bluuebunny/crossref_metadata_2025_split huggingface dataset:
The monarch butterfly controversy: scientific interpretations of a phenomenon
Authors: Shelton Anthony M. , Sears Mark K. 
Published: March 2003

SummaryThe future development and use of agricultural biotechnology has been challenged by two preliminary studies indicating potential risk to monarch butterfly populations by pollen from corn engineered to express proteins from Bacillus thuringiensis. Likewise, these studies have also challenged the way in which science should be performed, published in scientific journals and communicated to the public at large. Herein, we provide a history of the monarch controversy to date. We believe a retrospective view may be useful for providing insights into the proper roles and responsibilities of scientists, the media and public agencies and the consequences when they go awry.
Local expression of enzymatically active class I β‐1, 3‐glucanase enhances symptoms of TMV infection in tobacco
Authors: Bucher Gregor L. , Tarina Corina , Heinlein Manfred , Di Serio Francesco , Meins Fred , Iglesias Victor Alejandro 
Published: March 2003

SummaryMutant tobacco plants deficient for class I β‐1,3‐glucanase (GLU I) are decreased in their susceptibility to virus infection. This is correlated with delayed virus spread, a reduction in the size exclusion limit of plasmodesmata and increased cell‐wall deposition of the β‐1,3‐glucan callose. To further investigate a role of GLU I during cell‐to‐cell movement of virus infection, we inserted the GLU I coding sequence into TMV for overexpression in infected cells. Compared with the size of local lesions produced on plants infected with virus expressing either an enzymatically inactive GLU I or a frameshift mutant of the gene, the size of local lesions caused by infection with virus expressing active GLU I was consistently increased. Viruses expressing antisense GLU I constructs led to lesions of decreased size. Similar effects were obtained for virus spread using plants grown at 32°C to block the hypersensitive response. Together, these results indicate that enzymatically active GLU I expressed in cells containing replicating virus can increase cell‐to‐cell movement of virus. This supports the view that GLU I induced locally during infection helps to promote cell‐to‐cell movement of virus by hydrolyzing callose. Moreover, our results provide the first direct evidence that a biological function of a plant β‐1,3‐glucanase depends on its catalytic activity.
Presence of an SAR‐like sequence in junction regions between an introduced transgene and genomic DNA of cultured tobacco cells: its effect on transformation frequency
Authors: Shimizu Katsuya , Takahashi Misa , Goshima Naoki , Kawakami Shigeki , Irifune Kohei , Morikawa Hiromichi 
Published: March 2003

SummaryA 12.5‐kb DNA fragment with junction regions between the transgene and genomic DNA was cloned from a transgenic tobacco cell line obtained by microprojectile bombardment of plasmid pCaMVNEO. Nucleotide sequence analysis of the fragment (DDBJ accession no. D84238) showed that it carried a 7.7‐kb core sequence (concatemer of a complete pCaMVNEO and a partial pCaMVNEO) and two identical 1.3‐kb junction sequences that flanked both the 5′ and 3′ ends of the core sequence and had inverted orientations. These sequences had topoisomerase II (Topo II) cleavage sites and adenine and thimine‐rich sequences known to be specific to nuclear scaffold‐attachment regions (SARs). An in vitro binding assay showed that a 507‐bp fragment (designated TJ1) from the 1.3‐kb sequence had the ability to bind to nuclear scaffold preparations of cultured tobacco cells, confirmation that the 1.3‐kb sequence is an SAR. Insertion of TJ1at the 5′ and 3′ sides of the expression cassette for the npt II gene increased transformant yields 5‐ to 10‐fold and the NPT II enzyme activity per copy of the gene 5‐fold. TJ1enhances the integration or expression of the transgene, or both. Clearly, TJ1is very useful for producing transgenic plants. This is the first report on an SAR‐like sequence that is located in the transgene locus and enhances transformation efficiency in eukaryotic cells. The possible role of TJ1‐SAR in the molecular evolution of plant genome is discussed.
Constitutive salicylic acid‐dependent signaling in cpr1 and cpr6 mutants requires PAD4
Authors: Jirage Dayadevi , Zhou Nan , Cooper Bret , Clarke Joseph D. , Dong Xinnian , Glazebrook Jane 
Published: March 2003

SummarySalicylic acid (SA)‐dependent signaling controls activation of a set of plant defense mechanisms that are important for resistance to a variety of microbial pathogens. Many Arabidopsis mutants that display altered SA‐dependent signaling have been isolated. We used double mutant analysis to determine the relative positions of the pad4, cpr1, cpr5, cpr6, dnd1 and dnd2 mutations in the signal transduction network leading to SA‐dependent activation of defense gene expression and disease resistance. The pad4 mutation causes failure of SA accumulation in response to infection by certain pathogens, while the other mutations cause constitutively high levels of SA, defense gene expression and resistance. The cpr1 pad4, cpr5 pad4, cpr6 pad4, dnd1 pad4 and dnd2 pad4 double mutants were constructed and assayed for stature, presence of spontaneous lesions, resistance to Pseudomonas syringae and Peronospora parasitica, SA levels, expression of PAD4, PR‐1 and PDF1.2, and accumulation of camalexin. We found that the effects of the cpr1 and cpr6 mutations on SA‐dependent gene expression are completely dependent on PAD4 function. In contrast, SA accumulation in the lesion‐mimic mutant cpr5 is partially PAD4‐independent, while in dnd1 and dnd2 mutants it is completely PAD4‐independent. A model describing a possible arrangement of activities in the signal transduction network is presented.
A novel higher plant protein tyrosine phosphatase interacts with SNF1‐related protein kinases via a KIS (kinase interaction sequence) domain
Authors: Fordham‐Skelton Anthony P. , Chilley Paul , Lumbreras Victoria , Reignoux Sabrina , Fenton Tim R. , Dahm Christina C. , Pages Montserrat , Gatehouse John A. 
Published: March 2003

SummaryA novel protein phosphatase in Arabidopsis thaliana was identified by database searching. This protein, designated AtPTPKIS1, contains a protein tyrosine phosphatase (PTP) catalytic domain and a kinase interaction sequence (KIS) domain. It is predicted to interact with plant SNF1‐related kinases (SnRKs), representing central regulators of metabolic and stress responses. AtPTPKIS1 has close homologues in other plant species, both dicots and monocots, but is not found in other kingdoms. The tomato homologue of AtPTPKIS1 was expressed as a recombinant protein and shown to hydrolyse a generic phosphatase substrate, and phosphotyrosine residues in synthetic peptides. The KIS domain of AtPTPKIS1 was shown to interact with the plant SnRK AKIN11 both in vivo in the yeast two‐hybrid system, and in vitro in a GST‐fusion ‘pull down’ assay. The genomes of Arabidopsis and other plants contain further predicted proteins related to AtPTPKIS1, which could also interact with SnRKs and act in novel regulatory and signalling pathways.
The cycloidea gene can respond to a common dorsoventral prepattern in Antirrhinum
Authors: Clark Jennifer I. , Coen Enrico S. 
Published: March 2003

SummaryDorsoventral asymmetry in flowers of Antirrhinum depends on expression of the cycloidea gene in dorsal regions of floral meristems. To determine how cycloidea might be regulated we analysed its expression in several contexts. We show that cycloidea is activated shortly after floral induction, and that in addition to flowers, cycloidea can be asymmetrically expressed in shoots, even though these shoots show no marked dorsoventral asymmetry. Shoots expressing cycloidea include secondary branches lying just below the inflorescence, and shoots of floricaula mutants. Asymmetric cycloidea expression may also be observed within organ primordia, such as the sepals of terminal flowers produced by centroradialis mutants. Later expression of cycloidea within flowers can be modified by mutations in organ identity genes. Taken together, the results suggest that cycloidea can respond to a common dorsoventral pre‐pattern in the apex and that the specific effects of cycloidea on the flower depend on interactions with floral‐specific genes.
Nitric oxide mediates iron‐induced ferritin accumulation in Arabidopsis
Authors: Murgia Irene , Delledonne Massimo , Soave Carlo 
Published: March 2003

SummaryNitric oxide (NO) is a signaling molecule that plays a critical role in the activation of innate immune and inflammatory responses in animals. During the last few years, NO has also been detected in several plant species and the increasing number of reports on its function in plants have implicated NO as an important effector of growth, development and defense. Analogously to animals, NO has been recently shown to inhibit tobacco aconitase. This suggests that NO may elevate free iron levels in the cells by converting tobacco cytoplasmic aconitase into a mRNA binding protein that negatively regulates accumulation of ferritin.    We investigated the possible role of NO as a regulator of ferritin levels in Arabidopsis and found that the NO‐donor sodium nitroprusside (SNP) induces accumulation of ferritin both at mRNA and protein level. Iron is not necessary for this NO‐mediated ferritin transcript accumulation, since SNP is still able to induce the accumulation of ferritin transcript in Arabidopsis suspension cultures pre‐treated with the iron chelants DFO or ferrozine. However, NO is required for iron‐induced ferritin accumulation, as the NO scavenger CPTIO prevents ferritin transcript accumulation in Arabidopsis suspension cultures treated with iron. The pathway is ser/thr phosphatase‐dependent and necessitates protein synthesis; furthermore, NO mediates ferritin regulation through the IDRS sequence of the Atfer1 promoter responsible for transcriptional repression under low iron supply.    NO, by acting downstream of iron in the induction of ferritin transcript accumulation is therefore a key signaling molecule for regulation of iron homeostasis in plants.
Molecular and biochemical mechanisms associated with dormancy and drought tolerance in the desert legume Retama raetam
Authors: Pnueli Lilach , Hallak‐Herr Elza , Rozenberg Mira , Cohen Mira , Goloubinoff Pierre , Kaplan Aaron , Mittler Ron 
Published: March 2003

SummaryDormancy is an important developmental program allowing plants to withstand extended periods of extreme environmental conditions, such as low temperature or drought. Seed dormancy, bud dormancy and desiccation tolerance have been extensively studied, but little is known about the mechanisms involved in the dormancy of drought‐tolerant plants, key to the survival of many plant species in arid and semi‐arid environments. Subtractive PCR cloning of cDNAs from Retama raetam, a C3 drought‐tolerant legume, revealed that dormancy in this plant is accompanied by the accumulation of transcripts encoding a pathogenesis‐related, PR‐10‐like protein; a low temperature‐inducible dehydrin; and a WRKY transcription factor. In contrast, non‐dormant plants subjected to stress conditions contained transcripts encoding a cytosolic small heat‐shock protein, HSP18; an ethylene‐response transcriptional co‐activator; and an early light‐inducible protein. Physiological and biochemical analysis of Rubisco activity and protein in dormant and non‐dormant tissues suggested a novel post‐translational mechanism of regulation that may be controlled by the redox status of cells. Ultrastructural analysis of dormant plants revealed that air spaces of photosynthetic tissues contained an extracellular matrix that may function to prevent water loss. The cytosol of dormant cells appeared to be in a glassy state, limiting metabolic activity. A combination of biochemical, molecular and structural mechanisms, in association with metabolic suppression, may be key to the extreme drought tolerance of R. raetam and its acclimation to the desert ecosystem. These may enable plants to withstand long periods of drought, as well as rapidly to exit dormancy upon rainfall.
Modifying the pollen coat protein composition in Brassica
Authors: Foster Elizabeth , Schneiderman Danielle , Cloutier Michel , Gleddie Stephen , Robert Laurian S. 
Published: March 2003

SummaryThe interactions between pollen and stigma are essential for plant reproduction and are made possible by compounds, such as proteins and lipids, located on their surfaces. The pollen coat is formed in part by compounds synthesized in, and released from, the tapetum, which become transferred to the pollen coat late in pollen development. In the Brassicaceae the predominant proteins of the mature pollen coat are the tapetal oleosin‐like proteins, which are highly expressed in, and ultimately transferred from, the tapetum. Here we report the modification of the protein composition of the pollen coat by the addition of an active enzyme which was synthesized in the tapetum. The marker enzyme β‐glucuronidase (GUS) was successfully targeted to the pollen coat in transgenic Brassica carinata plants expressing GUS translationally fused to a B. napus tapetal oleosin‐like protein (BnOlnB;4). To our knowledge this is the first demonstration of the targeting of an enzyme to the pollen coat.
Role of petunia pMADS3 in determination of floral organ and meristem identity, as revealed by its loss of function
Authors: Kapoor Meenu , Tsuda Shinzo , Tanaka Yoshikazu , Mayama Tomoko , Okuyama Yohei , Tsuchimoto Suguru , Takatsuji Hiroshi 
Published: March 2003

Summary pMADS3, a petunia class C gene, is the candidate homologue of Arabidopsis AGAMOUS (AG), which is involved in the specification of stamens and carpels. We report the characterization of loss‐of‐function phenotype of pMADS3 that resulted from silencing of this gene. Silencing of pMADS3 resulted in homeotic conversion of stamens into petaloid structures, whereas the carpels were only weakly affected. Ectopic secondary inflorescences emerged from the interstamenal region in the third whorl, which is unique and has not been reported for any class C gene of other plant species. Third‐order inflorescences emerged at corresponding positions in the third whorl of inner flowers of secondary inflorescences, indicating reiterative conversion of parts of the floral meristem into inflorescence meristem. On the basis of phenotypic analysis of the pMADS3‐silenced plants, we propose that pMADS3 is involved in determination of floral organ and floral meristem identity in petunia. Two hybrid studies in yeast showed that PMADS3 protein interacted specifically with FBP2, a candidate homologue of Arabidopsis SEPALLATA3 (SEP3). The evidence presented here suggest that a complex involving PMADS3 and FBP2 is responsible for specification of organ identity in the third whorl.
CO2 provides an intermediate link in the red light response of guard cells
Authors: Roelfsema M. Rob G. , Hanstein Stefan , Felle Hubert H. , Hedrich Rainer 
Published: March 2003

SummaryGuard cells in intact leafs display light‐induced membrane potential changes, which alter the direction of K+‐transport across the plasma membrane (Roelfsema et al., 2001). A beam of blue light, but not red light, directed at the impaled guard cell triggers this response, while both light qualities induce opening of stomata. To gain insight into this apparent contradiction, we explored the possible interaction between red light and CO2. Guard cells in the intact plant were impaled with double‐barrelled electrodes and illuminated with red light. Cells that were hyperpolarized in CO2‐free air, depolarized after a switch to air with 700 µl l−1 CO2, in a reversible manner. As a result, K+‐fluxes across the plasma membrane changed direction, to favour K+ extrusion and stomatal closure in the presence of CO2. Concurrent with the depolarization, an inward current across the plasma membrane appeared, most likely due to activation of anion channels. Guard cell responses to CO2 could be recorded in darkness as well as in red light. However, in darkness some cells spontaneously depolarized, these cells hyperpolarized again in red light. Here, red light was projected on a large area of the leaf and decreased the intracellular CO2 concentration by about 250 µl l−1, as measured with a miniature CO2 sensor placed in the substomatal cavity. We conclude, that in intact leaves the red light response of guard cells is mediated through a decrease of the intercellular CO2 concentration.
A chromatin immunoprecipitation (ChIP) approach to isolate genes regulated by AGL15, a MADS domain protein that preferentially accumulates in embryos
Authors: Wang Huai , Tang Weining , Zhu Cong , Perry Sharyn E. 
Published: March 2003

SummaryAGAMOUS‐like‐15 (AGL15) is a member of the MADS‐domain family of DNA‐binding regulatory factors that accumulates preferentially in tissue developing in an embryonic mode. To better understand how AGL15 functions, we developed a chromatin immunoprecipitation (ChIP) approach to isolate genes regulated directly by AGL15. ChIP allows purification of in vivo protein–DNA complexes. The co‐purified DNA is recovered and used to isolate the putatively regulated gene. Several tests must be performed to show that the putative downstream target gene is truly regulated by the DNA‐binding protein. The DNA‐binding regulatory protein must interact with cis regulatory elements. The downstream gene expression pattern should respond to the level of the trans‐acting regulatory factor. The cis element should be able to confer regulation in response to the trans‐acting factor. We describe, in this report, our ChIP protocol, and discuss in detail, tests to confirm regulation by AGL15 for two targets identified by ChIP. These targets are referred to as Downstream Target of AGL15 (DTA1 and DTA2). Expression of DTA1, which encodes a protein with high similarity to GA‐2 oxidase‐like proteins, is induced by AGL15. DTA2 encodes a novel protein and expression of this target is repressed by AGL15.
Activation tagging of the two closely linked genes LEP and VAS independently affects vascular cell number
Authors: Van Der Graaff Eric , Hooykaas Paul J.J. , Keller Beat 
Published: March 2003

SummaryThe complex dominant Arabidopsis thaliana mutant lettuce (let) shows the conversion of the leaf petiole into a leaf blade caused by an ectopic leaf blade formation. This is the result of the activation tagging of the LEAFY PETIOLE (LEP) gene encoding an AP2/EREBP‐like transcription factor. Here, we report that in addition to this leafy petiole phenotype, the size of the vascular bundles is increased in all aerial organs in let as a result of an increase in the number of xylem, phloem (pro)cambial and pericycle cells. This vascular phenotype is caused by activation tagging of the two genes VASCULAR TISSUE SIZE (VAS) and LEP. These genes are closely linked and arranged in tandem. Activation tagging of LEP only caused a specific increase in the number of xylem cells. This increased xylem cell number, together with the ectopic leaf blade formation, indicates that LEP functions as a cell division‐promoting factor. The activation tagging of VAS only resulted in a specific increase in phloem (pro)cambial and pericycle cells. We conclude that activation tagging of LEP and VAS results in additive phenotypes. Insertional mutants for LEP and VAS display wild‐type vascular development, indicating the relevance of activation tagging for functional analysis of novel genes involved in plant development.
Tomato tos1 mutation identifies a gene essential for osmotic tolerance and abscisic acid sensitivity
Authors: Borsani Omar , Cuartero Jesús , Valpuesta Victoriano , Botella Miguel A. 
Published: March 2003

SummaryOsmotic stress severely limits plant growth and agricultural productivity. We have used mutagenesis to identify plant genes that are required for osmotic stress tolerance in tomato. As a result, we have isolated a novel mutant in tomato (tos1) caused by a single recessive nuclear mutation that is hypersensitive to general osmotic stress. Growth measurements demonstrated that the tos1 mutant is less sensitive to intracellular abscisic acid (ABA) and this decreased ABA sensitivity of tos1 is a basic cellular trait expressed by the mutant at all developmental stages analysed. It is not caused by a deficiency in the synthesis of ABA because the tos1 seedlings accumulated more ABA than the wild type (WT) after osmotic stress. In contrast, the tss2 tomato mutant, which is also hypersensitive to osmotic stress, is hypersensitive to exogenous ABA. Comparative analysis of tos1 and tss2 indicates that appropriate ABA perception and signalling is essential for osmotic tolerance.
Poplar potassium transporters capable of controlling K+ homeostasis and K+‐dependent xylogenesis
Authors: Langer Katharina , Ache Peter , Geiger Dietmar , Stinzing Andrea , Arend Matthias , Wind Christa , Regan Sharon , Fromm Jörg , Hedrich Rainer 
Published: March 2003

SummaryThe cambial K+ content of poplar increases during the growth period in a K+ supply dependent manner. Upon K+ starvation or application of tetraethylammoniumchloride (TEA+), a K+ channel blocker, the average vessel lumen and expansion zone area were significantly reduced. In search for the molecular basis of potassium‐dependent xylogenesis in poplar, K+ transporters homologous to those of known function in Arabidopis phloem‐ and xylem‐physiology were isolated from a poplar wood EST library. The expression profile of three distinct K+ channel types and one K+ transporter, Populus tremula K+ uptake transporter 1 (PtKUP1), was analysed by quantitative RT‐PCR. Thereby, we found P. tremula outward rectifying K+ channel (PTORK) and P. tremula K+ channel 2 (PTK2) correlated with the seasonal wood production. K+ transporter P. tremula 1 (KPT1) was predominantly found in guard cells. Following the heterologous expression in Xenopus oocytes the biophysical properties of the different channels were determined. PTORK, upon membrane de‐polarization mediates potassium release. PTK2 is almost voltage independent, carrying inward K+ flux at hyperpolarized potential and K+ release upon de‐polarization. PtKUP1 was expressed in a K+ uptake‐deficient Escherichia coli strain, where this K+ transporter rescued K+‐dependent growth. In order to link the different K+ transporters to the cambial activity and wood production, we compared the expression profiles to seasonal changes in the K+ content of the bark as well as xylem vessel diameter. Thereby, we found PTORK and PTK2 transcripts to follow the annual K+ variations in poplar branches. PtKUP1 was expressed at a low level throughout the year, suggesting a housekeeping function. From these data, we conclude that K+ channels are involved in the regulation of K+‐dependent wood production.