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1.
Chemosphere ; 233: 954-965, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31340423

RESUMO

Heavy metals such as cadmium and zinc constitute major pollutants in coastal areas and frequently accumulate in salt marshes. The wetland halophyte plant species Kosteletzkya pentacarpos is a promising species for phytostabilization of contaminated areas. In order to assess the role of the antisenescing phytohormone cytokinin in heavy metal resistance in this species, seedlings were exposed for two weeks to Cd (10 µM), Zn (100 µM) or Cd + Zn (10 µM + 100 µM) in the presence or absence of 50 mM NaCl and half of the plants were sprayed every two days with the cytokinin trans-zeatine riboside (10 µM). Zinc reduced the endogenous cytokinin concentration. Exogenous cytokinin increased plant growth, stomatal conductance, net photosynthesis and total ascorbate and reduced oxidative stress estimated by malondialdehyde in Zn-treated plants maintained in the absence of NaCl. Heavy metal induced an increase in the senescing hormone ethylene which was reduced by cytokinin treatment. Plants exposed to the mixed treatment (Cd + Zn) exhibited a specific hormonal status in relation to accumulation of abscisic acid and depletion of salicylic acid. Non-protein thiols (glutathione and phytochelatins) accumulated in response to Cd and Cd + Zn. It is concluded that toxic doses of Cd and Zn have different impacts on the plant behavior and that the simultaneous presence of the two elements induces a specific physiological constraint at the plant level. Salinity helps the plant to cope with heavy metal toxicities and the plant hormone cytokinin assumes key function in Zn resistance but its efficiency is lower in the presence of NaCl.


Assuntos
Cádmio/toxicidade , Citocininas/metabolismo , Hibiscus/metabolismo , Reguladores de Crescimento de Planta/metabolismo , Cloreto de Sódio/farmacologia , Zinco/toxicidade , Ácido Abscísico/análise , Glutationa/metabolismo , Hibiscus/crescimento & desenvolvimento , Fotossíntese/efeitos dos fármacos , Fitoquelatinas/metabolismo , Desenvolvimento Vegetal/efeitos dos fármacos , Ácido Salicílico/análise , Salinidade , Plântula/fisiologia , Poluentes Químicos da Água/toxicidade , Áreas Alagadas
2.
World J Microbiol Biotechnol ; 35(6): 90, 2019 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-31147784

RESUMO

The ability of plant growth promoting rhizobacteria (PGPR) for imparting abiotic stress tolerance to plants has been widely explored in recent years; however, the diversity and potential of these microbes have not been maximally exploited. In this study, we characterized four bacterial strains, namely, Pseudomonas aeruginosa PM389, Pseudomonas aeruginosa ZNP1, Bacillus endophyticus J13 and Bacillus tequilensis J12, for potential plant growth promoting (PGP) traits under osmotic-stress, induced by 25% polyethylene glycol (PEG) in the growth medium. Growth curve analysis was performed in LB medium with or without PEG, in order to understand the growth patterns of these bacteria under osmotic-stress. All strains were able to grow and proliferate under osmotic-stress, although their growth rate was slower than that under non-stressed conditions (LB without PEG). Bacterial secretions were analyzed for the presence of exopolysaccharides and phytohormones and it was observed that all four strains released these compounds into the media, both, under stressed and non-stressed conditions. In the Pseudomonas strains, osmotic stress caused a decrease in the levels of auxin (IAA) and cytokinin (tZ), but an increase in the levels of gibberellic acid. The Bacillus strains on the other hand showed a stress-induced increase in the levels of all three phytohormones. P. aeruginosa ZNP1 and B. endophyticus J13 exhibited increased EPS production under osmotic-stress. While osmotic stress caused a decrease in the levels of EPS in P. aeruginosa PM389, B. tequilensis J12 showed no change in EPS quantities released into the media under osmotic stress when compared to non-stressed conditions. Upon inoculating Arabidopsis thaliana seedlings with these strains individually, it was observed that all four strains were able to ameliorate the adverse effects of osmotic-stress (induced by 25% PEG in MS-Agar medium) in the plants, as evidenced by their enhanced fresh weight, dry weight and plant water content, as opposed to osmotic-stressed, non-inoculated plants.


Assuntos
Arabidopsis/microbiologia , Fenômenos Fisiológicos Bacterianos , Secas , Pressão Osmótica , Desenvolvimento Vegetal , Reguladores de Crescimento de Planta/metabolismo , Polissacarídeos Bacterianos/metabolismo , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/metabolismo , Bacillus/crescimento & desenvolvimento , Bacillus/fisiologia , Bactérias/classificação , Bactérias/crescimento & desenvolvimento , Bactérias/metabolismo , Citocininas/metabolismo , Giberelinas/metabolismo , Ácidos Indolacéticos/metabolismo , Raízes de Plantas/microbiologia , Pseudomonas aeruginosa/crescimento & desenvolvimento , Pseudomonas aeruginosa/fisiologia , Rizosfera , Plântula/crescimento & desenvolvimento , Microbiologia do Solo , Estresse Fisiológico/fisiologia
3.
BMC Genomics ; 20(1): 373, 2019 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-31088345

RESUMO

BACKGROUND: Legumes can establish on nitrogen-deprived soils a symbiotic interaction with Rhizobia bacteria, leading to the formation of nitrogen-fixing root nodules. Cytokinin phytohormones are critical for triggering root cortical cell divisions at the onset of nodule initiation. Cytokinin signaling is based on a Two-Component System (TCS) phosphorelay cascade, involving successively Cytokinin-binding Histidine Kinase receptors, phosphorelay proteins shuttling between the cytoplasm and the nucleus, and Type-B Response Regulator (RRB) transcription factors activating the expression of cytokinin primary response genes. Among those, Type-A Response Regulators (RRA) exert a negative feedback on the TCS signaling. To determine whether the legume plant nodulation capacity is linked to specific features of TCS proteins, a genome-wide identification was performed in six legume genomes (Cajanus cajan, pigeonpea; Cicer arietinum, chickpea; Glycine max, soybean; Phaseolus vulgaris, common bean; Lotus japonicus; Medicago truncatula). The diversity of legume TCS proteins was compared to the one found in two non-nodulating species, Arabidopsis thaliana and Vitis vinifera, which are references for functional analyses of TCS components and phylogenetic analyses, respectively. RESULTS: A striking expansion of non-canonical RRBs was identified, notably leading to the emergence of proteins where the conserved phosphor-accepting aspartate residue is replaced by a glutamate or an asparagine. M. truncatula genome-wide expression datasets additionally revealed that only a limited subset of cytokinin-related TCS genes is highly expressed in different organs, namely MtCHK1/MtCRE1, MtHPT1, and MtRRB3, suggesting that this "core" module potentially acts in most plant organs including nodules. CONCLUSIONS: Further functional analyses are required to determine the relevance of these numerous non-canonical TCS RRBs in symbiotic nodulation, as well as of canonical MtHPT1 and MtRRB3 core signaling elements.


Assuntos
Citocininas/metabolismo , Histidina Quinase/genética , Medicago truncatula/genética , Fatores de Transcrição/genética , Evolução Molecular , Fabaceae/genética , Fabaceae/metabolismo , Regulação da Expressão Gênica de Plantas , Histidina Quinase/metabolismo , Medicago truncatula/metabolismo , Filogenia , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Nódulos Radiculares de Plantas/metabolismo , Transdução de Sinais , Fatores de Transcrição/metabolismo , Sequenciamento Completo do Genoma
4.
Plant Cell Physiol ; 60(8): 1842-1854, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31135032

RESUMO

Cytokinins are known to regulate various physiological events in plants. Cytokinin signaling is mediated by the phosphorelay system, one of the most ancient mechanisms controlling hormonal pathways in plants. The liverwort Marchantia polymorpha possesses all components necessary for cytokinin signaling; however, whether they respond to cytokinins and how the signaling is fine-tuned remain largely unknown. Here, we report cytokinin function in Marchantia development and organ formation. Our measurement of cytokinin species revealed that cis-zeatin is the most abundant cytokinin in Marchantia. We reduced the endogenous cytokinin level by overexpressing the gene for cytokinin oxidase, MpCKX, which inactivates cytokinins, and generated overexpression and knockout lines for type-A (MpRRA) and type-B (MpRRB) response regulators to manipulate the signaling. The overexpression lines of MpCKX and MpRRA, and the knockout lines of MpRRB, shared phenotypes such as inhibition of gemma cup formation, enhanced rhizoid formation and hyponastic thallus growth. Conversely, the knockout lines of MpRRA produced more gemma cups and exhibited epinastic thallus growth. MpRRA expression was elevated by cytokinin treatment and reduced by knocking out MpRRB, suggesting that MpRRA is upregulated by the MpRRB-mediated cytokinin signaling, which is antagonized by MpRRA. Our findings indicate that when plants moved onto land they already deployed the negative feedback loop of cytokinin signaling, which has an indispensable role in organogenesis.


Assuntos
Citocininas/metabolismo , Marchantia/metabolismo , Regulação da Expressão Gênica de Plantas/genética , Regulação da Expressão Gênica de Plantas/fisiologia , Marchantia/genética , Organogênese Vegetal/genética , Organogênese Vegetal/fisiologia , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/metabolismo , Transdução de Sinais/genética , Transdução de Sinais/fisiologia
5.
Int J Mol Sci ; 20(9)2019 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-31035389

RESUMO

The signaling of cytokinins (CKs), classical plant hormones, is based on the interaction of proteins that constitute the multistep phosphorelay system (MSP): catalytic receptors-sensor histidine kinases (HKs), phosphotransmitters (HPts), and transcription factors-response regulators (RRs). Any CK receptor was shown to interact in vivo with any of the studied HPts and vice versa. In addition, both of these proteins tend to form a homodimer or a heterodimeric complex with protein-paralog. Our study was aimed at explaining by molecular modeling the observed features of in planta protein-protein interactions, accompanying CK signaling. For this purpose, models of CK-signaling proteins' structure from Arabidopsis and potato were built. The modeled interaction interfaces were formed by rather conserved areas of protein surfaces, complementary in hydrophobicity and electrostatic potential. Hot spots amino acids, determining specificity and strength of the interaction, were identified. Virtual phosphorylation of conserved Asp or His residues affected this complementation, increasing (Asp-P in HK) or decreasing (His-P in HPt) the affinity of interacting proteins. The HK-HPt and HPt-HPt interfaces overlapped, sharing some of the hot spots. MSP proteins from Arabidopsis and potato exhibited similar properties. The structural features of the modeled protein complexes were consistent with the experimental data.


Assuntos
Citocininas/metabolismo , Proteínas de Plantas/metabolismo , Transdução de Sinais/fisiologia , Modelos Biológicos , Ligação Proteica
6.
Int J Mol Sci ; 20(8)2019 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-31027230

RESUMO

Leaf senescence is a highly-programmed developmental process regulated by an array of multiple signaling pathways. Our group previously reported that overexpression of the protein phosphatase-encoding gene SSPP led to delayed leaf senescence and significantly enhanced cytokinin responses. However, it is still unclear how the delayed leaf senescence phenotype is associated with the enhanced cytokinin responses. In this study, we introduced a cytokinin receptor AHK3 knockout into the 35S:SSPP background. The phenotypic analysis of double mutant revealed that AHK3 loss-of-function reversed the delayed leaf senescence induced by SSPP. Moreover, we found the hypersensitivity of 35S:SSPP to exogenous cytokinin treatment disappeared due to the introduction of AHK3 knockout. Collectively, our results demonstrated that AHK3-mediated cytokinin signaling is required for the delayed leaf senescence caused by SSPP overexpression and the detailed mechanism remains to be further elucidated.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Citocininas/metabolismo , Histidina Quinase/metabolismo , Fosfoproteínas Fosfatases/metabolismo , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/metabolismo , Transdução de Sinais , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Proteínas de Arabidopsis/genética , Regulação da Expressão Gênica de Plantas , Fosfoproteínas Fosfatases/genética , Plantas Geneticamente Modificadas , RNA Mensageiro/genética , RNA Mensageiro/metabolismo
7.
Planta ; 250(1): 145-162, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30949762

RESUMO

MAIN CONCLUSION: The possible molecular mechanisms regulating strawberry fruit ripening were revealed by plant hormone quantification, exogenous hormone application, and RNA-sequencing. Fruit ripening involves a complex interplay among plant hormones. Strawberry is a model for studies on non-climacteric fruit ripening. However, the knowledge on how plant hormones are involved in strawberry ripening is still limited. To understand hormonal actions in the ripening process, we performed genome-wide transcriptome and hormonal analysis for the five major hormones (abscisic acid and catabolites, auxins, cytokinins, gibberellins, and ethylene) in achenes and receptacles (flesh) at different ripening stages of the woodland strawberry Fragaria vesca. Our results demonstrate that the pre-turning stage (a stage with white flesh and red achenes defined in this study) is the transition stage from immature to ripe fruits. The combinatorial analyses of hormone content, transcriptome data, and exogenous hormone treatment indicate that auxin is synthesized predominantly in achenes, while abscisic acid (ABA), bioactive free base cytokinins, gibberellins, and ethylene are mainly produced in receptacles. Furthermore, gibberellin may delay ripening, while ethylene and cytokinin are likely involved at later stages of the ripening process. Our results also provide additional evidence that ABA promotes ripening, while auxin delays it. Although our hormone analysis demonstrates that the total auxin in receptacles remains relatively low and unchanged during ripening, our experimental evidence further indicates that ABA likely enhances expression of the endoplasmic reticulum-localized auxin efflux carrier PIN-LIKES, which may subsequently reduce the auxin level in nucleus. This study provides a global picture for hormonal regulation of non-climacteric strawberry fruit ripening and also evidence for a possible mechanism of ABA and auxin interaction in the ripening process.


Assuntos
Fragaria/genética , Regulação da Expressão Gênica de Plantas , Reguladores de Crescimento de Planta/metabolismo , Proteínas de Plantas/metabolismo , Transcriptoma , Ácido Abscísico/análise , Ácido Abscísico/metabolismo , Citocininas/análise , Citocininas/metabolismo , Etilenos/análise , Etilenos/metabolismo , Fragaria/fisiologia , Frutas/genética , Frutas/fisiologia , Giberelinas/análise , Giberelinas/metabolismo , Ácidos Indolacéticos/análise , Ácidos Indolacéticos/metabolismo , Reguladores de Crescimento de Planta/análise , Proteínas de Plantas/genética
9.
Nat Plants ; 5(3): 290-299, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30833710

RESUMO

Plants have evolved sophisticated systems in response to environmental changes, and growth arrest is a common strategy used to enhance stress tolerance. Despite the growth-survival trade-off being essential to the shaping of plant productivity, the mechanisms balancing growth and survival remain largely unknown. Aquaporins play a crucial role in growth and stress responses by controlling water transport across membranes. Here, we show that RhPIP2;1, an aquaporin from rose (Rosa sp.), interacts with a membrane-tethered MYB protein, RhPTM. Water deficiency triggers nuclear translocation of the RhPTM C terminus. Silencing of RhPTM causes continuous growth under drought stress and a consequent decrease in survival rate. RNA sequencing (RNA-seq) indicated that RhPTM influences the expression of genes related to carbohydrate metabolism. Water deficiency induces phosphorylation of RhPIP2;1 at Ser 273, which is sufficient to promote nuclear translocation of the RhPTM C terminus. These results indicate that the RhPIP2;1-RhPTM module serves as a key player in orchestrating the trade-off between growth and stress survival in Rosa.


Assuntos
Aquaporinas/metabolismo , Proteínas de Plantas/metabolismo , Rosa/fisiologia , Fatores de Transcrição/metabolismo , Aquaporinas/genética , Arabidopsis/genética , Metabolismo dos Carboidratos , Núcleo Celular/metabolismo , Citocininas/metabolismo , Desidratação , Secas , Regulação da Expressão Gênica de Plantas , Ácidos Indolacéticos/metabolismo , Fosforilação , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas , Mapeamento de Interação de Proteínas , Rosa/crescimento & desenvolvimento , Serina/metabolismo , Transdução de Sinais , Fatores de Transcrição/genética
10.
BMC Plant Biol ; 19(1): 112, 2019 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-30902042

RESUMO

BACKGROUND: Mal de Río Cuarto virus (MRCV) infects several monocotyledonous species including maize and wheat. Infected plants show shortened internodes, partial sterility, increased tillering and reduced root length. To better understand the molecular basis of the plant-virus interactions leading to these symptoms, we combined RNA sequencing with metabolite and hormone measurements. RESULTS: More than 3000 differentially accumulated transcripts (DATs) were detected in MRCV-infected wheat plants at 21 days post inoculation compared to mock-inoculated plants. Infected plants exhibited decreased levels of TaSWEET13 transcripts, which are involved in sucrose phloem loading. Soluble sugars, starch, trehalose 6-phosphate (Tre6P), and organic and amino acids were all higher in MRCV-infected plants. In addition, several transcripts related to plant hormone metabolism, transport and signalling were increased upon MRCV infection. Transcripts coding for GA20ox, D14, MAX2 and SMAX1-like proteins involved in gibberellin biosynthesis and strigolactone signalling, were reduced. Transcripts involved in jasmonic acid, ethylene and brassinosteroid biosynthesis, perception and signalling and in auxin transport were also altered. Hormone measurements showed that jasmonic acid, brassinosteroids, abscisic acid and indole-3-acetic acid were significantly higher in infected leaves. CONCLUSIONS: Our results indicate that MRCV causes a profound hormonal imbalance that, together with alterations in sugar partitioning, could account for the symptoms observed in MRCV-infected plants.


Assuntos
Interações Hospedeiro-Patógeno/fisiologia , Reguladores de Crescimento de Planta/metabolismo , Reoviridae/patogenicidade , Açúcares/metabolismo , Triticum/virologia , Brassinosteroides/metabolismo , Citocininas/metabolismo , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Giberelinas/metabolismo , Ácidos Indolacéticos/metabolismo , Doenças das Plantas/virologia , Folhas de Planta/metabolismo , Folhas de Planta/virologia , Triticum/genética , Triticum/metabolismo
11.
Plant Sci ; 281: 122-132, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30824045

RESUMO

Cytokinins (CKs) regulate many developmental processes and environmental stress responses in plants. In this study, our data provide evidence that CK negatively regulates Arabidopsis selenium (Se) stress response. CK-deficient plant ipt1 3 5 7 exhibited enhanced Se tolerance which was abolished by exogenous benzylaminopurine (BA) application, while CK- receptor -deficient mutants ahk2 and ahk3 were sensitive to Se stress. Further investigation suggested that CK regulated Se tolerance of ipt1 3 5 7 through reduction of Se uptake and activation of metabolism detoxification, which had significantly lower transcriptions of high-affinity transporters PHT1;1, PHT1;8, PHT1;9 and the higher transcription of selenocysteine methyltransferase (SMT) respectively. Moreover, Se tolerance of ipt1 3 5 7 was associated with the enhanced antioxidant levels which had the higher catalase (CAT), ascorbate peroxidase (APX) and glutathione peroxidase (GPX) activities as well as the higher glutathione (GSH) content. On the other hand, loss-of-function mutations in single CK receptor genes could increase Se uptake and reactive oxygen species (ROS) accumulation, which caused Se sensitivity in ahk2 and ahk3 mutants. Taken together, these findings provide new insights to the role of CK in Se stress response in Arabidopsis.


Assuntos
Arabidopsis/efeitos dos fármacos , Arabidopsis/metabolismo , Citocininas/metabolismo , Selênio/farmacologia , Antioxidantes/metabolismo , Proteínas de Arabidopsis/metabolismo , Ascorbato Peroxidases/metabolismo , Catalase/metabolismo , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Regulação da Expressão Gênica de Plantas/genética , Mutação/genética , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/genética
12.
Fungal Biol ; 123(3): 255-266, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30798881

RESUMO

Fusarium pseudograminearum is an agronomically important fungus, which infects many crop plants, including wheat, where it causes Fusarium crown rot. Like many other fungi, the Fusarium genus produces a wide range of secondary metabolites of which only few have been characterized. Recently a novel gene cluster was discovered in F. pseudograminearum, which encodes production of cytokinin-like metabolites collectively named Fusarium cytokinins. They are structurally similar to plant cytokinins and can activate cytokinin signalling in vitro and in planta. Here, the regulation of Fusarium cytokinin production was analysed in vitro. This revealed that, similar to deoxynivalenol (DON) production in Fusariumgraminearum, cytokinin production can be induced in vitro by specific nitrogen sources in a pH-dependent manner. DON production was also induced in both F. graminearum and F. pseudograminearum in cytokinin-inducing conditions. In addition, microscopic analyses of wheat seedlings infected with a F. pseudograminearum cytokinin reporter strain showed that the fungus specifically induces its cytokinin production in hyphae, which are in close association with the plant, suggestive of a function of Fusarium cytokinins during infection.


Assuntos
Citocininas/metabolismo , Fusarium/genética , Fusarium/metabolismo , Regulação Fúngica da Expressão Gênica , Reguladores de Crescimento de Planta/metabolismo , Fusariose , Hifas/metabolismo , Plântula/microbiologia , Triticum/microbiologia
13.
J Sci Food Agric ; 99(8): 4142-4149, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30767237

RESUMO

BACKGROUND: 'Nules Clementine' mandarin was used to investigate the potential involvement of endogenous plant hormones in mediating citrus fruit susceptibility to rind breakdown disorder (RBD). The effect of light exposure (namely canopy position and bagging treatments) on the endogenous concentration of ABA, 7'-hydroxy-abscisic acid (7-OH-ABA), ABA-glucose ester (ABA-GE) and dihydrophaseic acid (DPA), and t-zeatin was tested using four preharvest treatments: outside, outside bagged, inside and inside bagged. Phytohormones concentration was evaluated during nine weeks of postharvest storage at 8 °C. RESULTS: The shaded fruit inside the canopy had the highest RBD score (0.88) at the end of postharvest storage, while sun-exposed fruit had the lowest score (0.12). Before storage, ABA concentration was lowest (462.8 µg kg-1 ) for inside fruit, and highest in outside bagged fruit (680.5 µg kg-1 ). Although ABA concentration suddenly increased from the third week, reaching a maximum concentration of 580 µg kg-1 at week 6 in fruit from inside position, it generally reduced 1.6-fold ranging from 240.52 to 480.65 µg kg-1 throughout storage. The increase of 7-OH-ABA was more prominent in fruit from inside canopy. Overall, the concentration of ABA-GE increased three-fold with storage time. DPA concentration of bagged fruit from inside canopy position was significantly higher compared to outside fruit. The lower ABA-GE and higher DPA concentration in inside bagged fruit throughout storage also coincided with higher RBD. CONCLUSION: The strong positive correlations between 7-OH-ABA, DPA and RBD incidence demonstrated that these ABA catabolites could be used as biomarkers for fruit susceptibility to the disorder. © 2019 Society of Chemical Industry.


Assuntos
Ácido Abscísico/metabolismo , Citrus/metabolismo , Citocininas/metabolismo , Frutas/crescimento & desenvolvimento , Reguladores de Crescimento de Planta/metabolismo , Ácido Abscísico/química , Citrus/crescimento & desenvolvimento , Citrus/efeitos da radiação , Citocininas/química , Frutas/metabolismo , Frutas/efeitos da radiação , Luz , Reguladores de Crescimento de Planta/química
14.
Int J Mol Sci ; 20(4)2019 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-30791522

RESUMO

The international symposium "Auxins and Cytokinins in Plant Development" (ACPD), which is held every 4⁻5 years in Prague, Czech Republic, is a meeting of scientists interested in the elucidation of the action of two important plant hormones-auxins and cytokinins. It is organized by a group of researchers from the Laboratory of Hormonal Regulations in Plants at the Institute of Experimental Botany, the Czech Academy of Sciences. The symposia already have a long tradition, having started in 1972. Thanks to the central role of auxins and cytokinins in plant development, the ACPD 2018 symposium was again attended by numerous experts who presented their results in the opening, two plenary lectures, and six regular sessions, including two poster sessions. Due to the open character of the research community, which is traditionally very well displayed during the meeting, a lot of unpublished data were presented and discussed. In this report, we summarize the contributions in individual sessions that attracted our attention.


Assuntos
Citocininas/metabolismo , Ácidos Indolacéticos/metabolismo , Desenvolvimento Vegetal , Reguladores de Crescimento de Planta/metabolismo , Transporte Biológico , Meio Ambiente , Redes e Vias Metabólicas , Transdução de Sinais
15.
BMC Plant Biol ; 19(1): 83, 2019 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-30786853

RESUMO

BACKGROUND: Cytokinin is a negative regulator of root growth, and a reduction of the cytokinin content or signalling causes the formation a larger root system in model plants, improves their growth under drought and nutrient limitation and causes increased accumulation of elements in the shoot. Roots are an important but understudied target of plant breeding. Here we have therefore explored whether root enhancement by lowering the cytokinin content can also be achieved in oilseed rape (Brassica napus L.) plants. RESULTS: Transgenic plants overexpressing the CKX2 gene of Arabidopsis thaliana encoding a cytokinin-degrading cytokinin oxidase/dehydrogenase showed higher CKX activity and a strongly reduced cytokinin content. Cytokinin deficiency led to the formation of a larger root system under different growth conditions, which was mainly due to an increased number of lateral and adventitious roots. In contrast, shoot growth was comparable to wild type, which caused an enhanced root-to-shoot ratio. Transgenic plants accumulated in their leaves higher concentrations of macro- and microelements including P, Ca, Mg, S, Zn, Cu, Mo and Mn. They formed more chlorophyll under Mg- and S-deficiency and accumulated a larger amount of Cd and Zn from contaminated medium and soil. CONCLUSIONS: These findings demonstrate the usefulness of ectopic CKX gene expression to achieve root enhancement in oilseed rape and underpin the functional relevance of a larger root system. Furthermore, the lack of major developmental consequences on shoot growth in cytokinin-deficient oilseed rape indicates species-specific differences of CKX gene and/or cytokinin action.


Assuntos
Biodegradação Ambiental , Brassica napus/metabolismo , Clorofila/metabolismo , Citocininas/metabolismo , Folhas de Planta/metabolismo , Raízes de Plantas/metabolismo , Brassica napus/genética , Brassica napus/crescimento & desenvolvimento , Cádmio/análise , Cádmio/metabolismo , Clorofila/análise , Citocininas/genética , Nutrientes/análise , Nutrientes/metabolismo , Oxirredutases/genética , Oxirredutases/metabolismo , Folhas de Planta/química , Raízes de Plantas/crescimento & desenvolvimento , Plantas Geneticamente Modificadas , Solo/química , Zinco/análise , Zinco/metabolismo
16.
BMC Plant Biol ; 19(1): 72, 2019 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-30760212

RESUMO

BACKGROUND: Drought is an important constraint on grapevine sustainability. Vitis riparia, widely used in rootstock and scion breeding, has been studied in isolated leaf drying response studies; however, it is essential to identify key root and shoot water deficit signaling traits in intact plants. This information will aid improved scion and rootstock selection and management practices in grapevine. RNAseq data were generated from V. riparia roots and shoots under water deficit and well-watered conditions to determine root signaling and shoot responses to water deficit. RESULTS: Shoot elongation, photosynthetic rate, and stomatal conductance were significantly reduced in water deficit (WD) treated than in well-watered grapevines. RNAseq analysis indicated greater transcriptional differences in shoots than in roots under WD, with 6925 and 1395 genes differentially expressed, respectively (q-value < 0.05). There were 50 and 25 VitisNet pathways significantly enriched in WD relative to well-watered treatments in grapevine shoots and roots, respectively. The ABA biosynthesis genes beta-carotene hydroxylase, zeaxanthin epoxidase, and 9-cis-epoxycarotenoid dioxygenases were up-regulated in WD root and WD shoot. A positive enrichment of ABA biosynthesis genes and signaling pathways in WD grapevine roots indicated enhanced root signaling to the shoot. An increased frequency of differentially expressed reactive oxygen species scavenging (ROS) genes were found in the WD shoot. Analyses of hormone signaling genes indicated a strong ABA, auxin, and ethylene network and an ABA, cytokinin, and circadian rhythm network in both WD shoot and WD root. CONCLUSIONS: This work supports previous findings in detached leaf studies suggesting ABA-responsive binding factor 2 (ABF2) is a central regulator in ABA signaling in the WD shoot. Likewise, ABF2 may have a key role in V. riparia WD shoot and WD root. A role for ABF3 was indicated only in WD root. WD shoot and WD root hormone expression analysis identified strong ABA, auxin, ethylene, cytokinin, and circadian rhythm signaling networks. These results present the first ABA, cytokinin, and circadian rhythm signaling network in roots under water deficit. These networks point to organ specific regulators that should be explored to further define the communication network from soil to shoot.


Assuntos
Regulação da Expressão Gênica de Plantas , Reguladores de Crescimento de Planta/metabolismo , Proteínas de Plantas/metabolismo , Transdução de Sinais , Transcriptoma , Vitis/genética , Ácido Abscísico/metabolismo , Citocininas/metabolismo , Desidratação , Secas , Etilenos/metabolismo , Especificidade de Órgãos , Folhas de Planta/genética , Folhas de Planta/fisiologia , Proteínas de Plantas/genética , Raízes de Plantas/genética , Raízes de Plantas/fisiologia , Brotos de Planta/genética , Brotos de Planta/fisiologia , Vitis/fisiologia
17.
Nature ; 565(7740): 490-494, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30626969

RESUMO

Apical growth in plants initiates upon seed germination, whereas radial growth is primed only during early ontogenesis in procambium cells and activated later by the vascular cambium1. Although it is not known how radial growth is organized and regulated in plants, this system resembles the developmental competence observed in some animal systems, in which pre-existing patterns of developmental potential are established early on2,3. Here we show that in Arabidopsis the initiation of radial growth occurs around early protophloem-sieve-element cell files of the root procambial tissue. In this domain, cytokinin signalling promotes the expression of a pair of mobile transcription factors-PHLOEM EARLY DOF 1 (PEAR1) and PHLOEM EARLY DOF 2 (PEAR2)-and their four homologues (DOF6, TMO6, OBP2 and HCA2), which we collectively name PEAR proteins. The PEAR proteins form a short-range concentration gradient that peaks at protophloem sieve elements, and activates gene expression that promotes radial growth. The expression and function of PEAR proteins are antagonized by the HD-ZIP III proteins, well-known polarity transcription factors4-the expression of which is concentrated in the more-internal domain of radially non-dividing procambial cells by the function of auxin, and mobile miR165 and miR166 microRNAs. The PEAR proteins locally promote transcription of their inhibitory HD-ZIP III genes, and thereby establish a negative-feedback loop that forms a robust boundary that demarks the zone of cell division. Taken together, our data establish that during root procambial development there exists a network in which a module that links PEAR and HD-ZIP III transcription factors integrates spatial information of the hormonal domains and miRNA gradients to provide adjacent zones of dividing and more-quiescent cells, which forms a foundation for further radial growth.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/citologia , Arabidopsis/genética , Câmbio/crescimento & desenvolvimento , Câmbio/genética , Regulação da Expressão Gênica de Plantas , Fatores de Transcrição/metabolismo , Arabidopsis/crescimento & desenvolvimento , Arabidopsis/metabolismo , Proteínas de Arabidopsis/biossíntese , Proteínas de Arabidopsis/genética , Câmbio/citologia , Câmbio/metabolismo , Divisão Celular/genética , Sinais (Psicologia) , Citocininas/metabolismo , Ácidos Indolacéticos/metabolismo , MicroRNAs/genética , MicroRNAs/metabolismo , Floema/citologia , Floema/metabolismo , Reguladores de Crescimento de Planta/metabolismo , Raízes de Plantas/citologia , Raízes de Plantas/genética , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Transdução de Sinais , Fatores de Transcrição/biossíntese , Fatores de Transcrição/genética , Transcrição Genética
18.
Phytopathology ; 109(5): 810-818, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30614377

RESUMO

Exploring the mechanism of plant resistance has become the basis for selection of resistance varieties but reports on revealing resistant mechanism in Brassica napus against Plasmodiophora brassicae are rare. In this study, RNA-seq was conducted in the clubroot-resistant B. napus breeding line ZHE-226 and in the clubroot-susceptible rapeseed cultivar Zhongshuang 11 at 0, 3, 6, 9, and 12 days after inoculation. Strong alteration was detected specifically in ZHE-226 as soon as the root hair infection happened, and significant promotion was found in ZHE-226 on cell division or cell cycle, DNA repair and synthesis, protein synthesis, signaling, antioxidation, and secondary metabolites. Combining results from physiological, biochemical, and histochemical assays, our study highlights an effective signaling in ZHE-226 in response to P. brassicae. This response consists of a fast initiation of receptor kinases by P. brassicae; the possible activation of host intercellular G proteins which might, together with an enhanced Ca2+ signaling, promote the production of reactive oxygen species; and programmed cell death in the host. Meanwhile, a strong ability to maintain homeostasis of auxin and cytokinin in ZHE-226 might effectively limit the formation of clubs on host roots. Our study provides initial insights into resistance mechanism in rapeseed to P. brassicae.


Assuntos
Brassica napus/microbiologia , Resistência à Doença , Doenças das Plantas/microbiologia , Plasmodioforídeos/patogenicidade , Sinalização do Cálcio , Morte Celular , Citocininas/metabolismo , Ácidos Indolacéticos/metabolismo , Raízes de Plantas/microbiologia , Espécies Reativas de Oxigênio/metabolismo
19.
Molecules ; 24(2)2019 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-30669410

RESUMO

The biology of the group of plant hormones termed cytokinins is reviewed to reveal areas where further studies of cytokinin-binding proteins could be significant. Such areas include: inhibition of human tumour cell growth by cytokinin ribosides, the role of cytokinins in the development of diverse micro-organisms including the cyanobacteria and Mycobacterium tuberculosis, the very rapid responses of plant cells to exogenous cytokinins, and other aspects of cytokinin plant biology. Photoaffinity labelling (PAL) coupled to the recent advances in HPLC of proteins and mass spectral analysis and sequencing of proteins, may have relevance to these areas. To facilitate PAL, we present experimental details for two methods for synthesis of 8-azido-N6-benzyladenine, which has the azido affinity group in the preferred position of the purine ring. Synthesis from [2-³H]adenosine yielded the above-mentioned PAL reagent with ³H in the purine ring and also gave labelled 9-riboside and 8-azido-N6,9-dibenzyladenine. 8-Azido-N6-benzyladenine was also prepared from 6,8-dichloropurine by a facile synthesis, which would allow a label to be sited in the benzyl group where substituents can also be introduced to vary cytokinin activity. The use of inactive cytokinin analogues in assessing the significance of PAL is discussed.


Assuntos
Compostos de Benzil/síntese química , Proteínas de Transporte/química , Proteínas de Transporte/metabolismo , Técnicas de Química Sintética , Citocininas/metabolismo , Processos Fotoquímicos , Purinas/síntese química , Adenosina/análogos & derivados , Adenosina/química , Compostos de Benzil/química , Cloroquinolinóis/química , Estrutura Molecular , Purinas/química , Coloração e Rotulagem
20.
Int J Mol Sci ; 20(3)2019 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-30678102

RESUMO

The spacing and distribution of lateral roots are critical determinants of plant root system architecture. In addition to providing anchorage, lateral roots explore the soil to acquire water and nutrients. Over the past several decades, we have deepened our understanding of the regulatory mechanisms governing lateral root formation and development. In this review, we summarize these recent advances and provide an overview of how auxin and cytokinin coordinate the regulation of lateral root formation and development.


Assuntos
Citocininas/metabolismo , Ácidos Indolacéticos/metabolismo , Desenvolvimento Vegetal , Fenômenos Fisiológicos Vegetais , Raízes de Plantas/fisiologia , Citocininas/genética , Regulação da Expressão Gênica de Plantas , Redes e Vias Metabólicas , Desenvolvimento Vegetal/genética , Transdução de Sinais
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