to be dependent on SA action. These results indicate that the plants response to a virulent pathogen is a composite of multiple signaling pathways.
The GLOBULAR ARREST1 gene, which is involved in the biosynthesis of folates, is essential for embryogenesis in Arabidopsis thaliana
Authors: Ishikawa Takaaki , Machida Chiyoko , Yoshioka Yasushi , Kitano Hidemi , Machida Yasunori 
Published: March 2003

SummaryWe identified a mutation in Arabidopsis that resulted in defective embryos, and we designated this mutation globular arrest1 (gla1). The predicted amino acid sequence encoded by the GLA1 gene is homologous to the amino acid sequences of folylpolyglutamate synthetase (FPGS) and dihydrofolate synthetase (DHFS), which participate in folate biosynthesis. The defect of gla1 in the formation of calli was rescued by the supplement of 5‐formyl tetrahydrofolate. These results indicated that GLA1 is involved in the biosynthesis of tetrahydrofolate. The gla1 embryos developed normally in the early stage of development but did not undergo the transition to the heart stage. Thus, the function of the GLA1 gene in embryogenesis appears to be required after the globular stage. However, when the levels of GLA1 transcripts in transgenic plants were increased by introduction of several copies of a GLA1 transgene (GLA6.8), the gla1 embryos that grew on gla1/gla1 GLA6.8/– plants developed as far as the heart to bent‐cotyledon stage. This result suggests that the GLA1 function is provided to embryos by maternal tissues until embryos reach the globular stage.
GeBP, the first member of a new gene family in Arabidopsis, encodes a nuclear protein with DNA‐binding activity and is regulated by KNAT1
Authors: Curaba Julien , Herzog Michel , Vachon Gilles 
Published: March 2003

SummaryTrichomes of Arabidopsis are single‐celled epidermal hair that are a useful model for studying plant cell fate determination. Trichome initiation requires the activity of the GLABROUS1 (GL1) gene whose expression in epidermal and trichome cells is dependent on the presence of a 3′‐cis‐regulatory element. Using a one‐hybrid screen, we have isolated a cDNA, which encodes for a protein, GL1 enhancer binding protein (GeBP), that binds this regulatory element in yeast and in vitro. GeBP and its three homologues in Arabidopsis share two regions: a central region with no known motifs and a C‐terminal region with a putative leucine‐zipper motif. We show that both regions are necessary for trans‐activation in yeast. A translational fusion with the Yellow Fluorescent Protein (YFP) indicates that GeBP is a nuclear protein whose localization is restricted to, on average, 3–5 subnuclear foci that might correspond to nucleoli. Transcriptional fusion with the GUS reporter indicates that GeBP is mainly expressed in vegetative meristematic tissues and in very young leaf primordia. We looked at GeBP expression in plants mutated in or misexpressing KNAT1, a KNOX gene, expressed in the shoot apical meristem and downregulated in leaf founder cells, and found that GeBP transcript level is regulated by KNAT1 suggesting that KNAT1 is a transcriptional activator of GeBP. This regulation suggests that GeBP is acting as a repressor of leaf cell fate.
Structure and expression of the rice class‐I type histone deacetylase genes OsHDAC1–3: OsHDAC1 overexpression in transgenic plants leads to increased growth rate and altered architecture
Authors: Jang In‐Cheol , Pahk Yoon‐Mok , Song Sang Ik , Kwon Ho Jeong , Nahm Baek Hie , Kim Ju‐Kon 
Published: March 2003

SummaryHistone deacetylases (HDACs) modulate chromatin structure and transcription. HDACs have been studied as negative regulators in eukaryotic transcription. We isolated the rice OsHDAC1–3 genes for class I‐type histone deacetylases, which are related to the RPD3 family. The OsHDAC1 gene encoded a protein of approximately 57 kDa that shared 73.5, 72.7, 79.9, and 57.1% amino acid sequence identity with the OsHDAC2, OsHDAC3, maize RPD3, and human HDAC1 proteins, respectively. Genomic structures and Southern blot analyses revealed that OsHDAC1–3 contained seven, six, and seven exons, respectively, and constituted a class I‐type family in the rice genome. OsHDAC1 was expressed at similar levels in the leaves, roots, and callus cells, whereas OsHDAC2 and 3 were expressed in the roots and callus cells, but not in the leaves, exhibiting distinct tissue specificity. To explore the role of histone deacetylases in transgenic plants, we inserted the OsHDAC1 cDNA fragment into the expression vector Ai::OsHDAC1 under the control of the ABA‐inducible promoter Ai, and transformed the construct into rice. Levels of mRNA, protein, and HDAC activity were significantly increased in Ai::OsHDAC1 callus cells. The amount of tetra‐acetylated H4 in the transgenic cells was greatly reduced, and the reduction was abolished upon treatment with trichostatin A. These results demonstrate that OsHDAC1 overexpression in transgenic cells both yields enzymatically active HDAC complexes and induces changes in histone acetylation in vivo. The overexpression leads to a range of novel phenotypes, involving increased growth rate and altered plant architecture, suggesting that OsHDAC1 functions in the genome‐wide programming of gene expression.
Interactions between gene activity and cell layers during floral development
Authors: Vincent Coral A. , Carpenter Rosemary , Coen Enrico S. 
Published: March 2003

SummaryThe DEFICIENS (DEF) gene is required for establishing petal and stamen identity in Antirrhinum and is expressed in all three layers of the floral meristem in whorls 2 and 3. Expression of DEF in a subset of meristem layers gives rise to organs with characteristic shapes and cell types, reflecting altered patterns and levels of DEF gene activity. To determine how the contributions of layers and gene activity interact, we exploited a DEF allele which carries a transposon insertion in the MADS box region to generate periclinal chimeras expressing alleles with different activities. By comparing the phenotype, development and expression patterns of these chimeras we show that expression of DEF in L1 makes a major contribution to morphology in whorl 2, irrespective of the allele. By contrast L1 expression is largely unable to rescue whorl 3, possibly because of a non‐autonomous inhibitor of DEF activity in this whorl.