Non-Recognition-of-BTH4, an Arabidopsis Mediator Subunit Homolog, Is Necessary for Development and Response to Salicylic Acid

[EN] Salicylic acid (SA) signaling acts in defense and plant development. The only gene demonstrated to be required for the response to SA is Arabidopsis thaliana NON-EXPRESSER OF PATHOGENESIS-RELATED GENE 1 (NPR1), and npr1 mutants are insensitive to SA. By focusing on the effect of analogs of SA on plant development, we identified mutants in additional genes acting in the SA response. In this work, we describe a gene necessary for the SA Non-Recognition-of-BTH4 (NRB4). Three nrb4 alleles recovered from the screen cause phenotypes similar to the wild type in the tested conditions, except for SA-related phenotypes. Plants with NRB4 null alleles express profound insensitivity to SA, even more than npr1. NRB4 null mutants are also sterile and their growth is compromised. Plants carrying weaker nrb4 alleles are also insensitive to SA, with some quantitative differences in some phenotypes, like systemic acquired resistance or pathogen growth restriction. When weak alleles are used, NPR1 and NRB4 mutations produce an additive phenotype, but we did not find evidence of a genetic interaction in F1 nor biochemical interaction in yeast or in planta. NRB4 is predicted to be a subunit of Mediator, the ortholog of MED15 in Arabidopsis. Mechanistically, NRB4 functions downstream of NPR1 to regulate the SA response.This work was supported by the "Ministerio de Economia y Competitividad" (MINECO) of Spain (Grant BIO201018896 to P.T., a Junta de Ampliacion de Estudios-Consejo Superior de Investigaciones Cientificas Fellowship to J.V.C., and a Formacion del Personal Investigador-MINECO to A.D.) and "Generalitat Valenciana" of Spain (Grant ACOMP/2012/105 to P.T.). We appreciate the opinions and generous help of Jeff Dangl and Pablo Vera with the article as well as the revision of Philippa Borrill.Canet Perez, JV.; Dobón Alonso, A.; Tornero Feliciano, P. (2012). Non-Recognition-of-BTH4, an Arabidopsis Mediator Subunit Homolog, Is Necessary for Development and Response to Salicylic Acid. Plant Cell. 24(10):4220-4235. https://doi.org/10.1105/tpc.112.103028S42204235241

The Blade-On-Petiole genes of Arabidopsis are essential for resistance induced by methyl jasmonate

Background: NPR1 is a gene of Arabidopsis thaliana required for the perception of salicylic acid. This perception triggers a defense response and negatively regulates the perception of jasmonates. Surprisingly, the application of methyl jasmonate also induces resistance, and NPR1 is also suspected to be relevant. Since an allelic series of npr1 was recently described, the behavior of these alleles was tested in response to methyl jasmonate. Results: The response to methyl jasmonate of different npr1s alleles and NPR1 paralogs null mutants was measured by the growth of a pathogen. We have also tested the subcellular localization of some npr1s, along with the protein-protein interactions that can be measured in yeast. The localization of the protein in npr1 alleles does not affect the response to methyl jasmonate. In fact, NPR1 is not required. The genes that are required in a redundant fashion are the BOPs. The BOPs are paralogs of NPR1, and they physically interact with the TGA family of transcription factors. Conclusions: Some npr1 alleles have a phenotype in this response likely because they are affecting the interaction between BOPs and TGAs, and these two families of proteins are responsible for the resistance induced by methyl jasmonate in wild type plants.This work was supported by the "Ministerio de Economia y Competitividad" (MINECO) of Spain (grant BIO201018896 to PT, a JAE-CSIC Fellowship to JVC and a FPI-MINECO to AD) and "Generalitat Valenciana" of Spain (grant ACOMP/2012/105 to PT). Thanks to Dr. Xinnian Dong for NPR1 overexpression lines and to Dr. Ove Nilsson for BOPs overexpression lines. We appreciate the opinions and generous help of Drs. Vicente Ramirez, Pablo Vera, and Shelley Hepworth about the manuscript.Dobón Alonso, A.; Fajmonova, J.; Tornero Feliciano, P.; Canet, JV. (2012). 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β-carbonic anhydrases play a role in salicylic acid perception in Arabidopsis

The plant hormone salicylic acid (SA) is required for defense responses. NON EXPRESSER OF PATHOGENESIS RELATED 1 (NPR1) and NON RECOGNITION OF BTH-4 (NRB4) are required for the response to SA in Arabidopsis (Arabidopsis thaliana). Here, we isolated several interactors of NRB4 using yeast two-hybrid assays. Two of these interactors, βCA1 and βCA2, are β-carbonic anhydrase family proteins. Since double mutant βca1 βca2 plants did not show any obvious phenotype, we investigated other βCAs and found that NRB4 also interacts with βCA3 and βCA4. Moreover, several βCAs interacted with NPR1 in yeast, including one that interacted in a SA-dependent manner. This interaction was abolished in loss-of-function alleles of NPR1. Interactions between βCAs and both NRB4 and NPR1 were also detected in planta, with evidence for a triple interaction, NRB4- βCA1-NPR1. The quintuple mutant βca1 βca2 βca3 βca4 βca6 showed partial insensitivity to SA. These findings suggest that one of the functions of carbonic anhydrases is to modulate the perception of SA in plants.Facultad de Ciencias Exacta

Obstetric outcomes of sars-cov-2 infection in asymptomatic pregnant women

Altres ajuts: Fondo Europeo de Desarrollo Regional (FEDER)Around two percent of asymptomatic women in labor test positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Spain. Families and care providers face childbirth with uncertainty. We determined if SARS-CoV-2 infection at delivery among asymptomatic mothers had different obstetric outcomes compared to negative patients. This was a multicenter prospective study based on universal antenatal screening for SARS-CoV-2 infection. A total of 42 hospitals tested women admitted for delivery using polymerase chain reaction, from March to May 2020. We included positive mothers and a sample of negative mothers asymptomatic throughout the antenatal period, with 6-week postpartum follow-up. Association between SARS-CoV-2 and obstetric outcomes was evaluated by multivariate logistic regression analyses. In total, 174 asymptomatic SARS-CoV-2 positive pregnancies were compared with 430 asymptomatic negative pregnancies. No differences were observed between both groups in key maternal and neonatal outcomes at delivery and follow-up, with the exception of prelabor rupture of membranes at term (adjusted odds ratio 1.88, 95% confidence interval 1.13-3.11; p = 0.015). Asymptomatic SARS-CoV-2 positive mothers have higher odds of prelabor rupture of membranes at term, without an increase in perinatal complications, compared to negative mothers. Pregnant women testing positive for SARS-CoV-2 at admission for delivery should be reassured by their healthcare workers in the absence of symptoms

An allele of Arabidopsis COI1 with hypo- and hypermorphic phenotypes in plant growth, defence and fertility

Resistance to biotrophic pathogens is largely dependent on the hormone salicylic acid (SA) while jasmonic acid (JA) regulates resistance against necrotrophs. JA negatively regulates SA and is, in itself, negatively regulated by SA. A key component of the JA signal transduction pathway is its receptor, the COI1 gene. Mutations in this gene can affect all the JA phenotypes, whereas mutations in other genes, either in JA signal transduction or in JA biosynthesis, lack this general effect. To identify components of the part of the resistance against biotrophs independent of SA, a mutagenised population of NahG plants (severely depleted of SA) was screened for suppression of susceptibility. The screen resulted in the identification of intragenic and extragenic suppressors, and the results presented here correspond to the characterization of one extragenic suppressor, coi1-40. coi1-40 is quite different from previously described coi1 alleles, and it represents a strategy for enhancing resistance to biotrophs with low levels of SA, likely suppressing NahG by increasing the perception to the remaining SA. The phenotypes of coi1-40 lead us to speculate about a modular function for COI1, since we have recovered a mutation in COI1 which has a number of JA-related phenotypes reduced while others are equal to or above wild type levels.This work was supported by grant BIO201018896 from "Ministerio de Economia y Competitividad" (MINECO) of Spain and by grant ACOMP/2012/105 from "Generalitat Valenciana" to PT, a JAE-CSIC Fellowship to JVC, a FPI-MINECO to AD, and Fellowships from the European Molecular Biology Organization and the Human Frontier Science Program to BBHW. 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Novel Disease Susceptibility Factors for Fungal Necrotrophic Pathogens in Arabidopsis

Host cells use an intricate signaling system to respond to invasions by pathogenic microorganisms. Although several signaling components of disease resistance against necrotrophic fungal pathogens have been identified, our understanding for how molecular components and host processes contribute to plant disease susceptibility is rather sparse. Here, we identified four transcription factors (TFs) from Arabidopsis that limit pathogen spread. Arabidopsis mutants defective in any of these TFs displayed increased disease susceptibility to Botrytis cinerea and Plectosphaerella cucumerina, and a general activation of non-immune host processes that contribute to plant disease susceptibility. Transcriptome analyses revealed that the mutants share a common transcriptional signature of 77 up-regulated genes. We characterized several of the up-regulated genes that encode peptides with a secretion signal, which we named PROVIR (for provirulence) factors. Forward and reverse genetic analyses revealed that many of the PROVIRs are important for disease susceptibility of the host to fungal necrotrophs. The TFs and PROVIRs identified in our work thus represent novel genetic determinants for plant disease susceptibility to necrotrophic fungal pathogens.Funding: This work was supported by the Spanish MINECO (BFU2012 to PV), and Generalitat Valenciana (Prometeo2014/020 to PV). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Dobón Alonso, A.; Canet Perez, JV.; García-Andrade Serrano, J.; Angulo, C.; Neumetzler, L.; Persson, S.; Vera Vera, P. (2015). Novel Disease Susceptibility Factors for Fungal Necrotrophic Pathogens in Arabidopsis. PLoS Pathogens. 11(4):1-30. https://doi.org/10.1371/journal.ppat.1004800S13011

Non-Recognition-of-BTH-4, an Arabidopsis Mediator subunit homolog, is necessary for development and response to salicylic acid.

Salicylic acid (SA) signaling acts in defense and plant development. The only gene demonstrated to be required for the response to SA is Arabidopsis thaliana NON-EXPRESSER OF PATHOGENESIS-RELATED GENE 1 (NPR1), and npr1 mutants are insensitive to SA. By focusing on the effect of analogs of SA on plant development, we identified mutants in additional genes acting in the SA response. In this work, we describe a gene necessary for the SA Non-Recognition-of-BTH4 (NRB4). Three nrb4 alleles recovered from the screen cause phenotypes similar to the wild type in the tested conditions, except for SA-related phenotypes. Plants with NRB4 null alleles express profound insensitivity to SA, even more than npr1. NRB4 null mutants are also sterile and their growth is compromised. Plants carrying weaker nrb4 alleles are also insensitive to SA, with some quantitative differences in some phenotypes, like systemic acquired resistance or pathogen growth restriction. When weak alleles are used, NPR1 and NRB4 mutations produce an additive phenotype, but we did not find evidence of a genetic interaction in F1 nor biochemical interaction in yeast or in planta. NRB4 is predicted to be a subunit of Mediator, the ortholog of MED15 in Arabidopsis. Mechanistically, NRB4 functions downstream of NPR1 to regulate the SA response."Ministerio de Economia y Competitividad" (MINECO) of Spain and Generalitat Valenciana" of SpainPeer reviewe

Análisis genético de la percepción del ácido salicílico en Arabidopsis thaliana

El ácido salicílico (SA) es una hormona esencial para la defensa de la planta y la única fitohormona para la que aún no se ha descrito un receptor. Además, solo se ha identificado un gen implicado en su percepción (NPR1). Este proyecto parte de la hipótesis de que existen otros componentes genéticos en la percepción del SA. Para poder encontrarlos, se ha planteado un nuevo modelo para el estudio de la percepción del SA basado en la pérdida de biomasa producida por la aplicación de uno de sus análogos químicos: el benzotiadiazol (BTH). Este modelo ha sido validado en Arabidopsis thaliana con el análisis tanto de dos colecciones nucleares de ecotipos como de una vasta colección de mutantes. Además, se ha realizado un rastreo genético aplicando este modelo, cuyos resultados confirman la hipótesis de partida y el papel clave de NPR1. Todos los alelos de npr1 encontrados por su insensibilidad al BTH son también insensibles al SA, validando así el modelo planteado. No se han obtenido alelos nulos de NPR1 en este rastreo, debido a su fenotipo intermedio, que puede ser explicado por la existencia de una redundancia parcial en la ruta. Los datos presentados indican que los cinco parálogos de NPR1 son los responsables de esta redundancia parcial.Canet Perez, JV. (2009). Análisis genético de la percepción del ácido salicílico en Arabidopsis thaliana. http://hdl.handle.net/10251/13674Archivo delegad

Análisis genético de la percepción del ácido salicílico en Arabidopsis thaliana. Caracterización de NRB4

Interés del estudio: Profundizar en el conocimiento de algunos de los mecanismos de resistencia que han desarrollado las plantas frente a patógenos, tomando como referencia principal la interacción entre Arabidopsis thaliana y Pseudomonas syringae. Objetivos: 1- Desarrollar y validar un nuevo modelo para el estudio de la percepción del ácido salicílico (SA) basándose en el crecimiento de la planta, no en la inoculación de un patógeno y el posterior análisis de su crecimiento. 2- Aplicar este nuevo modelo para obtener información sobre las señales que empiezan tras la aplicación y/o inducción del SA y que desencadenan la activación de las defensas de la planta. Para ello se realizará un rastreo genético con el que se pretende responder a la pregunta de si el gen NPR1 es el único necesario para la percepción de esta hormona. 3- Clasificar los candidatos obtenidos por grupos de complementación. Mapear aquel grupo más interesante e iniciar su caracterización fenotípica. Elementos de la metodología a destacar: Se han utilizado metodologías tanto comunes a toda la biología molecular de plantas (mutagénesis, secuenciación de DNA, análisis de QTLs, inmunodetección de proteínas, cultivo in vitro de plantas, expresión transitoria de proteínas, doble híbrido en levadura, RT-qPCR, microscopía, análisis de transcriptomas, etc.), como más específicas del campo de la interacción planta-patógeno (cultivo de bacterias, inoculación de bacterias, tratamientos con inductores de resistencia, etc.). Resultados logrados: El análisis de la reducción del peso fresco de la planta provocada por la inducción de resistencia tras la aplicación del BTH (análogo del SA) constituye un modelo biológico válido y eficaz para el estudio de la percepción del SA en Arabidopsis. Además, permite realizar un rastreo genético en busca de mutaciones que afecten a la percepción del SA que ha permitido concluir que el gen NPR1 no es el único implicado en dicho proceso. Por una parte, los cinco parálogos deCanet Perez, JV. (2012). Análisis genético de la percepción del ácido salicílico en Arabidopsis thaliana. Caracterización de NRB4 [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/16962Palanci

Quantitative genetic analysis of salicylic acid perception in Arabidopsis

Salicylic acid (SA) is a phytohormone required for a full resistance against some pathogens in Arabidopsis, and NPR1 (Non-Expressor of Pathogenesis Related Genes 1) is the only gene with a strong effect on resistance induced by SA which has been described. There can be additional components of SA perception that escape the traditional approach of mutagenesis. An alternative to that approach is searching in the natural variation of Arabidopsis. Different methods of analyzing the variation between ecotypes have been tried and it has been found that measuring the growth of a virulent isolate of Pseudomonas syringae after the exogenous application of SA is the most effective one. Two ecotypes, Edi-0 and Stw-0, have been crossed, and their F2 has been studied. There are two significant Quantitative Trait Loci (QTLs) in this population, and there is one QTL in each one of the existing mapping populations Col-4 x Laer-0 and Laer-0 x No-0. They have different characteristics: while one QTL is only detectable at low concentrations of SA, the other acts after the point of crosstalk with methyl jasmonate signalling. Three of the QTLs have candidates described in SA perception as NPR1, its interactors, and a calmodulin binding protein.This work was supported by the Ministerio de Ciencia e Innovación (MICINN) of Spain (grant BIO201018896 to PT, a JAE-CSIC Fellowship to JVC and a FPI-MICINN to AD). We appreciate the BTH provided by Syngenta and the genotyping by CEGEN (Fundación Genoma España). The authors declare that they have no conflict of interest.Peer reviewe