RESUMEN
Owing to their sessile lifestyle, it is crucial for plants to acquire stress tolerance. The function of heat-shock proteins, including small heat-shock proteins (smHSPs), in stress tolerance is not fully explored. To gain further knowledge about the smHSPs, the gene that encoded the cytosolic class II smHSP in Arabidopsis thaliana (At-HSP17.6A) was characterized. The At-HSP17.6A expression was induced by heat and osmotic stress, as well as during seed development. Accumulation of At-HSP17.6A proteins could be detected with heat and at a late stage of seed development, but not with osmotic stress, suggesting stress-induced post-transcriptional regulation of At-HSP17.6A expression. Overproduction of At-HSP17.6A could increase salt and drought tolerance in Arabidopsis. The chaperone activity of At-HSP17.6A was demonstrated in vitro.
Asunto(s)
Proteínas de Arabidopsis/fisiología , Arabidopsis/fisiología , Proteínas de Choque Térmico/fisiología , Chaperonas Moleculares/fisiología , Proteínas de Plantas/fisiología , Adaptación Biológica , Citosol , Desecación , Regulación de la Expresión Génica , Genes de Plantas , Calor , Presión Osmótica , Proteínas Recombinantes , Semillas/fisiologíaRESUMEN
The steady-state level of transcripts coding for the pyrroline-5-carboxylate reductase of Arabidopsis (At-P5R) increased under salt and heat stress, mainly because of an enhanced mRNA stability. However, the At-P5R protein level was not induced, and its translation was inhibited at initiation stage and probably also at later stages. Replacement of the 5' untranslated region (5'UTR) and beta-glucuronidase (gus) fusion analysis revealed that the first 92 bp region of the At-P5R 5'UTR was sufficient to mediate transcript stabilization and translation inhibition during salt and heat stresses. Furthermore, the first 92 bp region of the At-P5R 5'UTR was also involved in transcription efficiency in a promoter-dependent manner. The results demonstrated that the stress regulation of At-P5R is complex and involves the 5'UTR which acts at three levels, partly in opposing directions.
Asunto(s)
Regiones no Traducidas 5' , Arabidopsis/genética , Regulación Enzimológica de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Proteínas de Plantas/genética , Pirrolina Carboxilato Reductasas/genética , Secuencia de Bases , Northern Blotting , Glucuronidasa/genética , Calor , Datos de Secuencia Molecular , Polirribosomas/genética , Regiones Promotoras Genéticas , Biosíntesis de Proteínas , ARN , Procesamiento Postranscripcional del ARN , ARN Mensajero/genética , ARN Mensajero/metabolismo , ARN de Planta , Proteínas Recombinantes de Fusión , Cloruro de Sodio , Factores de Transcripción/metabolismo , Transcripción Genética , delta-1-Pirrolina-5-Carboxilato ReductasaRESUMEN
Hyperosmotic stress severely affects plant growth and development. To examine the effect of salt stress on cell cycle activity in Arabidopsis thaliana (L.) Heynh., the transcriptional regulation of a cyclin-dependent kinase, CDC2aAt, and two mitotic cyclins, Arath;CycB1;1 and Arath;CycA2;1, was studied by using the beta-glucuronidase (gus) reporter gene. Moreover, the mRNA abundance of these cell cycle genes as well as CDC2bAt were monitored during salt stress. Upon NaCl treatment, the promoter activities and transcript levels of all cell cycle genes diminished initially in the shoot apex and were subsequently induced during salt-stress adaptation. Additionally, the promoter activities of CDC2aAt and CycA2;1 decreased in the vascular cylinder of the root in correlation with reduced lateral root formation. In the root tips, a regression of CDC2aAt, CycA2;1, and CycB1;1:gus expression was observed, concomitant with a shrinkage of the root meristem and inhibition of root growth. Our data indicate that salt stress interferes with cell cycle regulation at the transcriptional level, resulting in an adaptive growth response.
Asunto(s)
Arabidopsis/fisiología , Ciclo Celular/genética , Quinasas Ciclina-Dependientes/genética , Ciclinas/genética , Regulación de la Expresión Génica de las Plantas , Regiones Promotoras Genéticas , Arabidopsis/citología , Arabidopsis/genética , Ciclo Celular/efectos de los fármacos , Genes Reporteros , Glucuronidasa/genética , Raíces de Plantas/citología , Raíces de Plantas/fisiología , Brotes de la Planta/citología , Brotes de la Planta/fisiología , Plantas Modificadas Genéticamente , Regiones Promotoras Genéticas/efectos de los fármacos , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Solución Salina Hipertónica/farmacologíaRESUMEN
The Arabidopsis thaliana gene that encodes pyrroline-5-carboxylate reductase (At-P5R), the last enzyme in proline biosynthesis in A. thaliana, is developmentally regulated and is highly expressed in cells that divide rapidly or undergo changes in osmotic potential. A 69 bp region (P69; -120 to -51) has previously been identified in a 5' deletion analysis of the At-P5R promoter to be necessary for the basal expression. Here, the essential role of P69 for tissue-specific expression of At-P5R is demonstrated by loss- and gain-of-function experiments.
Asunto(s)
Arabidopsis/genética , Caulimovirus/genética , Regulación de la Expresión Génica de las Plantas/fisiología , Fragmentos de Péptidos/genética , Regiones Promotoras Genéticas , Pirrolina Carboxilato Reductasas/genética , ARN Ribosómico/genética , Arabidopsis/enzimología , Secuencia de Bases , Regulación de la Expresión Génica/fisiología , Regulación Viral de la Expresión Génica/fisiología , Genes de Plantas , Genes Reporteros , Glucuronidasa/biosíntesis , Glucuronidasa/genética , Datos de Secuencia Molecular , Fragmentos de Péptidos/fisiología , Plantas Modificadas Genéticamente , Regiones Promotoras Genéticas/fisiología , Pirrolina Carboxilato Reductasas/fisiología , Semillas/genética , Eliminación de SecuenciaRESUMEN
At-P5R, a gene encoding the last enzyme of the proline (Pro) biosynthetic pathway in Arabidopsis thaliana, is developmentally regulated. To characterize the cis elements responsible for this developmental regulation, a series of 5' deletions of the At-P5R promoter were transcriptionally fused to a beta-glucuronidase (GUS)-coding region and transformed into Arabidopsis. The complete promoter of At-P5R directs strong GUS activity in root tips, the shoot meristem, guard cells, hydathodes, pollen grains, ovules, and developing seeds, all of which contain rapidly dividing cells and/or are undergoing changes in osmotic potential. This expression pattern is consistent with the function of Pro as an energy, nitrogen, and carbon source and as an osmoticum in response to dehydration. Promoters longer than 212 base pairs (bp) showed the same expression pattern, whereas those shorter than 143 bp did not direct any detectable GUS activity in any organs. This suggests that a 69-bp promoter region located between -212 and -143 bp is necessary to establish the tissue-specific expression of At-P5R during development. The Pro content measured in different organs suggests that, in addition to transcriptional control of the biosynthetic pathway, the transport of Pro may play a role in its distribution within Arabidopsis. Several aspects of the relationship between Pro metabolism and plant physiology are discussed.