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1.
Proc Natl Acad Sci U S A ; 113(3): E396-405, 2016 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-26719420

RESUMO

Regulation of ion transport in plants is essential for cell function. Abiotic stress unbalances cell ion homeostasis, and plants tend to readjust it, regulating membrane transporters and channels. The plant hormone abscisic acid (ABA) and the second messenger Ca(2+) are central in such processes, as they are involved in the regulation of protein kinases and phosphatases that control ion transport activity in response to environmental stimuli. The identification and characterization of the molecular mechanisms underlying the effect of ABA and Ca(2+) signaling pathways on membrane function are central and could provide opportunities for crop improvement. The C2-domain ABA-related (CAR) family of small proteins is involved in the Ca(2+)-dependent recruitment of the pyrabactin resistance 1/PYR1-like (PYR/PYL) ABA receptors to the membrane. However, to fully understand CAR function, it is necessary to define a molecular mechanism that integrates Ca(2+) sensing, membrane interaction, and the recognition of the PYR/PYL interacting partners. We present structural and biochemical data showing that CARs are peripheral membrane proteins that functionally cluster on the membrane and generate strong positive membrane curvature in a Ca(2+)-dependent manner. These features represent a mechanism for the generation, stabilization, and/or specific recognition of membrane discontinuities. Such structures may act as signaling platforms involved in the recruitment of PYR/PYL receptors and other signaling components involved in cell responses to stress.


Assuntos
Ácido Abscísico/metabolismo , Proteínas de Arabidopsis/metabolismo , Cálcio/metabolismo , Membrana Celular/metabolismo , Multimerização Proteica , Transdução de Sinais , Ácido Abscísico/farmacologia , Proteínas de Arabidopsis/química , Sítios de Ligação , Calorimetria , Membrana Celular/efeitos dos fármacos , Cristalografia por Raios X , Modelos Biológicos , Fenótipo , Fosfolipídeos/química , Ligação Proteica/efeitos dos fármacos , Multimerização Proteica/efeitos dos fármacos , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Transporte Proteico/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos , Soluções , Frações Subcelulares/efeitos dos fármacos , Frações Subcelulares/metabolismo
2.
Plant Cell ; 26(12): 4802-20, 2014 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25465408

RESUMO

Membrane-delimited abscisic acid (ABA) signal transduction plays a critical role in early ABA signaling, but the molecular mechanisms linking core signaling components to the plasma membrane are unclear. We show that transient calcium-dependent interactions of PYR/PYL ABA receptors with membranes are mediated through a 10-member family of C2-domain ABA-related (CAR) proteins in Arabidopsis thaliana. Specifically, we found that PYL4 interacted in an ABA-independent manner with CAR1 in both the plasma membrane and nucleus of plant cells. CAR1 belongs to a plant-specific gene family encoding CAR1 to CAR10 proteins, and bimolecular fluorescence complementation and coimmunoprecipitation assays showed that PYL4-CAR1 as well as other PYR/PYL-CAR pairs interacted in plant cells. The crystal structure of CAR4 was solved, which revealed that, in addition to a classical calcium-dependent lipid binding C2 domain, a specific CAR signature is likely responsible for the interaction with PYR/PYL receptors and their recruitment to phospholipid vesicles. This interaction is relevant for PYR/PYL function and ABA signaling, since different car triple mutants affected in CAR1, CAR4, CAR5, and CAR9 genes showed reduced sensitivity to ABA in seedling establishment and root growth assays. In summary, we identified PYR/PYL-interacting partners that mediate a transient Ca(2+)-dependent interaction with phospholipid vesicles, which affects PYR/PYL subcellular localization and positively regulates ABA signaling.


Assuntos
Ácido Abscísico/farmacologia , Proteínas de Arabidopsis/fisiologia , Arabidopsis/metabolismo , Reguladores de Crescimento de Plantas/farmacologia , Receptores de Superfície Celular/fisiologia , Arabidopsis/efeitos dos fármacos , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Modelos Moleculares , Receptores de Superfície Celular/genética , Receptores de Superfície Celular/metabolismo , Transdução de Sinais
3.
J Virol ; 85(10): 4974-81, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21367909

RESUMO

Transmission between hosts is required for the maintenance of parasites in the host population and determines their ultimate evolutionary success. The transmission ability of parasites conditions their evolution in two ways: on one side, it affects the genetic structure of founded populations in new hosts. On the other side, parasite traits that increase transmission efficiency will be selected for. Therefore, knowledge of the factors and parameters that determine transmission efficiency is critical to predict the evolution of parasites. For plant viruses, little is known about the parameters of contact transmission, a major way of transmission of important virus genera and species. Here, we analyze the factors determining the efficiency of contact transmission of Tobacco mosaic virus (TMV) that may affect virus evolution. As it has been reported for other modes of transmission, the rate of TMV transmission by contact depended on the contact opportunities between an infected and a noninfected host. However, TMV contact transmission differed from other modes of transmission, in that a positive correlation between the virus titer in the source leaf and the rate of transmission was not found within the range of our experimental conditions. Other factors associated with the nature of the source leaf, such as leaf age and the way in which it was infected, had an effect on the rate of transmission. Importantly, contact transmission resulted in severe bottlenecks, which did not depend on the host susceptibility to infection. Interestingly, the effective number of founders initiating the infection of a new host was highly similar to that reported for aphid-transmitted plant viruses, suggesting that this trait has evolved to an optimum value.


Assuntos
Evolução Biológica , Doenças das Plantas/virologia , Vírus do Mosaico do Tabaco/genética , Vírus do Mosaico do Tabaco/patogenicidade , Genótipo , Folhas de Planta/virologia , RNA Viral/genética
4.
Acta Crystallogr Sect F Struct Biol Cryst Commun ; 67(Pt 12): 1575-8, 2011 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-22139170

RESUMO

An uncharacterized protein from Arabidopsis thaliana consisting of a single C2 domain (At3g17980) was cloned into the pETM11 vector and expressed in Escherichia coli, allowing purification to homogeneity in a single chromatographic step. Good-quality diffracting crystals were obtained using vapour-diffusion techniques. The crystals diffracted to 2.2 Å resolution and belonged to space group P2(1)2(1)2(1), with unit-cell parameters a = 35.3, b = 88.9, c = 110.6 Å. A promising molecular-replacement solution has been found using the structure of the C2 domain of Munc13-C2b (PDB entry 3kwt) as the search model.


Assuntos
Proteínas de Arabidopsis/química , Arabidopsis/química , Proteínas de Transporte/química , Cristalização , Cristalografia por Raios X
5.
Nefrologia ; 35(2): 164-71, 2015.
Artigo em Inglês, Espanhol | MEDLINE | ID: mdl-26300510

RESUMO

INTRODUCTION: The correction of metabolic acidosis caused by renal failure is achieved by adding bicarbonate during dialysis. In order to avoid the precipitation of calcium carbonate and magnesium carbonate that takes place in the dialysis fluid (DF) when adding bicarbonate, it is necessary to add an acid, usually acetate, which is not free of side effects. Thus, citrate appears as an advantageous alternative to acetate, despite the fact that its acute effects are not accurately known. OBJECTIVE: To assess the acute effect of a dialysis fluid containing citrate instead of acetate on acid-base balance and calcium-phosphorus metabolism parameters. MATERIAL AND METHODS: A prospective crossover study was conducted with twenty-four patients (15 male subjects and 9 female subjects). All patients underwent dialysis with AK-200-Ultra-S monitor with SoftPac® dialysis fluid, made with 3 mmol/L of acetate and SelectBag Citrate®, with 1 mmol/L of citrate and free of acetate. The following were measured before and after dialysis: venous blood gas monitoring, calcium (Ca), ionic calcium (Cai), phosphorus (P) and parathyroid hormone (PTH). RESULTS: Differences (p<0.05) were found when using the citrate bath (C) compared to acetate (A) in the postdialysis values of: pH, C: 7.43 (0.04) vs. A: 7.47 (0.05); bicarbonate, C: 24.7 (2.7) vs. A: 27.3 (2.1) mmol/L; base excess (BEecf), C: 0.4 (3.1) vs. A: 3.7 (2.4) mmol/L; corrected calcium (Cac), C: 9.8 (0.8) vs. A: 10.1 (0.7) mg/dL; and Cai, C: 1.16 (0.05) vs. A: 1.27 (0.06) mmol/L. No differences were found in either of the parameters measured before dialysis. CONCLUSION: Dialysis with citrate provides better control of postdialysis acid-base balance, decreases/avoids postdialysis alkalaemia, and lowers the increase in Cac and Cai. This finding is of special interest in patients with predisposing factors for arrhythmia and patients with respiratory failure, carbon dioxide retention, calcifications and advanced liver disease.


Assuntos
Acidose/tratamento farmacológico , Citratos/farmacologia , Soluções para Hemodiálise/farmacologia , Acetatos/administração & dosagem , Acetatos/farmacologia , Desequilíbrio Ácido-Base/prevenção & controle , Acidose/etiologia , Adulto , Bicarbonatos/administração & dosagem , Bicarbonatos/farmacologia , Gasometria , Citratos/administração & dosagem , Estudos Cross-Over , Eletrólitos/sangue , Feminino , Soluções para Hemodiálise/administração & dosagem , Soluções para Hemodiálise/química , Humanos , Falência Renal Crônica/sangue , Falência Renal Crônica/terapia , Masculino , Estudos Prospectivos
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