Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 27
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Plant Cell Physiol ; 61(4): 712-721, 2020 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-31879778

RESUMO

Development of pollen, the male gametophyte of flowering plants, is tightly controlled by dynamic changes in gene expression. Recent research to clarify the molecular aspects of pollen development has revealed the involvement of several transcription factors in the induction of gene expression. However, limited information is available about the factors involved in the negative regulation of gene expression to eliminate unnecessary transcripts during pollen development. In this study, we revealed that AtNOT1 is an essential protein for proper pollen development and germination capacity. AtNOT1 is a scaffold protein of the AtCCR4-NOT complex, which includes multiple components related to mRNA turnover control in Arabidopsis. Phenotypic analysis using atnot1 heterozygote mutant pollen showed that the mature mutant pollen failed to germinate and also revealed abnormal localization of nuclei and a specific protein at the tricellular pollen stage. Furthermore, transcriptome analysis of atnot1 heterozygote mutant pollen showed that the downregulation of a large number of transcripts, along with the upregulation of specific transcripts required for pollen tube germination by AtNOT1 during late microgametogenesis, is important for proper pollen development and germination. Overall, our findings provide new insights into the negative regulation of gene expression during pollen development, by showing the severely defective phonotype of atnot1 heterozygote mutant pollen.

2.
Plant Biotechnol (Tokyo) ; 36(2): 107-112, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31768111

RESUMO

As major components of the ubiquitin system, ubiquitin ligases mediate the transfer of ubiquitin to specific target substrates, thereby playing important roles in regulating a wide range of cellular processes. The Arabidopsis Tóxicos en Levadura (ATL) family is a group of plant-specific RING-type ubiquitin ligases with N-terminal transmembrane-like domains. To date, 91 ATL isoforms have been identified in the Arabidopsis genome, with some reported to regulate plant responses to environmental stresses. However, the functions of most ATLs remain unclear. This study showed that ATL8 is a sugar starvation response gene and that ATL8 expression was significantly increased by sugar starvation conditions but repressed by exogenous sugar supply. The ATL8 protein was found to possess ubiquitin ligase activity in vitro and to localize to membrane-bound compartments in plant cells. In addition, Starch Synthase 4 was identified as a putative interactor with ATL8, suggesting that ATL8 may be involved in modulating starch accumulation in response to sugar availability. These findings suggest that ATL8 functions as a membrane-localized ubiquitin ligase likely to be involved in the adaptation of Arabidopsis plants to sugar starvation stress.

3.
Plant Cell Physiol ; 60(9): 2015-2025, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31093672

RESUMO

CCR4/CAF1 are widely conserved deadenylases in eukaryotes. They form a large complex that includes NOT1 as a scaffold protein and various NOT proteins that are core components of multiple levels of gene expression control. The CCR4-NOT complex also contains several RNA-binding proteins as accessory proteins, which are required for target recognition by CCR4/CAF1 deadenylases. AtCCR4a/b, orthologs of human CCR4 in Arabidopsis, have various physiological effects. AtCCR4 isoforms are likely to have specific target mRNAs related to each physiological effect; however, AtCCR4 does not have RNA-binding capability. Therefore, identifying factors that interact with AtCCR4a/b is indispensable to understand its function as a regulator of gene expression, as well as the target mRNA recognition mechanism. Here, we identified putative components of the AtCCR4-NOT complex using co-immunoprecipitation in combination with mass spectrometry using FLAG-tagged AtCCR4b and subsequent verification with a yeast two-hybrid assay. Interestingly, four of 11 AtCAF1 isoforms interacted with both AtCCR4b and AtNOT1, whereas two isoforms interacted only with AtNOT1 in yeast two-hybrid assays. These results imply that Arabidopsis has multiple CCR4-NOT complexes with various combinations of deadenylases. We also revealed that the RNA-binding protein Arabidopsis Pumilio 5 and 2 interacted with AtCCR4a/b in the cytoplasm with a few foci.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Proteínas de Ligação a RNA/metabolismo , Proteínas Repressoras/metabolismo , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Citoplasma/metabolismo , Filogenia , Isoformas de Proteínas , Proteínas de Ligação a RNA/genética , Receptores CCR4/genética , Proteínas Repressoras/genética , Técnicas do Sistema de Duplo-Híbrido
4.
Biochem Biophys Res Commun ; 491(1): 33-39, 2017 09 09.
Artigo em Inglês | MEDLINE | ID: mdl-28690153

RESUMO

Ubiquitin ligases play important roles in regulating various cellular processes by modulating the protein function of specific ubiquitination targets. The Arabidopsis Tóxicos en Levadura (ATL) family is a group of plant-specific RING-type ubiquitin ligases that localize to membranes via their N-terminal transmembrane-like domains. To date, 91 ATL isoforms have been identified in the Arabidopsis genome, with several ATLs reported to be involved in regulating plant responses to environmental stresses. However, the functions of most ATLs remain unknown. This study, involving transcriptome database analysis, identifies ATL15 as a sugar responsive ATL gene in Arabidopsis. ATL15 expression was rapidly down-regulated in the presence of sugar. The ATL15 protein showed ubiquitin ligase activity in vitro and localized to plasma membrane and endomembrane compartments. Further genetic analyses demonstrated that the atl15 knockout mutants are insensitive to high glucose concentrations, whereas ATL15 overexpression depresses plant growth. In addition, endogenous glucose and starch amounts were reciprocally affected in the atl15 knockout mutants and the ATL15 overexpressors. These results suggest that ATL15 protein plays a significant role as a membrane-localized ubiquitin ligase that regulates sugar-responsive plant growth in Arabidopsis.


Assuntos
Arabidopsis/enzimologia , Arabidopsis/crescimento & desenvolvimento , Membrana Celular/enzimologia , Glucose/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Ubiquitina/metabolismo , Proteínas de Arabidopsis/metabolismo , Regulação da Expressão Gênica de Plantas/fisiologia , Ubiquitinação/fisiologia
5.
Plant Cell Physiol ; 58(6): 1090-1102, 2017 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-28444357

RESUMO

Plants possess a cold acclimation system to acquire freezing tolerance through pre-exposure to non-freezing low temperatures. The transcriptional cascade of C-repeat-binding factors (CBFs)/dehydration response element-binding factors (DREBs) is considered a major transcriptional regulatory pathway during cold acclimation. However, little is known regarding the functional significance of mRNA stability regulation in the response of gene expression to cold stress. The actual level of individual mRNAs is determined by a balance between mRNA synthesis and degradation. Therefore, it is important to assess the regulatory steps to increase our understanding of gene regulation. Here, we analyzed temporal changes in mRNA amounts and half-lives in response to cold stress in Arabidopsis cell cultures based on genome-wide analysis. In this mRNA decay array method, mRNA half-life measurements and microarray analyses were combined. In addition, temporal changes in the integrated value of transcription rates were estimated from the above two parameters using a mathematical approach. Our results showed that several cold-responsive genes, including Cold-regulated 15a, were relatively destabilized, whereas the mRNA amounts were increased during cold treatment by accelerating the transcription rate to overcome the destabilization. Considering the kinetics of mRNA synthesis and degradation, this apparently contradictory result supports that mRNA destabilization is advantageous for the swift increase in CBF-responsive genes in response to cold stress.


Assuntos
Arabidopsis/metabolismo , RNA Mensageiro/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Temperatura Baixa , Regulação da Expressão Gênica de Plantas/genética , Regulação da Expressão Gênica de Plantas/fisiologia , Estabilidade de RNA/genética , Estabilidade de RNA/fisiologia , RNA Mensageiro/genética , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Transcrição Genética/genética , Transcrição Genética/fisiologia
6.
Inorg Chem ; 56(1): 138-146, 2017 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-27976888

RESUMO

Magnetic properties of dinuclear nickel(II) complex [Ni2(sym-hmp)2](BPh4)2·3.5DMF·0.5(2-PrOH) (1), where (sym-hmp)- is 2,6-bis[(2-hydroxyethyl)methylaminomethyl]-4-methylphenolate anion and DMF indicates dimethylformamide, were investigated using high-frequency and -field electron paramagnetic resonance (HFEPR). To magnetically characterize the mononuclear nickel(II) species forming the dimer, its two dinuclear zinc(II) analogues, [Zn2(sym-hmp)2](BPh4)2·3.5DMF·0.5(2-PrOH) (2) and [Zn2(sym-hmp)2](BPh4)2·2acetone·2H2O (2'), were prepared. One of them (2') was structurally characterized by X-ray diffractometry and doped with 5% mol nickel(II) ions to prepare a mixed crystal 3. From the HFEPR results on complex 1 obtained at 40 K, the spin Hamiltonian parameters of the first excited spin state (S = 1) of the dimer were accurately determined as |D1| = 9.99(2) cm-1, |E1| = 1.62(1) cm-1, and g1 = [2.25(1), 2.19(2), 2.27(2)], and for the second excited spin state (S = 2) at 150 K estimated as |D2| ≈ 3.5 cm-1. From these numbers, the single-ion zero-field splitting (ZFS) parameter of the Ni(II) ions forming the dimer was estimated as |DNi| ≈ 10-10.5 cm-1. The HFEPR spectra of 3 yielded directly the single-ion parameters for DNi = +10.1 cm-1, |ENi| = 3.1 cm-1, and giso = 2.2. On the basis of the HFEPR results, the previously obtained magnetic data (Sakiyama, H.; Tone, K.; Yamasaki, M.; Mikuriya, M. Inorg. Chim. Acta 2011, 365, 183) were reanalyzed, and the isotropic interaction parameter between the Ni(II) ions was determined as J = -70 cm-1 (Hex = -J SA·SB). Finally, density functional theory calculations yielded the J value of -90 cm-1 in a qualitative agreement with the experiment.

7.
Plant Cell ; 28(11): 2830-2849, 2016 11.
Artigo em Inglês | MEDLINE | ID: mdl-27760805

RESUMO

Upstream open reading frames (uORFs) are often translated ahead of the main ORF of a gene and regulate gene expression, sometimes in a condition-dependent manner, but such a role for the minimum uORF (hereafter referred to as AUG-stop) in living organisms is currently unclear. Here, we show that AUG-stop plays an important role in the boron (B)-dependent regulation of NIP5;1, encoding a boric acid channel required for normal growth under low B conditions in Arabidopsis thaliana High B enhanced ribosome stalling at AUG-stop, which was accompanied by the suppression of translation and mRNA degradation. This mRNA degradation was promoted by an upstream conserved sequence present near the 5'-edge of the stalled ribosome. Once ribosomes translate a uORF, reinitiation of translation must take place in order for the downstream ORF to be translated. Our results suggest that reinitiation of translation at the downstream NIP5;1 ORF is enhanced under low B conditions. A genome-wide analysis identified two additional B-responsive genes, SKU5 and the transcription factor gene ABS/NGAL1, which were regulated by B-dependent ribosome stalling through AUG-stop. This regulation was reproduced in both plant and animal transient expression and cell-free translation systems. These findings suggest that B-dependent AUG-stop-mediated regulation is common in eukaryotes.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Boro/metabolismo , Regulação da Expressão Gênica de Plantas , Fases de Leitura Aberta/genética , Estabilidade de RNA/fisiologia , Ribossomos/metabolismo , Aquaporinas/genética , Aquaporinas/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Glicoproteínas de Membrana/genética , Glicoproteínas de Membrana/metabolismo , Fases de Leitura Aberta/fisiologia , Estabilidade de RNA/genética , Ribossomos/genética , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
8.
Chemistry ; 22(2): 724-35, 2016 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-26728231

RESUMO

Polarized neutron diffraction (PND) experiments were carried out at low temperature to characterize with high precision the local magnetic anisotropy in two paramagnetic high-spin cobalt(II) complexes, namely [Co(II) (dmf)6 ](BPh4 )2 (1) and [Co(II) 2 (sym-hmp)2 ](BPh4 )2 (2), in which dmf=N,N-dimethylformamide; sym-hmp=2,6-bis[(2-hydroxyethyl)methylaminomethyl]-4-methylphenolate, and BPh4 (-) =tetraphenylborate. This allowed a unique and direct determination of the local magnetic susceptibility tensor on each individual Co(II) site. In compound 1, this approach reveals the correlation between the single-ion easy magnetization direction and a trigonal elongation axis of the Co(II) coordination octahedron. In exchange-coupled dimer 2, the determination of the individual Co(II) magnetic susceptibility tensors provides a clear outlook of how the local magnetic properties on both Co(II) sites deviate from the single-ion behavior because of antiferromagnetic exchange coupling.

9.
Plant Cell Physiol ; 56(5): 863-74, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-25630334

RESUMO

Removing the poly(A) tail is the first and rate-limiting step of mRNA degradation and apparently an effective step not only for modulating mRNA stability but also for translation of many eukaryotic transcripts. Carbon catabolite repressor 4 (CCR4) has been identified as a major cytoplasmic deadenylase in Saccharomyces cerevisiae. The Arabidopsis thaliana homologs of the yeast CCR4, AtCCR4a and AtCCR4b, were identified by sequence-based analysis; however, their role and physiological significance in plants remain to be elucidated. In this study, we revealed that AtCCR4a and AtCCR4b are localized to cytoplasmic mRNA processing bodies, which are specific granules consisting of many enzymes involved in mRNA turnover. Double mutants of AtCCR4a and AtCCR4b exhibited tolerance to sucrose application but not to glucose. The levels of sucrose in the seedlings of the atccr4a/4b double mutants were reduced, whereas no difference was observed in glucose levels. Further, amylose levels were slightly but significantly increased in the atccr4a/4b double mutants. Consistent with this observation, we found that the transcript encoding granule-bound starch synthase 1 (GBSS1), which is responsible for amylose synthesis, is accumulated to a higher level in the atccr4a/4b double mutant plants than in the control plants. Moreover, we revealed that GBSS1 has a longer poly(A) tail in the double mutant than in the control plant, suggesting that AtCCR4a and AtCCR4b can influence the poly(A) length of transcripts related to starch metabolism. Our results collectively suggested that AtCCR4a and AtCCR4b are involved in sucrose and starch metabolism in A. thaliana.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Poli A/metabolismo , Proteínas Repressoras/metabolismo , Sintase do Amido/metabolismo , Amido/metabolismo , Sacarose/metabolismo , Amilose/metabolismo , Arabidopsis/efeitos dos fármacos , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Mutação/genética , Fenótipo , Transporte Proteico/efeitos dos fármacos , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Proteínas Repressoras/genética , Sintase do Amido/genética , Sacarose/farmacologia
10.
Ecol Lett ; 17(10): 1299-309, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-25103959

RESUMO

The role of resource availability in determining the incidence of masting has been widely studied, but how floral transition and initiation are regulated by the resource level is unclear. We tested the hypothesis that floral transition is stimulated by high resource availabiltiy in Fagus crenata based on a new technique, the expression analyses of flowering genes. We isolated F. crenata orthologues of FLOWERING LOCUS T, LEAFY and APETALA1, and confirmed their functions using transgenic Arabidopsis thaliana. We monitored the gene expression levels for 5 years and detected a cycle of on and off years, which was correlated with fluctuations of the shoot-nitrogen concentration. Nitrogen fertilisation resulted in the significantly higher expression of flowering genes than the control, where all of the fertilised trees flowered, whereas the control did not. Our findings identified nitrogen as a key regulator of mast flowering, thereby providing new empirical evidence to support the resource budget model.


Assuntos
Fagus/genética , Flores/fisiologia , Regulação da Expressão Gênica de Plantas , Nitrogênio/fisiologia , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Carboidratos/análise , Fagus/fisiologia , Genes de Plantas , Japão , Proteínas de Domínio MADS/genética , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/fisiologia , Estações do Ano , Fatores de Transcrição/genética
11.
BMC Syst Biol ; 8 Suppl 5: S4, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25559748

RESUMO

BACKGROUND: Progress in systems biology offers sophisticated approaches toward a comprehensive understanding of biological systems. Yet, computational analyses are held back due to difficulties in determining suitable model parameter values from experimental data which naturally are subject to biological fluctuations. The data may also be corrupted by experimental uncertainties and sometimes do not contain all information regarding variables that cannot be measured for technical reasons. RESULTS: We show here a streamlined approach for the construction of a coarse model that allows us to set up dynamic models with minimal input information. The approach uses a hybrid between a pure mass action system and a generalized mass action (GMA) system in the framework of biochemical systems theory (BST) with rate constants of 1, normal kinetic orders of 1, and -0.5 and 0.5 for inhibitory and activating effects, named Unity (U)-system. The U-system model does not necessarily fit all data well but is often sufficient for predicting metabolic behavior of metabolites which cannot be simultaneously measured, identifying inconsistencies between experimental data and the assumed underlying pathway structure, as well as predicting system responses to a modification of gene or enzyme. The U-system approach was validated with small, generic systems and implemented to model a large-scale metabolic reaction network of a higher plant, Arabidopsis. The dynamic behaviors obtained by predictive simulations agreed with actually available metabolomic time-series data, identified probable errors in the experimental datasets, and estimated probable behavior of unmeasurable metabolites in a qualitative manner. The model could also predict metabolic responses of Arabidopsis with altered network structures due to genetic modification. CONCLUSIONS: The U-system approach can effectively predict metabolic behaviors and responses based on structures of an alleged metabolic reaction network. Thus, it can be a useful first-line tool of data analysis, model diagnostics and aid the design of next-step experiments.


Assuntos
Algoritmos , Metaboloma/fisiologia , Modelos Biológicos , Modelos Estatísticos , Proteoma/metabolismo , Transdução de Sinais/fisiologia , Animais , Humanos , Metabolômica/métodos , Método de Monte Carlo
12.
Plant Sci ; 213: 79-87, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-24157210

RESUMO

Complex plant defenses that include the hypersensitive response (HR) are mediated by plant hormones, such as salicylic acid (SA), jasmonic acid (JA) and ethylene. We previously isolated the Arabidopsis DEAR1 (DREB AND EAR MOTIF PROTEIN 1) regulator and showed that its overexpression DEAR1 (DEAR1ox) resulted in a dwarf phenotype and lesion-like cell death, accompanied by elevated expression of PR (PATHOGENESIS-RELATED) genes. Here, we show that transgenic Arabidopsis overexpressing DEAR1 (DEAR1ox) has enhanced resistance to the necrotrophic fungus Botrytis cinerea (B. cinerea). This result indicates that DEAR1 represses negative regulators of plant defense responses, including transcriptional repressors belonging to the ERF (ETHYLEN RESPONSE FACTOR) family. Knockout mutants of ERF9 (erf9), which were down-regulated in DEAR1ox plants, showed transcriptional promotion of PDF1.2 (PATHOGEN-INDUCIBLE PLANT DEFENSIN) genes, which serve as positive markers for the ethylene/jasmonic acid (JA) signaling pathway and provide enhanced resistance to B. cinerea. Biochemical assays demonstrated that the ERF9 in capable of binding to the GCC box, a cis-element contained in the promoters of the PDF1.2 gene that possesses trans-repression activity. Moreover, infection with B. cinerea resulted in the promotion of the PDF1.2 expression, coinciding with suppression of the ERF9 gene under the control of the DEAR1 gene. These results indicate that the transcriptional repressor ERF9 participates in plant defense mechanisms against necrotic fungi mediated by the DEAR1-dependent ethylene/JA signaling pathway.


Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Regulação da Expressão Gênica de Plantas , Doenças das Plantas/imunologia , Reguladores de Crescimento de Planta/metabolismo , Transdução de Sinais , Arabidopsis/imunologia , Arabidopsis/fisiologia , Proteínas de Arabidopsis/metabolismo , Botrytis/fisiologia , Núcleo Celular/metabolismo , Ciclopentanos/metabolismo , Defensinas/genética , Defensinas/metabolismo , Resistência à Doença , Etilenos/metabolismo , Expressão Gênica , Técnicas de Inativação de Genes , Modelos Moleculares , Oxilipinas/metabolismo , Doenças das Plantas/microbiologia , Plantas Geneticamente Modificadas , Regiões Promotoras Genéticas/genética , Pseudomonas syringae/fisiologia , Ácido Salicílico/metabolismo , Deleção de Sequência , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
13.
Nat Commun ; 4: 2303, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23941973

RESUMO

Understanding how climate warming has an impact on the life cycle schedule of terrestrial organisms is critical to evaluate ecosystem vulnerability to environmental change. Despite recent advances identifying the molecular basis of temperature responses, few studies have incorporated this knowledge into predictive models. Here we develop a method to forecast flowering phenology by modelling regulatory dynamics of key flowering-time genes in perennial life cycles. The model, parameterized by controlled laboratory experiments, accurately reproduces the seasonal changes in gene expression, the corresponding timing of floral initiation and return to vegetative growth after a period of flowering in complex natural environments. A striking scenario forecast by the model under climate warming is that the shift in the return time to vegetative growth is greater than that in floral initiation, which results in a significant reduction of the flowering period. Our study demonstrates the usefulness of gene expression assessment to predict unexplored risks of climate change.


Assuntos
Arabidopsis/crescimento & desenvolvimento , Arabidopsis/fisiologia , Mudança Climática , Flores/crescimento & desenvolvimento , Animais , Arabidopsis/genética , Flores/genética , Perfilação da Expressão Gênica , Estágios do Ciclo de Vida/genética , Estágios do Ciclo de Vida/fisiologia , Modelos Teóricos , Dados de Sequência Molecular , Fotoperíodo , Estações do Ano , Temperatura
14.
Plant Cell Physiol ; 54(5): 728-39, 2013 May.
Artigo em Inglês | MEDLINE | ID: mdl-23574698

RESUMO

Metabolomics analysis tools can provide quantitative information on the concentration of metabolites in an organism. In this paper, we propose the minimum pathway model generator tool for simulating the dynamics of metabolite concentrations (SS-mPMG) and a tool for parameter estimation by genetic algorithm (SS-GA). SS-mPMG can extract a subsystem of the metabolic network from the genome-scale pathway maps to reduce the complexity of the simulation model and automatically construct a dynamic simulator to evaluate the experimentally observed behavior of metabolites. Using this tool, we show that stochastic simulation can reproduce experimentally observed dynamics of amino acid biosynthesis in Arabidopsis thaliana. In this simulation, SS-mPMG extracts the metabolic network subsystem from published databases. The parameters needed for the simulation are determined using a genetic algorithm to fit the simulation results to the experimental data. We expect that SS-mPMG and SS-GA will help researchers to create relevant metabolic networks and carry out simulations of metabolic reactions derived from metabolomics data.


Assuntos
Algoritmos , Arabidopsis/metabolismo , Simulação por Computador , Redes e Vias Metabólicas , Metabolômica , Cinética , Modelos Biológicos , Análise de Componente Principal , Processos Estocásticos
15.
Genes Genet Syst ; 88(4): 241-9, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24463527

RESUMO

Cystathionine γ-synthase (CGS) catalyzes the first committed step of methionine (Met) biosynthesis in plants. Expression of the Arabidopsis thaliana CGS1 gene is negatively feedback-regulated in response to the direct Met metabolite S-adenosyl-L-methionine (AdoMet). This regulation occurs at the step of mRNA stability during translation and is coupled with AdoMet-induced CGS1-specific translation arrest. In general, mRNA decay is initiated by a shortening of the poly(A) tail. However, this process has not been studied in detail in cases where regulatory events, such as programmed translation arrest, are involved. Here, we report that the poly(A) tail of the full-length CGS1 mRNA showed an apparent increase from 50-80 nucleotides (nt) to 140-150 nt after the induction of CGS1 mRNA degradation. This finding was unexpected because mRNAs that are destined for degradation harbored longer poly(A) tail than mRNAs that were not targeted for degradation. The results suggest that poly(A) shortening is inhibited or delayed during AdoMet-induced translation arrest of CGS1 mRNA. We propose an explanation for this phenomenon that remains consistent with the recent model of actively translating mRNA. We also found that CGS1 mRNA degradation intermediates, which are 5'-truncated forms of CGS1 mRNA, had a short poly(A) tail of 10-30 nt. This suggests that poly(A) shortening occurs rapidly on the degradation intermediates. The present study highlights CGS1 mRNA degradation as a useful system to understand the dynamic features of poly(A) shortening.


Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/enzimologia , Carbono-Oxigênio Liases/genética , Genes de Plantas , Metionina/biossíntese , Poli A/metabolismo , RNA Mensageiro/metabolismo , Arabidopsis/genética , Carbono-Oxigênio Liases/metabolismo , Regulação da Expressão Gênica de Plantas , Mutação , Estabilidade de RNA , RNA de Plantas/metabolismo , Ribonuclease H/metabolismo , S-Adenosilmetionina/metabolismo
16.
Plant Cell Physiol ; 54(2): 180-94, 2013 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-23220693

RESUMO

Control of mRNA half-life is a powerful strategy to adjust individual mRNA levels to various stress conditions, because the mRNA degradation rate controls not only the steady-state mRNA level but also the transition speed of mRNA levels. Here, we analyzed mRNA half-life changes in response to cold stress in Arabidopsis cells using genome-wide analysis, in which mRNA half-life measurements and transcriptome analysis were combined. Half-lives of average transcripts were determined to be elongated under cold conditions. Taking this general shift into account, we identified more than a thousand transcripts that were classified as relatively stabilized or relatively destabilized. The relatively stabilized class was predominantly observed in functional categories that included various regulators involved in transcriptional, post-transcriptional and post-translational processes. On the other hand, the relatively destabilized class was enriched in categories related to stress and hormonal response proteins, supporting the idea that rapid decay of mRNA is advantageous for swift responses to stress. In addition, pentatricopeptide repeat, cyclin-like F-box and Myb transcription factor protein families were significantly over-represented in the relatively destabilized class. The global analysis presented here demonstrates not only the importance of mRNA turnover control in the cold stress response but also several structural characteristics that might be important in the control of mRNA stability.


Assuntos
Arabidopsis/genética , Regulação da Expressão Gênica de Plantas , Estabilidade de RNA , RNA Mensageiro/genética , RNA de Plantas/genética , Estresse Fisiológico , Adaptação Fisiológica , Arabidopsis/efeitos dos fármacos , Arabidopsis/metabolismo , Células Cultivadas , Temperatura Baixa , Desoxiadenosinas/farmacologia , Meia-Vida , Células Vegetais/efeitos dos fármacos , Células Vegetais/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Estrutura Terciária de Proteína , RNA Mensageiro/metabolismo , RNA de Plantas/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fatores de Tempo , Transcrição Genética/efeitos dos fármacos
17.
Plant Physiol ; 160(3): 1491-7, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-22992512

RESUMO

Silicon (Si) is a beneficial element for plant growth. In barley (Hordeum vulgare), Si uptake by the roots is mainly mediated by a Si channel, Low Silicon1 (HvLsi1), and an efflux transporter, HvLsi2. However, transporters involved in the distribution of Si in the shoots have not been identified. Here, we report the functional characterization of a homolog of HvLsi1, HvLsi6. HvLsi6 showed permeability for Si and localized to the plasma membrane. At the vegetative growth stage, HvLsi6 was expressed in both the roots and shoots. The expression level was unaffected by Si supply. In the roots, HvLsi6 was localized in epidermis and cortex cells of the tips, while in the leaf blades and sheaths, HvLsi6 was only localized at parenchyma cells of vascular bundles. At the reproductive growth stage, high expression of HvLsi6 was also found in the nodes. HvLsi6 in node I was polarly located at the transfer cells surrounding the enlarged vascular bundles toward the numerous xylem vessels. These results suggest that HvLsi6 is involved in Si uptake in the root tips, xylem unloading of Si in leaf blade and sheath, and intervascular transfer of Si in the nodes. Furthermore, HvLsi2 was found to be localized at the parenchyma cell layer adjacent to the transfer cells with opposite polarity of HvLsi6, suggesting that the coupling of HvLsi6 and HvLsi2 is involved in the intervascular transfer of Si at the nodes. Si translocated via the enlarged vascular bundles is unloaded to the transfer cells by HvLsi6, followed by HvLsi2 to reload Si to the diffuse vascular bundles, which are connected to the upper part of the plant, especially the panicles, the ultimate Si sink.


Assuntos
Genes de Plantas/genética , Hordeum/genética , Hordeum/metabolismo , Proteínas de Membrana Transportadoras/genética , Proteínas de Plantas/genética , Silício/metabolismo , Animais , Transporte Biológico/genética , Perfilação da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Hordeum/citologia , Hordeum/crescimento & desenvolvimento , Espaço Intracelular/metabolismo , Cinética , Proteínas de Membrana Transportadoras/metabolismo , Oócitos/metabolismo , Filogenia , Folhas de Planta/metabolismo , Proteínas de Plantas/metabolismo , Raízes de Plantas/metabolismo , Xenopus laevis
18.
Plant Mol Biol ; 79(3): 217-27, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22481162

RESUMO

In higher plants, the metabolism of carbon (C) and nitrogen nutrients (N) is mutually regulated and referred to as the C and N balance (C/N). Plants are thus able to optimize their growth depending on their cellular C/N status. Arabidopsis ATL31 and ATL6 encode a RING-type ubiquitin ligases which play a critical role in the C/N status response (Sato et al. in Plant J 60:852-864, 2009). Since many ATL members are involved in the plant defense response, the present study evaluated whether the C/N response regulators ATL31 and ATL6 are involved in defense responses. Our results confirmed that ATL31 and ATL6 expression is up-regulated with the microbe-associated molecular patterns elicitors flg22 and chitin as well as with infections with Pseudomonas syringae pv. tomato DC3000 (Pst. DC3000). Moreover, transgenic plants overexpressing ATL31 and ATL6 displayed increased resistance to Pst. DC3000. In accordance with these data, loss of ATL31 and ATL6 function in an atl31 atl6 double knockout mutant resulted in reduced resistance to Pst. DC3000. In addition, the molecular cross-talk between C/N and the defense response was investigated by mining public databases. The analysis identified the transcription factors MYB51 and WRKY33, which are involved in the defense response, and their transcripts levels correlate closely with ATL31 and ATL6. Further study demonstrated that the expression of ATL31, ATL6 and defense marker genes including MYB51 and WRKY33 were regulated by C/N conditions. Taken together, these results indicate that ATL31 and ATL6 function as key components of both C/N regulation and the defense response in Arabidopsis.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/imunologia , Arabidopsis/metabolismo , Carbono/metabolismo , Nitrogênio/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Arabidopsis/genética , Arabidopsis/microbiologia , Proteínas de Arabidopsis/genética , Regulação da Expressão Gênica de Plantas/genética , Regulação da Expressão Gênica de Plantas/imunologia , Doenças das Plantas/imunologia , Doenças das Plantas/microbiologia , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/imunologia , Plantas Geneticamente Modificadas/metabolismo , Plantas Geneticamente Modificadas/microbiologia , Pseudomonas syringae/patogenicidade , Ubiquitina-Proteína Ligases/genética
19.
Plant Cell ; 23(9): 3547-59, 2011 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-21908722

RESUMO

Boron (B) is an essential plant micronutrient that is toxic at higher levels. NIP5;1 is a boric acid channel required for B uptake and growth under B deficiency. Accumulation of the NIP5;1 transcript is upregulated under B deficiency in Arabidopsis thaliana roots. To elucidate the mechanism of regulation, the 5' untranslated region (UTR) of NIP5;1 was tested for its ability to confer B-dependent regulation using ß-glucuronidase and green fluorescent protein as reporters. This analysis showed that the 5' UTR was involved in NIP5;1 transcript accumulation in response to B conditions. We also found that high-B conditions trigger NIP5;1 mRNA degradation and that the sequence from +182 to +200 bp in the 5' UTR is required for this mRNA destabilization. In the nip5;1-1 mutant background, a NIP5;1 complementation construct without the 5' UTR produced high levels of mRNA accumulation, increased B concentrations in tissues, and reduced growth under high-B conditions. These data suggest that the 5' UTR controls B-dependent NIP5;1 mRNA degradation and that NIP5;1 mRNA degradation is important for plant acclimation to high-B conditions.


Assuntos
Aclimatação , Aquaporinas/metabolismo , Proteínas de Arabidopsis/metabolismo , Arabidopsis/efeitos dos fármacos , Boro/farmacologia , Estabilidade de RNA , Regiões 5' não Traduzidas , Aquaporinas/genética , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Regulação da Expressão Gênica de Plantas , Dados de Sequência Molecular , Raízes de Plantas/genética , Raízes de Plantas/metabolismo , Plantas Geneticamente Modificadas/efeitos dos fármacos , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/metabolismo , Regiões Promotoras Genéticas , RNA Mensageiro/metabolismo , RNA de Plantas/metabolismo
20.
Plant Cell ; 21(7): 2133-42, 2009 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-19574435

RESUMO

Silicon (Si) uptake has been extensively examined in rice (Oryza sativa), but it is poorly understood in other gramineous crops. We identified Low Silicon Rice 2 (Lsi2)-like Si efflux transporters from two important gramineous crops: maize (Zea mays) and barley (Hordeum vulgare). Both maize and barley Lsi2 expressed in Xenopus laevis oocytes showed Si efflux transport activity. Furthermore, barley Lsi2 was able to recover Si uptake in a rice mutant defective in Si efflux. Maize and barley Lsi2 were only expressed in the roots. Expression of maize and barley Lsi2 was downregulated in response to exogenously applied Si. Moreover, there was a significant positive correlation between the ability of roots to absorb Si and the expression levels of Lsi2 in eight barley cultivars, suggesting that Lsi2 is a key Si transporter in barley. Immunostaining showed that maize and barley Lsi2 localized only at the endodermis, with no polarity. Protein gel blot analysis indicated that maize and barley Lsi2 localized on the plasma membrane. The unique features of maize and barley Si influx and efflux transporters, including their cell-type specificity and the lack of polarity of their localization in Lsi2, indicate that these crops have a different Si uptake system from that in rice.


Assuntos
Hordeum/metabolismo , Oryza/metabolismo , Proteínas de Plantas/fisiologia , Silício/metabolismo , Zea mays/metabolismo , Sequência de Aminoácidos , Western Blotting , DNA de Plantas/genética , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Regulação da Expressão Gênica de Plantas/genética , Teste de Complementação Genética , Genótipo , Hordeum/genética , Modelos Biológicos , Dados de Sequência Molecular , Oryza/genética , Filogenia , Proteínas de Plantas/química , Proteínas de Plantas/classificação , Proteínas de Plantas/genética , Homologia de Sequência de Aminoácidos , Silício/farmacologia , Zea mays/genética
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA