Aproximación genómica al estudio de la abscisión de frutos cítricos: análisis transcriptómico de la zona de abscisión C

Determinar los cambios que se producen a nivel anatómico, transcripcional y bioquímico durante el desarrollo del proceso de abscisión en los frutos cítricos. La primera aproximación ha consistido en la caracterización anatómica de la zona de abscisión C del fruto (ZAC) durante el proceso de abscisión en dos variedades de naranjo dulce del grupo Navel bajo tratamientos in vitro con etileno y ácido 1-aminociclopropano-1-carboxílico. El estudio anatómico de la ZAC mediante el empleo de diferentes técnicas de microscopía ha permitido delimitar los cambios que se producen a nivel celular durante la activación del proceso de abscisión en frutos y determinar con exactitud el número y las características de las capas celulares que conforman la ZAC. El análisis de los cambios que se producen a nivel transcripcional durante el proceso de abscisión se ha llevado a cabo utilizando la micromatriz de cDNA del Proyecto Español de Genómica Funcional de Cítricos. Sobre esta micromatriz se han hibridado muestras aisladas mediante microdisección asistida por láser de la ZAC y de la corteza del fruto (CF). La comparación de la expresión génica asociada a cada tejido a lo largo del tratamiento con etileno permitió identificar genes o grupos de genes con una función reguladora potencial del proceso de abscisión. Las primeras respuestas al tratamiento con etileno en la ZAC consisten en la activación de la señalización, la regulación de la transcripción y el metabolismo de proteínas. Finalmente, la ZAC activa la maquinaria de remodelación de la pared celular, que permitirá la separación efectiva del órgano, el tráfico de vesículas, la biosíntesis de lignina y cutina y rutas de defensa. Un análisis más exhaustivo de las familias génicas relacionadas con el transporte intracelular de proteínas y con la modificación de la pared celular permitió establecer, dentro del elevado número de proteínas que normalmente conforman estas familias.Merelo Cremades, P. (2011). Aproximación genómica al estudio de la abscisión de frutos cítricos: análisis transcriptómico de la zona de abscisión C [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/12498Palanci

A cellular analysis of meristem activity at the end of flowering points to cytokinin as a major regulator of proliferative arrest in Arabidopsis

[EN] In monocarpic plants, all reproductive meristem activity arrests and flower production ceases after the production of a certain number of fruits. This proliferative arrest (PA) is an evolutionary adaptation that ensures nutrient availability for seed production. Moreover, PA is a process of agronomic interest because it affects the duration of the flowering period and therefore fruit production. While our knowledge of the inputs and genetic factors controlling the initiation of the flowering period is extensive, little is known about the regulatory pathways and cellular events that participate in the end of flowering and trigger PA. Here, we characterize with high spatiotemporal resolution the cellular and molecular changes related to cell proliferation and meristem activity in the shoot apical meristem throughout the flowering period and PA. Our results suggest that cytokinin (CK) signaling repression precedes PA and that this hormone is sufficient to prevent and revert the process. We have also observed that repression of known CK downstream factors, such as type B cyclins and WUSCHEL (WUS), correlates with PA. These molecular changes are accompanied by changes in cell size and number likely caused by the cessation of cell division and WUS activity during PA. Parallel assays in fruitfull (ful) mutants, which do not undergo PA, have revealed that FUL may promote PA via repression of these CK-dependent pathways. Moreover, our data allow to define two phases, based on the relative contribution of FUL, that lead to PA: an early reduction of CK-related events and a late blocking of these events.We thank Bruno Mudller and Venugopala Reddy for kindly providing the TCSn:GFP-ER and WUSpro:EGFP-WUS lines, respectively, as well as Vicente Balanza, Neha Bhatia, Antonio Serrano-Mislata, Concha Gomez-Mena, and Francisco Madueo for helpful feedback on the manuscript. P.M. acknowledges Fundacion General CSIC (ComFuturo program) for current funding. The laboratory of C.F. is supported by grants from Ministerio de Ciencia e In-novacion (RTI2018-099239-B-I00) and Generalitat Valenciana (PROMETEU/2019/004) .Merelo Cremades, P.; González-Cuadra, I.; Ferrandiz Maestre, C. (2022). A cellular analysis of meristem activity at the end of flowering points to cytokinin as a major regulator of proliferative arrest in Arabidopsis. Current Biology. 32(4):749-762. https://doi.org/10.1016/j.cub.2021.11.06974976232

Comparative transcriptional survey between laser-microdissected cells from laminar abscission zone and petiolar cortical tissue during ethylene-promoted abscission in citrus leaves

<p>Abstract</p> <p>Background</p> <p>Abscission is the cell separation process by which plants are able to shed organs. It has a great impact on the yield of most crop plants. At the same time, the process itself also constitutes an excellent model to study cell separation processes, since it occurs in concrete areas known as abscission zones (AZs) which are composed of a specific cell type. However, molecular approaches are generally hampered by the limited area and cell number constituting the AZ. Therefore, detailed studies at the resolution of cell type are of great relevance in order to accurately describe the process and to identify potential candidate genes for biotechnological applications.</p> <p>Results</p> <p>Efficient protocols for the isolation of specific citrus cell types, namely laminar abscission zone (LAZ) and petiolar cortical (Pet) cells based on laser capture microdissection (LCM) and for RNA microextraction and amplification have been developed. A comparative transcriptome analysis between LAZ and Pet from citrus leaf explants subjected to an <it>in-vitro </it>24 h ethylene treatment was performed utilising microarray hybridization and analysis. Our analyses of gene functional classes differentially represented in ethylene-treated LAZ revealed an activation program dominated by the expression of genes associated with protein synthesis, protein fate, cell type differentiation, development and transcription. The extensive repertoire of genes associated with cell wall biosynthesis and metabolism strongly suggests that LAZ layers activate both catabolic and anabolic wall modification pathways during the abscission program. In addition, over-representation of particular members of different transcription factor families suggests important roles for these genes in the differentiation of the effective cell separation layer within the many layers contained in the citrus LAZ. Preferential expression of stress-related and defensive genes in Pet reveals that this tissue is likely to be reprogrammed to prevent pathogen attacks and general abiotic stresses after organ shedding.</p> <p>Conclusion</p> <p>The LCM-based data generated in this survey represent the most accurate description of the main biological processes and genes involved in organ abscission in citrus. This study provides novel molecular insight into ethylene-promoted leaf abscission and identifies new putative target genes for characterization and manipulation of organ abscission in citrus.</p

Early gene expression events in the laminar abscission zone of abscission-promoted citrus leaves after a cycleof water stress/rehydration: involvement of CitbHLH1

[EN] Leaf abscission is a common response of plants to drought stress. Some species, such as citrus, have evolved a specific behaviour in this respect, keeping their leaves attached to the plant body during water stress until this is released by irrigation or rain. This study successfully reproduced this phenomenon under controlled conditions (24h of water stress followed by 24h of rehydration) and used it to construct a suppression subtractive hybridization cDNA library enriched in genes involved in the early stages of rehydration-promoted leaf abscission after water stress. Sequencing of the library yielded 314 unigenes, which were spotted onto nylon membranes. Membrane hybridization with petiole (Pet)- and laminar abscission zone (LAZ)-enriched RNA samples corresponding to early steps in leaf abscission revealed an almost exclusive preferential gene expression programme in the LAZ. The data identified major processes such as protein metabolism, cell-wall modification, signalling, control of transcription and vesicle production, and transport as the main biological processes activated in LAZs during the early steps of rehydration-promoted leaf abscission after water stress. Based on these findings, a model for the early steps of citrus leaf abscission is proposed. In addition, it is suggested that CitbHLH1, the putative citrus orthologue of Arabidopsis BIGPETAL, may play major roles in the control of abscission-related events in citrus abscission zonesWork at the Centre de Genomica was supported by INIA grant RTA08-00065-00-00 and Ministerio de Ciencia e Innovacion-FEDER grants AGL2007-65437-C04-01, PSG-06-0000-2009-8, IPT-01-0000-2010-43, and AGL2011-30240. J.A. and P. M. were recipients of INIA predoctoral fellowships and M. C. and A. C. of INIA/CCAA and 'Ramon y Cajal' postdoctoral contracts, respectively. The help and expertise of E. Blazquez, I. Sanchis, and A. Boix are gratefully acknowledged.Agustí, J.; Gimeno, J.; Merelo, P.; Serrano Salom, R.; Cercós, M.; Conesa, A.; Talón, M.... (2012). Early gene expression events in the laminar abscission zone of abscission-promoted citrus leaves after a cycleof water stress/rehydration: involvement of CitbHLH1. Journal of Experimental Botany. 63:6079-6091. https://doi.org/10.1093/jxb/ers270S607960916

Comparative transcriptome analysis of stylar canal cells identifies novel candidate genes implicated in the self-incompatibility response of Citrus clementina

<p>Abstract</p> <p>Background</p> <p>Reproductive biology in citrus is still poorly understood. Although in recent years several efforts have been made to study pollen-pistil interaction and self-incompatibility, little information is available about the molecular mechanisms regulating these processes. Here we report the identification of candidate genes involved in pollen-pistil interaction and self-incompatibility in clementine (<it>Citrus clementina </it>Hort. ex Tan.). These genes have been identified comparing the transcriptomes of laser-microdissected stylar canal cells (SCC) isolated from two genotypes differing for self-incompatibility response ('Comune', a self-incompatible cultivar and 'Monreal', a self- compatible mutation of 'Comune').</p> <p>Results</p> <p>The transcriptome profiling of SCC indicated that the differential regulation of few specific, mostly uncharacterized transcripts is associated with the breakdown of self-incompatibility in 'Monreal'. Among them, a novel F-box gene showed a drastic up-regulation both in laser microdissected stylar canal cells and in self-pollinated whole styles with stigmas of 'Comune' in concomitance with the arrest of pollen tube growth. Moreover, we identify a non-characterized gene family as closely associated to the self-incompatibility genetic program activated in 'Comune'. Three different aspartic-acid rich (Asp-rich) protein genes, located in tandem in the clementine genome, were over-represented in the transcriptome of 'Comune'. These genes are tightly linked to a DELLA gene, previously found to be up-regulated in the self-incompatible genotype during pollen-pistil interaction.</p> <p>Conclusion</p> <p>The highly specific transcriptome survey of the stylar canal cells identified novel genes which have not been previously associated with self-pollen rejection in citrus and in other plant species. Bioinformatic and transcriptional analyses suggested that the mutation leading to self-compatibility in 'Monreal' affected the expression of non-homologous genes located in a restricted genome region. Also, we hypothesize that the Asp-rich protein genes may act as Ca²⁺"entrapping" proteins, potentially regulating Ca²⁺homeostasis during self-pollen recognition.</p

The LOV Protein of Xanthomonas citri subsp. citri Plays a Significant Role in the Counteraction of Plant Immune Responses during Citrus Canker

Pathogens interaction with a host plant starts a set of immune responses that result in complex changes in gene expression and plant physiology. Light is an important modulator of plant defense response and recent studies have evidenced the novel influence of this environmental stimulus in the virulence of several bacterial pathogens. Xanthomonas citri subsp. citri is the bacterium responsible for citrus canker disease, which affects most citrus cultivars. The ability of this bacterium to colonize host plants is influenced by bacterial blue-light sensing through a LOV-domain protein and disease symptoms are considerably altered upon deletion of this protein. In this work we aimed to unravel the role of this photoreceptor during the bacterial counteraction of plant immune responses leading to citrus canker development. We performed a transcriptomic analysis in Citrus sinensis leaves inoculated with the wild type X. citri subsp. citri and with a mutant strain lacking the LOV protein by a cDNA microarray and evaluated the differentially regulated genes corresponding to specific biological processes. A down-regulation of photosynthesis-related genes (together with a corresponding decrease in photosynthesis rates) was observed upon bacterial infection, this effect being more pronounced in plants infected with the lov-mutant bacterial strain. Infection with this strain was also accompanied with the up-regulation of several secondary metabolism- and defense response-related genes. Moreover, we found that relevant plant physiological alterations triggered by pathogen attack such as cell wall fortification and tissue disruption were amplified during the lov-mutant strain infection. These results suggest the participation of the LOV-domain protein from X. citri subsp. citri in the bacterial counteraction of host plant defense response, contributing in this way to disease development.Fil: Kraiselburd, Ivana. Consejo Nacional de Invest.cientif.y Tecnicas. Centro Cientifico Tecnol.conicet - Rosario. Instituto de Biologia Molecular y Celular de Rosario;Fil: Daurelio, Lucas Damian. Consejo Nacional de Invest.cientif.y Tecnicas. Centro Cientifico Tecnol.conicet - Rosario. Instituto de Biologia Molecular y Celular de Rosario;Fil: Tondo, Maria Laura. Consejo Nacional de Invest.cientif.y Tecnicas. Centro Cientifico Tecnol.conicet - Rosario. Instituto de Biologia Molecular y Celular de Rosario;Fil: Merelo, Paz. INSTITUT VALENCIÀ D'INVESTIGACIONS AGRÀRIES (IVIA);Fil: Cortadi, Adriana Amalia. Consejo Nacional de Invest.cientif.y Tecnicas. Centro Cientifico Tecnol.conicet - Rosario. Instituto de Biologia Molecular y Celular de Rosario;Fil: Talón, Manuel. INSTITUT VALENCIÀ D'INVESTIGACIONS AGRÀRIES (IVIA);Fil: Tadeo, Francisco R.. INSTITUT VALENCIÀ D'INVESTIGACIONS AGRÀRIES (IVIA);Fil: Orellano, Elena Graciela. Consejo Nacional de Invest.cientif.y Tecnicas. Centro Cientifico Tecnol.conicet - Rosario. Instituto de Biologia Molecular y Celular de Rosario

EL TRABAJO COLABORATIVO COMO ESTRATEGIA DIDÁCTICA PARA EL DESARROLLO DEL PENSAMIENTO CRÍTICO

El presente artículo se enfoca en el análisis del trabajo colaborativo como estrategia didáctica para el desarrollo del pensamiento crítico en estudiantes de sexto semestre de la carrera de enfermería de la Universidad técnica de Babahoyo. Este estudio se enmarca dentro de una investigación mixta, por cuanto permite cualificar y cuantificar la información recolectada a través de encuestas y entrevistas. La muestra de estudio fue de 43 estudiantes. Los resultados obtenidos de este estudio apuntaron a describir la forma como el trabajo colaborativo en tanto estrategia didáctica favorece el desarrollo del pensamiento crítico en los estudiantes dejan en claro que el trabajo colaborativo se consolida cada vez más como una estrategia didáctica válida y pertinente en la enseñanza/aprendizaje. &nbsp

EXPERIENCIA EN EL MANEJO DE COVID-19 EN LA SALA DE EMERGENCIA DEL HOSPITAL DR. ABEL GILBERT PONTÓN

La emergencia del hospital Dr. Abel gilbert Pontón fue considerado como un espacio analógico a la cuidad Gótica de New Jersey durante la pandemia. Este lugar era custodiado por un superhéroe anónimo de gran ingenio que elaboraba sus propias armas en respuesta a eventos negativos sobre la sociedad. Contexto que fue reconocido en los médicos que hicieron frente a la pandemia por COVID 19, en cumplimiento al juramento hipocrático de “No llevar otro propósito que el bien y la salud de los enfermos”. El 29 de febrero del 2020 se dio a conocer el primer caso de COVID-19 confirmado en el Ecuador de forma oficial. Esto alerto al Ministerio de Salud Pública (MSP) exigiendo la ejecución de las tácticas de contención como una barrera epidemiológica para evitar la propagación del virus en el país, sin éxito. Consecuentemente el 11 de marzo y de forma inesperada se declaró estado de emergencia a nivel nacional según acuerdo ministerial No 00126-2020, debido al incremento intempestivo de casos COVID-19. Según los análisis clínico-epidemiológicos aproximadamente el 80% de afectados por COVID-19 tienen la capacidad de no presentar sintomatología. Situación que ayudo a su distribución a nivel nacional en contra tiempo y sin distinción de edades, razas y sexo; resultando en una emergencia epidemiológica de carácter mundial.(Dr. C. Luis Eugenio Valdés García, 2020

Distributed evolutionary algorithms and their models: A survey of the state-of-the-art

The increasing complexity of real-world optimization problems raises new challenges to evolutionary computation. Responding to these challenges, distributed evolutionary computation has received considerable attention over the past decade. This article provides a comprehensive survey of the state-of-the-art distributed evolutionary algorithms and models, which have been classified into two groups according to their task division mechanism. Population-distributed models are presented with master-slave, island, cellular, hierarchical, and pool architectures, which parallelize an evolution task at population, individual, or operation levels. Dimension-distributed models include coevolution and multi-agent models, which focus on dimension reduction. Insights into the models, such as synchronization, homogeneity, communication, topology, speedup, advantages and disadvantages are also presented and discussed. The study of these models helps guide future development of different and/or improved algorithms. Also highlighted are recent hotspots in this area, including the cloud and MapReduce-based implementations, GPU and CUDA-based implementations, distributed evolutionary multiobjective optimization, and real-world applications. Further, a number of future research directions have been discussed, with a conclusion that the development of distributed evolutionary computation will continue to flourish