RESUMO
Growth at the shoot apical meristem (SAM) is essential for shoot architecture construction. The phytohormones gibberellins (GA) play a pivotal role in coordinating plant growth, but their role in the SAM remains mostly unknown. Here, we developed a ratiometric GA signaling biosensor by engineering one of the DELLA proteins, to suppress its master regulatory function in GA transcriptional responses while preserving its degradation upon GA sensing. We demonstrate that this degradation-based biosensor accurately reports on cellular changes in GA levels and perception during development. We used this biosensor to map GA signaling activity in the SAM. We show that high GA signaling is found primarily in cells located between organ primordia that are the precursors of internodes. By gain- and loss-of-function approaches, we further demonstrate that GAs regulate cell division plane orientation to establish the typical cellular organization of internodes, thus contributing to internode specification in the SAM.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Técnicas Biossensoriais , Regulação da Expressão Gênica de Plantas , Giberelinas , Meristema , Transdução de Sinais , Giberelinas/metabolismo , Meristema/metabolismo , Meristema/crescimento & desenvolvimento , Arabidopsis/metabolismo , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Reguladores de Crescimento de Plantas/metabolismo , Brotos de Planta/metabolismo , Brotos de Planta/crescimento & desenvolvimento , Plantas Geneticamente ModificadasRESUMO
The plant hormone gibberellin (GA) regulates multiple developmental processes. It accumulates in the root elongating endodermis, but how it moves into this cell file and the significance of this accumulation are unclear. Here we identify three NITRATE TRANSPORTER1/PEPTIDE TRANSPORTER (NPF) transporters required for GA and abscisic acid (ABA) translocation. We demonstrate that NPF2.14 is a subcellular GA/ABA transporter, presumably the first to be identified in plants, facilitating GA and ABA accumulation in the root endodermis to regulate suberization. Further, NPF2.12 and NPF2.13, closely related proteins, are plasma membrane-localized GA and ABA importers that facilitate shoot-to-root GA12 translocation, regulating endodermal hormone accumulation. This work reveals that GA is required for root suberization and that GA and ABA can act non-antagonistically. We demonstrate how the clade of transporters mediates hormone flow with cell-file-specific vacuolar storage at the phloem unloading zone, and slow release of hormone to induce suberin formation in the maturation zone.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/genética , Arabidopsis/metabolismo , Ácido Abscísico/metabolismo , Giberelinas/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Proteínas de Arabidopsis/metabolismo , Transportadores de Nitrato , Hormônios/metabolismo , Regulação da Expressão Gênica de PlantasRESUMO
Nitrate, one of the main nitrogen (N) sources for crops, acts as a nutrient and key signaling molecule coordinating gene expression, metabolism, and various growth processes throughout the plant life cycle. It is widely accepted that nitrate-triggered developmental programs cooperate with hormone synthesis and transport to finely adapt plant architecture to N availability. Here, we report that nitrate, acting through its signaling pathway, promotes growth in Arabidopsis and wheat, in part by modulating the accumulation of gibberellin (GA)-regulated DELLA growth repressors. We show that nitrate reduces the abundance of DELLAs by increasing GA contents through activation of GA metabolism gene expression. Consistently, the growth restraint conferred by nitrate deficiency is partially rescued in global-DELLA mutant that lacks all DELLAs. At the cellular level, we show that nitrate enhances both cell proliferation and elongation in a DELLA-dependent and -independent manner, respectively. Our findings establish a connection between nitrate and GA signaling pathways that allow plants to adapt their growth to nitrate availability.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Regulação da Expressão Gênica de Plantas , Giberelinas/metabolismo , Nitratos , Reguladores de Crescimento de Plantas/metabolismo , Proteínas de Plantas/metabolismo , Plantas/genética , Transdução de Sinais/fisiologiaRESUMO
Shoot branching is a pivotal process during plant growth and development, and is antagonistically orchestrated by auxin and sugars. In contrast to extensive investigations on hormonal regulatory networks, our current knowledge on the role of sugar signalling pathways in bud outgrowth is scarce. Based on a comprehensive stepwise strategy, we investigated the role of glycolysis/the tricarboxylic acid (TCA) cycle and the oxidative pentose phosphate pathway (OPPP) in the control of bud outgrowth. We demonstrated that these pathways are necessary for bud outgrowth promotion upon plant decapitation and in response to sugar availability. They are also targets of the antagonistic crosstalk between auxin and sugar availability. The two pathways act synergistically to down-regulate the expression of BRC1, a conserved inhibitor of shoot branching. Using Rosa calluses stably transformed with GFP-fused promoter sequences of RhBRC1 (pRhBRC1), glycolysis/TCA cycle and the OPPP were found to repress the transcriptional activity of pRhBRC1 cooperatively. Glycolysis/TCA cycle- and OPPP-dependent regulations involve the -1973/-1611 bp and -1206/-709 bp regions of pRhBRC1, respectively. Our findings indicate that glycolysis/TCA cycle and the OPPP are integrative parts of shoot branching control and can link endogenous factors to the developmental programme of bud outgrowth, likely through two distinct mechanisms.
Assuntos
Rosa , Regulação da Expressão Gênica de Plantas , Ácidos Indolacéticos , Brotos de Planta , AçúcaresRESUMO
Plants are able to sense a rise in temperature of several degrees, and appropriately adapt their metabolic and growth processes. To this end, plants produce various signalling molecules that act throughout the plant body. Here, we report that root-derived GA12, a precursor of the bioactive gibberellins, mediates thermo-responsive shoot growth in Arabidopsis. Our data suggest that root-to-shoot translocation of GA12 enables a flexible growth response to ambient temperature changes.
Assuntos
Arabidopsis/metabolismo , Giberelinas/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Raízes de Plantas/metabolismo , Brotos de Planta/crescimento & desenvolvimento , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Regulação da Expressão Gênica de Plantas , Raízes de Plantas/genética , Raízes de Plantas/crescimento & desenvolvimento , Brotos de Planta/genética , Brotos de Planta/metabolismo , TemperaturaRESUMO
INDETERMINATE DOMAIN (IDD)/ BIRD proteins are a highly conserved plant-specific family of transcription factors which play multiple roles in plant development and physiology. Here, we show that mutation in IDD4/IMPERIAL EAGLE increases resistance to the hemi-biotrophic pathogen Pseudomonas syringae, indicating that IDD4 may act as a repressor of basal immune response and PAMP-triggered immunity. Furthermore, the idd4 mutant exhibits enhanced plant-growth indicating IDD4 as suppressor of growth and development. Transcriptome comparison of idd4 mutants and IDD4ox lines aligned to genome-wide IDD4 DNA-binding studies revealed major target genes related to defense and developmental-biological processes. IDD4 is a phospho-protein that interacts and becomes phosphorylated on two conserved sites by the MAP kinase MPK6. DNA-binding studies of IDD4 after flg22 treatment and with IDD4 phosphosite mutants show enhanced binding affinity to ID1 motif-containing promoters and its function as a transcriptional regulator. In contrast to the IDD4-phospho-dead mutant, the IDD4 phospho-mimicking mutant shows altered susceptibility to PstDC3000, salicylic acid levels and transcriptome reprogramming. In summary, we found that IDD4 regulates various hormonal pathways thereby coordinating growth and development with basal immunity.
Assuntos
Arabidopsis/crescimento & desenvolvimento , Arabidopsis/imunologia , Imunidade Vegetal/genética , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Resistência à Doença/imunologia , Regulação da Expressão Gênica de Plantas/genética , Mutação , Desenvolvimento Vegetal/genética , Doenças das Plantas/genética , Plantas Geneticamente Modificadas/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
The thickening of plant organs is supported by secondary growth, a process by which new vascular tissues (xylem and phloem) are produced. Xylem is composed of several cell types, including xylary fibers, parenchyma and vessel elements. In Arabidopsis, it has been shown that fibers are promoted by the class-I KNOX gene KNAT1 and the plant hormones gibberellins, and are repressed by a small set of receptor-like kinases; however, we lack a mechanistic framework to integrate their relative contributions. Here, we show that DELLAs, negative elements of the gibberellin signaling pathway, physically interact with KNAT1 and impair its binding to KNAT1-binding sites. Our analysis also indicates that at least 37% of the transcriptome mobilized by KNAT1 is potentially dependent on this interaction, and includes genes involved in secondary cell wall modifications and phenylpropanoid biosynthesis. Moreover, the promotion by constitutive overexpression of KNAT1 of fiber formation and the expression of genes required for fiber differentiation were still reverted by DELLA accumulation, in agreement with post-translational regulation of KNAT1 by DELLA proteins. These results suggest that gibberellins enhance fiber development by promoting KNAT1 activity.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/citologia , Arabidopsis/metabolismo , Diferenciação Celular , Giberelinas/farmacologia , Proteínas de Homeodomínio/metabolismo , Xilema/citologia , Xilema/metabolismo , Arabidopsis/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Mutação com Ganho de Função/genética , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Fenótipo , Feixe Vascular de Plantas/efeitos dos fármacos , Feixe Vascular de Plantas/metabolismo , Regiões Promotoras Genéticas/genética , Ligação Proteica/efeitos dos fármacos , Transcriptoma/efeitos dos fármacos , Transcriptoma/genética , Xilema/efeitos dos fármacosAssuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Regulação da Expressão Gênica de Plantas , N-Acetilglucosaminiltransferases/metabolismo , Proteínas Repressoras/metabolismo , Giberelinas/metabolismo , Modelos Biológicos , Plantas Geneticamente Modificadas , Processamento de Proteína Pós-Traducional , Nicotiana/genéticaRESUMO
Phytohormones are a group of low abundance molecules that activate various metabolic and developmental processes in response to environmental and endogenous signals. Like animal hormones, plant hormones often have distinct source and target tissues, hence ensuring long-range communication at the whole-plant level. Plants rely on various hormone distribution mechanisms depending on the distance and the direction of the transport. Here, we highlight the recent findings on the long-distance movement of plant hormones within the vasculature, from the physiological role to the molecular mechanism of the transport.
Assuntos
Reguladores de Crescimento de Plantas/metabolismo , Plantas/metabolismo , Transporte Biológico/genética , Transporte Biológico/fisiologia , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Transdução de Sinais/genética , Transdução de Sinais/fisiologiaRESUMO
Iron is an essential element for most living organisms. Plants acquire iron from the rhizosphere and have evolved different biochemical and developmental responses to adapt to a low-iron environment. In Arabidopsis, FIT encodes a basic helix-loop-helix transcription factor that activates the expression of iron-uptake genes in root epidermis upon iron deficiency. Here, we report that the gibberellin (GA)-signaling DELLA repressors contribute substantially in the adaptive responses to iron-deficient conditions. When iron availability decreases, DELLAs accumulate in the root meristem, thereby restraining root growth, while being progressively excluded from epidermal cells in the root differentiation zone. Such DELLA exclusion from the site of iron acquisition relieves FIT from DELLA-dependent inhibition and therefore promotes iron uptake. Consistent with this mechanism, expression of a non-GA-degradable DELLA mutant protein in root epidermis interferes with iron acquisition. Hence, spatial distribution of DELLAs in roots is essential to fine-tune the adaptive responses to iron availability.
Assuntos
Arabidopsis/metabolismo , Regulação da Expressão Gênica de Plantas/fisiologia , Giberelinas/metabolismo , Ferro/metabolismo , Proteínas de Arabidopsis/metabolismo , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Reguladores de Crescimento de Plantas/farmacologia , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/metabolismoRESUMO
Gibberellins (GAs) are phytohormones controlling major aspects of plant growth and development. Although previous studies suggested the existence of a transport of GAs in plants, the nature and properties associated with this transport were unknown. We recently showed through micrografting and biochemical approaches that the GA12 precursor is the chemical form of GA undergoing long-distance transport across plant organs in Arabidopsis. Endogenous GA12 moves through the plant vascular system from production sites to recipient tissues, in which GA12 can be converted to bioactive forms to support growth via the activation of GA-dependent processes. GAs are also essential to promote seed germination; hence GA biosynthesis mutants do not germinate without exogenous GA treatment. Our results suggest that endogenous GAs are not (or not sufficiently) transmitted to the offspring to successfully complete the germination under permissive conditions.
Assuntos
Arabidopsis/metabolismo , Giberelinas/metabolismo , Arabidopsis/efeitos dos fármacos , Arabidopsis/crescimento & desenvolvimento , Transporte Biológico/efeitos dos fármacos , Germinação/efeitos dos fármacos , Giberelinas/farmacologia , Sementes/efeitos dos fármacos , Sementes/metabolismo , Transdução de Sinais/efeitos dos fármacosRESUMO
Plant phenotypic plasticity is controlled by diverse hormone pathways, which integrate and convey information from multiple developmental and environmental signals. Moreover, in plants many processes such as growth, development, and defense are regulated in similar ways by multiple hormones. Among them, gibberellins (GAs) are phytohormones with pleiotropic actions, regulating various growth processes throughout the plant life cycle. Previous work has revealed extensive interplay between GAs and other hormones, but the molecular mechanism became apparent only recently. Molecular and physiological studies have demonstrated that DELLA proteins, considered as master negative regulators of GA signaling, integrate multiple hormone signaling pathways through physical interactions with transcription factors or regulatory proteins from different families. In this review, we summarize the latest progress in GA signaling and its direct crosstalk with the main phytohormone signaling, emphasizing the multifaceted role of DELLA proteins with key components of major hormone signaling pathways.
Assuntos
Giberelinas/metabolismo , Proteínas de Plantas/metabolismo , Plantas/metabolismo , Transdução de Sinais , Proteínas de Arabidopsis/metabolismo , Desenvolvimento Vegetal , Sementes/crescimento & desenvolvimento , Sementes/metabolismoRESUMO
Global inspection of plant genomes identifies genes maintained in low copies across taxa and under strong purifying selection, which are likely to have essential functions. Based on this rationale, we investigated the function of the low-duplicated CYP715 cytochrome P450 gene family that appeared early in seed plants and evolved under strong negative selection. Arabidopsis CYP715A1 showed a restricted tissue-specific expression in the tapetum of flower buds and in the anther filaments upon anthesis. cyp715a1 insertion lines showed a strong defect in petal development, and transient alteration of pollen intine deposition. Comparative expression analysis revealed the downregulated expression of genes involved in pollen development, cell wall biogenesis, hormone homeostasis, and floral sesquiterpene biosynthesis, especially TPS21 and several key genes regulating floral development such as MYB21, MYB24, and MYC2. Accordingly, floral sesquiterpene emission was suppressed in the cyp715a1 mutants. Flower hormone profiling, in addition, indicated a modification of gibberellin homeostasis and a strong disturbance of the turnover of jasmonic acid derivatives. Petal growth was partially restored by the active gibberellin GA3 or the functional analog of jasmonoyl-isoleucine, coronatine. CYP715 appears to function as a key regulator of flower maturation, synchronizing petal expansion and volatile emission. It is thus expected to be an important determinant of flower-insect interaction.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/crescimento & desenvolvimento , Sistema Enzimático do Citocromo P-450/metabolismo , Flores/enzimologia , Sementes/enzimologia , Arabidopsis/classificação , Arabidopsis/enzimologia , Arabidopsis/genética , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/genética , Sequência Conservada , Sistema Enzimático do Citocromo P-450/química , Sistema Enzimático do Citocromo P-450/genética , Flores/classificação , Flores/genética , Flores/crescimento & desenvolvimento , Regulação da Expressão Gênica no Desenvolvimento , Regulação da Expressão Gênica de Plantas , Filogenia , Plantas/classificação , Plantas/enzimologia , Plantas/genética , Sementes/classificação , Sementes/genética , Sementes/crescimento & desenvolvimentoRESUMO
The gibberellin (GA) phytohormones play important roles in plant growth and development, promoting seed germination, elongation growth and reproductive development(1). Over the years, substantial progress has been made in understanding the regulation of GA signalling and metabolism, which ensures appropriate levels of GAs for growth and development(2). Moreover, an additional level of regulation may reside in the transport of GAs from production sites to recipient tissues that require GAs for growth. Although there is considerable evidence suggesting the existence of short- and long-distance movement of GAs in plants(3-8), the nature and the biological properties of this transport are not yet understood. Here, we combine biochemical and conventional micrografting experiments in Arabidopsis thaliana to show that the GA precursor GA12, although biologically inactive by itself, is the major mobile GA signal over long distances. Quantitative analysis of endogenous GAs in xylem and phloem exudates further indicates that GA12 moves through the plant vascular system. Finally, we demonstrate that GA12 is functional in recipient tissues, supporting growth via the activation of the GA signalling cascade. Collectively, these results reveal the existence of long-range transport of endogenous GA12 in plants that may have implications for the control of developmental phase transitions and the adaptation to adverse environments.
RESUMO
Regulation of plant height, one of the most important agronomic traits, is the focus of intensive research for improving crop performance. Stem elongation takes place as a result of repeated cell divisions and subsequent elongation of cells produced by apical and intercalary meristems. The gibberellin (GA) phytohormones have long been known to control stem and internodal elongation by stimulating the degradation of nuclear growth-repressing DELLA proteins; however, the mechanism allowing GA-responsive growth is only slowly emerging. Here, we show that DELLAs directly regulate the activity of the plant-specific class I TCP transcription factor family, key regulators of cell proliferation. Our results demonstrate that class I TCP factors directly bind the promoters of core cell-cycle genes in Arabidopsis inflorescence shoot apices while DELLAs block TCP function by binding to their DNA-recognition domain. GAs antagonize such repression by promoting DELLA destruction and therefore cause a concomitant accumulation of TCP factors on promoters of cell-cycle genes. Consistent with this model, the quadruple mutant tcp8 tcp14 tcp15 tcp22 exhibits severe dwarfism and reduced responsiveness to GA action. Altogether, we conclude that GA-regulated DELLA-TCP interactions in inflorescence shoot apex provide a novel mechanism to control plant height.
Assuntos
Arabidopsis/crescimento & desenvolvimento , Arabidopsis/genética , Regulação da Expressão Gênica de Plantas , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Giberelinas/metabolismo , Inflorescência/genética , Inflorescência/crescimento & desenvolvimento , Inflorescência/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Brotos de Planta/genética , Brotos de Planta/crescimento & desenvolvimento , Brotos de Planta/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
Ent-kaurenoic acid oxidase (KAO), a class of cytochrome P450 monooxygenases of the subfamily CYP88A, catalyzes the conversion of ent-kaurenoic acid (KA) to gibberellin (GA) GA12 , the precursor of all GAs, thereby playing an important role in determining GA concentration in plants. Past work has demonstrated the importance of KAO activity for growth in various plant species. In Arabidopsis, this enzyme is encoded by two genes designated KAO1 and KAO2. In this study, we used various approaches to determine the physiological roles of KAO1 and KAO2 throughout plant development. Analysis of gene expression pattern reveals that both genes are mainly expressed in germinating seeds and young developing organs, thus suggesting functional redundancy. Consistent with this, kao1 and kao2 single mutants are indistinguishable from wild-type plants. By contrast, the kao1 kao2 double mutant exhibits typical non-germinating GA-dwarf phenotypes, similar to those observed in the severely GA-deficient ga1-3 mutant. Phenotypic characterization and quantitative analysis of endogenous GA contents of single and double kao mutants further confirm an overlapping role of KAO1 and KAO2 throughout Arabidopsis development.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/enzimologia , Regulação da Expressão Gênica de Plantas , Giberelinas/metabolismo , Oxigenases de Função Mista/metabolismo , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Proteínas de Arabidopsis/genética , Regulação Enzimológica da Expressão Gênica , Germinação , Giberelinas/análise , Oxigenases de Função Mista/genética , Mutação , FenótipoRESUMO
Upon insect herbivory, many plant species change the direction of metabolic flux from growth into defence. Two key pathways modulating these processes are the gibberellin (GA)/DELLA pathway and the jasmonate pathway. In this study, the effect of caterpillar herbivory on plant-induced responses was compared between wild-type Arabidopsis thaliana (L.) Heynh. and quad-della mutants that have constitutively elevated GA responses. The labial saliva (LS) of caterpillars of the beet armyworm, Spodoptera exigua, is known to influence induced plant defence responses. To determine the role of this herbivore cue in determining metabolic shifts, plants were subject to herbivory by caterpillars with intact or impaired LS secretions. In both wild-type and quad-della plants, a jasmonate burst is an early response to caterpillar herbivory. Negative growth regulator DELLA proteins are required for the LS-mediated suppression of hormone levels. Jasmonate-dependent marker genes are induced in response to herbivory independently of LS, with the exception of AtPDF1.2 that showed LS-dependent expression in the quad-della mutant. Early expression of the salicylic acid (SA)-marker gene, AtPR1, was not affected by herbivory which also reflected SA hormone levels; however, this gene showed LS-dependent expression in the quad-della mutant. DELLA proteins may positively regulate glucosinolate levels and suppress laccase-like multicopper oxidase activity in response to herbivory. The present results show a link between DELLA proteins and early, induced plant defences in response to insect herbivory; in particular, these proteins are necessary for caterpillar LS-associated attenuation of defence hormones.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/imunologia , Arabidopsis/parasitologia , Herbivoria/fisiologia , Spodoptera/fisiologia , Animais , Arabidopsis/genética , Ciclopentanos/metabolismo , Regulação da Expressão Gênica de Plantas , Glucosinolatos/metabolismo , Indóis , Larva/fisiologia , Modelos Biológicos , Oxilipinas/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Folhas de Planta/metabolismo , Saliva/metabolismoRESUMO
Gibberellins (GA) are phytohormones controlling major aspects of plant lifecycle including seed germination, growth and flower development. GA signaling is also involved in resistance to adverse conditions, thus providing a mechanism for environmentally responsive growth regulation. We recently characterized the function of a core component of the GA signal transduction pathway: RGL3. RGL3 belongs to the DELLA family of negative GA response regulators. Jasmonate (JA) rapidly induces RGL3 expression, which in turn enhances the expression of JA-responsive genes by inhibiting the activity of key repressors of JA signaling, the JAZ proteins. JA and ethylene (ET) are well known to play synergistic roles in plant disease resistance. Accordingly, we showed that RGL3 regulates plant defense responses by modulating JA/ET-mediated defense signaling pathway.