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Arabidopsis
Kinds of Arabidopsis Terms modified by Arabidopsis Selected AbstractsEvolutionary origins of the purinergic signalling systemACTA PHYSIOLOGICA, Issue 4 2009G. Burnstock Abstract Purines appear to be the most primitive and widespread chemical messengers in the animal and plant kingdoms. The evidence for purinergic signalling in plants, invertebrates and lower vertebrates is reviewed. Much is based on pharmacological studies, but important recent studies have utilized the techniques of molecular biology and receptors have been cloned and characterized in primitive invertebrates, including the social amoeba Dictyostelium and the platyhelminth Schistosoma, as well as the green algae Ostreococcus, which resemble P2X receptors identified in mammals. This suggests that contrary to earlier speculations, P2X ion channel receptors appeared early in evolution, while G protein-coupled P1 and P2Y receptors were introduced either at the same time or perhaps even later. The absence of gene coding for P2X receptors in some animal groups [e.g. in some insects, roundworms (Caenorhabditis elegans) and the plant Arabidopsis] in contrast to the potent pharmacological actions of nucleotides in the same species, suggests that novel receptors are still to be discovered. [source] Plant profilin isovariants are distinctly regulated in vegetative and reproductive tissuesCYTOSKELETON, Issue 1 2002Muthugapatti K. Kandasamy Abstract Profilin is a low-molecular weight, actin monomer-binding protein that regulates the organization of actin cytoskeleton in eukaryotes, including higher plants. Unlike the simple human or yeast systems, the model plant Arabidopsis has an ancient and highly divergent multi-gene family encoding five distinct profilin isovariants. Here we compare and characterize the regulation of these profilins in different organs and during microspore development using isovariant-specific monoclonal antibodies. We show that PRF1, PRF2, and PRF3 are constitutive, being strongly expressed in all vegetative tissues at various stages of development. These profilin isovariants are also predominant in ovules and microspores at the early stages of microsporogenesis. In contrast, PRF4 and PRF5 are late pollen-specific and are not detectable in other cell types of the plant body including microspores and root hairs. Immunocytochemical studies at the subcellular level reveal that both the constitutive and pollen-specific profilins are abundant in the cytoplasm. In vegetative cell types, such as root apical cells, profilins showed localization to nuclei in addition to the cytoplasmic staining. The functional diversity of profilin isovariants is discussed in light of their spatio-temporal regulation during vegetative development, pollen maturation, and pollen tube growth. Cell Motil. Cytoskeleton 52:22,32, 2002. © 2002 Wiley-Liss, Inc. [source] Scaling up evolutionary responses to elevated CO2: lessons from ArabidopsisECOLOGY LETTERS, Issue 5 2004Joy K. Ward Abstract Results from norm of reaction studies and selection experiments indicate that elevated CO2 will act as a selective agent on natural plant populations, especially for C3 species that are most sensitive to changes in atmospheric CO2 concentration. Evolutionary responses to CO2 may alter plant physiology, development rate, growth, and reproduction in ways that cannot be predicted from single generation studies. Moreover, ecological and evolutionary changes in plant communities will have a range of consequences at higher spatial scales and may cause substantial deviations from ecosystem level predictions based on short-term responses to elevated CO2. Therefore, steps need to be taken to identify the plant traits that are most likely to evolve at elevated CO2, and to understand how these changes may affect net primary productivity within ecosystems. These processes may range in scale from molecular and physiological changes that occur among genotypes at the individual and population levels, to changes in community- and ecosystem-level productivity that result from the integrative effects of different plant species evolving simultaneously. In this review, we (1) synthesize recent studies investigating the role of atmospheric CO2 as a selective agent on plants, (2) discuss possible control points during plant development that may change in response to selection at elevated CO2 with an emphasis at the primary molecular level, and (3) provide a quantitative framework for scaling the evolutionary effects of CO2 on plants in order to determine changes in community and ecosystem productivity. Furthermore, this review points out that studies integrating the effects of plant evolution in response to elevated CO2 are lacking, and therefore more attention needs be devoted to this issue among the global change research community. [source] Comparison of the Electrochemical Behavior of the High Molecular Mass Cadmium Proteins in Arabidopsis thaliana and in Vegetable Plants on Using Preparative Native Continuous Polyacrylamide Gel Electrophoresis (PNC-PAGE)ELECTROANALYSIS, Issue 1 2006Bernd Kastenholz Abstract In Arabidopsis cytosol (supernatant) and in supernatants of vegetable plants high molecular mass cadmium proteins with molecular mass 200,kDa were isolated by using preparative native continuous polyacrylamide gel electrophoresis (PNC-PAGE). Because of a different electrochemical behavior of the Cd proteins in Arabidopsis and endive supernatants on using the same PAGE method, it is concluded that the high molecular mass cadmium proteins of Arabidopsis and endive possess different isoelectric points. Consequently, different chemical structures of the Cd proteins with molecular mass 200,kDa are present in Arabidopsis thaliana and in endive. During the electrophoretic separation of vegetable metalloproteins by using the Model 491 Prep Cell from BioRad, electroanalytical processes like electrode reactions may play an important role. [source] Developing transgenic arabidopsis plants to be metal-specific bioindicatorsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2003Beth A. Krizek Abstract Deoxyribonucleic acid (DNA) microarrays provide a means to assess genome-wide expression patterns after exposure of an organism to different xenobiotics. Potential uses for this technology include identification of unknown toxicants, assessment of toxicity of new compounds, and characterization of the cellular mechanisms of toxicant action. Here we describe another use of DNA microarrays in toxicant-specific gene discovery. Combining results from two DNA microarray experiments, we have identified genes from the model plant Arabidopsis thaliana that are induced in response to one but not other heavy metals. The promoters of these genes should be useful in developing metal-specific transgenic biomonitors. To test this idea, we have fused the promoter of one of the newly identified Ni-inducible genes (AHB1) to the ,-glucuronidase (GUS) reporter gene. Arabidopsis plants containing the AHB1::GUS transgene show reporter gene activity when they are grown on media containing Ni but not when grown on media containing Cd, Cu, Zn, or without added metals. Thus, this approach has resulted in the creation of a transgenic strain of Arabidopsis that can report on the presence and concentration of Ni in plant growth media. Such transgenic models can serve as cheap and efficient biomonitors of bioavailable heavy metal contamination in soils and sediments. [source] TOWARD A REALISTIC MODEL OF MUTATIONS AFFECTING FITNESSEVOLUTION, Issue 3 2003Peter D. Keightley Abstract Analysis of a recent mutation accumulation (MA) experiment has led to the suggestion that as many as one-half of spontaneous mutations in Arabidopsis are advantageous for fitness. We evaluate this in the light of data from other MA experiments, along with molecular evidence, that suggest the vast majority of new mutations are deleterious. [source] PLASTICITY TO LIGHT CUES AND RESOURCES IN ARABIDOPSIS THALIANA: TESTING FOR ADAPTIVE VALUE AND COSTSEVOLUTION, Issue 6 2000Lisa A. Dorn Abstract Plants shaded by neighbors or overhead foliage experience both a reduction in the ratio of red to far red light (R:FR), a specific cue perceived by phytochrome, and reduced photosynthetically active radiation (PAR), an essential resource. We tested the adaptive value of plasticity to crowding and to the cue and resource components of foliage shade in the annual plant Arabidopsis thaliana by exposing 36 inbred families from four natural populations to four experimental treatments: (1) high density, full sun; (2) low density, full sun; (3) low density, neutral shade; and (4) low density, low R:FR-simulated foliage shade. Genotypic selection analysis within each treatment revealed strong environmental differences in selection on plastic life-history traits. We used specific contrasts to measure plasticity to density and foliage shade, to partition responses to foliage shade into phytochrome-mediated responses to the R:FR cue and responses to PAR, and to test whether plasticity was adaptive (i.e., in the same direction as selection in each environment). Contrary to expectation, we found no evidence for adaptive plasticity to density. However, we observed both adaptive and maladaptive responses to foliage shade. In general, phytochrome-mediated plasticity to the R:FR cue of foliage shade was adaptive and counteracted maladaptive growth responses to reduced PAR. These results support the prediction that active developmental responses to environmental cues are more likely to be adaptive than are passive resource-mediated responses. Multiple regression analysis detected a few costs of adaptive plasticity and adaptive homeostasis, but such costs were infrequent and their expression depended on the environment. Thus, costs of plasticity may occasionally constrain the evolution of adaptive responses to foliage shade in Arabidopsis, but this constraint may differ among environments and is far from ubiquitous. [source] Cross-species divergence of the major recognition pathways of ubiquitylated substrates for ubiquitin/26S proteasome-mediated proteolysisFEBS JOURNAL, Issue 3 2010Antony S. Fatimababy The recognition of ubiquitylated substrates is an essential element of ubiquitin/26S proteasome-mediated proteolysis (UPP), which is mediated directly by the proteasome subunit RPN10 and/or RPN13, or indirectly by ubiquitin receptors containing ubiquitin-like and ubiquitin-associated domains. By pull-down and mutagenesis assays, we detected cross-species divergence of the major recognition pathways. RPN10 plays a major role in direct recognition in Arabidopsis and yeast based on the strong affinity for the long and K48-linked ubiquitin chains. In contrast, both the RPN10 and RPN13 homologs play major roles in humans. For indirect recognition, the RAD23 and DSK2 homologs (except for the human DSK2 homolog) are major receptors. The human RAD23 homolog is targeted to the 26S proteasome by the RPN10 and RPN13 homologs. In comparison, Arabidopsis uses UIM1 and UIM3 of RPN10 to bind DSK2 and RAD23, respectively. Yeast uses UIM in RPN10 and LRR in RPN1. Overall, multiple proteasome subunits are responsible for the direct and/or indirect recognition of ubiquitylated substrates in yeast and humans. In contrast, a single proteasome subunit, RPN10, is critical for both the direct and indirect recognition pathways in Arabidopsis. In agreement with these results, the accumulation of ubiquitylated substrates and severe pleiotropic phenotypes of vegetative and reproductive growth are associated with the loss of RPN10 function in an Arabidopsis T-DNA insertion mutant. This implies that the targeting and proteolysis of the critical regulators involved are affected. These results support a cross-species mechanistic and functional divergence of the major recognition pathways for ubiquitylated substrates of UPP. Structured digital abstract ,,A list of the large number of protein-protein interactions described in this article is available via the MINT article ID MINT-7307429 [source] EMBRYO YELLOW gene, encoding a subunit of the conserved oligomeric Golgi complex, is required for appropriate cell expansion and meristem organization in Arabidopsis thalianaGENES TO CELLS, Issue 6 2008Takaaki Ishikawa We identified an embryo yellow (eye) mutation in Arabidopsis that leads to the abnormal coloration and morphology of embryos. The eye mutant formed bushy plants, with aberrant organization of the shoot apical meristem (SAM) and unexpanded leaves with irregular phyllotaxy. The epidermal cells of the eye mutant were much smaller than that of the wild-type. Thus, EYE is required for expansion of cells and organs, and for formation of the organized SAM. Hydrophobic layers of epidermal cells were also disrupted, suggesting that EYE might be involved in the generation of the extra-cellular matrix. The mutated gene encoded a protein that is homologous to Cog7, a subunit of the conserved oligomeric Golgi (COG) complex, which is required for the normal morphology and function of the Golgi appratus. The eye mutation caused mislocalization of a Golgi protein. In addition, the size of the Golgi apparatus was also altered. Thus, EYE might be involved in transport or retention of Golgi-localized proteins and in maintenance of Golgi morphology. We propose that some Golgi-localized proteins, distributions of which are controlled by EYE, play important roles in expansion of cells and organs, and in formation of the properly organized SAM in plants. [source] The VAR1 locus of Arabidopsis encodes a chloroplastic FtsH and is responsible for leaf variegation in the mutant allelesGENES TO CELLS, Issue 8 2002Wataru Sakamoto Background: A leaf-variegated mutation var1 of Arabidopsis results in the development of abnormal plastids and the formation of a green/white sector. Genetic analysis of the var1 mutant indicated that it acts synergistically with another mutation var2, suggesting that the two genes are relevant. The VAR2 locus has been shown to encode a chloroplastic FtsH, an ATP-dependent protease which is possibly involved in the degradation of thylakoid proteins and plastid development. Results: In this study we show that the VAR1 locus encodes a chloroplastic FtsH protein homologous to VAR2. VAR1 contains a conserved motif for ATPase and a metalloprotease characteristic to FtsH proteins, and is targeted into chloroplasts. A VAR1-fusion protein synthesized in vitro exhibited ATPase activity and partial metalloprotease activity. The maximum yield of photochemistry, measured by chlorophyll fluorescence, showed that the var1 mutants were sensitive to photoinhibitory light exposure at 800 µmol/m2/s. Conclusion:VAR1 and VAR2 comprise an FtsH small gene family together with other FtsH genes in Arabidopsis. VAR1 as well as VAR2 may play an important role in degrading photodamaged subunits in photosystem II. Loss of VAR1 and VAR2 perhaps impairs the photoprotection mechanism and thylakoid development, causing leaf variegation as a consequence. [source] The whorl-specific action of a petunia class B floral homeotic geneGENES TO CELLS, Issue 2 2000Suguru Tsuchimoto Background GREEN PETAL (GP) is thought to be a petunia class B floral homeotic gene, because the gp mutant flower displays a severe homeotic conversion of petals into sepals in the second whorl. However, since the third whorl stamens remain unaffected in the gp null mutant, gp is different from class B mutants in Arabidopsis and Antirrhinum, which also show a conversion of the third whorl stamens into the carpelloid tissue. BLIND (BL) is thought to be a petunia class A floral homeotic gene, because the bl mutant flower displays homeotic conversions of sepals into the stigmatoid tissue in the first whorl and of the corolla limb into antheroid structures in the second whorl. Results A double mutant line homozygous for both bl and gp mutations was constructed. The bl gp double mutant flower displays homeotic conversions of sepals into the stigmatoid tissue in the first whorl and of the corolla limb into antheroid structures with stigmatoid tips in the second whorl. In the third and fourth whorls of the mutant flower, organs remained unchanged. In the gp flower, a petunia B-type gene FBP1 is expressed strongly in the third whorl organs, but much more weakly in the second whorl organs. In the bl gp flower, FBP1 was found to be expressed strongly in the second whorl organs as well as in the third whorl organs. Conclusions Petunia has a class B gene other than GP that determines organ identities, both in the second and third whorls of the double mutant flower, and the action of the postulated class B gene (here called PhBX) is prevented by the BL gene in the second whorl of the gp flower. PhBX appears to be a gene that specifically interacts with the FBP1 gene, and is involved in the up-regulation of FBP1. [source] Polyploidy-Associated Genomic Instability in Arabidopsis thalianaGENESIS: THE JOURNAL OF GENETICS AND DEVELOPMENT, Issue 4 2010Yixing Wang Formation of polyploid organisms by fertilization of unreduced gametes in meiotic mutants is believed to be a common phenomenon in species evolution. However, not well understood is how species in nature generally exist as haploid and diploid organisms in a long evolutionary time while polyploidization must have repeatedly occurred via meiotic mutations. Here, we show that the ploidy increased for two consecutive generations due to unreduced but viable gametes in the Arabidopsis cyclin a1;2-2 (also named tardy asynchronousmeiosis-2) mutant, but the resultant octaploid plants produced progeny of either the same or reduced ploidy via genomic reductions during meiosis and pollen mitosis. Ploidy reductions through sexual reproduction were also observed in independently generated artificial octaploid and hexaploid Arabidopsis plants. These results demonstrate that octaploid is likely the maximal ploidy produced through sexual reproduction in Arabidopsis. The polyploidy-associated genomic instability may be a general phenomenon that constrains ploidy levels in species evolution. [source] Antagonistic Effects of Hydrogen Peroxide and Glutathione on Acclimation to Excess Excitation Energy in ArabidopsisIUBMB LIFE, Issue 1 2000Barbara Karpinska Abstract The redox status of the quinone B (QB) and plastoquinone (PQ) pools plays a key role in the cellular and systemic signalling processes that control acclimatory responses in plants. In this study, we demonstrate the effects of hydrogen peroxide and glutathione on acclimatory responses controlled by redox events in the proximity of the QB-PQ pools. Our results suggest that the chloroplast is a sink for H2O2 and that, paradoxically, high concentrations of H2O2 in the chloroplast protect the photosynthetic apparatus and the plant cell from photoinhibition and photooxidative damage. Excess glutathione, however, caused an effect antagonistic to that observed for high H2O2. An explanation of this apparent paradox and a hypothetical redox-signalling model are suggested. [source] Research Article: The Cysteine Pairs in CLV2 are Not Necessary for Sensing the CLV3 Peptide in Shoot and Root MeristemsJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 9 2010Xiufen Song Receptor-like proteins (RLPs) are involved in both plant defense and developmental processes. Previous genetic and biochemical studies show that the leucine-rich repeat (LRR) receptor-like protein CLAVATA2 (CLV2) functions together with CLAVATA1 (CLV1) and CORYNE (CRN) in Arabidopsis to limit the stem cell number in shoot apical meristem, while in root it acts with CRN to trigger a premature differentiation of the stem cells after sensing the exogenously applied peptides of CLV3p, CLE19p or CLE40p. It has been proposed that disulfide bonds might be formed through two cysteine pairs in the extracellular LRR domains of CLV1 and CLV2 to stabilize the receptor complex. Here we tested the hypothesis by replacing these cysteines with alanines and showed that depletions of one or both of the cysteine pairs do not hamper the function of CLV2 in SAM maintenance. In vitro peptide assay also showed that removal of the cysteine pairs did not affect the perception of CLV3 peptides in roots. These observations allow us to conclude that the formation of disulfide bonds is not needed for the function of CLV2. [source] Molecular Mechanisms Regulating Rapid Stress Signaling Networks in ArabidopsisJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 4 2010Justin W. Walley As sessile organisms plants must cope with ever changing environmental conditions. To survive plants have evolved elaborate mechanisms to perceive and rapidly respond to a diverse range of abiotic and biotic stresses. Central to this response is the ability to modulate gene expression at both the transcriptional and post-transcriptional levels. This review will focus on recent progress that has been made towards understanding the rapid reprogramming of the transcriptome that occurs in response to stress as well as emerging mechanisms underpinning the reprogramming of gene expression in response to stress. [source] Gibberellin and Jasmonate Crosstalk during Stamen DevelopmentJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 12 2009Jinrong Peng Abstract Gibberellin (GA) and jasmonate (JA) are two types of phytohormones that play important roles during stamen development. For example, Arabidopsis plants deficient in either of GA or JA develop short stamens. An apparent question to ask is whether GA action and JA action during stamen filament development are independent of each other or are in a hierarchy. Recent studies showed that GA modulates the expression of genes essential for JA biosynthesis to promote JA production and high levels of JA will induce the expression of three MYB genes MYB21, MYB24 and MYB57. These three MYB genes are crucial factors for the normal development of stamen filament in Arabidopsis. [source] AKIN,1 is Involved in the Regulation of Nitrogen Metabolism and Sugar Signaling in ArabidopsisJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 5 2009Xiao-Fang Li Abstract Sucrose non-fermenting-1-related protein kinase 1 (SnRK1) has been located at the heart of the control of metabolism and development in plants. The active SnRK1 form is usually a heterotrimeric complex. Subcellular localization and specific target of the SnRK1 kinase are regulated by specific beta subunits. In Arabidopsis, there are at least seven genes encoding beta subunits, of which the regulatory functions are not yet clear. Here, we tried to study the function of one beta subunit, AKIN,1. It showed that AKIN,1 expression was dramatically induced by ammonia nitrate but not potassium nitrate, and the investigation of AKIN,1 transgenic Arabidopsis and T-DNA insertion lines showed that AKIN,1 negatively regulated the activity of nitrate ruductase and was positively involved in sugar repression in early seedling development. Meanwhile AKIN,1 expression was reduced upon sugar treatment (including mannitol) and did not affect the activity of sucrose phosphate synthase. The results indicate that AKIN,1 is involved in the regulation of nitrogen metabolism and sugar signaling. [source] Expression of a High Mobility Group Protein Isolated from Cucumis sativus Affects the Germination of Arabidopsis thaliana under Abiotic Stress ConditionsJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 5 2008Ji Young Jang Abstract Although high mobility group B (HMGB) proteins have been identified from a variety of plant species, their importance and functional roles in plant responses to changing environmental conditions are largely unknown. Here, we investigated the functional roles of a CsHMGB isolated from cucumber (Cucumis sativus L.) in plant responses to environmental stimuli. Under normal growth conditions or when subjected to cold stress, no differences in plant growth were found between the wild-type and transgenic Arabidopsis thaliana overexpressing CsHMGB. By contrast, the transgenic Arabidopsis plants displayed retarded germination compared with the wild-type plants when grown under high salt or dehydration stress conditions. Germination of the transgenic plants was delayed by the addition of abscisic acid (ABA), implying that CsHMGB affects germination through an ABA-dependent way. The expression of CsHMGB had affected only the germination stage, and CsHMGB did not affect the seedling growth of the transgenic plants under the stress conditions. The transcript levels of several germination-responsive genes were modulated by the expression of CsHMGB in Arabidopsis. Taken together, these results suggest that ectopic expression of a CsHMGB in Arabidopsis modulates the expression of several germination-responsive genes, and thereby affects the germination of Arabidopsis plants under different stress conditions. [source] PPF1 May Suppress Plant Senescence via Activating TFL1 in Transgenic Arabidopsis PlantsJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 4 2008Da-Yong Wang Abstract Senescence, a sequence of biochemical and physiological events, constitutes the final stage of development in higher plants and is modulated by a variety of environmental factors and internal factors. PPF1 possesses an important biological function in plant development by controlling the Ca2+ storage capacity within chloroplasts. Here we show that the expression of PPF1 might play a pivotal role in negatively regulating plant senescence as revealed by the regulation of overexpression and suppression of PPF1 on plant development. Moreover, TFL1, a key regulator in the floral repression pathway, was screened out as one of the downstream targets for PPF1 in the senescence-signaling pathway. Investigation of the senescence-related phenotypes in PPF1(,) tfl1-1 and PPF1(+) tfl1-1 double mutants confirmed and further highlighted the relation of PPF1 with TFL1 in transgenic plants. The activation of TFL1 expression by PPF1 defines an important pathway possibly essential for the negative regulation of plant senescence in transgenic Arabidopsis. [source] Genetic Analyses of Meiotic Recombination in ArabidopsisJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 8 2007Asela J. Wijeratne Abstract Meiosis is essential for sexual reproduction and recombination is a critical step required for normal meiosis. Understanding the underlying molecular mechanisms that regulate recombination is important for medical, agricultural and ecological reasons. Readily available molecular and cytological tools make Arabidopsis an excellent system to study meiosis. Here we review recent developments in molecular genetic analyses on meiotic recombination. These include studies on plant homologs of yeast and animal genes, as well as novel genes that were first identified in plants. The characterizations of these genes have demonstrated essential functions from the initiation of recombination by double-strand breaks to repair of such breaks, from the formation of double-Holliday junctions to possible resolution of these junctions, both of which are critical for crossover formation. The recent advances have ushered a new era in plant meiosis, in which the combination of genetics, genomics, and molecular cytology can uncover important gene functions. [source] A Microarray Based Genomic Hybridization Method for Identification of New Genes in Plants: Case Analyses of Arabidopsis and OryzaJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 6 2007Chuanzhu Fan Abstract To systematically estimate the gene duplication events in closely related species, we have to use comparative genomic approaches, either through genomic sequence comparison or comparative genomic hybridization (CGH). Given the scarcity of complete genomic sequences of plant species, in the present study we adopted an array based CGH to investigate gene duplications in the genus Arabidopsis. Fragment genomic DNA from four species, namely Arabidopsis thaliana, A. lyrata subsp. lyrata, A. lyrata subsp. petraea, and A. halleri, was hybridized to Affymetrix (Santa Clara, CA, USA) tiling arrays that are designed from the genomic sequences of A. thaliana. Pairwise comparisons of signal intensity were made to infer the potential duplicated candidates along each phylo-genetic branch. Ninety-four potential candidates of gene duplication along the genus were identified. Among them, the majority (69 of 94) were A. thaliana lineage specific. This result indicates that the array based CGH approach may be used to identify candidates of duplication in other plant genera containing closely related species, such as Oryza, particularly for the AA genome species. We compared the degree of gene duplication through retrotransposon between O. sativa and A. thaliana and found a strikingly higher number of chimera retroposed genes in rice. The higher rate of gene duplication through retroposition and other mechanisms may indicate that the grass species is able to adapt to more diverse environments. [source] Ubiquitination in Abscisic Acid-Related PathwayJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 1 2007Yi-Yue Zhang Abstract Ubiquitination is emerging as a tight regulatory mechanism that is necessary for all aspects of development and survival of all eukaryotes. Recent genomic and genetic analysis in Arabidopsis suggests that ubiquitination may also play important roles in plant response to the phytohormone abscisic acid (ABA). Many components of the ubiquitination pathway, such as ubiquitin-conjugating enzyme E2, ubiquitin ligase E3 and components of the proteasome, have been identified or predicted to be essential in ABA biosynthesis, catabolism and signaling. In addition, the ubiquitination-related pathway, sumoylation, is also involved in ABA signaling. We summarize in this report recent developments to elucidate their roles in the ABA-related pathway. [source] Tomato Fruit Development and Ripening Are Altered by the Silencing of LeEIN2 GeneJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 12 2006Hong-Liang Zhu Abstract Loss-of-function ethylene insensitive 2 (EIN2) mutations showed ethylene insensitivity in Arabidopsis, which indicated an essential role of EIN2 in ethylene signaling. However, the function of EIN2 in fruit ripening has not been investigated. To gain a better understanding of EIN2, the temporal regulation of LeEIN2 expression during tomato fruit development was analyzed. The expression of LeEIN2 was constant at different stages of fruit development, and was not regulated by ethylene. Moreover, LeEIN2-silenced tomato fruits were developed using a virus-induced gene silencing fruit system to study the role of LeEIN2 in tomato fruit ripening. Silenced fruits had a delay in fruit development and ripening, related to greatly descended expression of ethylene-related and ripening-related genes in comparison with those of control fruits. These results suggested LeEIN2 positively mediated ethylene signals during tomato development. In addition, there were fewer seeds and locules in the silenced fruit than those in the control fruit, like the phenotype of parthenocarpic tomato fruit. The content of auxin and the expression of auxin-regulated gene were declined in silenced fruit, which indicated that EIN2 might be important for crosstalk between ethylene and auxin hormones. (Managing editor: Li-Hui Zhao) [source] Overexpression of the Wounding-Responsive Gene AtMYB15 Activates the Shikimate Pathway in ArabidopsisJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 9 2006Yanhui Chen Abstract The MYB transcription factor genes play important roles in many developmental processes and various defense responses of plants. The shikimate pathway is a major biosynthetic pathway for the production of three aromatic amino acids and other aromatic compounds that are involved in multiple responses of plants, including protection against UV and defense. Herein, we describe the characterization of the R2R3-MYB gene AtMYB15 as an activator of the shikimate pathway in Arabidopsis. The AtMYB15 protein is nuclear localized and a transcriptional activation domain is found in its C-terminal portion. Northern blots showed that AtMYB15 is an early wounding-inducible gene. Resutls of microarray analysis, confirmed using quantitative real-time polymerase chain reaction, showed that overexpression of AtMYB15 in transgenic plants resulted in elevated expression of almost all the genes involved in the shikimate pathway. Bioinformatics analysis showed that one or more AtMYB15-binding AC elements were detected in the promoters of these upregulated genes. Furthermore, these genes in the shikimate pathway were also found to be induced by wounding. These data suggest an important role of AtMYB15 as a possible direct regulator of the Arabidopsis shikimate pathway in response to wounding. (Managing editor: Ya-Qin Han) [source] Isolation and Expression Analysis of Two Cold-Inducible Genes Encoding Putative CBF Transcription Factors from Chinese Cabbage (Brassica pekinensis Rupr.)JOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 7 2006Yong Zhang Abstract Two homologous genes of the Arabidopsis C-repeat/dehydration-responsive element binding factors (CBF/DREB1) transcriptional activator were isolated by RT-PCR from Chinese cabbage (Brassica pekinensis Rupr. cv. Qinbai 5) and were designated as BcCBF1 and BcCBF2. Each encodes a putative CBF/DREB1 protein with an AP2 (Apetal2) DNA-binding domain, a putative nuclear localization signal, and a possible acidic activation domain. Deduced amino acid sequences show that BcCBF1 is very similar to the Arabidopsis CBF1, whereas BcCBF2 is different in that it contains two extra regions of 24 and 20 amino acids in the acidic domain. The mRNA accumulation profiles indicated that the expression of BcCBF1 and BcCBF2 is strongly induced by cold treatment, but does not respond similarly to dehydration or abscisic acid (ABA) treatment. However, the cold-induced accumulation of BcCBF2 mRNA was rapid but short-lived compared with that of BcCBF1. The mRNA levels of both BcCBF1 and BcCBF2 were higher in leaves than in roots when plants were exposed to cold, whereas, salt stress caused higher accumulation of BcCBF2 mRNA in roots than in leaves, suggesting that the organ specificity of the gene expression of the BcCBFs is probably stress dependent. In addition, the accumulation of BcCBF1 and BcCBF2 mRNAs was greatly enhanced by light compared with darkness when seedlings were exposed to cold. It is concluded that the two BcCBF proteins may be involved in the process of plant response to cold stress through an ABA-independent pathway and that there is also a cross-talk between the light signaling conduction pathway and the cold response pathway in B. pekinensis as in Arabidopsis. (Managing editor: Li-Hui Zhao) [source] Florigen: One Found, More to Follow?JOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 6 2006Xuhong Yu Abstract Florigen(s) are molecules that are synthesized in response to appropriate photoperiods and transmitted from leaves to shoot apices to promote floral initiation. It has been recently discovered in Arabidopsis that mRNA of the FT gene acts as a florigen. In Arabidopsis, cryptochromes and phytochromes mediate long-day promotion of CO protein expression, which activates FT mRNA expression in leaves. FT mRNA is transmitted to the shoot apex, where it acts together with FD to activate transcription of floral meristem identity genes, resulting in floral initiation. The discovery of the molecular nature of a florigen was a major scientific breakthrough in 2005. (Managing editor: Li-Hui Zhao) [source] Gene Discovery and Functional Analyses in the Model Plant ArabidopsisJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 1 2006Cai-Ping Feng Abstract The present mini-review describes newer methods and strategies, including transposon and T-DNA insertions, TILLING, Deleteagene, and RNA interference, to functionally analyze genes of interest in the model plant Arabidopsis. The relative advantages and disadvantages of the systems are also discussed. (Managing editor: Ping He) [source] CHARACTERIZATION OF A DINOFLAGELLATE CRYPTOCHROME BLUE-LIGHT RECEPTOR WITH A POSSIBLE ROLE IN CIRCADIAN CONTROL OF THE CELL CYCLE,JOURNAL OF PHYCOLOGY, Issue 3 2007Stephanie A. Brunelle Karenia brevis (C. C. Davis) G. Hansen et Moestrup is a dinoflagellate responsible for red tides in the Gulf of Mexico. The signaling pathways regulating its cell cycle are of interest because they are the key to the formation of toxic blooms that cause mass marine animal die-offs and human illness. Karenia brevis displays phased cell division, in which cells enter S phase at precise times relative to the onset of light. Here, we demonstrate that a circadian rhythm underlies this behavior and that light quality affects the rate of cell-cycle progression: in blue light, K. brevis entered the S phase early relative to its behavior in white light of similar intensity, whereas in red light, K. brevis was not affected. A data base of 25,000 K. brevis expressed sequence tags (ESTs) revealed several sequences with similarity to cryptochrome blue-light receptors, but none related to known red-light receptors. We characterized the K. brevis cryptochrome (Kb CRY) and modeled its three-dimensional protein structure. Phylogenetic analysis of the photolyase/CRY gene family showed that Kb CRY is a member of the cryptochrome DASH (CRY DASH) clade. Western blotting with an antibody designed to bind a conserved peptide within Kb CRY identified a single band at ,55 kDa. Immunolocalization showed that Kb CRY, like CRY DASH in Arabidopsis, is localized to the chloroplast. This is the first blue-light receptor to be characterized in a dinoflagellate. As the Kb CRY appears to be the only blue-light receptor expressed, it is a likely candidate for circadian entrainment of the cell cycle. [source] Light and Electron Microscopy of the Compatible Interaction Between Arabidopsis and the Downy Mildew Pathogen Peronospora parasiticaJOURNAL OF PHYTOPATHOLOGY, Issue 6 2003E. M. Soylu Abstract In this study, we focused on compatible interactions between Peronospora parasitica isolate Emoy-2 and wild-type (Oy-0) and mutant (Ws- eds1) Arabidopsis thaliana accessions by using light and transmission electron microscopy (TEM). Light microscopy of compatible interactions revealed that conidia germinated and penetrated through the anticlinal cell walls of two epidermal cells. Rapid spreading of the hyphal growth with formation of numerous haustoria within the mesophyll cells was subsequently followed by profuse sporulation in the absence of host cell necrosis on both wild-type and mutant accessions. TEM observations revealed that coenocytic intercellular hyphae ramified and spread intercellularly throughout the host tissue forming several haustoria in host mesophyll cells. Intracellular haustoria were lobed with the diameter of 6,7 ,m. Each haustorium was connected to intercellular hyphae in the absence of apparent haustorial neck. The cytoplasm of the haustorium included the organelles characteristic of the pathogen. Callose-like deposits were frequently observed at sites of penetration around the proximal region of the haustorial neck. Apart from a few callose ensheatments, no obvious response was observed in host cells following formation of haustoria. Most of mesophyll cells contained normal haustoria and the host cytoplasm displayed a high degree of structural integrity. Absence of host cell wall alteration and cell death in penetrated host cell of both accessions suggest that the pathogen exerts considerable control over basic cellular processes and in this respect, response to this biotroph oomycete differs considerably from responses to other pathogens such as necrotrophs. [source] Extreme breeding: Leveraging genomics for crop improvementJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 6 2007Siobhan M Brady Abstract The genomic revolution has led to dramatic increases in our understanding of plant biology in the past 10 years, especially in model plant species such as Arabidopsis. The technologies associated with this revolution, such as tilling, array mapping, and association mapping, will see widespread application to crop improvement in the near future. The genes for desirable traits identified through such efforts may be introgressed at an accelerated rate into elite germplasm by marker-assisted breeding. Copyright © 2007 Society of Chemical Industry [source] | |||||||||||||||||||||||||