The sunflower HD-Zip transcription factor HAHB4 is up-regulated in darkness, reducing the transcription of photosynthesis-related genes

HAHB4 belongs to the sunflower subfamily I of HD-Zip proteins and is involved in drought-tolerance response and ethylene-mediated senescence. Cross-talk between these two processes through this transcription factor was recently described. In this study it is shown that the expression of HAHB4 is induced in darkness and quickly disappears when plants are exposed to light. This regulation of HAHB4 was confirmed at the transcriptional level through the use of transgenic Arabidopsis plants bearing constructs in which different segments of the HAHB4 promoter were fused with the reporter gene GUS. Together with electrophoretic mobility shift assays performed with sunflower nuclear proteins, these experiments allowed a cis-acting element involved in this response to be located. Transient overexpression of the HAHB4 cDNA in sunflower leaf discs and HAHB4 knockdown by iRNA were performed, demonstrating the participation of this transcription factor in the transcriptional down-regulation of a large group of photosynthesis-related genes. In accordance with the reduction in the transcripts encoding chlorophyll a/b-binding proteins, the content of these pigments is diminished in Arabidopsis HAHB4-expressing transgenic plants. Thus, it appears that HAHB4 may participate with other factors in the intricate regulation mechanism of the photosynthetic machinery in darkness. © The Author [2008]. Published by Oxford University Press [on behalf of the Society for Experimental Biology]. All rights reserved.Fil: Manavella, Pablo Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; ArgentinaFil: Dezar, Carlos Alberto Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; ArgentinaFil: Ariel, Federico Damian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; ArgentinaFil: Drincovich, Maria Fabiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Centro de Estudios Fotosintéticos y Bioquímicos. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Centro de Estudios Fotosintéticos y Bioquímicos; ArgentinaFil: Chan, Raquel Lia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; Argentin

Rewiring of auxin signaling under persistent shade

Pucciariello, Ornella. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA). Buenos Aires, Argentina.Legris, Martina. CONICET. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires. Buenos Aires, Argentina.Costigliolo Rojas, Cecilia. CONICET. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires. Buenos Aires, Argentina.Iglesias, María José. CONICET. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires. Buenos Aires, Argentina.Hernando, Carlos Esteban. CONICET. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires. Buenos Aires, Argentina.Dezar, Carlos. Instituto de Agrobiotecnología de Rosario. Rosario, Argentina.Vazquez, Martín P. Instituto de Agrobiotecnología de Rosario. Rosario, Argentina.Casal, Jorge José. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA). Buenos Aires, Argentina.5612-5617Light cues from neighboring vegetation rapidly initiate plant shade - avoidance responses. Despite our detailed knowledge of the early steps of this response, the molecular events under prolonged shade are largely unclear. Here we show that persistent neighbor cues reinforce growth responses in addition to promoting auxin - responsive gene expression in Arabidopsis and soybean. However, while the elevation of auxin levels is well established as an early event, in Arabidopsis, the response to prolonged shade occurs when auxin levels have declined to the prestimulation values. Remarkably, the sustained low activity of phytochrome B under prolonged shade led to (i) decreased levels of PHYTOCHROME INTERACTING FACTOR 4 (PIF4) in the cotyledons (the organs that supply auxin) along with increased levels in the vascular tissues of the stem, (ii) elevated expression of the PIF4 targets INDOLE-3-ACETIC ACID 19 (IAA19) and IAA29, which in turn reduced the expression of the growth-repressive IAA17 regulator, (iii) reduced abundance of AUXIN RESPONSE FACTOR 6, (iv) reduced expression of MIR393 and increased abundance of its targets, the auxin receptors, and (v) elevated auxin signaling as indicated by molecular markers. Mathematical and genetic analyses support the physiological role of this system - level rearrangement. We propose that prolonged shade rewires the connectivity between light and auxin signaling to sustain shade avoidance without enhanced auxin levels

Shade delays flowering in Medicago sativa

Shade intolerant plants respond to the decrease in the red (R) to far-red light (FR) ratio (R:FR) occurring under shade by elongating stems and petioles and re-positioning leaves, in a race to out-compete neighbors for the sunlight resource. In some annual species, these shade-avoidance responses (SAS) are accompanied by the early induction of flowering. Anticipated flowering is viewed as a strategy to set seeds before the resources become severely limiting. Little is known about the molecular mechanisms of SAS in perennial forage crops like alfalfa (Medicago sativa). To study SAS in alfalfa, we exposed alfalfa plants to simulated shade by supplementing with FR. Low R:FR produced a classical SAS, such as increased internode and petiole length but, unexpectedly, delayed flowering. To understand the molecular mechanisms involved in uncoupling SAS from early flowering, we used a transcriptomic approach. SAS were likely mediated by increased expression of msPIF3 and msHB2 in low R:FR. Constitutive expression of these genes in Arabidopsis led to SAS, including early flowering, strongly suggesting their roles are conserved. Delayed flowering was likely to be mediated by the downregulation of msSPL3, which promotes flowering in both Arabidopsis and alfalfa. Shade-delayed flowering in alfalfa may be important to extend the vegetative phase under sub-optimal light conditions and thus assure the accumulation of reserves necessary to resume growth after the next season. This article is protected by copyright. All rights reserved.Fil: Lorenzo, Christian Damián. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Iserte, Javier Alonso. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Sanchez Lamas, Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Antonietti, Mariana Sofía. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Garcia Gagliardi, Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Hernando, Carlos Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Dezar, Carlos Alberto Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Agrobiotecnología de Rosario; ArgentinaFil: Vazquez, Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Agrobiotecnología de Rosario; ArgentinaFil: Casal, Jorge José. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: Yanovsky, Marcelo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Cerdan, Pablo Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; Argentin

Improvement of alfalfa forage quality and management through the down-regulation of MsFTa1

Alfalfa (Medicago sativa L.) is one of the most important forage crops worldwide. As a perennial, alfalfa is cut several times each year. Farmers face a dilemma: If cut earlier, forage nutritive value is much higher but regrowth is affected and the longevity of the stand is severely compromised. On the other hand, if alfalfa is cut later at full flower, stands persist longer, more biomass may be harvested, but the nutritive value diminishes. Alfalfa is a strict long‐days plant. We reasoned that by manipulating the response to photoperiod, we could delay flowering to improve forage quality and widen each harvesting window, facilitating management. With this aim, we functionally characterised the FLOWERING LOCUS T family of genes, represented by five members: MsFTa1, MsFTa2, MsFTb1, MsFTb2 and MsFTc. The expression of MsFTa1 correlated with photoperiodic flowering and its downregulation led to severe delayed flowering. Altogether, with late flowering, low expression of MsFTa1 led to changes in plant architecture resulting in increased leaf to stem biomass ratios and forage digestibility. By manipulating photoperiodic flowering we were able to improve the quality of alfalfa forage and management, which may allow farmers to cut alfalfa of high nutritive value without compromising stand persistence.Fil: Lorenzo, Christian Damián. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Gagliardi, Raul Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Antonietti, Mariana Sofía. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Sanchez Lamas, Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Mancini, Estefania. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Dezar, Carlos Alberto Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Agrobiotecnología de Rosario; ArgentinaFil: Vazquez, Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Agrobiotecnología de Rosario; ArgentinaFil: Watson, Geronimo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Agrobiotecnología de Rosario; ArgentinaFil: Yanovsky, Marcelo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Cerdan, Pablo Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentin

Mecanismos moleculares de respuesta a distintos tipos de estrés abiótico en las plantas

Los cambios desfavorables en el ambiente, provocados por factores climáticos, edáficos y por la actividad del hombre, generan estrés en las plantas afectando severamente su productividad. Los estreses abióticos constituyen la principal causa de pérdidas en los cultivos. Estas pérdidas de productividad superan a veces, según cálculos estimativos, el 50% (Bray y col., 2000) y es por eso que los mejoradores se han dedicado, y lo hacen continuamente a elaborar estrategias de mejoramiento.Trabajo galardonado con el Premio "Pérez Companc", versión 2007Academia Nacional de Agronomía y Veterinari

Mecanismos moleculares de respuesta a distintos tipos de estrés abiótico en las plantas

Los cambios desfavorables en el ambiente, provocados por factores climáticos, edáficos y por la actividad del hombre, generan estrés en las plantas afectando severamente su productividad. Los estreses abióticos constituyen la principal causa de pérdidas en los cultivos. Estas pérdidas de productividad superan a veces, según cálculos estimativos, el 50% (Bray y col., 2000) y es por eso que los mejoradores se han dedicado, y lo hacen continuamente a elaborar estrategias de mejoramiento.Trabajo galardonado con el Premio "Pérez Companc", versión 2007Academia Nacional de Agronomía y Veterinari

Nicotiana attenuata NaHD20 plays a role in leaf ABA accumulation during water stress, benzylacetone emission from flowers, and the timing of bolting and flower transitions

Homeodomain-leucine zipper type I (HD-Zip I) proteins are plant-specific transcription factors associated with the regulation of growth and development in response to changes in the environment. Nicotiana attenuata NaHD20 was identified as an HD-Zip I-coding gene whose expression was induced by multiple stress-associated stimuli including drought and wounding. To study the role of NaHD20 in the integration of stress responses with changes in growth and development, its expression was silenced by virus-induced gene silencing (VIGS), and control and silenced plants were metabolically and developmentally characterized. Phytohormone profiling showed that NaHD20 plays a positive role in abscisic acid (ABA) accumulation in leaves during water stress and in the expression of some dehydration-responsive genes including ABA biosynthetic genes. Moreover, consistent with the high levels of NaHD20 expression in corollas, the emission of benzylacetone from flowers was reduced in NaHD20-silenced plants. Additionally, bolting time and the opening of the inflorescence buds was decelerated in these plants in a specific developmental stage without affecting the total number of flowers produced. Water stress potentiated these effects; however, after plants recovered from this condition, the opening of the inflorescence buds was accelerated in NaHD20-silenced plants. In summary, NaHD20 plays multiple roles in N. attenuata and among these are the coordination of responses to dehydration and its integration with changes in flower transitions

Hahb-10, a sunflower homeobox-leucine zipper gene, is regulated by light quality and quantity, and promotes early flowering when expressed in Arabidopsis

Homeodomain-leucine zipper proteins constitute a family of transcription factors found only in plants. Expression patterns of the sunflower homeobox-leucine zipper gene Hahb-10 (Helianthus annuus homeobox-10), that belongs to the HD-Zip II subfamily, were analysed. Northern blots showed that Hahb-10 is expressed primarily in mature leaves, although expression is clearly detectable in younger leaves and also in stems. Considerably higher expression levels were detected in etiolated seedlings compared with light-grown seedlings. Induction of Hahb-10 expression was observed when seedlings were subjected to treatment with gibberellins. Transgenic Arabidopsis thaliana plants that express Hahb-10 under the 35S cauliflower mosaic virus promoter show special phenotypic characteristics such as darker cotyledons and planar leaves. A reduction in the life cycle of about 25% allowing earlier seed collection was also observed, and this phenomenon is clearly related to a shortened flowering time. When the number of plants per pot increased, the difference in developmental rate between transgenic and non-transformed individuals became larger. After gibberellin treatment, the relative difference in life cycle duration was considerably reduced. Several light-regulated genes have been tested as possible target genes of Hahb-10. One of them, PsbS, shows a different response to illumination conditions in transgenic plants compared with the response in wild-type plants while the other genes behave similarly in both genotypes. We propose that Hahb-10 functions in a signalling cascade(s) that control(s) plant responses to light quality and quantity, and may also be involved in gibberellin transduction pathways.Fil: Rueda, Eva Carolina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Dezar, Carlos Alberto Alejandro. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Gonzalez, Daniel Hector. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Chan, Raquel Lia. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentin

HAHB4, a sunflower HD-Zip protein, integrates signals from the jasmonic acid and ethylene pathways during wounding and biotic stress responses

The Helianthus annuus (sunflower) HAHB4 transcription factor belongs to the HD-Zip family and its transcript levels are strongly induced when sunflower plants are attacked by herbivores, mechanically damaged or treated with methyl-jasmonic acid (MeJA) or ethylene (ET). Promoter fusion analysis, in Arabidopsis and in sunflower, demonstrated that induction of HAHB4 expression by these treatments is regulated at the transcriptional level. In transiently transformed sunflower plants HAHB4 expression upregulates the transcript levels of several genes involved in JA biosynthesis and defense-related processes such as the production of green leaf volatiles and trypsin protease inhibitors (TPI). In HAHB4 sunflower overexpressing tissue, increased activities of lipoxygenase, hydroperoxide lyase and TPI are detected whereas in HAHB4-silenced tissue these activities are reduced. Transgenic Arabidopsis thaliana and Zea mays plants ecotopically expressing HAHB4 also exhibit higher transcript levels of defense-related genes and when Spodoptera littoralis or Spodoptera frugiperda larvae are placed on each species, respectively, larvae consumed less and gain less mass compared with larvae feeding on control plants. Arabidopsis plants ectopically expressing HAHB4 had higher amounts of JA, JA-isoleucine and ET compared with control plants both before and after wounding, but reduced levels of salicylic acid (SA) after wounding and bacterial infection. We conclude that HAHB4 coordinates the production of phytohormones during biotic stress responses and mechanical damage, specifically by positively regulating JA and ET production and negatively regulating ET sensitivity and SA accumulation.Fil: Manavella, Pablo Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; ArgentinaFil: Dezar, Carlos Alberto Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; ArgentinaFil: Bonaventure, Gustavo. Instituto Max Planck Institut für Chemische Okologie; AlemaniaFil: Baldwin Ian Thomas. Instituto Max Planck Institut für Chemische Okologie; AlemaniaFil: Chan, Raquel Lia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Agrobiotecnología del Litoral. Universidad Nacional del Litoral. Instituto de Agrobiotecnología del Litoral; Argentin

The promoter of the sunflower HD-Zip protein gene Hahb4 directs tissue-specific expression and is inducible by water stress, high salt concentrations and ABA

In the present work, we have analysed the promoter region of the sunflower nuclear gene Hahb4, encoding an homeodomain-leucine zipper protein involved in water stress responses. This region is represented in two different but highly conserved alleles of 1015 and 1221 bp, respectively, in the sunflower hybrid studied. To gain insight into the structure and function of these promoter forms, we have obtained plants stably transformed with different fragments fused to the b-glucuronidase (gus) reporter gene. Histochemical staining indicated that both protein involved in water stress responses. This region is represented in two different but highly conserved alleles of 1015 and 1221 bp, respectively, in the sunflower hybrid studied. To gain insight into the structure and function of these promoter forms, we have obtained plants stably transformed with different fragments fused to the b-glucuronidase (gus) reporter gene. Histochemical staining indicated that both Hahb4, encoding an homeodomain-leucine zipper protein involved in water stress responses. This region is represented in two different but highly conserved alleles of 1015 and 1221 bp, respectively, in the sunflower hybrid studied. To gain insight into the structure and function of these promoter forms, we have obtained plants stably transformed with different fragments fused to the b-glucuronidase (gus) reporter gene. Histochemical staining indicated that bothb-glucuronidase (gus) reporter gene. Histochemical staining indicated that both Hahb4 promoter forms direct expression in roots, cotyledons and leaves during the entire plant life cycle. No expression was observed in reproductive organs. The analysis of progressive upstream deletions of the promoters suggested that a minimal 417/421 bp fragment is required for basal expression. The presence of positive regulatory elements between nucleotides -601/608 and -818/-1024 from the transcription initiation site (depending on the promoter) and a sequence required for specific expression in the root central cylinder between transcription initiation site (depending on the promoter) and a sequence required for specific expression in the root central cylinder between reproductive organs. The analysis of progressive upstream deletions of the promoters suggested that a minimal 417/421 bp fragment is required for basal expression. The presence of positive regulatory elements between nucleotides -601/608 and -818/-1024 from the transcription initiation site (depending on the promoter) and a sequence required for specific expression in the root central cylinder between transcription initiation site (depending on the promoter) and a sequence required for specific expression in the root central cylinder between promoter forms direct expression in roots, cotyledons and leaves during the entire plant life cycle. No expression was observed in reproductive organs. The analysis of progressive upstream deletions of the promoters suggested that a minimal 417/421 bp fragment is required for basal expression. The presence of positive regulatory elements between nucleotides -601/608 and -818/-1024 from the transcription initiation site (depending on the promoter) and a sequence required for specific expression in the root central cylinder between transcription initiation site (depending on the promoter) and a sequence required for specific expression in the root central cylinder between 601/608 and -818/-1024 from the transcription initiation site (depending on the promoter) and a sequence required for specific expression in the root central cylinder between -818/-1024 and -1015/-1221 has been detected. Water stress, ABA or NaCl treatments induced Hahb4 promoter-dependent-818/-1024 and -1015/-1221 has been detected. Water stress, ABA or NaCl treatments induced Hahb4 promoter-dependent b-glucuronidase expression as observed by Northern blot hybridization experiments. Putative regulatory elements involved in the regulation of other genes were detected in the promoter fragment required for expression. These elements, together with experimental evidence, were analysed with the aim of elucidating the molecular mechanisms that participate in the expression of this gene. of other genes were detected in the promoter fragment required for expression. These elements, together with experimental evidence, were analysed with the aim of elucidating the molecular mechanisms that participate in the expression of this gene. -glucuronidase expression as observed by Northern blot hybridization experiments. Putative regulatory elements involved in the regulation of other genes were detected in the promoter fragment required for expression. These elements, together with experimental evidence, were analysed with the aim of elucidating the molecular mechanisms that participate in the expression of this gene.Fil: Dezar, Carlos Alberto Alejandro. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Departamento de Ciencias Biológicas. Cátedra de Biología Celular y Molecular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Fedrigo, Griselda Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Departamento de Ciencias Biológicas. Cátedra de Biología Celular y Molecular; ArgentinaFil: Chan, Raquel Lia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas. Departamento de Ciencias Biológicas. Cátedra de Biología Celular y Molecular; Argentin