RESUMEN
Vascular tissues are very important for providing both mechanical strength and long-distance transport. The molecular mechanisms of regulation of vascular tissue development are still not fully understood. In this study we identified ANAC005 as a membrane-associated NAC family transcription factor that regulates vascular tissue development. Reporter gene assays showed that ANAC005 was expressed mainly in the vascular tissues. Increased expression of ANAC005 protein in transgenic Arabidopsis caused dwarf phenotype, reduced xylem differentiation, decreased lignin content, repression of a lignin biosynthetic gene and genes related to cambium and primary wall, but activation of genes related to the secondary wall. Expression of a dominant repressor fusion of ANAC005 had overall the opposite effects on vascular tissue differentiation and lignin synthetic gene expression. The ANAC005-GFP fusion protein was localized at the plasma membrane, whereas deletion of the last 20 amino acids, which are mostly basic, caused its nuclear localization. These results indicate that ANAC005 is a cell membrane-associated transcription factor that inhibits xylem tissue development in Arabidopsis.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/crecimiento & desarrollo , Arabidopsis/metabolismo , Haz Vascular de Plantas/crecimiento & desarrollo , Haz Vascular de Plantas/metabolismo , Factores de Transcripción/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/genética , Diferenciación Celular/genética , Membrana Celular/metabolismo , Regulación de la Expresión Génica de las Plantas , Proteínas Fluorescentes Verdes/metabolismo , Morfogénesis , Fenotipo , Fracciones Subcelulares/metabolismo , Factores de Transcripción/química , Factores de Transcripción/genética , Xilema/citología , Xilema/metabolismoRESUMEN
Seed development is important for agriculture productivity. We demonstrate that brassinosteroid (BR) plays crucial roles in determining the size, mass, and shape of Arabidopsis (Arabidopsis thaliana) seeds. The seeds of the BR-deficient mutant de-etiolated2 (det2) are smaller and less elongated than those of wild-type plants due to a decreased seed cavity, reduced endosperm volume, and integument cell length. The det2 mutant also showed delay in embryo development, with reduction in both the size and number of embryo cells. Pollination of det2 flowers with wild-type pollen yielded seeds of normal size but still shortened shape, indicating that the BR produced by the zygotic embryo and endosperm is sufficient for increasing seed volume but not for seed elongation, which apparently requires BR produced from maternal tissues. BR activates expression of SHORT HYPOCOTYL UNDER BLUE1, MINISEED3, and HAIKU2, which are known positive regulators of seed size, but represses APETALA2 and AUXIN RESPONSE FACTOR2, which are negative regulators of seed size. These genes are bound in vivo by the BR-activated transcription factor BRASSINAZOLE-RESISTANT1 (BZR1), and they are known to influence specific processes of integument, endosperm, and embryo development. Our results demonstrate that BR regulates seed size and seed shape by transcriptionally modulating specific seed developmental pathways.
Asunto(s)
Arabidopsis/fisiología , Brasinoesteroides/metabolismo , Semillas/fisiología , Proteínas de Arabidopsis/efectos de los fármacos , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Brasinoesteroides/farmacología , Sistema Enzimático del Citocromo P-450/genética , Proteínas de Unión al ADN , Regulación de la Expresión Génica de las Plantas , Proteínas de Homeodominio/genética , Mutación , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Plantas Modificadas Genéticamente , Proteínas Quinasas/genética , Proteínas Represoras/genética , Semillas/anatomía & histología , Semillas/efectos de los fármacos , Factores de Transcripción/genéticaRESUMEN
Photomorphogenesis is controlled by multiple signaling pathways, including the light and brassinosteroid (BR) pathways. BR signaling activates the BZR1 transcription factor, which is required for suppressing photomorphogenesis in the dark. We identified a suppressor of the BR hypersensitive mutant bzr1-1D and named it bzr1-1D suppressor1-Dominant (bzs1-D). The bzs1-D mutation was caused by overexpression of a B-box zinc finger protein BZS1, which is transcriptionally repressed by BZR1. Overexpression of BZS1 causes de-etiolation in the dark, short hypocotyls in the light, reduced sensitivity to BR treatment, and repression of many BR-activated genes. Knockdown of BZS1 by co-suppression partly suppressed the short hypocotyl phenotypes of BR-deficient or insensitive mutants. These results support that BZS1 is a negative regulator of BR response. BZS1 overexpressors are hypersensitive to different wavelengths of light and loss of function of BZS1 reduces plant sensitivity to light and partly suppresses the constitutive photomorphogenesis 1 (cop1) mutant in the dark, suggesting a positive role in light response. BZS1 protein accumulates at an increased level after light treatment of dark-grown BZS1-OX plants and in the cop1 mutants, and BZS1 interacts with COP1 in vitro, suggesting that light regulates BZS1 through COP1-mediated ubiquitination and proteasomal degradation. These results demonstrate that BZS1 mediates the crosstalk between BR and light pathways.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/crecimiento & desarrollo , Arabidopsis/efectos de la radiación , Brasinoesteroides/metabolismo , Luz , Morfogénesis/efectos de la radiación , Transducción de Señal/efectos de la radiación , Factores de Transcripción/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Regulación de la Expresión Génica de las Plantas/efectos de la radiación , Genes de Plantas/genética , Genes Supresores , Morfogénesis/genética , Mutación/genética , Fenotipo , Transducción de Señal/genética , Factores de Transcripción/genéticaRESUMEN
Brassinosteroids (BR) are essential growth hormones found throughout the plant kingdom. BR bind to the receptor kinase BRI1 on the cell surface to activate a signal transduction pathway that regulates nuclear gene expression and plant growth. To understand the downstream BR signaling mechanism in rice, we studied the function of OsBZR1 using reverse genetic approaches and identified OsBZR1-interacting proteins. Suppressing OsBZR1 expression by RNAi resulted in dwarfism, erect leaves, reduced BR sensitivity, and altered BR-responsive gene expression in transgenic rice plants, demonstrating an essential role of OsBZR1 in BR responses in rice. Moreover, a yeast two-hybrid screen identified 14-3-3 proteins as OsBZR1-interacting proteins. Mutation of a putative 14-3-3-binding site of OsBZR1 abolished its interaction with the 14-3-3 proteins in yeast and in vivo. Such mutant OsBZR1 proteins suppressed the phenotypes of the Arabidopsis bri1-5 mutant and showed an increased nuclear distribution compared with the wild-type protein, suggesting that 14-3-3 proteins directly inhibit OsBZR1 function at least in part by reducing its nuclear localization. These results demonstrate a conserved function of OsBZR1 and an important role of 14-3-3 proteins in brassinosteroid signal transduction in rice.
Asunto(s)
Proteínas 14-3-3/metabolismo , Proteínas Nucleares/metabolismo , Oryza/metabolismo , Transducción de Señal , Esteroides/metabolismo , Proteínas 14-3-3/genética , Secuencia de Aminoácidos , Núcleo Celular/metabolismo , Secuencia Conservada , Regulación de la Expresión Génica de las Plantas , Proteínas Nucleares/química , Proteínas Nucleares/genética , Oryza/efectos de los fármacos , Oryza/genética , Oryza/crecimiento & desarrollo , Fenotipo , Unión Proteica , Interferencia de ARN , Transducción de Señal/efectos de los fármacos , Esteroides/farmacologíaRESUMEN
Upland cotton (Gossypium hirsutum) produces the most widely used natural fibers, yet the regulatory mechanisms governing fiber cell elongation are not well understood. Through sequencing of a cotton fiber cDNA library and subsequent microarray analysis, we found that ethylene biosynthesis is one of the most significantly upregulated biochemical pathways during fiber elongation. The 1-Aminocyclopropane-1-Carboxylic Acid Oxidase1-3 (ACO1-3) genes responsible for ethylene production were expressed at significantly higher levels during this growth stage. The amount of ethylene released from cultured ovules correlated with ACO expression and the rate of fiber growth. Exogenously applied ethylene promoted robust fiber cell expansion, whereas its biosynthetic inhibitor l-(2-aminoethoxyvinyl)-glycine (AVG) specifically suppressed fiber growth. The brassinosteroid (BR) biosynthetic pathway was modestly upregulated during this growth stage, and treatment with BR or its biosynthetic inhibitor brassinazole (BRZ) also promoted or inhibited, respectively, fiber growth. However, the effect of ethylene treatment was much stronger than that of BR, and the inhibitory effect of BRZ on fiber cells could be overcome by ethylene, but the AVG effect was much less reversed by BR. These results indicate that ethylene plays a major role in promoting cotton fiber elongation. Furthermore, ethylene may promote cell elongation by increasing the expression of sucrose synthase, tubulin, and expansin genes.