bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photomorphogenic development of the Arabidopsisshy2–1D mutation and its interaction with phytochromes in darkness
Authors: Kim Byung Chul , Soh Moon Soo , Hong Sung Hyun , Furuya Masaki , Nam Hong Gil 
Published: March 2003

SummaryWe previously reported a photomorphogenic mutation of Arabidopsis thaliana, shy2–1D, as a dominant suppressor of a hy2 mutation. Here, we report that shy2–1D confers various photo‐responsive phenotypes in darkness and the dark phenotypes of the mutant are affected by phytochrome deficiency. Dark‐grown seedlings of the mutant developed several photomorphogenic characteristics such as short hypocotyls, cotyledon expansion and opening, and partial differentiation of plastids. When grown further in darkness, the mutant plant underwent most of the developmental stages of a light‐grown wild‐type plant, including development of foliar leaves, an inflorescence stem with cauline leaves, and floral organs. In addition, two light‐inducible genes, the nuclear‐encoded CAB and the plastid‐encoded PSBA genes, were highly expressed in the dark‐grown mutant seedlings. Furthermore, reduced gravitropism, a phytochrome‐modulated response, was observed in the mutant hypocotyl in darkness. Thus, shy2–1D is one of the most pleiotropic photomorphogenic mutations identified so far. The results indicate that SHY2 may be a key component regulating photomorphogenesis in Arabidopsis. Surprisingly, double mutants of the shy2–1D mutant with the phytochrome‐deficient mutants hy2, hy3 (phyB‐1) and fre1–1 (phyA‐201) showed reduced photomorphogenic response in darkness with a longer hypocotyl, a longer inflorescence stem, and a lower level expression of the CAB gene than the shy2–1D single mutant. These results showed that phytochromes function in darkness in the shy2–1D mutant background. The implications of these results are discussed.
Germination‐related genes encoding proteolytic enzymes are expressed in the nucellus of developing wheat grains
Authors: Domínguez Fernando , Cejudo Francisco J. 
Published: March 2003

SummaryDuring wheat (Triticum aestivum) grain germination the aleurone layer shows a high expression of genes encoding hydrolytic enzymes. In this study we analyzed the spatio‐temporal pattern of expression of two of these genes, a carboxypeptidase III and a thiol protease, in developing grains. Our results show that transcripts of both genes accumulate at early stages of grain development (5–15 dpa) in the nucellus, a maternal tissue that degenerates during wheat grain development. In addition, the thiol protease gene is expressed in the nucellar projections and the modified aleurone cells, the cellular pathway of photosynthate transfer in the developing wheat grain. These results show that genes related to the germination programme are also expressed in the development programme where they may be implicated in the degenerative process that takes place in the nucellar tissue and the cytoplasm of nucellar projections cells.
Cytoplasmic polyamines block the fast‐activating vacuolar cation channel
Authors: Brüggemann Lioubov I. , Pottosin Igor I. , Schönknecht Gerald 
Published: March 2003

Summary The fast‐activating vacuolar (FV) channel dominates the electrical characteristics of the tonoplast at physiological free Ca2+ concentrations. Since polyamines are known to increase in plant cells in response to stress, the regulation of FV channels by polyamines was investigated. Patch‐clamp measurements were performed on whole barley (

Hordeum vulgare

) mesophyll vacuoles and on excised tonoplast patches. The trivalent polyamine spermidine and the tetravalent polyamine spermine blocked FV channels with Kd≈ 100 μM and Kd≈ 5 μM, respectively. Increasing cytosolic and vacuolar Ca2+ had no effect on putrescine and spermidine binding to FV channels but slightly decreased the affinity for spermine. The inhibition of FV channels by all three polyamines was not voltage‐dependent. This points to a different mode of binding compared to inward rectifier K+ channels and Ca2+‐permeable glutamate receptor channels from animal cells, which show rectification due to a voltage‐dependent block by polyamines. In plant cells, the common polyamines (putrescine, spermidine and spermine) are likely to mediate a salt stress‐induced decrease of ion flux across the vacuolar membrane by blocking FV channels.
A 100 kDa polypeptide associates with the Vo membrane sector but not with the active oat vacuolar H+‐ATPase, suggesting a role in assembly
Authors: Li Xuhang , Sze Heven 
Published: March 2003

Summary The vacuolar H+‐ATPase (V‐ATPase) is responsible for acidifying endomembrane compartments in eukaryotic cells. Although a 100 kDa subunit is common to many V‐ATPases, it is not detected in a purified and active pump from oat (Ward J.M. & Sze H. (1992)

Plant Physiol

. 99, 925–931). A 100 kDa subunit of the yeast V‐ATPase is encoded by

VPH1

. Immunostaining revealed a Vph1p‐related polypeptide in oat membranes, thus the role of this polypeptide was investigated. Membrane proteins were detergent‐solubilized and size‐fractionated, and V‐ATPase subunits were identified by immunostaining. A 100 kDa polypeptide was not associated with the fully assembled ATPase; however, it was part of an approximately 250 kDa Vo complex including subunits of 36 and 16 kDa. Immunostaining with an affinity‐purified antibody against the oat 100 kDa protein confirmed that the polypeptide was part of a 250 kDa complex and that it had not degraded in the ≈≈ 670 kDa holoenzyme. Co‐immunoprecipitation with a monoclonal antibody against A subunit indicated that peripheral subunits exist as assembled V1 subcomplexes in the cytosol. The free V1 subcomplex became attached to the detergent‐solubilized Vo sector after mixing, as subunits of both sectors were co‐precipitated by an antibody against subunit A. The absence of this polypeptide from the active enzyme suggests that, unlike the yeast Vph1p, the 100 kDa polypeptide in oat is not required for activity. Its association with the free Vo subcomplex would support a role of this protein in V‐ATPase assembly and perhaps in sorting.
Inter‐organ signaling in plants: regulation of ATP sulfurylase and sulfate transporter genes expression in roots mediated by phloem‐translocated compound
Authors: Lappartient Anne G. , Vidmar J. John , Leustek Thomas , Glass Anthony D. M. , Touraine Bruno 
Published: March 2003

SummarySulfate uptake and ATP sulfurylase activity in the roots of Arabidopsis thaliana and Brassica napus were enhanced by S deprivation and reduced following resupply of SO42–. Similar responses occurred in split‐root experiments where only a portion of the root system was S‐deprived, suggesting that the regulation involves inter‐organ signaling. Phloem‐translocated glutathione (GSH) was identified as the likely transducing molecule responsible for regulating SO42– uptake rate and ATP sulfurylase activity in roots. The regulatory role of GSH was confirmed by the finding that ATP sulfurylase activity was inhibited by supplying Cys except in the presence of buthionine sulfoximine, an inhibitor of GSH synthesis. In direct and remote (split‐root) exposures, levels of protein detected by antibodies against the Arabidopsis APS3 ATP sulfurylase increased in the roots of A. thaliana and B. napus during S starvation, decreased after SO42– restoration, and declined after feeding GSH. RNA blot analysis revealed that the transcript level of APS1, which codes for ATP sulfurylase, was reduced by direct and remote GSH treatments. The abundance of AST68 (a gene encoding an SO42– transporter) was similarly affected by altered sulfur status. This report presents the first evidence for the regulation of root genes involved in nutrient acquisition and assimilation by a signal that is translocated from shoot to root.
Molecular cloning and functional expression of codeinone reductase: the penultimate enzyme in morphine biosynthesis in the opium poppy Papaver somniferum
Authors: Unterlinner Bernhard , Lenz Rainer , Kutchan Toni M. 
Published: March 2003

Summary The narcotic analgesic morphine is the major alkaloid of the opium poppy Papaver somniferum
. Its biosynthetic precursor codeine is currently the most widely used and effective antitussive agent. Along the morphine biosynthetic pathway in opium poppy, codeinone reductase catalyzes the NADPH‐dependent reduction of codeinone to codeine. In this study, we have isolated and characterized four cDNAs encoding codeinone reductase isoforms and have functionally expressed them in Escherichia coli
. Heterologously expressed codeinone reductase‐calmodulin‐binding peptide fusion protein was purified from E. coli using calmodulin affinity column chromatography in a yield of 10 mg enzyme l

‐1

. These four isoforms demonstrated very similar physical properties and substrate specificity. As least six alleles appear to be present in the poppy genome. A comparison of the translations of the nucleotide sequences indicate that the codeinone reductase isoforms are 53% identical to 6′‐deoxychalcone synthase from soybean suggesting an evolutionary although not a functional link between enzymes of phenylpropanoid and alkaloid biosynthesis. By sequence comparison, both codeinone reductase and 6′‐deoxy‐ chalcone synthase belong to the aldo/keto reductase family, a group of structurally and functionally related NADPH‐dependent oxidoreductases, and thereby possibly arise from primary metabolism.
Transcriptional activation by Arabidopsis GT‐1 may be through interaction with TFIIA–TBP–TATA complex
Authors: Le Gourrierec José , Li You‐Fang , Zhou Dao‐Xiu 
Published: March 2003

SummaryGT‐1 belongs to the class of trihelix DNA‐binding proteins and binds to a promoter sequence found in many different genes. Data presented in this report show that GT‐1 contains a trans‐activation function in yeast and in plant cells. However, in tobacco BY‐2 protoplasts, this activity functions only when an internal region containing the DNA‐binding domain is deleted. Gel‐shift and co‐immunoprecipitation assays have revealed that GT‐1 can interact with and stabilize the TFIIA–TBP–TATA complex. These results suggest that GT‐1 may activate transcription through direct inter‐ action with the transcriptional pre‐initiation complex.
Cloning and characterisation of PGA1 and PGA2: two G protein α‐subunits from pea that promote growth in the yeast Saccharomyces cerevisiae
Authors: John F. Marsh III  , Kaufman Lon S. 
Published: March 2003

SummaryWe report here on the cloning and characterization of two G protein α‐subunits from pea: PGA1 and PGA2. Based on DNA gel blot analysis, PGA1 and PGA2 are the only Gα homologous sequences in pea. RT–PCR analysis reveals that PGA1 and PGA2 transcripts are present in a variety of adult pea tissues. However, PGA2 mRNA is consistently detected at a lower level than PGA1 and demonstrates some degree of tissue specificity relative to PGA1. In the apical bud of pea seedlings, PGA1 and PGA2 transcripts decrease in response to 24 h of white light following growth for 6 days in darkness. The G protein mediated, yeast mating pathway was used to analyse the function of PGA1 and PGA2 in vivo. PGA1 downregulates the mating pathway, but through a mechanism that is independent of Gβγ sequestration. Unexpectedly, both PGA1 and PGA2 promote growth through a mating pathway independent mechanism.
Diterpene synthesis in Stevia rebaudiana: recruitment and up‐regulation of key enzymes from the gibberellin biosynthetic pathway
Authors: Richman Alex S. , Gijzen Mark , Starratt Al N. , Yang Zhiyi , Brandle Jim E. 
Published: March 2003

Summary
Stevia rebaudiana Bertoni leaves accumulate a mixture of at least eight different glycosides derived from the tetracyclic diterpene steviol. These natural products taste intensely sweet and have similar biosynthetic origins to those of gibberellic acid (GA). The initial steps leading to the formation of GA result from the two‐step cyclization of geranylgeranyl diphosphate (GGDP) to (–)‐kaurene via the action of two terpene cyclases (–)‐copalyl diphosphate synthase (CPS) and (–)‐kaurene synthase (KS). Steviol biosynthesis probably uses the same mechanism although the genes and enzymes from S. rebaudiana that are involved in the cyclization of GGDP have not been characterized. We have isolated both the CPS and KS genes from S. rebaudiana and found that recombinant CPS and KS were catalytically active, suggesting that the CPS and KS genes participate in steviol biosynthesis. The genes coding for CPS and KS are usually present in single copies in most plant species and their expression is normally low and limited to rapidly growing tissues. The KS gene has been duplicated in the S. rebaudiana genome and both the KS and CPS genes are highly expressed in mature leaves, a pattern opposite to that found with GA biosynthesis. This pattern may, at least in part, lead to temporal and spatial separation of GA and steviol biosynthesis and probably helps to prevent over‐expression from interfering with normal GA metabolism. Our results show that CPS and KS are part of the steviol glycoside biosynthetic pathway and that Stevia rebaudiana has recruited two genes to secondary metabolism from a highly regulated pathway involved in hormone biosynthesis.
The DIF1 gene of Arabidopsis is required for meiotic chromosome segregation and belongs to the REC8/RAD21 cohesin gene family
Authors: Bhatt Anuj M. , Lister Clare , Page Tania , Fransz Paul , Findlay Kim , Jones Gareth H. , Dickinson Hugh G. , Dean Caroline 
Published: March 2003

SummaryCohesins are a group of conserved proteins responsible for cohesion between replicated sister chromatids during mitosis and meiosis and which are implicated in double‐strand break repair and meiotic recombination. We describe here the identification and characterisation of an Arabidopsis gene –DETERMINATE, INFERTILE1 (DIF1), which is a homolog of the Schizosaccharomyces pombe REC8/RAD21 cohesin genes, and is essential for meiotic chromosome segregation. Five independent alleles of the DIF1 gene were isolated by transposon mutagenesis, and the mutants show complete male and female sterility. Pollen mother cells (PMCs) of dif1 mutants show multiple meiotic defects which are represented by univalent chromosomes and chromosome fragmentation at metaphase I, and acentric fragments and chromatin bridges in meiosis I and II. Consequently, chromosome segregation is strongly affected, resulting in meiotic products of uneven size, shape and of variable ploidy. The similarities in phenotype, and the sequence homology between DIF1 and the REC8/RAD21 cohesins suggests that cohesin function is largely conserved between eukaryotes and highlights the essential role cohesins play in plant meiosis.
Some thaumatin‐like proteins hydrolyse polymeric β‐1,3‐glucans
Authors: Grenier Jean , Potvin Claude , Trudel Jean , Asselin Alain 
Published: March 2003

SummaryThaumatin and 12 purified thaumatin‐like (TL) proteins were surveyed for their capacity to hydrolyse β‐1,3‐glucans by using an in‐gel glucanase assay. Six TL proteins identified by N‐terminal amino acid microsequencing were found to be active on carboxymethyl(CM)‐pachyman: a barley leaf stress‐related permatin, two tomato fruit osmotins, a cherry fruit and two tobacco stigma proteins. TL enzymes ranged in specific activity from 0.07 to 89 nkat mg–1 with CM‐pachyman as substrate. Hydrolytic activities were not restricted to TL proteins strongly binding to water‐insoluble β‐1,3‐glucans since the two osmotins were active without tight binding to pachyman. Some TL proteins hydrolysed crude fungal walls and one barley TL enzyme even lysed fungal spores. No activity was observed on laminarin in the in‐gel hydrolase assay. Thin‐layer chromatography revealed that the six enzymes acted as endo‐β‐1,3‐glucanases leading to the formation of various oligoglucosides. Thus far, the TL enzymes (EC 3.2.1.x) appeared different from the well‐known β‐1,3‐glucanases (EC 3.2.1.39). No activity was found with thaumatin, zeamatin, tobacco leaf PR‐R protein and four stress‐related TL proteins from barley and pea. This is the first demonstration that diverse TL proteins are enzymatically active. The functions of some TL proteins must be reassessed because they display endo‐β‐1,3‐glucanase activity on polymeric β‐1,3‐glucans.
Molecular analysis of rice plants harboring an Ac/Ds transposable element‐mediated gene trapping system
Authors: Chin Hang Gyeong , Choe Mi Sook , Lee Sung‐Ho , Park Sung Han , Park Su Hyun , Koo Ja Choon , Kim No Youl , Lee Jeung Joo , Oh Byeong Geun , Yi Gi Hwan , Kim Soon Chul , Choi Hae Chune , Cho Moo Je , Han Chang‐deok 
Published: March 2003

SummaryIn rice, limited efforts have been made to identify genes by the use of insertional mutagens, especially hetero‐ logous transposons such as the maize Ac/Ds. We constructed Ac and gene trap Ds vectors and introduced them into the rice genome by Agrobacterium‐mediated transformation. In this report, rice plants that contained single and simple insertions of T‐DNA were analysed in order to evaluate the gene‐tagging efficiency. The 3′ end of Ds was examined for putative splicing donor sites. As observed in maize, three splice donor sites were identified at the 3′ end of the Ds in rice. Nearly 80% of Ds elements were excised from the original T‐DNA sites, when Ac cDNA was expressed under a CaMV 35S promoter. Repetitive ratoon culturing was performed to induce new transpositions of Ds in new plants derived from cuttings. About 30% of the plants carried at least one Ds which underwent secondary transposition in the later cultures. Eight per cent of transposed Ds elements expressed GUS in various tissues of rice panicles. With cloned DNA adjacent to Ds, the genomic complexities of the insertion sites were examined by Southern hybridization. Half of the Ds insertion sites showed simple hybridization patterns which could be easily utilized to locate the Ds. Our data demonstrate that the Ac/Ds‐mediated gene trap system could prove an excellent tool for the analysis of functions of genes in rice. We discuss genetic strategies that could be employed in a large scale mutagenesis using a hetero‐ logous Ac/Ds family in rice.
Millisecond UV‐B irradiation evokes prolonged elevation of cytosolic‐free Ca2+ and stimulates gene expression in transgenic parsley cell cultures
Authors: Frohnmeyer Hanns , Loyall Linda , Blatt Michael R. , Grabov Alexander 
Published: March 2003

SummaryChalcone synthase (CHS) is a key enzyme leading to the generation of protective flavonoids in plants under environmental stress. Expression of the CHS gene is strongly upregulated by exposures to UV light, a response also observed in heterotrophic parsley cell cultures. Although there are hints that the stimulus for CHS expression may be coupled to UV‐B irradiation through a rise in cytosolic‐free Ca2+ ([Ca2+]i), the temporal relationship of these events has never been investigated critically. To explore this question, we have used a CHS promoter/luciferase (CHS/LUC) reporter gene fusion and recorded its expression and [Ca2+]i elevation in a transgenic parsley cell culture following millisecond light pulses. Luciferase expression was enhanced maximally seven‐ (± 2) fold by 30 10 ms flashes of UV‐B light. The response was specific to wavelengths of 300–330 nm and could be inhibited in the presence of the Ca2+ channel blocker nifedipine. In parallel measurements, using Fura‐2 fluorescence ratio microphotometry, we found that 10 ms UV‐B flashes also evoked a gradual and prolonged rise of [Ca2+]i in the parsley cells which was irreversible within the timescale of these experiments, but could be prevented by prior treatment with nifedipine. These, and additional results, indicate a remarkably high temporal sensitivity to, and specificity for, UV‐B light in CHS gene expression independent of UV‐mediated DNA damage by thymine dimerization. The ability of transient UV‐B stimulation to evoke prolonged elevations of [Ca2+]i suggests a functional coupling between the initial light stimulus and subsequent gene expression that takes place many tens of minutes later.
The UNUSUAL FLORAL ORGANS gene of Arabidopsis thaliana is an F‐box protein required for normal patterning and growth in the floral meristem
Authors: Samach Alon , Klenz Jennifer E. , Kohalmi Susanne E. , Risseeuw Eddy , Haughn George W. , Crosby William L. 
Published: March 2003

SummaryGenetic and molecular studies have suggested that the UNUSUAL FLORAL ORGANS (UFO) gene, from Arabidopsis thaliana, is expressed in all shoot apical meristems, and is involved in the regulation of a complex set of developmental events during floral development, including floral meristem and floral organ identity. Results from in situ hybridization using genes expressed early in floral development as probes indicate that UFO controls growth of young floral primordia. Transgenic constructs were used to provide evidence that UFO regulates floral organ identity by activating or maintaining transcription of the class B organ‐identity gene APETALA 3, but not PISTILLATA. In an attempt to understand the biochemical mode of action of the UFO gene product, we show here that UFO is an F‐box protein that interacts with Arabidopsis SKP1‐like proteins, both in the yeast two‐hybrid system and in vitro. In yeast and other organisms both F‐box proteins and SKP1 homologues are subunits of specific ubiquitin E3 enzyme complexes that target specific proteins for degradation. The protein selected for degradation by the complex is specified by the F‐box proteins. It is therefore possible that the role of UFO is to target for degradation specific proteins controlling normal growth patterns in the floral primordia, as well as proteins that negatively regulate APETALA 3 transcription.
Interactions of the developmental regulator ABI3 with proteins identified from developing Arabidopsis seeds
Authors: Kurup Smita , Jones Huw D. , Holdsworth Michael John 
Published: March 2003

SummaryThe ABI3 locus is a major regulator of embryo development in Arabidopsis and is essential for the simultaneous activation of the maturation pathway, as well as repression of germination and seedling development. We used a two‐hybrid screen in yeast in order to identify proteins that interact with ABI3. Four ABI3‐interacting proteins (AIPs) were identified which showed specific in vivo and in vitro interactions with the C‐terminal region of ABI3 that contains the B2 and B3 domains, previously shown to have DNA binding activity. The expression characteristics of the genes encoding the AIPs have also been analysed in wild‐type and abi3, lec1 and fus3 embryo mutants. This analysis demonstrated differential expression of these genes during normal embryo development and in the mutant lines. All the AIPs show homology to existing transcription factors and therefore they may function with ABI3 within the network of transcriptional regulators that control embryo development in Arabidopsis.