Chloroplast redox homeostasis is essential for lateral root formation in Arabidopsis

Redox regulation based on dithiol-disulphide interchange is an essential component of the control of chloroplast metabolism. In contrast to heterotrophic organisms, and non-photosynthetic plant tissues, chloroplast redox regulation relies on ferredoxin (Fd) reduced by the photosynthetic electron transport chain, thus being highly dependent on light. The finding of the NADPH-dependent thioredoxin reductase C (NTRC), a chloroplast-localized NTR with a joint thioredoxin domain, showed that NADPH is also used as source of reducing power for chloroplast redox homeostasis. Recently we have found that NTRC is also in plastids of non-photosynthetic tissues. Because these non-green plastids lack photochemical reactions, their redox homeostasis depends exclusively on NADPH produced from sugars and, thus, NTRC may play an essential role maintaining the redox homeostasis in these plastids. The fact that redox regulation occurs in any type of plastids raises the possibility that the functions of chloroplasts and non-green plastids, such as amyloplasts, are integrated to harmonize the growth of the different organs of the plant. To address this question, we generated Arabidopsis plants the redox homeostasis of which is recovered exclusively in chloroplasts, by leaf-specific expression of NTRC in the ntrc mutant, or exclusively in amyloplasts, by root-specific expression of NTRC. The analysis of these plants suggests that chloroplasts exert a pivotal role on plant growth, as expected because chloroplasts constitute the major source of nutrients and energy, derived from photosynthesis, for growth of heterotrophic tissues. However, NTRC deficiency causes impairment of auxin synthesis and lateral root formation. Interestingly, recovery of redox homeostasis of chloroplasts, but not of amyloplasts, was sufficient to restore wild type levels of lateral roots, showing the important signalling function of chloroplasts for the development of heterotrophic organs.España MINECO BIO2010-15430Junta de Andalucía BIO-182 and CVI-591

Metabolic control of tobacco pollination by sugars and invertases

Pollination in flowering plants is initiated by germination of pollen grains on stigmas followed by fast growth of pollen tubes representing highly energy-consuming processes. The symplastic isolation of pollen grains and tubes requires import of Suc available in the apoplast. We show that the functional coupling of Suc cleavage by invertases and uptake of the released hexoses by monosaccharide transporters are critical for pollination in tobacco (Nicotiana tabacum). Transcript profiling, in situ hybridization, and immunolocalization of extracellular invertases and two monosaccharide transporters in vitro and in vivo support the functional coupling in supplying carbohydrates for pollen germination and tube growth evidenced by spatiotemporally coordinated expression. Detection of vacuolar invertases in maternal tissues by these approaches revealed metabolic cross talk between male and female tissues and supported the requirement for carbohydrate supply in transmitting tissue during pollination. Tissue-specific expression of an invertase inhibitor and addition of the chemical invertase inhibitor miglitol strongly reduced extracellular invertase activity and impaired pollen germination. Measurements of (competitive) uptake of labeled sugars identified two import pathways for exogenously available Suc into the germinating pollen operating in parallel: direct Suc uptake and via the hexoses after cleavage by extracellular invertase. Reduction of extracellular invertase activity in pollen decreases Suc uptake and severely compromises pollen germination. We further demonstrate that Glc as sole carbon source is sufficient for pollen germination, whereas Suc is supporting tube growth, revealing an important regulatory role of both the invertase substrate and products contributing to a potential metabolic and signaling-based multilayer regulation of pollination by carbohydrate

NADPH thioredoxin reductase C is localized in plastids of photosynthetic and nonphotosynthetic tissues and is involved in lateral root formation in Arabidopsis

Plastids are organelles present in photosynthetic and nonphotosynthetic plant tissues. While it is well known that thioredoxin-dependent redox regulation is essential for leaf chloroplast function, little is known of the redox regulation in plastids of nonphotosynthetic tissues, which cannot use light as a direct source of reducing power. Thus, the question remains whether redox regulation operates in nonphotosynthetic plastid function and how it is integrated with chloroplasts for plant growth. Here, we show that NADPH-thioredoxin reductase C (NTRC), previously reported as exclusive to green tissues, is also expressed in nonphotosynthetic tissues of Arabidopsis thaliana, where it is localized to plastids. Moreover, we show that NTRC is involved in maintaining the redox homeostasis of plastids also in nonphotosynthetic organs. To test the relationship between plastids of photosynthetic and nonphotosynthetic tissues, transgenic plants were obtained with redox homeostasis restituted exclusively in leaves or in roots, through the expression of NTRC under the control of organspecific promoters in the ntrc mutant. Our results show that fully functional root amyloplasts are not sufficient for root, or leaf, growth, but fully functional chloroplasts are necessary and sufficient to support wild-type rates of root growth and lateral root formation. © 2012 American Society of Plant Biologists. All rights reserved.España, Ministerio de Ciencia e Innovación BIO2010-15430Junta de Andalucía BIO-182 and CVI-591

Rhetorical structure and persuasive language in the subgenre of online advertisements

p. 38-47This paper aims to reveal the rhetorical structure and the linguistic features of persuasive language in online advertisements of electronic products. Nowadays, the bulk of e-commerce is carried out in English, and it is often the case that non-native speakers are required to write different text types for various professional purposes, including promotional texts. This need has prompted the present study and the results have been used to build software to help native speakers of Spanish when writing promotional texts in English. The analysis reveals that these texts typically have two main rhetorical moves: one for identifying the product and another one for describing it. The latter move is further divided into two steps: one including objective features (size, weight, etc.) and the other focusing on persuading the potential customer. This is mainly achieved with the use of a relatively informal style (imperatives, contractions, clipping, subject/auxiliary omissions, etc.) and lexico-grammatical elements conveying positive evaluation (multiple modification, multal quantifying expressions, etc.). The findings show that online advertisements of electronic products may be regarded as a specific subgenre with particular macro- and microlinguistic characteristics, which have been identified in this paper for technical writing assistance.S

Using an Ontology-based Approach to Build Open Assisting Tools in Foreign Language Writing

[EN] In today’s globalised world where there is a growing need for international communication, non-native speakers (NNS) from a wide range of professional fields are increasingly called upon to write specialised texts in English. More often than not, however, the linguistic competence required to do so is well beyond that of the majority of NNS. While software applications can serve to assist NNS in their English writing tasks, most of the applications available are designed for users of English for general purposes as opposed to English for professional purposes. Therefore, these applications lack the specific vocabulary, style guidelines and common structures required in more specialised documents. Necessary modifications to meet the needs of English for professional purposes tend to be viewed as representing an overly complex and expensive task. To overcome these challenges, we present a software called O-WEAA (Ontology-Writing English Assistant Architecture) which makes use of an ontology that represents the knowledge which, according to our formalisation, is required to write most types of specialised professional documents in the English language. Our formalisation of the required knowledge is based on an exhaustive linguistic analysis of several written genres. The proposed software is composed of two parts: i) a web application named Acquisition Interface Module, which allows experts to populate the ontology with new data and ii) a userfriendly, general web interface named Writing Assistant Interface Module which guides the user throughout the writing process of the English document in the specific domain described in the ontology.S

Photosynthetic activity of cotyledons is critical during post-germinative growth and seedling establishment

Thioredoxins (Trxs) play a relevant role in thiol-dependent redox regulation, which allows the rapid adaptation of chloroplast metabolism to unpredictable environmental conditions. In chloroplasts, Trxs use reducing equivalents provided by photoreduced ferredoxin (Fdx) via the action of a ferredoxin-thioredoxin reductase (FTR), thus linking redox regulation to light. In addition, these organelles contain an NADPH-thioredoxin reductase, NTRC, with a Trx domain at the C-terminus. NTRC efficiently reduces 2-Cys peroxiredoxins (Prxs), hence having antioxidant function. However, NTRC also participates in the redox regulation of processes, such as starch and chlorophyll biosynthesis, which are known to be regulated by Trxs. Thus, the question arising is whether there is a cross-talk between the 2 redox systems. Arabidopsis mutants simultaneously devoid of NTRC and Trx x or Trxs f show a dramatic growth inhibition phenotype, indicating that NTRC is required for the function of these unrelated Trxs. Remarkably, both the ntrc-trxx double mutant and, to a higher extent, the ntrc-trxf1f2 triple mutant show high mortality at the seedling stage, which is rescued by sucrose. These findings show the relevant role of redox regulation for chloroplast performance and uncover the key function of cotyledons chloroplasts at the transition to autotrophic metabolism during seedling establishment

TIC como estrategia de enseñanza aprendizaje en el área de Ciencias Naturales en el contenido fuerza y movimiento

Las Tecnologías de la Información y Comunicación (TIC) han venido a revolucionar la forma en que las instituciones educativas las transfieren a sus propósitos. Esta realidad se ve reflejada por el número de estudiantes que actualmente utilizan las herramientas tecnológicas en su ámbito diario, ya sea en el centro educativo como en sus hogares. Ante esta realidad las diferentes áreas del saber se están acomodando para que el aprendizaje de las mismas sea en forma fluida, motivadora y actualizada, aspecto que el docente debe de considerar cuando planifica actividades que estén mediadas didácticamente. En este trabajo se detalla la evolución de las TIC en el campo educativo, sus fortalezas y debilidades en su implementación, así como las valiosas sugerencias para su correcto desempeño en los aprendizajes de los estudiantes. Los cambios que experimentan los estudiantes al aprender con TIC y sin las mismas, se evidencian en los resultados al final de una sesión de clase, al igual que con sus opiniones diversas en relación a su uso por parte del docente. Por tal razón, el crear actividades que lleven un componente tecnológico es una prioridad para la educación de este siglo, sin quedarse en el pasado como único método de enseñanza. Es ahí, donde propuestas didácticas elaboradas por los docentes le dan un sentido amplio a la palabra educación integral, ya que promueven aspectos que solamente con el uso de las tecnologías se logran apreciar, tal es el caso de: Actualización, innovación tecnológico-educativa y la destreza tecnológica del docente y el estudiante. La unidad didáctica (UD) se plantea como una forma de planificación mediada con el uso de componentes TIC y con materiales del contexto, unida al entorno circundante del estudiante. Estos elementos brindan un alcance real de lo que es enseñar para la vida, aspecto muy utilizado en los programas y currículo de educación nicaragüense. Por tal razón, se utiliza ese esquema de UD para presentar una propuesta en Ciencias Naturales usando para ello, diversas herramientas TIC que actualmente tenemos

Estudio de la dependencia al teléfono móvil en universitarios/as del Grado de Educación Social de la UHU

El teléfono móvil es un instrumento tecnológico relativamente nuevo y accesible, especialmente para los jóvenes, cuyo abuso del uso conlleva el comportamiento adictivo. ¿Existe más dependencia al teléfono móvil en mujeres que en hombres?; ¿Influye la edad en la dependencia al teléfono móvil? El interés por este problema ha aumentado al paso de los años, especialmente por la implicación de población cada vez más joven. El objetivo general de la presente investigación es averiguar el número de alumnos/as que disponen de teléfono móvil y de Internet, así como también analizar la dependencia al móvil entre las distintas edades (19-24/25- 30 y de 30 en adelante), y averiguar el grado de dependencia en los estudiantes universitarios de Educación Social, comparándolo entre ambos sexos. Para ello, se realizó un cuestionario a los alumnos/as de los cuatro años de carrera de la Universidad de Huelva del grado de Educación Social. Se realizaron 133 cuestionarios, indicando los resultados que en su mayoría son mujeres de edades comprendidas entre 19 y 24 años. Se confirma que el 100% de los alumnos/ as de dicho grado tienen teléfono móvil e internet

Hormonal and metabolic regulation of tomato fruit sink activity and yield under salinity

Salinization of water and soil has a negative impact on tomato (Solanum lycopersicum L.) productivity by reducing growth of sink organs and by inducing senescence in source leaves. It has been hypothesized that yield stability implies the maintenance or increase of sink activity in the reproductive structures, thus contributing to the transport of assimilates from the source leaves through changes in sucrolytic enzymes and their regulation by phytohormones. In this study, classical and functional physiological approaches have been integrated to study the influence of metabolic and hormonal factors on tomato fruit sink activity, growth, and yield: (i) exogenous hormones were applied to plants, and (ii) transgenic plants overexpressing the cell wall invertase (cwInv) gene CIN1 in the fruits and de novo cytokinin (CK) biosynthesis gene IPT in the roots were constructed. Although salinity reduces fruit growth, sink activity, and trans-zeatin (tZ) concentrations, it increases the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) during the actively growing period (25 days after anthesis). Indeed, exogenous application of the CK analogue kinetin to salinized actively growing fruits recovered sucrolytic activities (mainly cwInv and sucrose synthase), sink strength, and fruit weight, whereas the ethylene-releasing compound ethephon had a negative effect in equivalent non-stressed fruits. Fruit yield was increased by both the constitutive expression of CIN1 in the fruits (up to 4-fold) or IPT in the root (up to 30%), owing to an increase in the fruit number (lower flower abortion) and in fruit weight. This is possibly related to a recovery of sink activity in reproductive tissues due to both (i) increase in sucrolytic activities (cwInv, sucrose synthase, and vacuolar and cytoplasmic invertases) and tZ concentration, and (ii) a decrease in the ACC levels and the activity of the invertase inhibitor. This study provides new functional evidences about the role of metabolic and hormonal inter-regulation of local sink processes in controlling tomato fruit sink activity, growth, and yield under salinity

Ectopic overexpression of the cell wall invertase gene CIN1 leads to dehydration avoidance in tomato

Drought stress conditions modify source–sink relations, thereby influencing plant growth, adaptive responses, and consequently crop yield. Invertases are key metabolic enzymes regulating sink activity through the hydrolytic cleavage of sucrose into hexose monomers, thus playing a crucial role in plant growth and development. However, the physiological role of invertases during adaptation to abiotic stress conditions is not yet fully understood. Here it is shown that plant adaptation to drought stress can be markedly improved in tomato (Solanum lycopersicum L.) by overexpression of the cell wall invertase (cwInv) gene CIN1 from Chenopodium rubrum. CIN1 overexpression limited stomatal conductance under normal watering regimes, leading to reduced water consumption during the drought period, while photosynthetic activity was maintained. This caused a strong increase in water use efficiency (up to 50%), markedly improving water stress adaptation through an efficient physiological strategy of dehydration avoidance. Drought stress strongly reduced cwInv activity and induced its proteinaceous inhibitor in the leaves of the wild-type plants. However, the CIN1-overexpressing plants registered 3- to 6-fold higher cwInv activity in all analysed conditions. Surprisingly, the enhanced invertase activity did not result in increased hexose concentrations due to the activation of the metabolic carbohydrate fluxes, as reflected by the maintenance of the activity of key enzymes of primary metabolism and increased levels of sugar-phosphate intermediates under water deprivation. The induced sink metabolism in the leaves explained the maintenance of photosynthetic activity, delayed senescence, and increased source activity under drought stress. Moreover, CIN1 plants also presented a better control of production of reactive oxygen species and sustained membrane protection. Those metabolic changes conferred by CIN1 overexpression were accompanied by increases in the concentrations of the senescence-delaying hormone trans-zeatin and decreases in the senescence-inducing ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) in the leaves. Thus, cwInv critically functions at the integration point of metabolic, hormonal, and stress signals, providing a novel strategy to overcome drought-induced limitations to crop yield, without negatively affecting plant fitness under optimal growth conditions.España Ministerio de Ciencia e Innovación AT2009-0038 and AGL2011-2799