The Polycistronic miR166k-166h positively regulates rice immunity via post-transcriptional control of EIN2

MicroRNAs (miRNAs) are small RNAs acting as regulators of gene expression at the post-transcriptional level. In plants, most miRNAs are generated from independent transcriptional units, and only a few polycistronic miRNAs have been described. miR166 is a conserved miRNA in plants targeting the HD-ZIP III transcription factor genes. Here, we show that a polycistronic miRNA comprising two miR166 family members, miR166k and miR166h, functions as a positive regulator of rice immunity. Rice plants with activated MIR166k-166h expression showed enhanced resistance to infection by the fungal pathogens Magnaporthe oryzae and Fusarium fujikuroi, the causal agents of the rice blast and bakanae disease, respectively. Disease resistance in rice plants with activated MIR166k-166h expression was associated with a stronger expression of defense responses during pathogen infection. Stronger induction of MIR166k-166h expression occurred in resistant but not susceptible rice cultivars. Notably, the ethylene-insensitive 2 (EIN2) gene was identified as a novel target gene for miR166k. The regulatory role of the miR166h-166k polycistron on the newly identified target gene results from the activity of the miR166k-5p specie generated from the miR166k-166h precursor. Collectively, our findings support a role for miR166k-5p in rice immunity by controlling EIN2 expression. Because rice blast is one of the most destructive diseases of cultivated rice worldwide, unraveling miR166k-166h-mediated mechanisms underlying blast resistance could ultimately help in designing appropriate strategies for rice protection

OsDCL1a activation impairs phytoalexin biosynthesis and compromises disease resistance in rice

MicroRNAs (miRNAs) are small non-coding RNAs that act as post-transcriptional regulators of gene expression via sequence-specific cleavage or translational repression of target transcripts. They are transcribed as long single-stranded RNA precursors with unique stem-loop structures that are processed by a DICER-Like (DCL) ribonuclease, typically DCL1, to produce mature miRNAs. Although a plethora of miRNAs have been found to be regulated by pathogen infection in plants, the biological function of most miRNAs remains largely unknown. Here, the contribution of OsDCL1 to rice immunity was investigated. OsDCL1a activation enhances susceptibility to infection by fungal pathogens in rice. Activation of OsDCL1a represses the pathogen-inducible host defence response and negatively regulates diterpenoid phytoalexin production. These findings provide a basis to understand the molecular mechanisms through which OsDCL1a mediates rice immunity

Role of plant miRNAs in disease resistance

Las plantas han desarrollado un potente sistema inmune para defenderse de la infección por patógenos. Este sistema requiere una delicada regulación de la expresión de genes codificantes para proteínas antimicrobianas y de señalización, factores de transcripción y proteínas de regulación hormonal. La regulación transcripcional es esencial para una adecuada defensa, pero también se ha demostrado el papel fundamental de los pequeños RNAs en la regulación post-transcripcional. Los microRNAs (miRNAs) son pequeños RNA no codificantes, reguladores de la expresión génica a nivel post-transcripcional. Su funcionamiento está basado en la degradación o represión de la traducción de sus tránscritos diana. La función reguladora de los miRNAs en el desarrollo de plantas ha sido ampliamente estudiada, sin embargo, la información sobre el papel de los miRNAs en la respuesta de defensa frente a patógenos está más limitada. Esta tesis comprende el estudio de miRNAs en la inmunidad de plantas. El trabajo ha sido desarrollado en arroz (Capítulo I y Capítulo II) y Arabidopsis (Capítulo III), siendo modelos para estudios de genómica funcional en plantas monocotiledóneas y dicotiledóneas. El Capítulo I describe la funcionalidad de un miRNA policistrónico en la interacción con el hongo patógeno Magnaporthe oryzae. Este hongo es el responsable de la piriculariosis, una de las enfermedades del arroz más devastadoras a nivel mundial. La previa identificación de un nuevo miRNA policistrónico (miR166k-166h) nos ha permitido investigar cómo está regulado durante la infección y qué genes están bajo su control. La disponibilidad de una línea transgénica de inserción de T-DNA ha hecho posible demostrar que la activación transcripcional de este miRNA policistrónico confiere resistencia, por lo tanto, funciona como regulador positivo de la inmunidad de las plantas. En el Capítulo II se demuestra la importancia de la expresión del gen Dicer-like 1a (DCL1a), implicado en la biogénesis de miRNAs, en la respuesta de defensa frente a M. oryzae. La sobreexpresión de DCL1a desencadena susceptibilidad a este patógeno. Los mecanismos por los cuales la sobreexpresión de DCL1a produce susceptibilidad son diversos, desde la represión de la expresión de genes de defensa y de genes implicados en la síntesis de fitoalexinas diterpenoides, hasta la producción de especies reactivas de oxígeno (ROS) y la falta de regulación de la expresión de miRNAs. En el Capítulo III se describe el papel del miR773 de Arabidopsis en la inmunidad innata. Este miRNA promueve el corte de tránscritos del gen methyltransferase2 (MET2). Cuando la acción del miR773 se ve reprimida por el mecanismo “target mimic” de imitación de diana, las plantas (MIM773) son más resistentes a la infección fúngica (Plectosphaerella cucumerina, Fusarium oxysporum f. sp. conglutinans and Colletotrichum higginsianum). Sin embargo, tanto la sobreexpresión del miR773 como la mutación de met2 confieren susceptibilidad a la infección fúngica. En conjunto, los resultados obtenidos en esta tesis doctoral demuestran que los miRNAs y los genes de biogénesis de miRNAs son componentes importantes de las respuestas inmunes frente patógenos, tanto en arroz como en Arabidopsis. Un mejor conocimiento de la función de miRNAs puede ser de utilidad para el diseño de nuevas estrategias para la protección de cultivos.Plants have evolved a strong innate immunity system to defend themselves against pathogen infection. The defense responses require a fine-tune reprogramming of gene expression and transcriptional regulation of genes coding for antimicrobial and signaling proteins, transcription factors and proteins associated with hormone-regulation and defense responses. The transcriptional regulation of protein coding genes is essential for a proper defense against pathogens, but evidences have also demonstrated the important role of small RNAs in post-transcriptional regulation. MicroRNAs (miRNAs) are small non-coding RNAs which are regulators of gene expression at post-transcriptional level. The regulatory mechanisms of miRNAs are based on degradation or translational repression of their target gene transcripts. The function of miRNAs in plant development processes has been widely studied, however, there is still a lack of information about the involvement of miRNAs in defense responses against pathogens. This thesis comprises the study of miRNAs in plant innate immunity. The work has been developed in rice (Chapter I and Chapter II) and Arabidopsis (Chapter III). These plants are respectively monocotyledonous and dicotyledonous model systems for functional genomics studies. Chapter I describes the functional role of a polycistronic miRNA in the interaction with the pathogenic fungus Magnaporthe oryzae. This fungus is responsible of rice blast disease, one of the most devastating diseases worldwide. Previous identification of a new rice polycistronic miRNA (miR166k-166h) let us to investigate how it is regulated during the infection and which genes are under its regulation. The availability of a T-DNA insertion transgenic line has made possible to demonstrate that the transcriptional activation of this polycistronic miRNA confers resistance to M. oryzae, thus, acting as positive regulator of innate immunity. The Chapter II elucidates the importance of expression regulation of the miRNA biogenesis gene Dicer-like 1a (DCL1a) in resistance against M. oryzae. In this chapter it is demonstrated that overexpression of DCL1a triggers rice susceptibility to blast disease. The mechanisms by which DCL1a overexpression renders susceptibility are diverse, from a down-regulation of defense-related genes and diterpenoid phytoalexins genes to a misregulation of reactive oxygen species (ROS) and miRNA homeostasis. In Chapter III Arabidopsis miR773 functional role in immunity has been described. This miRNA promotes the cleavage of methyltransferase2 (MET2) transcripts. When the action of miR773 by a target mimic mechanism is repressed, plants (MIM773) are more resistance to fungal infection (Plectosphaerella cucumerina, Fusarium oxysporum f. sp. conglutinans and Colletotrichum higginsianum). On the other hand, the miR773 overexpression and met2 knock-down mutation confers susceptibility to fungal infection. Altogether, the results obtained during this PhD thesis demonstrate that miRNA and miRNA biogenesis genes are important components in the plant innate immunity responses to pathogens in rice and Arabidopsis. A better knowledge of miRNA function could be useful for the designing of new crop protection strategies

The Polycistronic miR166k-166h Positively Regulates Rice Immunity via Post-transcriptional Control of EIN2

MicroRNAs (miRNAs) are small RNAs acting as regulators of gene expression at the post-transcriptional level. In plants, most miRNAs are generated from independent transcriptional units, and only a few polycistronic miRNAs have been described. miR166 is a conserved miRNA in plants targeting the HD-ZIP III transcription factor genes. Here, we show that a polycistronic miRNA comprising two miR166 family members, miR166k and miR166h, functions as a positive regulator of rice immunity. Rice plants with activated MIR166k-166h expression showed enhanced resistance to infection by the fungal pathogens Magnaporthe oryzae and Fusarium fujikuroi, the causal agents of the rice blast and bakanae disease, respectively. Disease resistance in rice plants with activated MIR166k-166h expression was associated with a stronger expression of defense responses during pathogen infection. Stronger induction of MIR166k-166h expression occurred in resistant but not susceptible rice cultivars. Notably, the ethylene-insensitive 2 (EIN2) gene was identified as a novel target gene for miR166k. The regulatory role of the miR166h-166k polycistron on the newly identified target gene results from the activity of the miR166k-5p specie generated from the miR166k-166h precursor. Collectively, our findings support a role for miR166k-5p in rice immunity by controlling EIN2 expression. Because rice blast is one of the most destructive diseases of cultivated rice worldwide, unraveling miR166k-166h-mediated mechanisms underlying blast resistance could ultimately help in designing appropriate strategies for rice protection

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<p>MicroRNAs (miRNAs) are small RNAs acting as regulators of gene expression at the post-transcriptional level. In plants, most miRNAs are generated from independent transcriptional units, and only a few polycistronic miRNAs have been described. miR166 is a conserved miRNA in plants targeting the HD-ZIP III transcription factor genes. Here, we show that a polycistronic miRNA comprising two miR166 family members, miR166k and miR166h, functions as a positive regulator of rice immunity. Rice plants with activated MIR166k-166h expression showed enhanced resistance to infection by the fungal pathogens Magnaporthe oryzae and Fusarium fujikuroi, the causal agents of the rice blast and bakanae disease, respectively. Disease resistance in rice plants with activated MIR166k-166h expression was associated with a stronger expression of defense responses during pathogen infection. Stronger induction of MIR166k-166h expression occurred in resistant but not susceptible rice cultivars. Notably, the ethylene-insensitive 2 (EIN2) gene was identified as a novel target gene for miR166k. The regulatory role of the miR166h-166k polycistron on the newly identified target gene results from the activity of the miR166k-5p specie generated from the miR166k-166h precursor. Collectively, our findings support a role for miR166k-5p in rice immunity by controlling EIN2 expression. Because rice blast is one of the most destructive diseases of cultivated rice worldwide, unraveling miR166k-166h-mediated mechanisms underlying blast resistance could ultimately help in designing appropriate strategies for rice protection.</p

OsDCL1a activation impairs phytoalexin biosynthesis and compromises disease resistance in rice

MicroRNAs (miRNAs) are small non-coding RNAs that act as post-transcriptional regulators of gene expression via sequence-specific cleavage or translational repression of target transcripts. They are transcribed as long single-stranded RNA precursors with unique stem-loop structures that are processed by a DICER-Like (DCL) ribonuclease, typically DCL1, to produce mature miRNAs. Although a plethora of miRNAs have been found to be regulated by pathogen infection in plants, the biological function of most miRNAs remains largely unknown. Here, the contribution of OsDCL1 to rice immunity was investigated. OsDCL1a activation enhances susceptibility to infection by fungal pathogens in rice. Activation of OsDCL1a represses the pathogen-inducible host defence response and negatively regulates diterpenoid phytoalexin production. These findings provide a basis to understand the molecular mechanisms through which OsDCL1a mediates rice immunity

Recomendaciones de actuación en cirugía oncológica hepatobiliopancreática durante la pandemia COVID-19.

The SARS-CoV-2 (COVID-19) pandemic requires an analysis in the field of oncological surgery, both on the risk of infection, with very relevant clinical consequences, and on the need to generate plans to minimize the impact on possible restrictions on health resources. The AEC is making a proposal for the management of patients with hepatopancreatobiliary (HPB) malignancies in the different pandemic scenarios in order to offer the maximum benefit to patients, minimising the risks of COVID-19 infection, and optimising the healthcare resources available at any time. This requires the coordination of the different treatment options between the departments involved in the management of these patients: medical oncology, radiotherapy oncology, surgery, anaesthesia, radiology, endoscopy department and intensive care. The goal is offer effective treatments, adapted to the available resources, without compromising patients and healthcare professionals safety