RESUMEN
Galactinol synthase (GolS) catalyzes the first and rate-limiting step in the synthesis of raffinose family of oligosaccharides (RFOs), which serve as storage and transport sugars, signal transducers, compatible solutes and antioxidants in higher plants. The present work aimed to assess the potential functions of citrus GolS in mechanisms of stress response and tolerance. By homology searches, eight GolS genes were found in the genomes of Citrus sinensis and C. clementina. Phylogenetic analysis showed that there is a GolS ortholog in C. clementina for each C. sinensis GolS, which have evolved differently from those of Arabidopsis thaliana. Transcriptional analysis indicated that most C. sinensis GolS (CsGolS) genes show a low-level tissue-specific and stress-inducible expression in response to drought and salt stress treatments, as well as to 'Candidatus Liberibacter asiaticus' infection. CsGolS6 overexpression resulted in improved tobacco tolerance to drought and salt stresses, contributing to an increased mesophyll cell expansion, photosynthesis and plant growth. Primary metabolite profiling revealed no significant changes in endogenous galactinol, but different extents of reduction of raffinose in the transgenic plants. On the other hand, a significant increase in the levels of metabolites with antioxidant properties, such as ascorbate, dehydroascorbate, alfa-tocopherol and spermidine, was observed in the transgenic plants. These results bring evidence that CsGolS6 is a potential candidate for improving stress tolerance in citrus and other plants.
Asunto(s)
Arabidopsis , Citrus , Antioxidantes/metabolismo , Arabidopsis/genética , Arabidopsis/metabolismo , Citrus/genética , Citrus/metabolismo , Galactosiltransferasas , Oligosacáridos/metabolismo , Filogenia , Plantas Modificadas Genéticamente/genética , Plantas Modificadas Genéticamente/metabolismo , Rafinosa/metabolismo , Espermidina/metabolismo , Tocoferoles/metabolismoRESUMEN
Nuclear factor Y (NF-Y) is a ubiquitous transcription factor found in eukaryotes. It is composed of three distinct subunits called NF-YA, NF-YB and NF-YC. NF-Ys have been identified as key regulators of multiple pathways in the control of development and tolerance to biotic and abiotic factors. The present study aimed to identify and characterize the complete repertoire of genes coding for NF-Y in citrus, as well as to perform the functional characterization of one of its members, namely CsNFYA5, in transgenic tobacco plants. A total of 22 genes coding for NF-Y were identified in the genomes of sweet orange (Citrus sinensis) and Clementine mandarin (C. clementina), including six CsNF-YAs, 11 CsNF-YBs and five CsNF-YCs. Phylogenetic analyses showed that there is a NF-Y orthologous in the Clementine genome for each sweet orange NF-Y gene; this was not observed when compared to Arabidopsis thaliana. CsNF-Y proteins shared the same conserved domains with their orthologous proteins in other organisms, including mouse. Analysis of gene expression by RNA-seq and EST data demonstrated that CsNF-Ys have a tissue-specific and stress inducible expression profile. qRT-PCR analysis revealed that CsNF-YA5 exhibits differential expression in response to water deficit in leaves and roots of citrus plants. Overexpression of CsNF-YA5 in transgenic tobacco plants contributed to the reduction of H2O2 production under dehydration conditions and increased plant growth and photosynthetic rate under normal conditions and drought stress. These biochemical and physiological responses to drought stress promoted by CsNF-YA5 may confer a productivity advantage in environments with frequent short-term soil water deficit.
Asunto(s)
Factor de Unión a CCAAT/genética , Citrus/genética , Sequías , Proteínas de Plantas/genética , Estrés Fisiológico , Arabidopsis/genética , Factor de Unión a CCAAT/metabolismo , Citrus/metabolismo , Genes de Plantas/genética , Filogenia , Proteínas de Plantas/metabolismo , Plantas Modificadas Genéticamente/genética , Alineación de Secuencia , Nicotiana/genéticaRESUMEN
MAIN CONCLUSION: Overexpression of the citrus CsTIP2;1 improves plant growth and tolerance to salt and drought stresses by enhancing cell expansion, H 2 O 2 detoxification and stomatal conductance. Tonoplast intrinsic proteins (TIPs) are a subfamily of aquaporins, belonging to the major intrinsic protein family. In a previous study, we have shown that a citrus TIP isoform, CsTIP2;1, is highly expressed in leaves and also transcriptionally regulated in leaves and roots by salt and drought stresses and infection by 'Candidatus Liberibacter asiaticus', the causal agent of the Huanglongbing disease, suggesting its involvement in the regulation of the flow of water and nutrients required during both normal growth and stress conditions. Here, we show that the overexpression of CsTIP2;1 in transgenic tobacco increases plant growth under optimal and water- and salt-stress conditions and also significantly improves the leaf water and oxidative status, photosynthetic capacity, transpiration rate and water use efficiency of plants subjected to a progressive soil drying. These results correlated with the enhanced mesophyll cell expansion, midrib aquiferous parenchyma abundance, H2O2 detoxification and stomatal conductance observed in the transgenic plants. Taken together, our results indicate that CsTIP2;1 plays an active role in regulating the water and oxidative status required for plant growth and adaptation to stressful environmental conditions and may be potentially useful for engineering stress tolerance in citrus and other crop plants.
Asunto(s)
Adaptación Fisiológica , Antioxidantes/metabolismo , Acuaporinas/metabolismo , Citrus/genética , Proteínas de la Membrana/metabolismo , Proteínas de Plantas/metabolismo , Acuaporinas/genética , Citrus/citología , Citrus/crecimiento & desarrollo , Citrus/fisiología , Sequías , Expresión Génica , Peróxido de Hidrógeno/metabolismo , Proteínas de la Membrana/genética , Fotosíntesis , Hojas de la Planta/citología , Hojas de la Planta/genética , Hojas de la Planta/crecimiento & desarrollo , Hojas de la Planta/fisiología , Proteínas de Plantas/genética , Raíces de Plantas/citología , Raíces de Plantas/genética , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/fisiología , Estomas de Plantas/citología , Estomas de Plantas/genética , Estomas de Plantas/crecimiento & desarrollo , Estomas de Plantas/fisiología , Transpiración de Plantas , Isoformas de Proteínas , Cloruro de Sodio/metabolismo , Estrés Fisiológico , Nicotiana/citología , Nicotiana/genética , Nicotiana/crecimiento & desarrollo , Nicotiana/fisiología , Agua/fisiologíaRESUMEN
Erythrina fusca is an important legume used for shade cover in cacao plantations in Brazil. Cacao plantations receive large quantities of copper (Cu)-containing agrochemicals, mainly for control of diseases. Therefore, Cu toxicity was investigated in seedlings grown in hydroponics with increasing concentrations of Cu (0.005-32 mg L-1) in a greenhouse. Ultrastructural analyses showed cell plasmolysis in the root cortical area and changes in thylakoid membranes at 8 mg Cu L-1 and higher. There were changes in epicuticular wax deposition on the leaf surface at the 16 and 32 mg Cu L-1 treatments. Leaf gas exchanges were highly affected 24 hours after application of treatments beginning at 8 mg Cu L-1 and higher Cu concentrations. Chemical analyses showed that Cu content in E. fusca roots increased as Cu concentration in the nutrient solution increased, whereas the shoot did not show significant changes. It is also observed that excess Cu interfered with Zn, Fe, Mn, Mg, K, P, and Ca content in the different E. fusca organs. Investigation of Cu toxicity symptoms focusing on morphophysiological, ultrastructural, gas exchange, and nutritional changes would be useful to alleviate Cu toxicity in E. fusca under field conditions, an important agroforestry species in cacao plantation.
Asunto(s)
Cobre/toxicidad , Contaminantes Ambientales/toxicidad , Erythrina , Biodegradación Ambiental , Brasil , Erythrina/crecimiento & desarrollo , Erythrina/fisiología , Raíces de Plantas , PlantonesRESUMEN
Soil flooding causes changes in gene transcription, synthesis and degradation of proteins and cell metabolism. The main objective of this study was to understand the biological events of Theobroma cacao during soil flooding-induced stress, using the analyses of gene expression and activity of key enzymes involved in fermentation, as well as the identification of differentially expressed proteins by mass spectrometry in two contrasting genotypes for flooding tolerance (tolerant - TSA-792 and susceptible - TSH-774). Soil anoxia caused by flooding has led to changes in the expression pattern of genes associated with the biosynthesis of alcohol dehydrogenase (ADH), pyruvate decarboxylase (PDC) and lactate dehydrogenase (LDH) in leaves and roots of the two evaluated genotypes. Significant differences were observed between the enzyme activities of the two genotypes. Leaves and roots of the TSA-792 genotype showed higher ADH activity as compared to the TSH-774 genotype, whereas the activities of PDC and LDH have varied over the 96 h of soil flooding, being higher for TSA-792 genotype, at the initial stage, and TSH-774 genotype, at the final stage. Some of the identified proteins are those typical of the anaerobic metabolism-involved in glycolysis and alcoholic fermentation-and different proteins associated with photosynthesis, protein metabolism and oxidative stress. The ability to maintain glycolysis and induce fermentation was observed to play an important role in anoxia tolerance in cacao and may also serve to distinguish tolerant and susceptible genotypes in relation to this stressor.
Asunto(s)
Cacao/genética , Cacao/metabolismo , Inundaciones , Genotipo , Proteoma , Suelo , Transcriptoma , Alcohol Deshidrogenasa/genética , Alcohol Deshidrogenasa/metabolismo , Perfilación de la Expresión Génica , Regulación Enzimológica de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Raíces de Plantas/genética , Raíces de Plantas/metabolismo , Proteómica , Piruvato Descarboxilasa/genética , Piruvato Descarboxilasa/metabolismoRESUMEN
In ecological setting, sodium (Na(+)) can be beneficial or toxic, depending on plant species and the Na(+) level in the soil. While its effects are more frequently studied at high saline levels, Na(+) has also been shown to be of potential benefit to some species at lower levels of supply, especially in C4 species. Here, clonal plants of the major tropical C3 crop Theobroma cacao (cacao) were grown in soil where potassium (K(+)) was partially replaced (at six levels, up to 50% replacement) by Na(+), at two concentrations (2.5 and 4.0 mmol(c) dm(-3)). At both concentrations, net photosynthesis per unit leaf area (A) increased more than twofold with increasing substitution of K(+) by Na(+). Concomitantly, instantaneous (A/E) and intrinsic (A/g(s)) water-use efficiency (WUE) more than doubled. Stomatal conductance (g(s)) and transpiration rate (E) exhibited a decline at 2.5 mmol dm(-3), but remained unchanged at 4 mmol dm(-3). Leaf nitrogen content was not impacted by Na(+) supplementation, whereas sulfur (S), calcium (Ca(2+)), magnesium (Mg(2+)) and zinc (Zn(2+)) contents were maximized at 2.5 mmol dm(-3) and intermediate (30-40%) replacement levels. Leaf K(+) did not decline significantly. In contrast, leaf Na(+) content increased steadily. The resultant elevated Na(+)/K(+) ratios in tissue correlated with increased, not decreased, plant performance. The results show that Na(+) can partially replace K(+) in the nutrition of clonal cacao, with significant beneficial effects on photosynthesis, WUE and mineral nutrition in this major perennial C3 crop.
Asunto(s)
Cacao/efectos de los fármacos , Fotosíntesis/efectos de los fármacos , Potasio/farmacología , Sodio/farmacología , Agua/metabolismo , Cacao/metabolismo , Cacao/fisiología , Calcio/metabolismo , Magnesio/metabolismo , Minerales/metabolismo , Hojas de la Planta/efectos de los fármacos , Hojas de la Planta/metabolismo , Hojas de la Planta/fisiología , Estomas de Plantas/efectos de los fármacos , Estomas de Plantas/metabolismo , Estomas de Plantas/fisiología , Transpiración de Plantas/efectos de los fármacos , Análisis de Regresión , Suelo/química , Azufre/metabolismo , Zinc/metabolismoRESUMEN
The aim of the present study was to identify the sites of accumulation of Cr in the species of macrophytes that are abundant in the Cachoeira river, namely, Alternanthera philoxeroides, Borreria scabiosoides, Polygonum ferrugineum and Eichhornia crassipes. Plants were grown in nutritive solution supplemented with 0.25 and 50 mg l(-1) of CrCl(3)·6H(2)O. Samples of plant tissues were digested with HNO(3)/HCl in a closed-vessel microwave system and the concentrations of Cr determined using inductively-coupled plasma mass spectrometry (ICP-MS). The ultrastructure of root, stem and leaf tissue was examined using transmission electron microscopy (TEM) and secondary ion mass spectrometry (SIMS) in order to determine the sites of accumulation of Cr and to detect possible alterations in cell organelles induced by the presence of the metal. Chromium accumulated principally in the roots of the four macrophytes (8.6-30 mg kg(-1) dw), with much lower concentrations present in the stems and leaves (3.8-8.6 and 0.01-9.0 mg kg(-1) dw, respectively). Within root tissue, Cr was present mainly in the vacuoles of parenchyma cells and cell walls of xylem and parenchyma. Alterations in the shape of the chloroplasts and nuclei were detected in A. philoxeroides and B. scabiosoides, suggesting a possible application of these aquatic plants as biomarkers from Cr contamination.
Asunto(s)
Amaranthaceae , Cromo/farmacología , Eichhornia , Polygonum , Rubiaceae , Contaminantes Químicos del Agua/farmacología , Amaranthaceae/anatomía & histología , Amaranthaceae/efectos de los fármacos , Cromo/análisis , Eichhornia/anatomía & histología , Eichhornia/efectos de los fármacos , Microscopía Electrónica de Transmisión , Hojas de la Planta/química , Hojas de la Planta/ultraestructura , Raíces de Plantas/química , Raíces de Plantas/ultraestructura , Tallos de la Planta/química , Tallos de la Planta/ultraestructura , Polygonum/anatomía & histología , Polygonum/efectos de los fármacos , Ríos , Rubiaceae/anatomía & histología , Rubiaceae/efectos de los fármacos , Espectrometría de Masa de Ion Secundario , Contaminantes Químicos del Agua/análisisRESUMEN
Cadmium (Cd) originating from atmospheric deposits, from industrial residues and from the application of phosphate fertilizers may accumulate in high concentrations in soil, water and food, thus becoming highly toxic to plants, animals and human beings. Once accumulated in an organism, Cd discharges and sets off a sequence of biochemical reactions and morphophysiological changes which may cause cell death in several tissues and organs. In order to test the hypothesis that Cd interferes in the metabolism of G. americana, a greenhouse experiment was conducted to measure eventual morphophysiological responses and cell death induced by Cd in this species. The plants were exposed to Cd concentrations ranging from 0 to 16 mg l(-1), in a nutritive solution. In TUNEL reaction, it was shown that Cd caused morphological changes in the cell nucleus of root tip and leaf tissues, which are typical for apoptosis. Cadmium induced anatomical changes in roots and leaves, such as the lignification of cell walls in root tissues and leaf main vein. In addition, the leaf mesophyll showed increase of the intercellular spaces. On the other hand, Cd caused reductions in the net photosynthetic rate, stomatal conductance and leaf transpiration, while the maximum potential quantum efficiency of PS2 (Fv/Fm) was unchanged. Cadmium accumulated in the root system in high concentrations, with low translocation for the shoot, and promoted an increase of Ca and Zn levels in the roots and a decrease of K level in the leaves. High concentrations of Cd promoted morphophysiological changes and caused cell death in roots and leaves tissues of G. americana.
Asunto(s)
Cadmio/farmacología , Hojas de la Planta/efectos de los fármacos , Raíces de Plantas/efectos de los fármacos , Rubiaceae/efectos de los fármacos , Muerte Celular/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Hojas de la Planta/citología , Hojas de la Planta/metabolismo , Raíces de Plantas/citología , Raíces de Plantas/metabolismo , Teoría Cuántica , Rubiaceae/citología , Rubiaceae/metabolismoRESUMEN
This study aimed to evaluate if Parisoschoenus obesulus Casey only attacks naturally aborting coconuts and, consequently, is not a pest of young fruits of coconut tree. Aiming to test this hypothesis, inflorescences at diverse stages of physiological development were offered to individuals of P. obesulus. The results showed that only aborting fruits were colonized by P. obesulus corroborating the established hypothesis.
Asunto(s)
Cocos/parasitología , Frutas/parasitología , Gorgojos/fisiología , AnimalesRESUMEN
Este estudo teve por objetivo avaliar se Parisoschoenus obesulus Casey só ataca frutos em processo de abortamento natural e, portanto, não é praga de frutos jovens do coqueiro. Para testar a hipótese, inflorescências em diversos estágios de desenvolvimento fisiológico foram oferecidas a indivíduos de P. obesulus. Os resultados mostraram que somente frutos abortivos foram colonizados por P. obesulus aceitando-se, portanto, a hipótese estabelecida.
This study aimed to evaluate if Parisoschoenus obesulus Casey only attacks naturally aborting coconuts and, consequently, is not a pest of young fruits of coconut tree. Aiming to test this hypothesis, inflorescences at diverse stages of physiological development were offered to individuals of P. obesulus. The results showed that only aborting fruits were colonized by P. obesulus corroborating the established hypothesis.