bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gain of function assays identify non‐rolgenes fromAgrobacterium rhizogenesTL‐DNA that alter plant morphogenesis or hormone sensitivity
Authors: Lemcke Kai , Schmülling Thomas 
Published: March 2003

Summary This study tested the morphogenetic potential of 15 open reading frames of the TL‐DNA of

Agrobacterium rhizogenes

strain HRI. These open reading frames were expressed individually under the control of the 35S RNA promoter in transgenic tobacco plants (

Nicotiana tabacum

L.). Expression of three T‐DNA loci, ORF3n, ORF8 and ORF13, alters plant morphogenesis or the response of transgenic tissues to plant hormones. ORF3n transgenic plants are characterized by retarded flowering, altered internode elongation, altered leaf shape and, in particular, leaf tip necrosis. ORF3n and ORF8 expression reduces the sensitivity to auxin and cytokinin in combination or auxin alone. Tetracycline‐dependent expression of ORF13 overcomes a selection of low levels of expression during plant regeneration and reveals a strong inhibitory effect of the ORF13 gene product on cell division and cell elongation. We conclude that the

A. rhizogenes

TL‐DNA harbors genetic information that is important for pathogenicity apart from the well studied

rol

genes. We propose that these genes play mainly a negative regulatory role during pathogenesis. Moreover, these loci might be relevant to successful infections in specific host plants.
Disruption of chloroplast biogenesis and plant development upon down‐regulation of a chloroplast processing enzyme involved in the import pathway
Authors: Wan Jiangxin , Bringloe David , Lamppa Gayle K. 
Published: March 2003

Summary Typically, nuclear‐encoded chloroplast proteins are synthesized as precursors and require proteolytic processing upon import before their assembly into functional complexes within the organelle. A cDNA encoding a chloroplast processing enzyme (CPE), which was originally identified as a protease that cleaves the precursor for the major light‐harvesting chlorophyll binding protein (preLHCP), was introduced into the tobacco genome in an antisense orientation to investigate the role of the enzyme

in vivo

. The presence of the antisense‐CPE gene resulted in chlorotic leaves, and retarded shoot and root growth. The introduction of the antisense‐CPE gene disrupted the normal pattern of plastid division. Chloroplast numbers in cotyledon and first leaf cells were reduced 25% compared to the control plants. Chloroplasts contained fewer thylakoids and large starch grains, the latter an indication of a change in carbon flux. CPE levels and activity were significantly lower in stromal extracts in the transgenic plants. Interestingly,

in vitro

import of precursor proteins was defective. Most of the preLHCP remained on the exterior of the organelle, and only a small fraction of preRBCA was imported, suggesting that a change in CPE levels can influence translocation across the envelope. Our

in vivo

results support the conclusion that CPE plays a critical role during chloroplast biogenesis, and that the pleiotropic effects of CPE down‐regulation reflect its function as a general stromal processing peptidase as part of the import machinery. Furthermore, these findings indicate the importance of regulating the expression of components of the import machinery for normal plant development.
ICK1, a cyclin‐dependent protein kinase inhibitor fromArabidopsis thalianainteracts with both Cdc2a and CycD3, and its expression is induced by abscisic acid
Authors: Wang Hong , Qi Qungang , Schorr Peter , Cutler Adrian J. , Crosby William L. , Fowke Larry C. 
Published: March 2003

Summary Cyclin‐dependent kinase (CDK) inhibitor genes encode low molecular weight proteins which have important functions in cell cycle regulation, development and perhaps also in tumorigenesis. The first plant CDK inhibitor gene

ICK1

was recently identified from

Arabidopsis thaliana

. Although the C‐terminal domain of ICK1 contained an important consensus sequence with the mammalian CDK inhibitor p27Kip1, the remainder of the deduced ICK1 sequence showed little similarity to any known CDK inhibitors.

In vitro

assays showed that recombinant ICK1 exhibited unique kinase inhibitory properties. In the present study we characterized ICK1 in terms of its gene structure, its interaction with both

A. thaliana

Cdc2a and CycD3, and its induction by the plant growth regulator, abscisic acid (ABA).

ICK1

was expressed at a relatively low level in the tissues surveyed. However,

ICK1

was induced by ABA, and along with

ICK1

induction there was a decrease in Cdc2‐like histone H1 kinase activity. These results suggest a molecular mechanism by which plant cell division might be inhibited by ABA.

ICK1

clones were also identified from independent yeast two‐hybrid screens using the CycD3 construct. The implication that ICK1 protein could interact with both Cdc2a and CycD3 was confirmed by

in vitro

binding assays. Furthermore, deletion analysis indicated that different regions of ICK1 are required for the interactions with Cdc2a and CycD3. These results provide a mechanistic basis for understanding the role of CDK inhibitors in cell cycle regulation in plant cells.
An Arabidopsis immunophilin, AtFKBP12, binds to AtFIP37 (FKBP interacting protein) in an interaction that is disrupted by FK506
Authors: Faure Jean‐Denis , Gingerich Derek , Howell Stephen H. 
Published: March 2003

Summary AtFKBP12 is an Arabidopsis cDNA that encodes a protein similar to the mammalian immunophilin, FKBP12. AtFKBP12 was used as ‘bait’ in a yeast 2‐hybrid system to screen for cDNAs in Arabidopsis encoding proteins that bind to FKBP12. Two partial cDNAs were recovered encoding the C‐terminus of a protein we have called

Arabidopsis thaliana

FKBP12 interacting protein 37 (AtFIP37). AtFIP37 is similar to a mammalian protein, FAP48, that also binds to FKBP12. The interaction between AtFKBP12 and AtFIP37 in the 2‐hybrid system, as assessed by histidine auxotrophy and β‐galactosidase activity, was disrupted by FK506, but not by cyclosporin A, a drug that binds to cyclophilin A. AtFIP37 was also shown to bind

in vitro

to AtFKBP12 in GST‐fusion protein binding assays. The binding was abolished by prior incubation of AtFKBP12 with FK506. These findings indicate that an Arabidopsis FKBP12 ortholog encodes a protein that binds FK506 and that the interaction between AtFKBP12 and AtFIP37 may involve the FK506 binding site of AtFKBP12. The interaction provides interesting new opportunities for controlling protein:protein interactions

in vivo

in plants.
Distribution of TMV movement protein in single living protoplasts immobilized in agarose
Authors: Más Paloma , Beachy Roger N. 
Published: March 2003

SummaryRecent studies of the tobacco mosaic virus (TMV) P30 movement protein (MP) fused with green fluorescent protein (GFP) during TMV infection described the involvement of elements of the cytoskeleton and components of the endoplasmic reticulum (ER) in the intracellular trafficking of MP:GFP from the sites of synthesis in the cytoplasm to plasmodesmata. To examine in real‐time the pattern of synthesis, accumulation and degradation of MP:GFP, we developed a method to immobilize protoplasts in agarose such that they are maintained alive for extended periods of time. The pattern of MP:GFP accumulation in single living protoplasts visualized by confocal laser scanning microscopy (CLSM) was parallel to that previously described in a population of protoplasts harvested at different times post‐infection. Additionally, a network of weakly fluorescent filaments, which are apparently different from microtubules, was observed to surround the nucleus and these filaments were associated with fluorescent bodies (previously identified as ER‐derived structures). Later in infection, the fluorescent bodies increased in size and coalesced to form larger structures that accumulated near the periphery of the cells while highly fluorescent non‐cortical filaments were observed distributed in the cytoplasm. The putative involvement of these filaments in targeting the fluorescent bodies to the periphery of the cell is discussed. Studies of single, embedded protoplasts make it possible to observe changes in amount and subcellular localization of viral and other proteins.
Activation of MAPK homologues by elicitors in tobacco cells
Authors: Lebrun‐Garcia Angela , Ouaked Fatma , Chiltz Annick , Pugin Alain 
Published: March 2003

Summary Elicitors of plant defence reactions (such as cryptogein, an elicitin produced by

Phytophthora cryptogea

, or oligogalacturonides (OGs)), induced in tobacco cell suspensions (

Nicotiana tabacum

var Xanthi) a rapid and transient activation of two protein kinases (PKs) with apparent molecular masses of 50 and 46 kDa, respectively. These PKs activated and phosphorylated at tyrosine residues, phosphorylated myelin basic protein (MBP) at serine/threonine residues. Both are recognized by anti‐MAPK antibodies. The two MBP kinases possessed the same kinetics of activation, and their activation depended, to the same extent, on different exogenously applied compounds (staurosporine, lanthanum, EGTA). We demonstrate here that the activation of the MBP kinases is calcium dependent and sensitive to staurosporine, a protein kinase inhibitor which annihilates all known responses of tobacco cells to cryptogein. The activation of MBP kinases appeared to be independent of the production of active oxygen species (AOS) and insensitive to calyculin A, a protein phosphatase type 1 and 2A inhibitor. The activation of MAPKs is discussed in relation to the early responses induced by cryptogein.
Suppression of endogenous α and β tubulin synthesis in transgenic maize calli overexpressing α and β tubulins
Authors: Anthony Richard G. , Hussey Patrick J. 
Published: March 2003

Summary Maize Black Mexican Sweetcorn cells have been transformed with constructs containing α and β tubulin coding sequences either singly or together. It is shown that recovery of stable maize transformants is dependent on the co‐expression of transfected α and β tubulin in the same lines, indicating that plant cells cannot tolerate an imbalance in the ratio of α tubulin to β tubulin within the cytoplasm. The co‐expression of transfected α and β tubulin in maize cells results in an increase in the overall tubulin content (approximately threefold). The transfected α and β tubulins are incorporated into cortical, spindle and phragmoplast microtubule arrays indicating that they are functional. Furthermore, the co‐expression of the transfected α and β tubulins results in the suppression of endogenous α and β tubulin synthesis. This suppression increases both with the strength of the promoter in the constructs and with the number of copies of the transgenes inserted into the maize genome. The implications for the post‐transcriptional and post‐translational regulation of tubulin synthesis in plant cells are discussed.
Molecular characterization of plastidic phosphoserine aminotransferase in serine biosynthesis fromArabidopsis
Authors: Ho Chai‐Ling , Noji Masaaki , Saito Maiko , Yamazaki Mami , Saito Kazuki 
Published: March 2003

Summary Serine biosynthesis in plants proceeds by two pathways; a photorespiratory pathway which is associated with photorespiration and a pathway from phosphoglycerate. A cDNA encoding plastidic phosphoserine aminotransferase (PSAT) which catalyzes the formation of phosphoserine from phosphohydroxypyruvate has been isolated from

Arabidopsis thaliana

. Genomic DNA blot analysis indicated that this enzyme is most probably encoded by a single gene and is mapped on the lower arm of chromosome 4. The deduced protein contains an N‐terminal extension exhibiting the general features of a plastidic transit peptide, which was confirmed by subcellular organelle localization using GFP (green flourescence protein). Northern analysis indicated preferential expression of PSAT in roots of light‐grown plants, supporting the idea that the phosphorylated pathway may play an important role in supplying the serine requirement of plants in non‐green tissues.

In situ

hybridization analysis of PSAT revealed that the gene is generally expressed in all types of cells with a significantly higher amount in the meristem tissue of root tips.
A relic S‐RNase is expressed in the styles of self‐compatibleNicotiana sylvestris
Authors: Golz John F. , Clarke Adrienne E. , Newbigin Ed , Anderson Marilyn 
Published: March 2003

Summary We surveyed ribonuclease activity in the styles of

Nicotiana

spp. and found little or no activity in self‐compatible species and in a self‐compatible accession of a self‐incompatible species. All self‐incompatible species had high levels of ribonuclease activity in their style. Interestingly, one self‐compatible species,

N. sylvestris

, had a level of stylar ribonuclease activity comparable to that of some self‐incompatible

Nicotiana

species. A ribonuclease with biochemical properties similar to those of the self‐incompatibility (S‐)RNases of

N. alata

was purified from

N. sylvestris

styles. The N‐terminal sequence of this protein was used to confirm the identity of a cDNA corresponding to the stylar RNase. The amino acid sequence deduced from the cDNA was related to those of the S‐RNases and included the five conserved regions characteristic of these proteins. It appears that the

N. sylvestris

RNase may have evolved from the S‐RNases and is an example of a ‘relic S‐RNase’. A number of features distinguish the

N. sylvestris

RNase from the S‐RNases, and the role these may have played in the presumed loss of the self‐incompatibility response during the evolution of this species are discussed.
Retrotransposon‐based insertion polymorphisms (RBIP) for high throughput marker analysis
Authors: Flavell Andrew J. , Knox Maggie R. , Pearce Stephen R. , Ellis T. H. Noel 
Published: March 2003

Summary Two assays based upon PCR detection of a polymorphic PDR1 retrotransposon insertion in

Pisum sativum

have been developed. Both methods involve PCR with primers derived from the transposon and flanking DNA. The first method uses a dot assay for PCR product detection which could be fully automated for handling thousands of samples. The second method, which is designed to handle lower numbers, requires a single PCR and gel lane per sample. Both methods yield co‐dominant markers, with presence and absence of the transposon insertion independently scorable, and both could in principle be applied to any transposable element in any plant species.
Interaction of maize actin‐depolymerising factor with actin and phosphoinositides and its inhibition of plant phospholipase C.
Authors: Gungabissoon Ravine A. , Jiang Chang‐Jie , Drøbak Bjørn K. , Maciver Sutherland K. , Hussey Patrick J. 
Published: March 2003

Summary We have previously reported the isolation of three

Zea mays

genes that encode actin‐depolymerising factors/cofilins, a family of low molecular weight actin regulating proteins. In the present study, we have characterised one of these proteins, ZmADF3. We report that ZmADF3 binds G‐actin with a 1:1 stoichiometry, and that the interaction with F‐actin is pH‐sensitive. ZmADF3 co‐sediments mainly with F‐actin at pH 6.0 and mainly with G‐actin at pH 9.0. This response is more similar to that of vertebrate cofilin and ADF than to that of

Acanthamoeba

actophorin which, although more similar in primary sequence to ZmADF3, is not pH sensitive. However, ZmADF3 requires a more basic environment to depolymerise actin relative to either vertebrate ADF or cofilin. Filaments decorated with ZmADF3 at low pH are very rapidly depolymerised upon raising the pH, which is consistent with a severing mechanism for the disruption of actin filaments. Also, we demonstrate that ZmADF3 binds specific polyphosphatidylinositol lipids, especially phosphatidylinositol 4,5‐bisphosphate (PIP2), and we show that this binding inhibits the actin‐depolymerising function of ZmADF3. Moreover, we show that a consequence of ZmADF3 binding PIP2 is the inhibition of the activity of polyphosphatidylinositol specific plant phospholipase C, indicating the possibility of reciprocal modulation of this major signalling pathway and the actin cytoskeleton.
Molecular and cytogenetic characterization of a transgene locus that induces silencing and methylation of homologous promoters intrans
Authors: Jakowitsch Johannes , Papp István , Moscone Eduardo A. , Van Der Winden Johannes , Matzke Marjori , Matzke Antonius J. M. 
Published: March 2003

Summary One type of homology‐dependent gene silencing in transgenic plants involves a silencing locus that is able to transcriptionally inactivate and methylate an unlinked target locus with which it shares sequence identity in promoter regions. In a manner resembling paramutation of endogenous genes, the target locus reactivates and loses methylation progressively over several generations after segregating away from the silencing locus, which autonomously acquires stable methylation. To investigate the origins of

trans

‐silencing ability and susceptibility, we have analyzed the structures, flanking DNA sequences and chromosomal locations of a nopaline synthase promoter silencing locus,

H2

, and a sensitive target locus,

K81

. A partially resistant target locus,

Kα

, has been characterized molecularly. The complex and scrambled

H2

locus comprises six copies of the nopaline synthase promoter, two of which are collinear with prokaryotic non‐T‐DNA sequences, and is integrated close to a region of intercalary heterochromatin. These features probably contribute collectively to the silencing ability because

H2

subclones reintroduced into random locations in the K81 genome did not frequently induce silencing. Both the

K81

and

Kα

loci have simple structures, although the former contains non‐T‐DNA prokaryotic sequences that are also present at

H2

, and they are flanked by low copy plant DNA.

H2

and

K81

might interact effectively because they are present on morphologically similar chromosomes from the T subgenome of allotetraploid tobacco.
Localisation of glutathione and homoglutathione inMedicago truncatulais correlated to a differential expression of genes involved in their synthesis
Authors: Frendo Pierre , Gallesi Daniela , Turnbull Ruth , Van de Sype Ghislaine , Hérouart Didier , Puppo Alain 
Published: March 2003

Summary Glutathione (GSH) and homoglutathione (hGSH) were quantified in

Medicago truncatula

during plant development. hGSH was detectable only 48 h after seed germination whereas GSH was present in the dry seeds, indicating that only GSH is used for sulphur storage in seeds. The hGSH was detectable only in the underground part of mature plants whereas GSH was present in all the organs. γ‐EC synthetase (γ‐ECS) and GSH synthetase (GSHS) activities were found in roots and leaves whereas hGSH synthetase (hGSHS) was found only in roots. Full‐length cDNA encoding γ‐ECS and two partial cDNAs (

gshs1

and

gshs2

) showing high identity with GSHS were isolated in

M. truncatula

. High γ‐ECS activity was detected in protein extracts of a γ‐ECS‐deficient

E. coli

strain expressing the

M. truncatula

γ‐ECS. Northern blot analysis showed that the γ‐ECS gene was similarly expressed in all the mature plant organs tested, whereas

gshs1

had a higher expression in leaves and flowers and

gshs2

was preferentially expressed in roots and nodules. We hypothesise that

gshs1

and

gshs2

encode a GSHS and an hGSHS, respectively.
Expression of cysteine proteinase during developmental events associated with programmed cell death in brinjal
Authors: Xu Fang‐Xiu , Chye Mee‐Len 
Published: March 2003

Summary Here we show that the expression of a cysteine proteinase coincides with several developmental events associated with programmed cell death (PCD) in

Solanum melongena

(brinjal), i.e. during leaf senescence, fruit senescence, xylogenesis, nucellar cell degeneration and anther senescence. We have isolated a cDNA encoding brinjal cysteine proteinase (SmCP) that shares high (90–92%) amino acid identity to cysteine proteinases of tobacco (CYP‐8) and tomato (LCYP‐2) that have not been previously reported to be senescence‐associated. In contrast, SmCP shows lower (39–41%) amino acid identity to other senescence‐related cysteine proteinases and, unlike most of them, it is not preferentially expressed in certain organs or cell types. Northern analysis of leaves, fruits and flowers at different stages of development showed that

SmCP

expression increased significantly at senescence in leaf and fruit, but was highly expressed throughout flower development.

In situ

hybridization studies on flower sections using an antisense RNA probe localized the

SmCP

mRNA to the xylem, the epidermis and the endothecium of the anther and the nucellar cells, suggesting its involvement in PCD during xylogenesis, anther senescence and ovule development, respectively. Its expression during nucellar cell degeneration suggests that protein reserves of the nucellus are released to the developing embryo. Polarity in its pattern of expression in the nucellus of the developing seed (40DAP) further implies a directional flow of these nutrients.
Ozone‐induced cell death occurs via two distinct mechanisms in Arabidopsis: the role of salicylic acid
Authors: Rao Mulpuri V. , Davis Keith R. 
Published: March 2003

Summary Previous studies suggest that salicylic acid (SA) plays an important role in influencing plant resistance to ozone (O3). To further define the role of SA in O3‐induced responses, we compared the responses of two
Arabidopsis
genotypes that accumulate different amounts of SA in response to O3 and a SA‐deficient transgenic Col‐0 line expressing salicylate hydroxylase (NahG). The differences observed in O3‐induced changes in SA levels, the accumulation of active oxygen species, defense gene expression, and the kinetics and severity of lesion formation indicate that SA influences O3 tolerance via two distinct mechanisms. Detailed analyses indicated that features associated with a hypersensitive response (HR) were significantly greater in O3‐exposed Cvi‐0 than in Col‐0, and that NahG plants failed to exhibit these HR‐like responses. Furthermore, O3‐induced antioxidant defenses, including the redox state of glutathione, were greatly reduced in NahG plants compared to Col‐0 and Cvi‐0. This suggests that O3‐induced cell death in NahG plants is due to the loss of SA‐mediated potentiation of antioxidant defenses, while O3‐induced cell death in Cvi‐0 is due to activation of a HR. This hypothesis is supported by the observation that inhibition of NADPH‐oxidases reduced O3‐induced H2O2 levels and the O3‐induced cell death in Cvi‐0, while no major changes were observed in NahG plants. We conclude that although SA is required to maintain the cellular redox state and potentiate defense responses in O3 exposed plants, high levels of SA also potentiate activation of an oxidative burst and a cell death pathway that results in apparent O3 sensitivity.