bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anoxia tolerance in tobacco roots: effect of overexpression of pyruvate decarboxylase
Authors: Tadege Million , Brändle Roland , Kuhlemeier Cris 
Published: March 2003

SummaryPlant survival during flooding relies on ethanolic fermentation for energy production. The available literature indicates that the first enzyme of the ethanolic fermentation pathway, pyruvate decarboxylase (PDC), is expressed at very low levels and is likely to be rate‐limiting during oxygen deprivation. The authors expressed high levels of bacterial PDC in tobacco to study the modulation of PDC activity in vivo, and assess its impact on the physiology of ethanolic fermentation and survival under oxygen stress. In contrast to leaves, wild‐type normoxic roots contained considerable PDC activity, and overexpression of the bacterial PDC caused only a moderate increase in acetaldehyde and ethanol production under anoxia compared to wild‐type roots. No significant lactate production could be measured at any time, making it unlikely that lactate‐induced acidification (LDH/PDC pH‐stat) triggers the onset of ethanol synthesis. Instead, the authors favour a model in which the flux through the pathway is regulated by substrate availability. The increased ethanolic flux in the transgenics compared to the wild‐type did not enhance anoxia tolerance. On the contrary, rapid utilisation of carbohydrate reserves enhanced premature cell death in the transgenics while replenishment of carbohydrates improved survival under anoxia.
A single nuclear locus is involved in both chloroplast RNAtrans‐splicing and 3′ end processing
Authors: Hahn Daniela , Nickelsen Jörg , Hackert Anke , Kück Ulrich 
Published: March 2003

Summary The complex maturation of the chloroplast

psaA

mRNA in

Chlamydomonas reinhardtii

requires the splicing of three separate exons in

trans

. At least 14 nuclear gene products and a small chloroplast RNA

(tscA)

seem to be involved in

psaA trans

‐splicing. To further elucidate the mechanisms that regulate

trans

‐splicing in

C. reinhardtii

, we have analyzed four different nuclear mutants; two affected in

trans

‐splicing of the

psaA

exons 1 and 2 (class C) and two blocked in both

psaA trans

‐splicing steps (class B). While mutants M18 (class C) and L118 (class B) have a mature chloroplast

tscA

RNA, no such transcripts could be detected in mutants TR72 (class C) and HN31 (class B). Northern hybridizations indicate that the absence of mature

tscA

transcripts in HN31 and TR72 results from a defect in the processing of a

tscA/chlN

precursor transcript. Since the

tscA

locus has been shown to mediate

psaA

exon 1 and 2

trans

‐splicing, the nucleus‐encoded factor affected in the class C mutant TR72 may be required for

tscA

3′ end maturation and only indirectly for

psaA

exon 1 and 2

trans

‐splicing. Moreover, further genetic analysis revealed that the nuclear HN31 locus is involved in both maturation of the

tscA/chlN

precursor and

trans

‐splicing of the

psaA

exons 2 and 3.
The control of source to sink carbon flux during tuber development in potato
Authors: Sweetlove Lee J. , Kossmann Jens , Riesmeier Jörg W. , Trethewey Richard N. , Hill Steven A. 
Published: March 2003

SummaryWe have used top‐down metabolic control analysis to investigate the control of carbon flux through potato (Solanum tuberosum) plants during tuberisation. The metabolism of the potato plant was divided into two blocks of reactions (the source and sink blocks) that communicate through the leaf apoplastic sucrose pool. Flux was measured as the transfer of 14C from CO2 to the tuber. Flux and apoplastic sucrose concentration were varied either by changing the light intensity or using transgenic manipulations that specifically affect the source or sink blocks, and elasticity coefficients were measured. We have provided evidence in support of our assumption that apoplastic sucrose is the only communicating metabolite between the source and sink blocks. The elasticity coefficients were used to calculate the flux control coefficients of the source and sink blocks, which were 0.8 and 0.2, respectively. This work suggests that the best strategy for the manipulation of tuber yield in potato will involve increases in photosynthetic capacity, rather than sink metabolism.
Jasmonate signaling mutants ofArabidopsisare susceptible to the soil fungusPythium irregulare
Authors: Staswick Paul E. , Yuen Gary Y. , Lehman Casey C. 
Published: March 2003

Summary Jasmonic acid has properties of a plant hormone, including the induction of specific genes associated with plant defense. We previously described

jar1‐1

, an

Arabidopsis

jasmonate response mutant that exhibits reduced sensitivity to methyl jasmonate. We have further characterized this mutant and two new alleles;

jar1‐2

from a gamma irradiated population, and

jar1‐4

from a T‐DNA mutant population. Seedling root growth in

jar1‐1

was equally insensitive to methyl jasmonate and jasmonic acid, indicating that the defect was not in the conversion of methyl jasmonate to the acid. None of the

jar1

mutants showed an altered sensitivity to auxin, cytokinin, or the ethylene precursor 1‐aminocyclopropane‐1‐carboxylic acid, indicating that the lesion does not affect the general uptake or transport of hormones. A soil fungus,

Pythium irregulare

, was found to blight

jar1‐1

. Cultures of this organism caused the symptoms in all three

jar1

mutants but not in wild type, indicating that increased susceptibility was due to the lesion in the

JAR1

locus. A fatty acid desaturase triple mutant that is defective in the biosynthesis of jasmonic acid (J. Browse, Washington State University) was also susceptible, confirming that jasmonate is involved in resistance. The

jar1‐1

locus was mapped to the lower end of chromosome 2, about 11.4 cM from

as1 and

1.6 cM from

cer8

. These results establish that jasmonate signaling plays an important role in resistance to soil micro‐organisms in plants.
Cytoplasmic acidification and current influx follow growth pulses ofLilium longiflorumpollen tubes
Authors: Messerli Mark A. , Robinson Kenneth R. 
Published: March 2003

Summary We confirm that there is not a standing pH gradient in the tips of lily pollen tubes, but show that there are pulses of H+ that occur during pulsatile growth. The [H+] increases in a zone at the tips of the tubes and travels rapidly as far as 60 μm down the shaft of the tube. The tip‐localized pH was found to drop to 6.0 during the largest pulses, from an average cytosolic level of 7.05 in tubes that had not yet begun to pulse. Correlation analysis indicates that the peaks of the pH pulses lag the peaks of the growth pulses by slightly more than 7.5 sec. Vibrating probe measurements reveal an influx of ionic current that peaks 7.5 sec after the peaks of the growth pulses. While this current may in part be H+ influx, we give evidence that K+ influx is also a component of the current pulses. The timing of the H+ and current pulses suggests that they may be involved in terminating the growth pulses.
The self‐incompatibility (S) locus inPetunia hybridais located on chromosome III in a region, syntenic for the Solanaceae
Authors: ten Hoopen Rogier , Harbord Robin M. , Maes Tamara , Nanninga Nanne , Robbins Timothy P. 
Published: March 2003

Summary Seven independent transformants were previously shown to carry T‐DNA inserts that are genetically linked to the self‐incompatibility (

S

)‐locus in

Petunia hybrida

. These T‐DNAs provided reliable targets for fluorescent

in situ

hybridisation (FISH) localisation. The T‐DNA loci were found to be distributed over the entire long arm of chromosome III. The most tightly linked T‐DNA loci were located in a subcentromeric position. Independent confirmation of this assignment of the

S

‐locus to chromosome III was obtained by RFLP analysis of a cDNA marker linked to the

S

‐locus of potato (CP100). Tight linkage was found between CP100 and a peroxidase isozyme locus previously mapped to chromosome III. The co‐localisation of CP100, peroxidase and the

S

‐locus in petunia reveals synteny around the

S

‐locus between four members of the Solanaceae family. The implications of a subcentromeric localisation of the

S

‐locus are discussed in relation to chromosome fragments associated with self‐compatible mutants.
Circadian dysfunction causes aberrant hypocotyl elongation patterns in Arabidopsis
Authors: Dowson‐Day Mandy J. , Millar Andrew J. 
Published: March 2003

Summary Many endogenous and environmental signals control seedling growth, including several phototransduction pathways. We demonstrate that the circadian clock controls the elongation of the Arabidopsis hypocotyl immediately upon germination. The pattern of hypocotyl elongation in constant light includes a daily growth arrest spanning subjective dawn and an interval of rapid growth at subjective dusk. Maximal hypocotyl growth coincides with the phase during which the cotyledons are raised, in the previously described rhythm of cotyledon movement. The rhythm of hypocotyl elongation was entrained by light–dark cycles applied to the imbibed seed and its period was shortened in the

toc1–1

mutant, indicating that it is controlled by a similar circadian system to other rhythmic markers. The daily growth arrest is abolished by the

early flowering 3
(elf3) mutation, suggesting that this defect may cause its long‐hypocotyl phenotype. Mutations that affect the circadian system can therefore cause gross morphological phenotypes, not because the wild‐type gene functions pleiotropically in several signalling pathways, but rather because the circadian clock exerts widespread control over plant physiology.
Comparative analysis ofShaplotypes with very similarSLGalleles inBrassica rapaandBrassica oleracea
Authors: Kusaba Makoto , Nishio Takeshi 
Published: March 2003

Summary Self‐incompatibility in

Brassica

is controlled by a single multi‐allelic locus (the

S

locus) which harbors at least two highly polymorphic genes,

SLG

and

SRK

. SRK is a putative transmembrane receptor kinase and its amino acid sequence of the extracellular domain of SRK (the S domain) exhibits high homology to that of SLG. The amino acid sequences of the SLGs of

S8

and

S46

haplotypes of

B. rapa

are very similar and those of

S23 and S29

haplotypes of

B. oleracea

were also found to be almost identical. In both cases, SLG and the S domain of SRK of the same haplotype were less similar. This seems to contradict the idea that SLG and SRK of the same haplotype have the same self‐recognition specificity. In the transmembrane‐kinase domain, the

SRK

alleles of the

S8

and

S46

haplotypes had almost identical nucleotide sequences in spite of their lower homology in the S domain. Such a cluster of nucleotide substitutions is probably due to recombination or related events, although recombination in the S locus is thought to be suppressed. Based on our observations, the recognition mechanism and the evolution of self‐incompatibility in

Brassica

are discussed.
Light regulates alternative splicing of hydroxypyruvate reductase in pumpkin
Authors: Mano Shoji , Hayashi Makoto , Nishimura Mikio 
Published: March 2003

Summary Hydroxypyruvate reductase (HPR) is a leaf peroxisomal enzyme that functions in the glycolate pathway of photorespiration in plants. We have obtained two highly similar cDNAs for pumpkin HPR (HPR1 and HPR2). It has been revealed that two HPR mRNAs might be produced by alternative splicing from a single type of pre‐mRNA. The HPR1 protein, but not the HPR2 protein, was found to have a targeting sequence into leaf peroxisomes at the C‐terminus, suggesting that alternative splicing controls the subcellular localization of the two HPR proteins. Immunoblot analysis and subcellular fractionation experiments showed that HPR1 and HPR2 proteins are localized in leaf peroxisomes and the cytosol, respectively. Moreover, indirect fluorescence microscopy and analyses of transgenic tobacco cultured cells and

Arabidopsis thaliana

expressing fusion proteins with green fluorescent protein (GFP) revealed the different subcellular localizations of the two HPR proteins. Both mRNAs were induced developmentally and by light, but with quantitative differences. Almost equal amounts of the mRNAs were detected in pumpkin cotyledons grown in darkness, but treatment with light greatly enhanced the production of HPR2 mRNA. These findings indicate that light regulates alternative splicing of HPR mRNA, suggesting the presence of a novel mechanism of mRNA maturation, namely light‐regulated alternative splicing, in higher plants.
AnArabidopsismutant with deregulated ABA gene expression: implications for negative regulator function
Authors: Foster Randy , Chua Nam‐Hai 
Published: March 2003

Summary The physiological acclimation of plants to osmotic stresses involves a complex programme of gene regulation. In one signalling pathway, elevated levels of abscisic acid (ABA) activate a subset of stress genes. Because ABA responses lack a definable morphological phenotype, we have screened for mutants that exhibit deregulated ABA‐responsive gene expression. To monitor this ABA response, a line of

Arabidopsis thaliana

carrying a transgene composed of the ABA‐responsive

Arabidopsis kin2

promoter fused to the coding sequence for the firefly luciferase gene,

kin2

::

luc

, was generated. Patterns of ABA‐responsive luciferase activity were monitored by photon counting. In contrast to wild‐type plants which display a transient activation of

kin2

::

luc

, an ABA deregulated gene expression mutant (

ade1

) exhibits both sustained and enhanced levels of transgene activity. Levels of

kin2

,

cor47

and

rab18

expression in

ade1

plants are also enhanced and prolonged indicating that the molecular mechanism(s) altered in

ade1

plants affects the regulation of other ABA‐responsive genes. The mutant phenotype is specific for the ABA response as cold‐inducible

kin2

expression is unaltered in

ade1

plants. Genetic analyses indicate that the

ade1

mutant is a monogenic recessive trait. A role for negative regulator function in ABA signalling is discussed.
Map positions ofSFRgenes in relation to other freezing‐related genes ofArabidopsis thaliana
Authors: Thorlby Glenn , Veale Emma , Butcher Kevin , Warren Gareth 
Published: March 2003

Summary We determined the map positions of seven

SFR

genes and compared them to the positions of 51 genes suspected of involvement in freezing tolerance in

Arabidopsis thaliana

. The

SFR

genes were recognized by the freezing sensitivity of mutants; the others (including 14 whose map positions we have determined) were genes whose expression is induced by low temperature, genes involved in abscisic acid (ABA) biosynthesis and perception, and genes involved in tolerance of oxidative stress. The comparison of map positions indicated a limited set of potential identities, some of which were eliminated by further mapping or by an allelism test.
Functional analysis of a Golgi‐localized Kex2p‐like protease in tobacco suspension culture cells
Authors: Jiang Liwen , Rogers John C. 
Published: March 2003

SummaryKex2p is the prototype of a Golgi‐resident protease responsible for the processing of prohormones in yeast and mammalian cells. A Kex2p‐like pathway was shown to be responsible for processing the fungal KP6 protoxin in transgenic tobacco plants. We previously described a chimeric integral membrane reporter protein that traffics through Golgi to the lytic prevacuole where it was proteolytically processed. As a first step to isolate and clone the Kex2p‐like protease in plant cells, we designed and used a similar chimeric reporter protein containing Kex2 cleavage sites to assay the Kex2p‐like activity and to determine its substrate specificity in tobacco cells. Here we demonstrate that the Kex2 cleavage sites of the reporter were specifically processed by a protease activity with a substrate specificity characteristic of yeast Kex2p. This Kex2p‐like protease in tobacco cells is also a Golgi‐resident enzyme. Thus, the reporter protein provides a biochemical marker for studying protein traffic through the Golgi in plant cells. These results additionally should allow the design of synthetic substrates for use in biochemical purification of the plant enzyme.
The Arabidopsis thaliana MERISTEM LAYER 1 promoter specifies epidermal expression in meristems and young primordia
Authors: Sessions Allen , Weigel Detlef , Yanofsky Martin F. 
Published: March 2003

SummaryThe Arabidopsis thaliana MERISTEM LAYER 1 (ATML1) gene is expressed in the epidermis of developing embryos and shoot meristems. To identify regulatory sequences necessary for epidermis‐specific expression, three fusions of overlapping ATML1 genomic sequences to the GUS reporter gene were introduced into Arabidopsis plants. All fusion genes conferred epidermis‐specific expression of both GUS mRNA and protein activity but varied in both the timing and relative levels of expression, suggesting partial redundancy of ATML1 regulatory elements. This study defines L1‐specific regulatory sequences that are sufficient to direct foreign gene expression in a layer‐specific manner.
Maize high chlorophyll fluorescent 60 mutation is caused by an Ac disruption of the gene encoding the chloroplast ribosomal small subunit protein 17
Authors: Schultes Neil P. , Sawers Ruairidh J. H. , Brutnell Thomas P. , Krueger Roger W. 
Published: March 2003

SummaryThe maize mutation high chlorophyll fluorescence 60‐muTable 1 (hcf60‐m1), generated through Activator (Ac) tagging, has insufficient photosynthetic electron transport. Here we show that the Hcf60 gene encodes a protein with substantial amino acid similarity to plant plastid and bacterial ribosomal small subunit protein 17 (RPS17) proteins. The lack of detectable HCF60 transcripts in mutant leaves, and insertion of the transposed Ac element 17 bp upstream of the start of translation in the mutated locus, suggest that little if any RPS17 is produced. The mutant phenotype is consistent with reduced plastid translation. Seedling lethal hcf60‐m1 plants display temperature and light‐dependent chlorophyll deficiencies, a depletion of plastid rRNA pools, and few high‐molecular‐weight polysomal complexes. Growth under moderate light conditions (27°C, 100 μE m−2 sec−1) allows for substantial chlorophyll accumulation in mutant leaves, yet the number of functional photosystem II complexes appears low. Nevertheless, the presence of a limited but intact C4 system indicates that some plastid translation occurs.

. Leaf chlorophyll content under different growth conditions

17°C, 100 μE m−2 sec−1
27°C, 100 μE m−2 sec−1
Greenhouse

1st leaf
1st leaf
2nd leaf
1st leaf

WT
hcf60
WT
hcf60
WT
hcf60
WT
hcf60

Total chlorophyll
0.385 ± 0.42
>0.002 ±0.00017
1.11 ±0.15
0.79 ± 0.1
1.3 ±0.2
0.71 ± 0.17
0.89 ±0.077
0.026 ± 0.012

μg mg−1 tissue
n = 4

n = 4

n= 7

n= 7

n= 7

n= 7

n = 4

n = 3

Total chlorophyll
100
>0.5
100
71
100
55
100
2.9

% WT

Chlorophyll a/b
2.12 ±0.2
–
2.54 ±0.22
1.89 ±0.16
2.65 ±0.26
1.97 ±0.12
3.02 ±0.11
2.87 ±0.23
A membrane‐potential dependent ABC‐like transporter mediates the vacuolar uptake of rye flavone glucuronides: regulation of glucuronide uptake by glutathione and its conjugates
Authors: Klein Markus , Martinoia Enrico , Hoffmann‐Thoma Gudrun , Weissenböck Gottfried 
Published: March 2003

SummaryIn this paper we present results on the vacuolar uptake mechanism for two flavone glucuronides present in rye mesophyll vacuoles. In contrast to barley flavone glucosides ( Klein et al. (1996
) J. Biol. Chem. 271, 29666–29671), the flavones luteolin 7‐O‐diglucuronyl‐4′‐O‐glucuronide (R1) and luteolin 7‐O‐diglucuronide (R2) were taken up into vacuoles isolated from rye via a directly energised mechanism. Kinetic studies suggested that the vacuolar glucuronide transport system is constitutively expressed throughout rye primary leaf development. Competition experiments argued for the existence of a plant MRP‐like transporter for plant‐specific and non‐plant glucuronides such as β‐estradiol 17‐(β‐
d‐glucuronide) (E217G). The interaction of ATP‐dependent vacuolar glucuronide uptake with glutathione and its conjugates turned out to be complex: R1 transport was stimulated by dinitrobenzene‐GS and reduced glutathione but was inhibited by oxidized glutathione in a concentration‐dependent manner. In contrast, R2 uptake was not increased in the presence of reduced glutathione. Thus, the transport system for plant‐derived glucuronides differed from the characteristic stimulation of vacuolar E217G uptake by glutathione conjugates but not by reduced glutathione (
Klein et al. (1998
) J. Biol. Chem. 273, 262–270). Using tonoplast vesicles isolated with an artificial K+ gradient, we demonstrate for the first time for plant MRPs that the ATP‐dependent uptake of R1 is membrane‐potential dependent. We discuss the kinetic capacity of the ABC‐type glucuronide transporter to explain net vacuolar flavone glucuronide accumulation in planta during rye primary leaf development and the possibility of an interaction of potential substrates at both the substrate binding and allosteric sites of the MRP transporter regulating the activity towards a certain substrate.
Evidence that auxin promotes gibberellin A1 biosynthesis in pea
Authors: Ross John J. , O'neill Damian P. , Smith Jennifer J. , Kerckhoffs L. Huub J. , Elliott Robert C. 
Published: March 2003

SummaryIn shoots of the garden pea, the bioactive gibberellin (GA1) is synthesised from GA20, and the enzyme which catalyses this step (a GA 3‐oxidase –‐ PsGA3ox1) is encoded by Mendel's LE gene. It has been reported previously that decapitation of the shoot (excision of the apical bud) dramatically reduces the conversion of [3H]GA20 to [3H]GA1 in stems, and here we show that endogenous GA1 and PsGA3ox1 transcript levels are similarly reduced. We show also that these effects of decapitation are completely reversed by application of the auxin indole‐3‐acetic acid (IAA) to the ‘stump’ of decapitated plants. Gibberellin A20 is also converted to an inactive product, GA29, and this step is catalysed by a GA 2‐oxidase, PsGA2ox1. In contrast to PsGA3ox1, PsGA2ox1 transcript levels were increased by decapitation and reduced by IAA application. Decapitation and IAA treatment did not markedly affect the level of GA1 precursors. It is suggested that in intact pea plants, auxin from the apical bud moves into the elongating internodes where it (directly or indirectly) maintains PsGA3ox1 transcript levels and, consequently, GA1 biosynthesis.
Ozone treatment rapidly activates MAP kinase signalling in plants
Authors: Samuel Marcus A. , Miles Godfrey P. , Ellis Brian E. 
Published: March 2003

SummaryBrief exposure to ozone, a potent cross‐inducer of plant stress responses, leads within minutes to activation of an ERK‐type MAP kinase (approximately 46 kDa) in tobacco. This activation process is calcium‐dependent and can be blocked both by free radical quenchers and by a specific inhibitor of MEK‐1 (MAPKK). Hydrogen peroxide and superoxide anion radicals can substitute for ozone as the activation stimulus, which does not appear to require salicylate as an intermediary. The properties of the ozone‐induced MAPK suggest that it may be SIPK (salicylate‐induced protein kinase), a tobacco MAPK that is activated by a variety of stress treatments. The ability of ozone to activate SIPK indicates that this protein kinase acts as a very early transducer of redox stress signals in plant cells.