bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regulation of spinach SNF1‐related (SnRK1) kinases by protein kinases and phosphatases is associated with phosphorylation of the T loop and is regulated by 5′‐AMP
Authors: Sugden Chris , Crawford Russell M. , Halford Nigel G. , Hardie D. Grahame 
Published: March 2003

SummaryMembers of the SNF1‐related protein kinase‐1 (SnRK1) subfamily of protein kinases are higher plant homologues of mammalian AMP‐activated and yeast SNF1 protein kinases. Based on analogies with the mammalian system, we surmised that the SnRK1 kinases would be regulated by phosphorylation on a threonine [equivalent to Thr175 in Arabidopsis thaliana SnRK1 (AKIN10)] within the ‘T loop’ between the conserved DFG and APE motifs. We have raised an antibody against a phosphopeptide based on this sequence, and used it to show that inactivation of two spinach SnRK1 kinases by protein phosphatases, and reactivation by a mammalian upstream protein kinase, is associated with changes in the phosphorylation state of this threonine. We also show that dephosphorylation of this threonine by protein phosphatases, and consequent inactivation, is inhibited by low concentrations of 5′‐AMP, via binding to the substrate (i.e. the kinase). This is the first report showing that the plant SnRK1 kinases are regulated by AMP in a manner similar to their mammalian counterparts. The possible physiological significance of these findings is discussed.
Modified expression of a carrot small heat shock protein gene, Hsp17.7, results in increased or decreased thermotolerance‡
Authors: Malik Mukesh K. , Slovin Janet P. , Hwang Cheol Ho , Zimmerman J. Lynn 
Published: March 2003

SummaryWe have determined that one small heat shock protein gene, encoding Hsp17.7, plays an important role in the ability of carrot cells and plants to survive thermal stress. Transgenic cells and regenerated plants were generated in which the carrotHsp17.7gene was either constitutively expressed (denoted CaS lines) or expressed as a heat inducible antisense RNA (denoted AH lines). Thermotolerance measurements demonstrated that CaS lines were more thermotolerant than vector controls and AH antisense lines were less thermo‐ tolerant than vector controls. RNA analysis demonstrated thatHsp17.7mRNA was detectable, but not abundant, prior to heat shock in CaS cells, but not in vector control cells. Conversely, RNA analysis of antisense cells showed that, after heat shock, the amounts of mRNA forHsp17.7was moderately less abundant in AH cells than in vector controls. Analysis of protein synthesis in CaS cells did not indicate substantial synthesis or accumulation of Hsp17.7, or any small Hsp, at 23°C. However, in the most thermotolerant line, protein synthesis was maintained at a higher rate than in other cell lines at a more extreme heat shock (42°C). In contrast, antisense AH cells showed reduced synthesis of many Hsp, large and small. These results suggest that theHsp17.7gene plays a critical, although as yet not understood, role in thermotolerance in carrot. This represents the first demonstration of the ability to both increase and decrease thermotolerance by the manipulation of expression of a single gene.
NRSA‐1: a resistance gene homolog expressed in roots of non‐host plants following parasitism by Striga asiatica (witchweed)
Authors: Gowda Bhavani S. , Riopel James L. , Timko Michael P. 
Published: March 2003

SummaryStudies of the initial interactions of Striga asiatica with the non‐host plant species Tagetes erecta (marigold) established that parasite penetration through the root is arrested most frequently in the cortex. The arrest of parasite ingress is associated with browning and necrosis of root cortical cells flanking the invading endophyte and with increased intracellular wall appositions on the root cell walls directly adjacent to the plant‐parasite interface. Using a polymerase chain reaction‐based differential cDNA amplification strategy followed by 5′‐RACE, we have identified several gene products whose expression is induced in marigold roots during attempted parasitism by Striga. Among these was a 917 bp cDNA encoding a 221 amino acid protein with significant homology to proteins encoded by disease resistance genes from other plant species, including N, RPP5, L6 and M. This cDNA was subsequently used to isolate a nuclear gene, designated NRSA‐1, for non‐host resistance to Striga asiatica. NRSA‐1 is a member of a small gene family in marigold consisting of two to four members. RNA gel blot analysis showed that NRSA‐1 transcripts accumulate to high levels in roots near the site of Striga invasion within 120 h after parasite attachment, and appear at lower levels throughout the rest of the plant under Striga parasitism. NRSA‐1 expression is rapidly induced by treatment with jasmonic acid (JA), but not by mechanical wounding, treatment with salicylic acid, paraquat or ABA. A possible role for NRSA‐1 in the non‐host resistance mechanism is discussed.
Pseudomonas syringae pv tomato induces the expression of tomato EREBP‐like genes Pti4 and Pti5 independent of ethylene, salicylate and jasmonate
Authors: Thara Venkatappa K. , Tang Xiaoyan , Gu Yong Q. , Martin Gregory B. , Zhou Jian‐Min 
Published: March 2003

SummaryThe tomato genes Pti4 and Pti5 encode ethylene‐responsive element binding protein‐like transcription factors that bind to the GCC box, a conserved cis‐element in many defense‐related genes. The Pti proteins have previously been shown to interact with the tomato disease resistance protein Pto. Here we report that the expression of both Pti4 and Pti5 are induced by a virulent strain of Pseudomonas syringae pv tomato. The expression of Pti5 is further enhanced by the interaction of the Pto gene in tomato and the corresponding avrPto gene in the bacterium. The enhancement of Pti5 expression by Pto–avrPto interaction requires a functional Prf gene in the plant. Pti5 appears to be expressed specifically during biotic stresses, suggesting a specific role in plant defense. Pti4 and several EREBP‐like genes are induced by ethylene, salicylate and wounding. However, the Pseudomonas bacterium induced a wild‐type level of Pti4 and Pti5 transcripts in tomato plants carrying the nahG transgene, the Nr mutation, or the def1 mutation. In addition, the ethylene action inhibitor norbornadiene did not inhibit the induction of Pti4 and Pti5 either in the compatible or incompatible interactions. The results suggest that the Pseudomonas bacterium induces Pti4 and Pti5 expression through a pathway independent of salicylic acid, ethylene and jasmonic acid.
The SERRATE locus controls the formation of the early juvenile leaves and phase length in Arabidopsis
Authors: Clarke Jonathan H. , Tack Dimitri , Findlay Kim , Van Montagu Marc , Van Lijsebettens Mieke 
Published: March 2003

SummaryThe development of the shoot can be divided into a series of distinct developmental phases based on leaf character‐istics and inflorescence architecture. The relationship between phase length, defined by the number of organs produced, and the timing of the floral induction (V3‐I1 transition) is relatively ill defined. Characterization of the serrate mutant (CS3257; Arabidopsis Biological Research Center) revealed defects in both vegetative and inflores‐cence phase lengths, the timing of phase transitions, leaf number, the leaf initiation rate, and phyllotaxy. The timing of floral induction, however, is the same as in wild‐type in extended short days as well as in short days, whereas the flowering time response to photoperiod is unaffected. SERRATE is shown to be required for the development of early juvenile leaves (V1) and to promote late juvenile leaf development (V2), while suppressing adult leaf (V3) and inflorescence development (I1 and I2). The se mutation supports the hypothesis that the timing of floral induction is independent of vegetative and inflorescence phase lengths. The role of SERRATE in the regulation of phase length and leaf identity is discussed.
Arabidopsis thaliana AtHAL3: a flavoprotein related to salt and osmotic tolerance and plant growth
Authors: Espinosa‐Ruiz Ana , Bellés Jose M. , Serrano Ramón , Culiáñez‐Macià Francisco A. 
Published: March 2003

SummaryWe have isolated two Arabidopsis thaliana genes, AtHAL3a and AtHAL3b, showing homology with HAL3, a yeast protein which regulates the cell cycle and tolerance to salt stress through inhibition of the PPZ1 type‐1 protein phosphatase. Expression of AtHAL3a in yeast hal3 mutants partially complements their LiCl sensitivity, suggesting possible conserved functions between both proteins. AtHAL3a and AtHAL3b are induced by salt stress and AtHAL3a is the most expressed in non‐stressed plants, particularly in seeds. In situ hybridization demonstrates enrichment of AtHAL3a mRNA in seed embryos and in the vascular phloem of different plant tissues. AtHAL3 proteins show striking homology with a group of proteins found in fungi, plants and animals and some homology with a large family of prokaryotic flavoproteins. Recombinant AtHAL3a protein purified from Escherichia coli was yellow because it contained a non‐covalently bound chromophore revealed as flavin mononucleotide. Trans‐ genic Arabidopsis plants, with gain of AtHAL3a function, show altered growth rates and improved tolerance to salt and osmotic stress.
The tomato I‐box binding factor LeMYBI is a member of a novel class of Myb‐like proteins
Authors: Rose Annkatrin , Meier Iris , Wienand Udo 
Published: March 2003

SummaryThe RBCS3A gene of tomato belongs to a small gene family consisting of five members. Although the RBCS1, RBCS2 and RBCS3A promoters contain closely related cis regulatory sequences, the expression patterns of the genes are different. Whereas the RBCS1 and RBCS2 genes are expressed in both leaves and young fruit, the RBCS3A promoter is highly active in leaves, but not in young fruit. This lack of transcription could be due to a mutation in the RBCS3A promoter creating the so‐called F‐box, a protein binding site located between the activating cis elements, the I‐box and G‐box. In order to identify proteins that bind to the RBCS3A I‐box/F‐box region, the yeast one‐hybrid system was used. One clone, LeMYBI was isolated which contains strong similarity to plant myb transcription factors. The encoded LeMYBI protein is at least 188 amino acids in length and contains two myb‐like domains located at the amino terminus and close to the carboxy terminus, separated by a negatively charged domain. The protein contains a SHAQKYF amino acid signature motif in the second myb‐like repeat, which is highly conserved in a number of recently identified plant myb‐related genes, thus defining a new class of plant DNA‐binding proteins. LeMYBI binds specifically to the I‐box sequence of the RBCS1, RBCS2 and RBCS3A promoters, therefore representing the first cloned I‐box binding factor. LeMYBI acts as a transcriptional activator in yeast and plants, and binds to the I‐box with a DNA‐binding domain located in the carboxyterminal domain.
The N‐terminal fragment of Arabidopsis photomorphogenic repressor COP1 maintains partial function and acts in a concentration‐dependent manner
Authors: Stoop‐Myer Chatanika , Torii Keiko U. , McNellis Timothy W. , Coleman Joseph E. , Deng Xing‐Wang 
Published: March 2003

SummaryArabidopsis seedlings exhibit distinct developmental patterns according to their light environment: photomorphogenesis in the light and etiolation or skotomorphogenesis in darkness. COP1 acts within the nucleus to repress photomorphogenesis in darkness, while light depletes COP1 from nucleus and abrogates this repression. COP1 contains three structural modules: a RING finger followed by a coiled‐coil domain, and a WD40 repeat domain at the C‐terminus. By introducing various domain deletion mutants of COP1 into cop1 null mutant backgrounds, we show that all three domains are essential for the function of COP1 in vivo. Interestingly, a fragment containing the N‐terminal 282 amino acids of COP1 (N282) with both the RING finger and coiled‐coil modules is sufficient to rescue the lethality of the cop1 null mutations at low expression level. However, high expression levels of the N282 fragment result in a phenocopy of the cop1 null mutation. The sensitivity of the seedling to levels of N282 could reflect the importance of the abundance of COP1 for the appropriate regulation of photomorpho‐ genic development.
Metabolic engineering of p‐hydroxybenzylglucosinolate in Arabidopsis by expression of the cyanogenic CYP79A1 from Sorghum bicolor
Authors: Bak Søren , Olsen Carl Erik , Petersen Bent Larsen , Møller Birger Lindberg , Halkier Barbara Ann 
Published: March 2003

SummaryGlucosinolates are natural products in cruciferous plants, including Arabidopsis thaliana. CYP79A1 is the cytochrome P450 catalysing the conversion of tyrosine to p‐hydroxyphenylacetaldoxime in the biosynthesis of the cyanogenic glucoside dhurrin in sorghum. Both glucosinolates and cyanogenic glucosides have oximes as intermediates. Expression of CYP79A1 in A. thaliana results in the production of high levels of the tyrosine‐derived glucosinolate p‐hydroxybenzylglucosinolate, which is not a natural constituent of A. thaliana. This provides further evidence that the enzymes have low substrate specificity with respect to the side chain. The ability of the cyanogenic CYP79A1 to integrate itself into the glucosinolate pathway has important implications for an evolutionary relationship between cyanogenic glucosides and glucosinolates, and for the possibility of genetic engineering of novel glucosinolates.
Arabidopsis ecotypes and mutants that are recalcitrant to Agrobacterium root transformation are susceptible to germ‐line transformation
Authors: Mysore Kirankumar S. , Kumar C. T. Ranjith , Gelvin Stanton B. 
Published: March 2003

SummaryGerm‐line transformation (vacuum infiltration) is frequently used to transform Arabidopsis thaliana using Agrobacterium tumefaciens. We have recently identified several Arabidopsis ecotypes and T‐DNA‐tagged mutants that are recalcitrant to Agrobacterium‐mediated transformation of cut root segments. Some of these ecotypes and mutants are deficient in their ability to bind bacteria. Some are deficient in T‐DNA integration. We report here that using a germ‐line transformation protocol we transformed these ecotypes and mutants, including attachment‐ and integration‐defective Arabidopsis plants, with a frequency similar to that of highly susceptible wild‐type plants. However, we could not transform otherwise highly susceptible Arabidopsis plants by germ‐line or root transformation using several vir and attachment‐deficient Agrobacterium mutants. These results indicate that certain plant factors important for transformation may exist in germ‐line tissue but may be lacking in some somatic cells.
Disruption of putative anion channel gene AtCLC‐a in Arabidopsis suggests a role in the regulation of nitrate content
Authors: Geelen Danny , Lurin Claire , Bouchez David , Frachisse Jean‐Marie , Lelièvre Françoise , Courtial Béatrice , Barbier‐Brygoo Hélène , Maurel Christophe 
Published: March 2003

SummaryIn animals and yeast, voltage‐dependent chloride channels of the CLC family play a role in basic cellular functions such as epithelial transport, plasma membrane excitability, and control of pH and membrane potential in intracellular compartments. To assess the function of CLCs in plants, we searched for CLC insertion mutants in a library of Arabidopsis lines transformed by Agrobacterium tumefaciens transferred DNA (T‐DNA). Using a polymerase chain reaction‐based screening procedure, an Arabidopsis line that carries a T‐DNA insertion within the C‐terminus of the AtCLC‐a coding sequence was identified. Progeny from this plant line, clca‐1, showed dramatically altered transcription of the AtCLC‐a gene. Plants homozygous for the clca‐1 mutation exhibited normal development and a morphology indistinguishable from the wild‐type. However, their capacity to accumulate nitrate under conditions of nitrate excess was reduced in roots and shoots, by approximately 50%, while chloride, sulphate and phosphate levels were similar to the wild‐type. In addition, the herbicide chlorate, an analogue of nitrate, induced a faster and more pronounced chlorosis in mutant plants. Hypersensitivity to chlorate as well as decreased nitrate levels co‐segregated with the T‐DNA insertion. They were found at various time points of the clca‐1 life cycle, supporting the idea that AtCLC‐a has a general role in the control of the nitrate status in Arabidopsis. Concordant with such a function, AtCLC‐a mRNA was found in roots and shoots, and its levels rapidly increased in both tissues upon addition of nitrate but not ammonium to the culture medium. The specificity of AtCLC‐a function with respect to nitrate is further supported by a similar free amino acid content in wild‐type and clca‐1 plants. Although the cellular localization of AtCLC‐a remains unclear, our results suggest that AtCLC‐a plays a role in controlling the intracellular nitrate status.
Understanding in vivo carbon precursor supply for fatty acid synthesis in leaf tissue
Authors: Bao Xiaoming , Focke Manfred , Pollard Mike , Ohlrogge John 
Published: March 2003

SummaryThe principal supply of carbon precursors for fatty acid synthesis in leaf tissue has been a much debated topic, with some experiments suggesting a direct supply from the C3 products of photosynthetic carbon fixation and colleagues suggesting the utilization of free acetate (for which concentrations in leaves in the range of 0.05–1.4 mM have been reported). To address this issue we first reassessed the in vivo rate of fatty acid synthesis using a new method, that of [13C]carbon dioxide labeling of intact Arabidopsis plants with the subsequent analysis of fatty acids by gas chromatography‐mass spectrometry (GC‐MS). This method gave an average value of 2.3 mmoles carbon atoms h−1 mg chlorophyll−1 for photosynthetic tissues. The method was extended by isotopic dilution analysis to measure the rate of fatty acid synthesis in the dark. There was negligible fatty acid synthesis (< 5% of the rate in the light) in the dark. In addition, the method allowed an estimate of the absolute rate of fatty acid degradation of about 4% of the total fatty acid content per day. With the in vivo rate of fatty acid synthesis in the light defined, if the bulk tissue acetate concentration available for fatty acid synthesis is 1 mM, this acetate pool can sustain fatty acid synthesis for approximately 60 min. When the leaves of Arabidopsis, barley and pea were given a 5 min pulse of [14C]carbon dioxide, the label rapidly appeared in fatty acids with a lag phase of less than 2–3 min. Continuous labeling with [14C]carbon dioxide, for up to 1 h, showed a similar result. Furthermore, 14C‐label in free acetate was less than 5% of that in fatty acids. In conclusion, these data suggest that either the bulk pool of acetate is not involved in fatty acid synthesis or the concentration of acetate must be less than 0.05 mM under strong illumination.
Disruption of an Arabidopsis cytoplasmic ribosomal protein S13‐homologous gene by transposon‐mediated mutagenesis causes aberrant growth and development
Authors: Ito Takuya , Kim Gyung‐Tae , Shinozaki Kazuo 
Published: March 2003

SummaryWe identified a Dissociation (Ds) transposon‐inserted Arabidopsis mutant of a gene (AtRPS13A) homologous to cytoplasmic ribosomal protein (RP) S13. We named our mutant pointed first leaf (pfl) 2 because of its similar phenotype to the pfl1 mutant of the RPS18 gene. This mutant caused multiple phenotypic changes, including aberrant leaf and trichome morphology, retarded root growth, and late flowering. Microscopic analysis showed that the first leaf blade of pfl2 contained a significantly reduced number of palisade cells, which suggests that the mutant phenotype was caused by reduced cell division. However, no phenotypic changes were observed during reproductive growth. In Arabidopsis, the RPS13 protein was encoded by a small expressed gene family including AtRPS13A. A pfl1 pfl2 double mutant showed no additive effect. These results suggest that RPS13 functions in quantitative and pleiotropic ways during growth and development, and that mutations at different kinds of RP gene loci are accumulatable without serious growth defects because they belong to small gene families.
Light‐induced nuclear import of phytochrome‐A:GFP fusion proteins is differentially regulated in transgenic tobacco and Arabidopsis
Authors: Kim Lana , Kircher Stefan , Toth Reka , Adam Eva , Schäfer Eberhard , Nagy Ferenc 
Published: March 2003

SummaryPhytochromes (phy) are a family of photoreceptors that control various aspects of light‐dependent plant development. Phytochrome A (phyA) is responsible for the very low fluence response (VLFR) under inductive light conditions and for the high irradiance response (HIR) under continuous far‐red light. We have recently shown that nuclear import of rice phyA:GFP is regulated by VLFR in transgenic tobacco. The import is preceded by very fast, light‐induced formation of sequestered areas of phyA:GFP in the cytosol. Here we report that expression of the Arabidopsis phyA:GFP fusion protein in phyA‐deficient Arabidopsis plants complements the mutant phenotype. In these transgenic Arabidopsis lines, both light‐dependent cytosolic formation of sequestered areas of the phyA:GFP as well as VLFR or HIR‐mediated nuclear import of the fusion protein was observed. By contrast, light‐dependent nuclear import of the same fusion protein was induced only by continuous far‐red light (HIR) but not by pulses of far‐red light (VLFR) in transgenic tobacco. These results demonstrate that photoregulation of intracellular partitioning of the Arabidopsis phyA:GFP differs significantly in different genetic backgrounds.
Expression of the Fusarium resistance gene I‐2 colocalizes with the site of fungal containment
Authors: Mes Jurriaan J. , Van Doorn Aveline A. , Wijbrandi Jelle , Simons Guus , Cornelissen Ben J. C. , Haring Michel A. 
Published: March 2003

SummaryThe tomato resistance gene I‐2 is one of at least six members of a gene family that are expressed at low levels in the roots, stems and leaves of young tomato plants. Plants transformed with constructs containing a functional I‐2 promoter fused to the β‐glucuronidase (GUS) reporter gene were used in detailed expression studies. Highest GUS activity was found in stems of young tomato plants. Histochemical analysis revealed that the I‐2 promoter drives expression of the reporter gene in vascular tissue of fruits, leaves, stems and mature roots. In younger roots, expression was most abundant at the base of lateral root primordia. Microscopical analysis of young tomato plants revealed expression in tissue surrounding the xylem vessels. We show that in resistant plants, fungal growth into this region of the vascular tissue is prevented, suggesting a correlation with the I‐2‐mediated resistance response.