RESUMEN
Thiol reduction proteins are key regulators of the redox state of the cell, managing development and stress response programs. In plants, thiol reduction proteins, namely thioredoxin (TRX), glutaredoxin (GRX), and their respective reducers glutathione reductase (GR) and thioredoxin reductase (TR), are organized in complex multigene families. In order to decipher the function of the different proteins, it is necessary to have a clear picture of their respective expression profiles. By collecting information from gene expression databases, we have performed a comprehensive in silico study of the expression of all members of different classes of thiol reduction genes (TRX, GRX) in Arabidopsis thaliana. Tissue expression profiles and response to many biotic and abiotic stress conditions have been studied systematically. Altogether, the significance of our data is discussed with respect to published biochemical and genetic studies.
Asunto(s)
Arabidopsis/genética , Arabidopsis/fisiología , Regulación del Desarrollo de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Estrés Fisiológico/genética , Compuestos de Sulfhidrilo/metabolismo , Arabidopsis/crecimiento & desarrollo , Regulación del Desarrollo de la Expresión Génica/efectos de los fármacos , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Glutarredoxinas/metabolismo , Glutatión/biosíntesis , Familia de Multigenes , Oxidación-Reducción/efectos de los fármacos , Filogenia , Reguladores del Crecimiento de las Plantas/farmacología , Raíces de Plantas/efectos de los fármacos , Raíces de Plantas/genética , Transporte de Proteínas/efectos de los fármacos , Estrés Fisiológico/efectos de los fármacos , Fracciones Subcelulares/efectos de los fármacos , Fracciones Subcelulares/metabolismo , Tiorredoxinas/metabolismoRESUMEN
Cyclin-dependent kinases (CDKs) control the key transitions in the eukaryotic cell cycle. All the CDKs known to control G(2)/M progression in yeast and animals are distinguished by the characteristic PSTAIRE motif in their cyclin-binding domain and are closely related. Higher plants contain in addition a number of more divergent non-PSTAIRE CDKs with still obscure functions. We show that a plant-specific type of non-PSTAIRE CDKs is involved in the control of the G(2)/M progression. In synchronized tobacco BY-2 cells, the corresponding protein, accumulated in a cell cycle-regulated fashion, peaking at the G(2)/M transition. The associated histone H1 kinase activity reached a maximum in mitosis and required a yet unidentified subunit to be fully active. Down-regulation of the associated kinase activity in transgenic tobacco plants using a dominant-negative mutation delayed G(2)/M transition. These results provide the first evidence that non-PSTAIRE CDKs are involved in the control of the G(2)/M progression in plants.
Asunto(s)
Proteínas de Arabidopsis , Quinasas Ciclina-Dependientes/genética , Quinasas Ciclina-Dependientes/fisiología , Fase G2 , Mitosis , Secuencias de Aminoácidos , Secuencia de Aminoácidos , Unión Competitiva , Ciclo Celular , Núcleo Celular , Células Cultivadas , Cromatografía en Gel , Regulación hacia Abajo , Citometría de Flujo , Genes Dominantes , Histonas/metabolismo , Immunoblotting , Datos de Secuencia Molecular , Mutación , Plantas Modificadas Genéticamente/metabolismo , Plantas Tóxicas , Plásmidos/metabolismo , Pruebas de Precipitina , Unión Proteica , Proteínas Quinasas/metabolismo , Estructura Terciaria de Proteína , Homología de Secuencia de Aminoácido , Factores de Tiempo , Nicotiana/citología , TransgenesRESUMEN
Activation of cell division in the root apical meristem after germination is essential for postembryonic root development. Arabidopsis plants homozygous for a mutation in the ROOT MERISTEMLESS1 (RML1) gene are unable to establish an active postembryonic meristem in the root apex. This mutation abolishes cell division in the root but not in the shoot. We report the molecular cloning of the RML1 gene, which encodes the first enzyme of glutathione (GSH) biosynthesis, gamma-glutamylcysteine synthetase, and which is allelic to CADMIUM SENSITIVE2. The phenotype of the rml1 mutant, which was also evident in the roots of wild-type Arabidopsis and tobacco treated with an inhibitor of GSH biosynthesis, could be relieved by applying GSH to rml1 seedlings. By using a synchronized tobacco cell suspension culture, we showed that the G(1)-to-S phase transition requires an adequate level of GSH. These observations suggest the existence of a GSH-dependent developmental pathway essential for initiation and maintenance of cell division during postembryonic root development.
Asunto(s)
Genes de Plantas , Glutatión/metabolismo , Plantas/genética , Plantas/metabolismo , Alelos , Secuencia de Aminoácidos , Arabidopsis/genética , Arabidopsis/crecimiento & desarrollo , Arabidopsis/metabolismo , Secuencia de Bases , División Celular , Clonación Molecular , ADN de Plantas/genética , Glutamato-Cisteína Ligasa/genética , Glutamato-Cisteína Ligasa/metabolismo , Datos de Secuencia Molecular , Mutación , Fenotipo , Desarrollo de la Planta , Raíces de Plantas/citología , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/metabolismo , Plantas Tóxicas , Homología de Secuencia de Aminoácido , Nicotiana/genética , Nicotiana/crecimiento & desarrollo , Nicotiana/metabolismoRESUMEN
In animal systems, indomethacin inhibits cAMP production via a prostaglandin-adenylyl cyclase pathway. To examine the possibility that a similar mechanism occurs in plants, the effect of indomethacin on the cell cycle of a tobacco bright yellow 2 (TBY-2) cell suspension was studied. Application of indomethacin during mitosis did not interfere with the M/G1 progression in synchronized BY-2 cells but it inhibited cAMP production at the beginning of the G1 phase and arrested the cell cycle progression at G1/S. These observations are discussed in relation to the putative involvement of cAMP biosynthesis in the cell cycle progression in TBY-2 cells.
Asunto(s)
Ciclo Celular/efectos de los fármacos , Indometacina/farmacología , Sulfanilamidas , Afidicolina/farmacología , Benzamidas/farmacología , Línea Celular , AMP Cíclico/metabolismo , Ciclina A/genética , Dinitrobencenos/farmacología , Citometría de Flujo , Fase G1/efectos de los fármacos , Herbicidas/farmacología , Índice Mitótico/efectos de los fármacos , Plantas Tóxicas , ARN Mensajero/metabolismo , Fase S/efectos de los fármacos , NicotianaRESUMEN
Although the basic mechanisms which control the progression through the cell cycle appear to be conserved in all higher eukaryotes, the unique features of the plant developmental programme must be somehow reflected in a plant-specific regulation of the factors which control cell division. In the last few years, considerable progress has been achieved in identifying the major components of the cell cycle in plants. The question of how these components direct expression of specific genes at specific stages of the cell cycle, and how they are themselves regulated, constitutes a challenge for the present and the next years. This review summarizes our current knowledge at molecular and biochemical levels of cell cycle-regulated expression in the model system, the synchronized tobacco BY2 cell suspension, and discusses the results in comparison to those obtained by different methods and in other plant systems.
Asunto(s)
Regulación de la Expresión Génica de las Plantas/fisiología , Genes cdc/fisiología , Nicotiana/genética , Fenómenos Fisiológicos de las Plantas , Plantas Tóxicas , Factores de TiempoRESUMEN
The respective involvement of transcriptional and post-transcriptional mechanisms in coupling H3 and H4 histone gene expression to the S phase of the cell cycle has been studied in synchronized tobacco cells. Induction of histone gene expression at the G1/S transition is shown to be essentially directed by an increase in the transcription rate in response to cellular signals occurring at the initiation step of DNA replication. Histone gene induction thus precedes the burst of DNA synthesis. However, when the elongation step of DNA replication is ineffective or artificially arrested, feedback mechanisms apparently act at the translation level to avoid overproduction of histone proteins from their mRNAs. At the end of S phase, post-transcriptional mechanisms ensure a rapid degradation of histone mRNAs. Transcription factors are bound to the cis -elements of histone promoters throughout the cell cycle, thus suggesting a post-translational modification of some of them to trigger promoter activation at the G1/S transition. Based on these results, a model is proposed for histone gene transcriptional induction in connection with the components of the cell cycle machinery.
Asunto(s)
Ciclo Celular , Regulación de la Expresión Génica de las Plantas , Histonas/genética , Nicotiana/genética , Plantas Tóxicas , Secuencia de Bases , Replicación del ADN , ADN de Plantas , Histonas/metabolismo , Datos de Secuencia Molecular , Regiones Promotoras Genéticas , Biosíntesis de Proteínas , Procesamiento Postranscripcional del ARN , Nicotiana/citología , Transcripción Genética , Activación TranscripcionalRESUMEN
The evolution of adenosine 3',5'-cyclic monophosphate (cAMP) levels was investigated in synchronised tobacco BY-2 cells by virtue of a method based on immunoaffinity purification and analysis on electrospray tandem mass spectrometry. A transient peak in cAMP content was observed during the S and G1 phases of the cell cycle. Application of the prostaglandin inhibiting drug indomethacin at early S phase resulted in the loss of the cAMP peak in S phase and inhibited mitotic division. This inhibition of cAMP accumulation suggests the presence of a prostaglandin-dependent adenylyl cyclase activity, analogous to animal cyclases. A potential role for cAMP during the plant cell cycle is postulated.
Asunto(s)
Ciclo Celular/fisiología , AMP Cíclico/metabolismo , Indometacina/farmacología , Nicotiana/efectos de los fármacos , Plantas Tóxicas , Afidicolina/farmacología , Ciclo Celular/efectos de los fármacos , Línea Celular , Inhibidores de la Ciclooxigenasa/farmacología , Fase G1 , Índice Mitótico/efectos de los fármacos , Fase S , Factores de Tiempo , Nicotiana/citología , Nicotiana/metabolismoRESUMEN
Four full-length and one partial cDNA clones encoding four different A-type cyclins were isolated from a tobacco S-phase-specific library. The corresponding mRNAs displayed sequential appearance and disappearance during the cell cycle of highly synchronized suspension-cultured tobacco cells. Sequence analysis showed that the plant A-type cyclins can be subdivided into three distinct structural groups that are likely to be represented in every plant species. Two of the isolated tobacco cyclins belonging to the same group were highly expressed throughout S and G2 phases but showed different kinetics of induction at the G1/S transition. Another one belonging to a second group was induced at mid-S phase and expressed until mid-M phase. A similar expression pattern was previously reported for a tobacco cyclin belonging to the third group. This sequential expression of multiple A-type cyclins in one type of plant cells makes a clear distinction from the situation in animal cells in which only one A-type cyclin exists in a given species. Furthermore, the expression of the different A-type cyclin genes responded differently upon a block at mid-S phase by DNA synthesis inhibitors. These results suggest that the multiple A-type cyclins act at different steps of the plant cell cycle and, therefore, exert distinct functions. In contrast, the expression of B-type cyclins was restricted to a narrow window corresponding to the M phase.