RESUMEN
ABCG46 of the legume Medicago truncatula is an ABC-type transporter responsible for highly selective translocation of the phenylpropanoids, 4-coumarate, and liquiritigenin, over the plasma membrane. To investigate molecular determinants of the observed substrate selectivity, we applied a combination of phylogenetic and biochemical analyses, AlphaFold2 structure prediction, molecular dynamics simulations, and mutagenesis. We discovered an unusually narrow transient access path to the central cavity of MtABCG46 that constitutes an initial filter responsible for the selective translocation of phenylpropanoids through a lipid bilayer. Furthermore, we identified remote residue F562 as pivotal for maintaining the stability of this filter. The determination of individual amino acids that impact the selective transport of specialized metabolites may provide new opportunities associated with ABCGs being of interest, in many biological scenarios.
Asunto(s)
Transportadoras de Casetes de Unión a ATP , Simulación de Dinámica Molecular , Transportador de Casetes de Unión a ATP, Subfamilia G/metabolismo , Filogenia , Transportadoras de Casetes de Unión a ATP/genética , Transportadoras de Casetes de Unión a ATP/metabolismo , MutagénesisRESUMEN
Knowledge about plant ATP-binding cassette (ABC) proteins is of great value for sustainable agriculture, economic yield, and the generation of high-quality products, especially under unfavorable growth conditions. We have learned much about ABC proteins in model organisms, notably Arabidopsis thaliana; however, the importance of research dedicated to these transporters extends far beyond Arabidopsis biology. Recent progress in genomic and transcriptomic approaches for nonmodel and noncanonical model plants allows us to look at ABC transporters from a wider perspective and consider chemodiversity and functionally driven adaptation as distinctive mechanisms during their evolution. Here, by considering several representatives from agriculturally important families and recent progress in functional characterization of nonArabidopsis ABC proteins, we aim to bring attention to understanding the evolutionary background, distribution among lineages and possible mechanisms underlying the adaptation of this versatile transport system for plant needs. Increasing the knowledge of ABC proteins in nonmodel plants will facilitate breeding and development of new varieties based on, for example, genetic variations of endogenous genes and/or genome editing, representing an alternative to transgenic approaches.
Asunto(s)
Transportadoras de Casetes de Unión a ATP , Arabidopsis , Transportadoras de Casetes de Unión a ATP/genética , Transportadoras de Casetes de Unión a ATP/metabolismo , Adaptación Fisiológica , Arabidopsis/genética , Arabidopsis/metabolismo , Fitomejoramiento , Plantas/genética , Plantas/metabolismoRESUMEN
Most land plants live in close contact with beneficial soil microbes: the majority of land plant species establish symbiosis with arbuscular mycorrhizal fungi, while most legumes, the third largest plant family, can form a symbiosis with nitrogen-fixing rhizobia. These microbes contribute to plant nutrition via endosymbiotic processes that require modulating the expression and function of plant transporter systems. The efficient contribution of these symbionts involves precisely controlled integration of transport, which is enabled by the adaptability and plasticity of their transporters. Advances in our understanding of these systems, driven by functional genomics research, are rapidly filling the gap in knowledge about plant membrane transport involved in these plant-microbe interactions. In this review, we synthesize recent findings associated with different stages of these symbioses, from the pre-symbiotic stage to nutrient exchange, and describe the role of host transport systems in both mycorrhizal and legume-rhizobia symbioses.
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Fabaceae/microbiología , Fabaceae/fisiología , Proteínas de Transporte de Membrana/efectos de los fármacos , Micorrizas/fisiología , Fijación del Nitrógeno/fisiología , Rhizobium/fisiología , Simbiosis/fisiología , Raíces de Plantas/microbiología , Raíces de Plantas/fisiologíaRESUMEN
Usage of effective classification techniques on Magnetic Resonance Imaging (MRI) helps in the proper diagnosis of brain tumors. Previous studies have focused on the classification of normal (nontumorous) or abnormal (tumorous) brain MRIs using methods such as Support Vector Machine (SVM) and AlexNet. In this paper, deep learning architectures are used to classify brain MRI images into normal or abnormal. Gender and age are added as higher attributes for more accurate and meaningful classification. A deep learning Convolutional Neural Network (CNN)-based technique and a Deep Neural Network (DNN) are also proposed for effective classification. Other deep learning architectures such as LeNet, AlexNet, ResNet, and traditional approaches such as SVM are also implemented to analyze and compare the results. Age and gender biases are found to be more useful and play a key role in classification, and they can be considered essential factors in brain tumor analysis. It is also worth noting that, in most circumstances, the proposed technique outperforms both existing SVM and AlexNet. The overall accuracy obtained is 88% (LeNet Inspired Model) and 80% (CNN-DNN) compared to SVM (82%) and AlexNet (64%), with best accuracy of 100%, 92%, 92%, and 81%, respectively.
Asunto(s)
Aprendizaje Profundo , Encéfalo/diagnóstico por imagen , Imagen por Resonancia Magnética , Redes Neurales de la Computación , Máquina de Vectores de SoporteRESUMEN
The plant hormone auxin must be transported throughout plants in a cell-to-cell manner to affect its various physiological functions. ABCB transporters are critical for this polar auxin distribution, but the regulatory mechanisms controlling their function is not fully understood. The auxin transport activity of ABCB1 was suggested to be regulated by a physical interaction with FKBP42/Twisted Dwarf1 (TWD1), a peptidylprolyl cis-trans isomerase (PPIase), but all attempts to demonstrate such a PPIase activity by TWD1 have failed so far. By using a structure-based approach, we identified several surface-exposed proline residues in the nucleotide binding domain and linker of Arabidopsis ABCB1, mutations of which do not alter ABCB1 protein stability or location but do affect its transport activity. P1008 is part of a conserved signature D/E-P motif that seems to be specific for auxin-transporting ABCBs, which we now refer to as ATAs. Mutation of the acidic residue also abolishes auxin transport activity by ABCB1. All higher plant ABCBs for which auxin transport has been conclusively proven carry this conserved motif, underlining its predictive potential. Introduction of this D/E-P motif into malate importer, ABCB14, increases both its malate and its background auxin transport activity, suggesting that this motif has an impact on transport capacity. The D/E-P1008 motif is also important for ABCB1-TWD1 interactions and activation of ABCB1-mediated auxin transport by TWD1. In summary, our data imply a new function for TWD1 acting as a putative activator of ABCB-mediated auxin transport by cis-trans isomerization of peptidyl-prolyl bonds.
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Miembro 1 de la Subfamilia B de Casetes de Unión a ATP , Nicotiana , Isomerasa de Peptidilprolil , Proteínas de Plantas , Proteínas de Unión a Tacrolimus , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/química , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/genética , Miembro 1 de la Subfamilia B de Casetes de Unión a ATP/metabolismo , Secuencias de Aminoácidos , Isomerasa de Peptidilprolil/química , Isomerasa de Peptidilprolil/genética , Isomerasa de Peptidilprolil/metabolismo , Proteínas de Plantas/química , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Proteínas de Unión a Tacrolimus/química , Proteínas de Unión a Tacrolimus/genética , Proteínas de Unión a Tacrolimus/metabolismo , Nicotiana/química , Nicotiana/genética , Nicotiana/metabolismoRESUMEN
Abscisic acid (ABA) integrates internal and external signals to coordinate plant development, growth and architecture. It plays a central role in stomatal closure, and prevents germination of freshly produced seeds and germination of non-dormant seeds under unfavorable circumstances. Here, we describe a Medicago truncatula ATP-binding cassette (ABC) transporter, MtABCG20, as an ABA exporter present in roots and germinating seeds. In seeds, MtABCG20 was found in the hypocotyl-radicle transition zone of the embryonic axis. Seeds of mtabcg20 plants were more sensitive to ABA upon germination, due to the fact that ABA translocation within mtabcg20 embryos was impaired. Additionally, the mtabcg20 produced fewer lateral roots and formed more nodules compared with wild-type plants in conditions mimicking drought stress. Heterologous expression in Arabidopsis thaliana provided evidence that MtABCG20 is a plasma membrane protein that is likely to form homodimers. Moreover, export of ABA from Nicotiana tabacum BY2 cells expressing MtABCG20 was faster than in the BY2 without MtABCG20. Our results have implications both in legume crop research and determination of the fundamental molecular processes involved in drought response and germination.
Asunto(s)
Ácido Abscísico/metabolismo , Medicago truncatula/metabolismo , Arabidopsis/genética , Arabidopsis/metabolismo , Regulación de la Expresión Génica de las Plantas/genética , Regulación de la Expresión Génica de las Plantas/fisiología , Germinación/genética , Germinación/fisiología , Medicago truncatula/genética , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismoRESUMEN
The ABCG10 protein of the model legume Medicago truncatula is required for efficient de novo production of the phenylpropanoid-derived phytoalexin medicarpin. Silencing the expression of MtABCG10 results, inter alia, in a lower accumulation of medicarpin and its precursors. In this study, we demonstrate that the impairment of medicarpin biosynthesis can be partially averted by the exogenous application of 4-coumarate, an early precursor of the core phenylpropanoid pathway, and the deoxyisoflavonoid formononetin. Experiments conducted using HPLC/MS in a heterologous system as well as in vitro transport assays with labelled substrate revealed that MtABCG10 is responsible for the membrane translocation of 4-coumarate and liquiritigenin, molecules representing key branching points in the phenylpropanoid pathway. The identification of transporters participating in the distribution of precursors is an important step in understanding phenylpropanoid biosynthesis.
Asunto(s)
Transportador de Casetes de Unión a ATP, Subfamilia G/genética , Flavanonas/metabolismo , Medicago truncatula/genética , Proteínas de Plantas/genética , Propionatos/metabolismo , Transportador de Casetes de Unión a ATP, Subfamilia G/metabolismo , Vías Biosintéticas , Ácidos Cumáricos , Medicago truncatula/metabolismo , Proteínas de Plantas/metabolismo , Pterocarpanos/metabolismoRESUMEN
Grape (Vitis vinifera) accumulates various polyphenolic compounds, which protect against environmental stresses, including ultraviolet-C (UV-C) light and pathogens. In this study, we looked at the transcriptome and metabolome in grape berry skin after UV-C irradiation, which demonstrated the effectiveness of omics approaches to clarify important traits of grape. We performed transcriptome analysis using a genome-wide microarray, which revealed 238 genes up-regulated more than 5-fold by UV-C light. Enrichment analysis of Gene Ontology terms showed that genes encoding stilbene synthase, a key enzyme for resveratrol synthesis, were enriched in the up-regulated genes. We performed metabolome analysis using liquid chromatography-quadrupole time-of-flight mass spectrometry, and 2,012 metabolite peaks, including unidentified peaks, were detected. Principal component analysis using the peaks showed that only one metabolite peak, identified as resveratrol, was highly induced by UV-C light. We updated the metabolic pathway map of grape in the Kyoto Encyclopedia of Genes and Genomes (KEGG) database and in the KaPPA-View 4 KEGG system, then projected the transcriptome and metabolome data on a metabolic pathway map. The map showed specific induction of the resveratrol synthetic pathway by UV-C light. Our results showed that multiomics is a powerful tool to elucidate the accumulation mechanisms of secondary metabolites, and updated systems, such as KEGG and KaPPA-View 4 KEGG for grape, can support such studies.
Asunto(s)
Vías Biosintéticas , Frutas/genética , Perfilación de la Expresión Génica , Metabolómica , Estilbenos/metabolismo , Rayos Ultravioleta , Vitis/genética , Vías Biosintéticas/efectos de la radiación , Calibración , Oscuridad , Fluorescencia , Frutas/metabolismo , Frutas/efectos de la radiación , Ontología de Genes , Genes de Plantas , Metaboloma/genética , Metaboloma/efectos de la radiación , Anotación de Secuencia Molecular , Análisis de Componente Principal , Metabolismo Secundario/genética , Metabolismo Secundario/efectos de la radiación , Vitis/metabolismo , Vitis/efectos de la radiaciónRESUMEN
The present study deals with two-phase non-Newtonian pseudoplastic crude oil and water flow inside horizontal pipes simulated by ANSYS. The study helps predict velocity and velocity profiles, as well as pressure drop during two-phase crude-oil-water flow, without complex calculations. Computational fluid dynamics (CFD) analysis will be very important in reducing the experimental cost and the effort of data acquisition. Three independent horizontal stainless steel pipes (SS-304) with inner diameters of 1 in., 1.5 in., and 2 in. were used to circulate crude oil with 5, 10, and 15% v/v water for simulation purposes. The entire length of the pipes, along with their surfaces, were insulated to reduce heat loss. A grid size of 221,365 was selected as the optimal grid. Two-phase flow phenomena, pressure drop calculations, shear stress on the walls, along with the rate of shear strain, and phase analysis were studied. Moreover, velocity changes from the wall to the center, causing a velocity gradient and shear strain rate, but at the center, no velocity variation (velocity gradient) was observed between the layers of the fluid. The precision of the simulation was investigated using three error parameters, such as mean square error, Nash-Sutcliffe efficiency, and RMSE-standard deviation of observation ratio. From the simulation, it was found that CFD analysis holds good agreement with experimental results. The uncertainty analysis demonstrated that our CFD model is helpful in predicting the rheological parameters very accurately. The study aids in identifying and predicting fluid flow phenomena inside horizontal straight pipes in a very effective way.
RESUMEN
Full-sized ATP-binding cassette (ABC) transporters of the G subfamily (ABCG) are considered to be essential components of the plant immune system. These proteins have been proposed to be implicated in the active transmembrane transport of various secondary metabolites. Despite the importance of ABCG-based transport for plant-microbe interactions, these proteins are still poorly recognized in legumes. The experiments described here demonstrated that the level of Medicago truncatula ABCG10 (MtABCG10) mRNA was elevated following application of fungal oligosaccharides to plant roots. Spatial expression pattern analysis with a reporter gene revealed that the MtABCG10 promoter was active in various organs, mostly within their vascular tissues. The corresponding protein was located in the plasma membrane. Silencing of MtABCG10 in hairy roots resulted in lower accumulation of the phenylpropanoid pathway-derived medicarpin and its precursors. PCR-based experiments indicated that infection with Fusarium oxysporum, a root-infecting pathogen, progressed faster in MtABCG10-silenced composite plants (consisting of wild-type shoots on transgenic roots) than in the corresponding controls. Based on the presented data, it is proposed that in Medicago, full-sized ABCG transporters might modulate isoflavonoid levels during the defence response associated with de novo synthesis of phytoalexins.
Asunto(s)
Flavonoides/metabolismo , Fusarium/patogenicidad , Regulación de la Expresión Génica de las Plantas , Medicago truncatula/metabolismo , Sesquiterpenos/metabolismo , Transporte Biológico , Membrana Celular/metabolismo , Resistencia a la Enfermedad , Flavonoides/genética , Fusarium/inmunología , Fusarium/metabolismo , Perfilación de la Expresión Génica , Genes Reporteros , Medicago truncatula/genética , Medicago truncatula/inmunología , Medicago truncatula/microbiología , Oligosacáridos/farmacología , Enfermedades de las Plantas/inmunología , Enfermedades de las Plantas/microbiología , Inmunidad de la Planta , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Raíces de Plantas/efectos de los fármacos , Raíces de Plantas/metabolismo , Plantas Modificadas Genéticamente/genética , Plantas Modificadas Genéticamente/metabolismo , Regiones Promotoras Genéticas , Interferencia de ARN , ARN Mensajero/genética , ARN Mensajero/metabolismo , Transformación Genética , FitoalexinasRESUMEN
The exporter of the auxin precursor indole-3-butyric acid (IBA), ABCG36/PDR8/PEN3, from the model plant Arabidopsis has recently been proposed to also function in the transport of the phytoalexin camalexin. Based on these bonafide substrates, it has been suggested that ABCG36 functions at the interface between growth and defense. Here, we provide evidence that ABCG36 catalyzes the direct, ATP-dependent export of camalexin across the plasma membrane. We identify the leucine-rich repeat receptor kinase, QIAN SHOU KINASE1 (QSK1), as a functional kinase that physically interacts with and phosphorylates ABCG36. Phosphorylation of ABCG36 by QSK1 unilaterally represses IBA export, allowing camalexin export by ABCG36 conferring pathogen resistance. As a consequence, phospho-dead mutants of ABCG36, as well as qsk1 and abcg36 alleles, are hypersensitive to infection with the root pathogen Fusarium oxysporum, caused by elevated fungal progression. Our findings indicate a direct regulatory circuit between a receptor kinase and an ABC transporter that functions to control transporter substrate preference during plant growth and defense balance decisions.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis , Transportadoras de Casetes de Unión a ATP/metabolismo , Arabidopsis/metabolismo , Tiazoles/metabolismo , Fitoalexinas , Proteínas de Arabidopsis/metabolismo , Enfermedades de las Plantas/microbiología , Regulación de la Expresión Génica de las PlantasRESUMEN
The need to identify the results to improve their quality is a mandatory practice in education. The scope and range of the indicated diagnoses vary at different stages of education. In elementary and secondary schools, the frequency of such practices is more intense compared to higher education. School diagnoses had to support processes to systematically communicate information to the environment about the status and level of education quality expressed with the results of the exams. Therefore, within school educational cycles, school diagnoses were incubated and developed, including initial diagnoses that create a supplement in the final stage (besides school grading). However, in higher education, such diagnoses need to be introduced and developed. Thus, this article proposes the methodology to perform initial diagnosis in higher education. In addition, a case study of the initial diagnosis performed at the selected Polish university was conducted. The presented example of diagnosis concerns the ecology problem and the awareness of the students under the corporate social responsibility approach. Additionally, diagnoses in mathematical problems are presented to present the continued diagnosis from the lower education stage.
RESUMEN
The results of gender equality indicators across the world in the form of prevalence of intimate partner violence (IPV) against women are striking and has thus drawn the attention of policy makers as well as necessitates the adoption of a comprehensive system to deal with. The situation of IPV in Pakistan is alarming. This study examines the acceptability attitude of women and men toward intimate partner violence against women through data science. It discovers and contrasts the frequently co-occurring reasons due to which husbands' behaviour of beating their wives is believed to be legitimate by both partners in the province of Punjab, Pakistan. Though the discovered frequently co-occurring reasons, such as "arguing with the husband and neglecting the children" altogether, are similar in both genders but the fraction of wives believing in such reasons are significantly greater than that of husbands. This psychological disparity across genders could help in identifying the social and cultural factors to whom this disparity is attributed. It is expected that the identified co-occurring groups of reasons would help to understand the problem to the next level and devise better strategies to mitigate them.
Asunto(s)
Ciencia de los Datos , Violencia de Pareja , Actitud , Niño , Femenino , Humanos , Violencia de Pareja/psicología , Masculino , Prevalencia , Factores de Riesgo , Parejas Sexuales , Esposos/psicologíaRESUMEN
Cytokinins are phytohormones regulating many biological processes that are vital to plants. CYTOKININ RESPONSE1 (CRE1), the main cytokinin receptor, has a modular architecture composed of a cytokinin-binding CHASE (Cyclases/Histidine kinases Associated Sensory Extracellular) domain, followed by a transmembrane fragment, an intracellular histidine kinase (HK) domain, and a receiver domain (REC). Perception of cytokinin signaling involves (i) a hormone molecule binding to the CHASE domain, (ii) CRE1 autophosphorylation at a conserved His residue in the HK domain, followed by a phosphorelay to (iii) a conserved Asp residue in the REC domain, (iv) a histidine-containing phosphotransfer protein (HPt), and (v) a response regulator (RR). This work focuses on the crystal structures of the REC domain of CRE1 from the model plant Arabidopsis thaliana and from the model legume Medicago truncatula. Both REC domains form tight 3D-domain-swapped dimers. Dimerization of the REC domain agrees with the quaternary assembly of the entire CRE1 but is incompatible with a model of its complex with HPt, suggesting that a considerable conformational change should occur to enable the signal transduction. Indeed, phosphorylation of the REC domain can change the HPt-binding properties of CRE1, as shown by functional studies.
RESUMEN
Growing evidence has highlighted the essential role of plant hormones, notably, cytokinins (CKs), in nitrogen-fixing symbiosis, both at early and late nodulation stages1,2. Despite numerous studies showing the central role of CK in nodulation, the importance of CK transport in the symbiosis is unknown. Here, we show the role of ABCG56, a full-size ATP-binding cassette (ABC) transporter in the early stages of the nodulation. MtABCG56 is expressed in roots and nodules and its messenger RNA levels increase upon treatment with symbiotic bacteria, isolated Nod factor and CKs, accumulating within the epidermis and root cortex. MtABCG56 exports bioactive CKs in an ATP-dependent manner over the plasma membrane and its disruption results in an impairment of nodulation. Our data indicate that ABCG-mediated cytokinin transport is important for proper establishment of N-fixing nodules.
Asunto(s)
Transportador de Casetes de Unión a ATP, Subfamilia G/genética , Citocininas/metabolismo , Medicago truncatula/genética , Reguladores del Crecimiento de las Plantas/metabolismo , Proteínas de Plantas/genética , Rhizobium/fisiología , Simbiosis/genética , Transportador de Casetes de Unión a ATP, Subfamilia G/metabolismo , Transporte Biológico , Medicago truncatula/microbiología , Fijación del Nitrógeno , Proteínas de Plantas/metabolismoRESUMEN
Nitrogen (N) as well as Phosphorus (P) are key nutrients determining crop productivity. Legumes have developed strategies to overcome nutrient limitation by, for example, forming a symbiotic relationship with N-fixing rhizobia and the release of P-mobilizing exudates and are thus able to grow without supply of N or P fertilizers. The legume-rhizobial symbiosis starts with root release of isoflavonoids that act as signaling molecules perceived by compatible bacteria. Subsequently, bacteria release nod factors, which induce signaling cascades allowing the formation of functional N-fixing nodules. We report here the identification and functional characterization of a plasma membrane-localized MATE-type transporter (LaMATE2) involved in the release of genistein from white lupin roots. The LaMATE2 expression in the root is upregulated under N deficiency as well as low phosphate availability, two nutritional deficiencies that induce the release of this isoflavonoid. LaMATE2 silencing reduced genistein efflux and even more the formation of symbiotic nodules, supporting the crucial role of LaMATE2 in isoflavonoid release and nodulation. Furthermore, silencing of LaMATE2 limited the P-solubilization activity of lupin root exudates. Transport assays in yeast vesicles demonstrated that LaMATE2 acts as a proton-driven isoflavonoid transporter.
RESUMEN
INTRODUCTION: Flavonoids are important plant compounds occurring in tissues mostly in the form of glycoconjugates. Most frequently the sugar moiety is comprised of mono- or oligosaccharides consisting of common sugars like glucose, rhamnose or galactose. In some plant species the glycosidic moiety contains glucuronic acid and may be acylated by phenylpropenoic acids. METHODOLOGY: Flavonoid glyconjugates were extracted from leaves of Medicago truncatula ecotype R108 and submitted to analysis using high-performance liquid chromatography combined with high-resolution tandem (quadrupole-time of flight, QToF) mass spectrometry. RESULTS: The studied leaf extracts contained 26 different flavonoid glycosides among which 22 compounds were flavone (apigenin, luteolin, chrysoeriol and tricin) glucuronides and 13 were acylated with aromatic acids (p-coumaric, ferulic or sinapic). The fragmentation pathways observed in positive and negative ion mass spectra differed substantially between each other and from these of flavonoid glycosides which did not contain acidic sugars. The application of high-resolution MS techniques allowed unequivocal differentiation between ions with the same nominal m/z values containing different substituents (e.g. ferulic acid or glucuronic acid). Eleven of the identified flavonoids have not been reported previously in this species. PERSPECTIVES: The presented unique fragmentation pathways of flavonoid glucuronates enable detection of these compounds in tissue extracts from different plant species.
Asunto(s)
Flavonoides/análisis , Glucurónidos/análisis , Medicago truncatula/química , Hojas de la Planta/química , Acilación , Apigenina/análisis , Cromatografía Líquida de Alta Presión , Ácidos Cumáricos/análisis , Flavonas , Flavonoides/química , Glucurónidos/química , Luteolina/análisis , Estructura Molecular , Espectrometría de Masas en TándemRESUMEN
Strigolactones (SLs) are plant-derived signaling molecules that stimulate the hyphal branching of arbuscular mycorrhizal fungi (AMF), and consequently promote symbiotic interaction between the fungus and the plant. Currently, our knowledge on the molecular mechanism of SL transport is restricted to the Solanaceae family. In the Solanaceae family, SL translocation toward the rhizosphere occurs through the exodermis via hypodermal passage cells and involves a member of the G subfamily, of the ATP-binding cassette (ABC) membrane transporters. Most Fabaceae species, including those that are agriculturally important, have a different root anatomy compared to most angiosperm plants (i.e., lacking an exodermis). Thus, we have investigated how SL transport occurs in the model legume Medicago truncatula. Here, we show that overexpression of a SL transporter from petunia (PaPDR1) enhances AMF colonization rates in M. truncatula. This result demonstrates the importance of ABCG proteins for the translocation of orobanchol-type molecules to facilitate arbuscular mycorrhiza, regardless of root anatomy and phylogenetic relationships. Moreover, our research has led to the identification of Medicago ABCG59, a close homologue of Petunia PDR1, that exhibits root specific expression and is up-regulated by phosphate starvation as well as in the presence of rac-GR24, a synthetic SL. Its promoter is active in cortical cells, root tips, and the meristematic zone of nodules. The mtabcg59 loss-of-function mutant displayed a reduced level of mycorrhization compared to the WT plants but had no impact on the number of nodules after Sinorhizobium meliloti inoculation. The reduced mycorrhization indicates that less SLs are secreted by the mutant plants, which is in line with the observation that mtabcg59 exudates exhibit a reduced stimulatory effect on the germination of the parasitic plant Phelipanche ramosa compared to the corresponding wild type.
RESUMEN
Full-size ATP-binding cassette (ABC) transporters belonging to the ABCG subfamily are unique for plants and fungi. There is growing evidence that certain of these proteins play a role in plant defense or signaling systems. As yet, a complete set of full-size ABCG protein genes has been inventoried and classified in only two plants: Arabidopsis thaliana and Oryza sativa. Recently, a domain-based clustering analysis has predicted the presence of at least 12 genes encoding such proteins in the Lotus japonicus genome. Here, we identify and classify 19 genes coding full-size ABCG proteins in Medicago truncatula, a model legume plant. We have found that the majority of these genes are expressed in roots and flowers whereas only a few are expressed in leaves. Expression of several has been induced upon pathogenic infection in both roots and leaves. ABCG messenger RNAs have been detected in root nodules forming during symbiosis of legume plants and nitrogen-fixing bacteria. The data presented provide a scaffold for further studies of the physiological function of Medicago ABCG transporters and their possible role in modulating plant-microorganism interactions.
Asunto(s)
Transportadoras de Casetes de Unión a ATP/genética , Medicago truncatula/genética , Proteínas de Plantas/genética , Transportadoras de Casetes de Unión a ATP/química , Transportadoras de Casetes de Unión a ATP/metabolismo , Expresión Génica , Medicago truncatula/metabolismo , Familia de Multigenes , Filogenia , Proteínas de Plantas/química , Proteínas de Plantas/metabolismoRESUMEN
Phenylpropanoids fulfill numerous physiological functions, essential for plant growth and development, as well as plant-environment interactions. Over the last few decades, many studies have shown that exquisite regulatory mechanisms at multiple levels control the phenylpropanoid metabolic pathway. Deciphering this pathway not only provides a greater, basic understanding of plant specialized metabolism, but also enhances our ability to rationally design plant metabolic pathways for future applications. Despite the identification of the participating enzymes of this complex, biosynthetic machinery, we still lack a complete picture of other genes, enzymes, and metabolites essential for regulation and compartmentation/distribution of phenylpropanoids. Compartmentation, as well as distribution, are critical for the fate/functioning of those molecules, and their effective biosynthesis. At the cellular level, we have narrowed down our understanding of these processes to organelles. Furthermore, various, overlapping, but not exclusive scenarios of phenylpropanoid distribution within the cell have also been described. The cross-membrane dynamics, but also intercellular communication of different branches from phenylpropanoid biosynthesis have become an exciting research frontier in plant science. The intra- and intercellular channeling of intermediates by various transport mechanisms and notably membrane transporters could be a meaningful tool that ensures, inter alia, efficient metabolite production.