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Arabidopsis Thaliana Mutants (arabidopsi + thaliana_mutant)
Selected AbstractsBacterial chemoattraction towards jasmonate plays a role in the entry of Dickeya dadantii through wounded tissuesMOLECULAR MICROBIOLOGY, Issue 3 2009Maria Antunez-Lamas Summary Jasmonate is a key signalling compound in plant defence that is synthesized in wounded tissues. In this work, we have found that this molecule is also a strong chemoattractant for the phythopathogenic bacteria Dickeya dadantii (ex- Erwinia chysanthemi). Jasmonic acid induced the expression of a subset of bacterial genes possibly involved in virulence/survival in the plant apoplast and bacterial cells pre-treated with jasmonate showed increased virulence in chicory and Saintpaulia leaves. We also showed that tissue wounding induced bacterial spread through the leaf surface. Moreover, the jasmonate-deficient aos1 Arabidopsis thaliana mutant was more resistant to bacterial invasion by D. dadantii than wild-type plants. These results are consistent with the hypothesis that sensing jasmonic acid by this bacterium helps the pathogen to ingress inside plant tissues. [source] A UVB-hypersensitive mutant in Arabidopsis thaliana is defective in the DNA damage responseTHE PLANT JOURNAL, Issue 3 2009Ayako N. Sakamoto Summary To investigate UVB DNA damage response in higher plants, we used a genetic screen to isolate Arabidopsis thaliana mutants that are hypersensitive to UVB irradiation, and isolated a UVB-sensitive mutant, termed suv2 (for sensitive to UV 2) that also displayed hypersensitivity to ,-radiation and hydroxyurea. This phenotype is reminiscent of the Arabidopsis DNA damage-response mutant atr. The suv2 mutation was mapped to the bottom of chromosome 5, and contains an insertion in an unknown gene annotated as MRA19.1. RT-PCR analysis with specific primers to MRA19.1 detected a transcript consisting of 12 exons. The transcript is predicted to encode a 646 amino acid protein that contains a coiled-coil domain and two instances of predicted PIKK target sequences within the N-terminal region. Fusion proteins consisting of the predicted MRA19.1 and DNA-binding or activation domain of yeast transcription factor GAL4 interacted with each other in a yeast two-hybrid system, suggesting that the proteins form a homodimer. Expression of CYCB1;1:GUS gene, which encodes a labile cyclin:GUS fusion protein to monitor mitotic activity by GUS activity, was weaker in the suv2 plant after ,-irradiation than in the wild-type plants and was similar to that in the atr plants, suggesting that the suv2 mutant is defective in cell-cycle arrest in response to DNA damage. Overall, these results suggest that the gene disrupted in the suv2 mutant encodes an Arabidopsis homologue of the ATR-interacting protein ATRIP. [source] The Arabidopsis her1 mutant implicates GABA in E -2-hexenal responsivenessTHE PLANT JOURNAL, Issue 2 2008Rossana Mirabella Summary When wounded or attacked by herbivores or pathogens, plants produce a blend of six-carbon alcohols, aldehydes and esters, known as C6-volatiles. Undamaged plants, when exposed to C6-volatiles, respond by inducing defense-related genes and secondary metabolites, suggesting that C6-volatiles can act as signaling molecules regulating plant defense responses. However, to date, the molecular mechanisms by which plants perceive and respond to these volatiles are unknown. To elucidate such mechanisms, we decided to isolate Arabidopsis thaliana mutants in which responses to C6-volatiles were altered. We observed that treatment of Arabidopsis seedlings with the C6-volatile E -2-hexenal inhibits root elongation. Among C6-volatiles this response is specific to E -2-hexenal, and is not dependent on ethylene, jasmonic and salicylic acid. Using this bioassay, we isolated 18 E -2-hexenal-response (her) mutants that showed sustained root growth after E -2-hexenal treatment. Here, we focused on the molecular characterization of one of these mutants, her1. Microarray and map-based cloning revealed that her1 encodes a ,-amino butyric acid transaminase (GABA-TP), an enzyme that degrades GABA. As a consequence of the mutation, her1 plants accumulate high GABA levels in all their organs. Based on the observation that E -2-hexenal treatment induces GABA accumulation, and that high GABA levels confer resistance to E -2-hexenal, we propose a role for GABA in mediating E -2-hexenal responses. [source] ABA-Hypersensitive Germination1 encodes a protein phosphatase 2C, an essential component of abscisic acid signaling in Arabidopsis seedTHE PLANT JOURNAL, Issue 6 2007Noriyuki Nishimura Summary The phytohormone abscisic acid (ABA) regulates physiologically important stress and developmental responses in plants. To reveal the mechanism of response to ABA, we isolated several novel ABA-hypersensitive Arabidopsis thaliana mutants, named ahg (ABA- hypersensitive germination). ahg1-1 mutants showed hypersensitivity to ABA, NaCl, KCl, mannitol, glucose and sucrose during germination and post-germination growth, but did not display any significant phenotypes in adult plants. ahg1-1 seeds accumulated slightly more ABA before stratification and showed increased seed dormancy. Map-based cloning of AHG1 revealed that ahg1-1 has a nonsense mutation in a gene encoding a novel protein phosphatase 2C (PP2C). We previously showed that the ahg3-1 mutant has a point mutation in the AtPP2CA gene, which encodes another PP2C that has a major role in the ABA response in seeds (Yoshida et al., 2006b). The levels of AHG1 mRNA were higher in dry seeds and increased during late seed maturation , an expression pattern similar to that of ABI5. Transcriptome analysis revealed that, in ABA-treated germinating seeds, many seed-specific genes and ABA-inducible genes were highly expressed in ahg1-1 and ahg3-1 mutants compared with the wild-type. Detailed analysis suggested differences between the functions of AHG1 and AHG3. Dozens of genes were expressed more strongly in the ahg1-1 mutant than in ahg3-1. Promoter,GUS analyses demonstrated both overlapping and distinct expression patterns in seed. In addition, the ahg1-1 ahg3-1 double mutant was more hypersensitive than either monogenic mutant. These results suggest that AHG1 has specific functions in seed development and germination, shared partly with AHG3. [source] Large-scale screening of Arabidopsis circadian clock mutants by a high-throughput real-time bioluminescence monitoring systemTHE PLANT JOURNAL, Issue 1 2004Kiyoshi Onai Summary Using a high-throughput real-time bioluminescence monitoring system, we screened large numbers of Arabidopsis thaliana mutants for extensively altered circadian rhythms. We constructed reporter genes by fusing a promoter of an Arabidopsis flowering-time gene , either GIGANTEA (GI) or FLOWERING LOCUS T (FT) , to a modified firefly luciferase gene (LUC+), and we transferred the fusion gene (PGI::LUC+ or PFT::LUC+) into the Arabidopsis genome. After mutagenesis with ethyl methanesulfonate, 50 000 M2 seedlings carrying the PGI::LUC+ and 50 000 carrying PFT::LUC+ were screened their bioluminescence rhythms. We isolated six arrhythmic (AR) mutants and 29 other mutants that showed more than 3 h difference in the period length or phase of rhythms compared with the wild-type strains. The shortest period length was 16 h, the longest 27 h. Five of the six AR mutants carrying PGI::LUC+ showed arrhythmia in bioluminescence rhythms in both constant light and constant dark. These five AR mutants also showed arrhythmia in leaf movement rhythms in constant light. Genetic analysis revealed that each of the five AR mutants carried a recessive mutation in a nuclear gene and the mutations belonged to three complementation groups, and at least one of which was mapped on a novel locus. Our results suggest that the three loci identified here may contain central clock or clock-related genes, at least one of which may be a novel. [source] Singlet Energy Dissipation in the Photosystem II Light-Harvesting Complex Does Not Involve Energy Transfer to CarotenoidsCHEMPHYSCHEM, Issue 6 2010Marc G. Müller Dr. Abstract The energy dissipation mechanism in oligomers of the major light-harvesting complex II (LHC II) from Arabidopsis thaliana mutants npq1 and npq2, zeaxanthin-deficient and zeaxanthin-enriched, respectively, has been studied by femtosecond transient absorption. The kinetics obtained at different excitation intensities are compared and the implications of singlet,singlet annihilation are discussed. Under conditions where annihilation is absent, the two types of LHC II oligomers show distributive biexponential (bimodal) kinetics with lifetimes of ,5,20 ps and ,200,400 ps having transient spectra typical for chlorophyll excited states. The data can be described kinetically by a two-state compartment model involving only chlorophyll excited states. Evidence is provided that neither carotenoid excited nor carotenoid radical states are involved in the quenching mechanism at variance with earlier proposals. We propose instead that a chlorophyll,chlorophyll charge-transfer state is formed in LHC II oligomers which is an intermediate in the quenching process. The relevance to non-photochemical quenching in vivo is discussed. [source] | ||||||||||