RESUMEN
An activation-tagging methodology was applied to dedifferentiated calli of Arabidopsis to identify new genes involved in salt tolerance. This identified salt tolerant callus 8 (stc8) as a gene encoding the basic helix-loop-helix transcription factor bHLH106. bHLH106-knockout (KO) lines were more sensitive to NaCl, KCl, LiCl, ABA, and low temperatures than the wild-type. Back-transformation of the KO line rescued its phenotype, and over-expression (OX) of bHLH106 in differentiated plants exhibited tolerance to NaCl. Green fluorescent protein (GFP) fused with bHLH106 revealed that it was localized to the nucleus. Prepared bHLH106 protein was subjected to electrophoresis mobility shift assays against E-box sequences (5'-CANNTG-3'). The G-box sequence 5'-CACGTG-3' had the strongest interaction with bHLH106. bHLH106-OX lines were transcriptomically analyzed, and resultant up- and down-regulated genes selected on the criterion of presence of a G-box sequence. There were 198 genes positively regulated by bHLH106 and 36 genes negatively regulated; these genes possessed one or more G-box sequences in their promoter regions. Many of these genes are known to be involved in abiotic stress response. It is concluded that bHLH106 locates at a branching point in the abiotic stress response network by interacting directly to the G-box in genes conferring salt tolerance on plants.
Asunto(s)
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Factores de Unión a la G-Box/genética , Genes de Plantas/fisiología , Secuencias Hélice-Giro-Hélice/genética , Tolerancia a la Sal/genética , Arabidopsis/fisiología , Proteínas de Arabidopsis/fisiología , Factores de Unión a la G-Box/fisiología , Técnicas de Inactivación de Genes , Genes de Plantas/genética , Secuencias Hélice-Giro-Hélice/fisiología , Plantas Modificadas Genéticamente , Reacción en Cadena en Tiempo Real de la Polimerasa , Tolerancia a la Sal/fisiologíaRESUMEN
Several transcriptional regulators have been identified and demonstrated to play either positive or negative regulatory roles in seedling development. However, the regulatory coordination between hypocotyl elongation and cotyledon expansion during early seedling development in plants remains unknown. We report the identification of a Z-box binding factor (ZBF2) and its functional characterization in cryptochrome-mediated blue light signaling. ZBF2 encodes a G-box binding factor (GBF1), which is a basic leucine zipper transcription factor. Our DNA-protein interaction studies reveal that ZBF2/GBF1 also interacts with the Z-box light-responsive element of light-regulated promoters. Genetic analyses of gbf1 mutants and overexpression studies suggest that GBF1 acts as a repressor of blue light-mediated inhibition in hypocotyl elongation, however, it acts as a positive regulator of cotyledon expansion during photomorphogenic growth. Furthermore, whereas GBF1 acts as a positive regulator of lateral root formation, it differentially regulates the expression of light-inducible genes. Taken together, these results demonstrate that GBF1 is a unique transcriptional regulator of photomorphogenesis in blue light.
Asunto(s)
Proteínas de Arabidopsis/fisiología , Factores de Unión a la G-Box/fisiología , Luz , Morfogénesis/efectos de la radiación , Factores de Transcripción/fisiología , Arabidopsis/crecimiento & desarrollo , Proteínas de Arabidopsis/genética , Factores de Transcripción Básicos con Cremalleras de Leucinas y Motivos Hélice-Asa-Hélice/fisiología , Cotiledón/crecimiento & desarrollo , Regulación de la Expresión Génica/efectos de la radiación , Hipocótilo/crecimiento & desarrollo , Datos de Secuencia Molecular , Regiones Promotoras Genéticas/efectos de la radiación , Semillas/crecimiento & desarrolloRESUMEN
In this study, we showed that overexpression of ethylene-responsive transcription factor (ERF) 2 activated the expression of endogenous genes that have the GCC box in their promoter region, in tobacco plants. These include not only a defense-related gene, CHN50, encoding class I basic chitinase, but also a transcriptional repressor gene, ERF3. In tobacco plants constitutively expressing ERF2:glucocorticoid receptor fusion protein, treatment with dexamethazone induced a rapid increase of ERF3 mRNA and a slow increase of CHN50 mRNA. These results suggest that an antagonistic interplay of ERF2 and ERF3 is involved in the transcriptional regulation of the class I basic chitinase genes in tobacco.
Asunto(s)
Regulación de la Expresión Génica de las Plantas , Genes de Plantas , Nicotiana/genética , Factores de Transcripción/fisiología , Transcripción Genética , Quitinasas/genética , ADN de Plantas/análisis , ADN de Plantas/genética , Dexametasona/farmacología , Factores de Unión a la G-Box/genética , Factores de Unión a la G-Box/fisiología , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Regiones Promotoras Genéticas , ARN Mensajero/análisis , Receptores de Glucocorticoides/genética , Receptores de Glucocorticoides/fisiología , Secuencias Reguladoras de Ácidos Nucleicos/genética , Secuencias Reguladoras de Ácidos Nucleicos/fisiología , Proteínas Represoras/genética , Proteínas Represoras/fisiologíaRESUMEN
Expression profiles of developmental genes in Dictyostelium were determined on microarrays during development of wild type cells and mutant cells lacking either the DNA binding protein GBF or the signaling protein LagC. We found that the mutant strains developed in suspension with added cAMP expressed the pulse-induced and early adenylyl cyclase (ACA)-dependent genes, but not the later ACA-dependent, post-aggregation genes. Since expression of lagC itself is dependent on GBF, expression of the post-aggregation genes might be controlled only by signaling from LagC. However, expression of lagC in a GBF-independent manner in a gbfA- null strain did not result in expression of the post-aggregation genes. Since GBF is necessary for accumulation of LagC and both the DNA binding protein and the LagC signal transduction pathway are necessary for expression of post-aggregation genes, GBF and LagC form a feed-forward loop. Such network architecture is a common motif in diverse organisms and can act as a filter for noisy inputs. Breaking the feed-forward loop by expressing lagC in a GBF-independent manner in a gbfA+ strain does not significantly affect the patterns of gene expression for cells developed in suspension with added cAMP, but results in a significant delay at the mound stage and asynchronous development on solid supports. This feed-forward loop can integrate temporal information with morphological signals to ensure that post-aggregation genes are only expressed after cell contacts have been made.