Jasmonic acid (JA) is a critical hormonal regulator of plant growth and defense. To advance our understanding of the architecture and dynamic regulation of the JA gene regulatory network, we performed a high-resolution RNA-seq time series of methyl JA-treated Arabidopsis thaliana at 15 time points over a 16-h period. Computational analysis showed that methyl JA (MeJA) induces a burst of transcriptional activity, generating diverse expression patterns over time that partition into distinct sectors of the JA response targeting specific biological processes. The presence of transcription factor (TF) DNA binding motifs correlated with specific TF activity during temporal MeJA-induced transcriptional reprogramming. Insight into the underlying dynamic transcriptional regulation mechanisms was captured in a chronological model of the JA gene regulatory network. Several TFs, including MYB59 and bHLH27, were uncovered as early network components with a role in pathogen and insect resistance. Analysis of subnetworks surrounding the TFs ORA47, RAP2.6L, MYB59, and ANAC055, using transcriptome profiling of overexpressors and mutants, provided insights into their regulatory role in defined modules of the JA network. Collectively, our work illuminates the complexity of the JA gene regulatory network, pinpoints and validates previously unknown regulators, and provides a valuable resource for functional studies on JA signaling components in plant defense and development.
Summary Plant hormones are essential for regulating the interactions between plants and their complex biotic and abiotic environments. Each hormone initiates a specific molecular pathway and these different hormone pathways are integrated in a complex network of synergistic, antagonistic and additive interactions. This inter‐pathway communication is called hormone crosstalk. By influencing the immune network topology, hormone crosstalk is essential for tailoring plant responses to diverse microbes and insects in diverse environmental and internal contexts. Crosstalk provides robustness to the immune system but also drives specificity of induced defense responses against the plethora of biotic interactors. Recent advances in dry‐lab and wet‐lab techniques have greatly enhanced our understanding of the broad‐scale effects of hormone crosstalk on immune network functioning and have revealed underlying principles of crosstalk mechanisms. Molecular studies have demonstrated that hormone crosstalk is modulated at multiple levels of regulation, such as by affecting protein stability, gene transcription and hormone homeostasis. These new insights into hormone crosstalk regulation of plant defense are reviewed here, with a focus on crosstalk acting on the jasmonic acid pathway in Arabidopsis thaliana, highlighting the transcription factors MYC2 and ORA59 as major targets for modulation by other hormones.
The phytohormone jasmonic acid (JA) is a critical regulator of plant growth and defense. To significantly advance our understanding of the architecture and dynamics of the JA gene regulatory network, we performed high-resolution RNA-Seq time series analyses of methyl JAtreated Arabidopsis thaliana. Computational analysis unraveled in detail the chronology of events that occur during the early and later phases of the JA response. Several transcription factors, including ERF16 and bHLH27, were uncovered as early components of the JA gene regulatory network with a role in pathogen and insect resistance. Moreover, analysis of subnetworks surrounding the JA-induced transcription factors ORA47, RAP2.6L, and ANAC055 provided novel insights into their regulatory role of defined JA network modules. Collectively, our work illuminates the complexity of the JA gene regulatory network, pinpoints to novel regulators, and provides a valuable resource for future studies on the function of JA signaling components in plant defense and development.
The phytohormone salicylic acid (SA) is a central regulator of plant immunity.Antagonistic and synergistic actions between SA and other defense-associated hormones like jasmonic acid (JA) play key roles in determining the outcome of the plant immune response. To obtain a deeper understanding of SA-mediated transcriptional reprogramming and SA/JA crosstalk, we generated a high-resolution time series of gene expression from Arabidopsis leaves treated with SA alone and a combination of SA and methyl JA (MeJA), sampled at 14 time points over a 16-h period. We found that approximately one-third of the Arabidopsis genome was differentially expressed in response to SA, and temporal changes in gene expression could be partitioned into 45 distinct clusters of process-specific coregulated genes, linked to specific cis-regulatory elements and binding of transcription factors (TFs).Integration of our expression data with information on TF-DNA binding allowed us to generate a dynamic gene regulatory network model of the SA response, recovering known regulators and identifying novel ones. We found that 12% of SA-responsive genes and 69% of the MeJA-responsive genes exhibited antagonistic or synergistic expression levels in the combination treatment. Multi-condition co-clustering of the single-and combined-hormone expression profiles predicted underlying regulatory mechanisms in signal integration. Finally, we identified the TFs ANAC061 and ANAC090 as negative regulators of SA pathway genes and defense against biotrophic pathogens. Collectively, our data provide an unprecedented level of detail about transcriptional changes during the SA response and SA/JA crosstalk, serving as a valuable resource for systems-level network studies and functional plant defense studies.
Resumo -A ferrugem asiática é a principal doença na cultura da soja. O objetivo do trabalho foi avaliar o efeito de fungicidas à base de estrobilurina + triazol aplicados em diferentes momentos, na detecção e após a detecção da ferrugem asiática na área experimental. A segunda aplicação três semanas após a primeira. Os experimentos foram conduzidos nas safras 2006/07, 2008/09, 2009/10 e 2010/11, em Dourados -MS. A doença foi quantificada, avaliando a área foliar lesionada, o número de lesões e urédias por folíolo de cada terço da planta foram avaliados. A partir destes dados calculou-se a área abaixo da curva de progresso de lesões e urédias (AACPD). Foram avaliados também produtividade, massa de mil grãos e desfolha. Todos os ensaios foram conduzidos no delineamento de blocos ao acaso, com cinco repetições, exceto o realizado na safra 2006/07 com seis repetições. Nas quatro safras, aplicações de fungicidas, independente da época resultou em menores quantidades de doença em relação a testemunha, nos terços médio e inferior. Na safra 2008/09 não foi detectado efeito do fungicida sobre a produtividade. Em 2006Em /2007Em , 2008/09 e 2009/10, parcelas que receberam fungicida apresentaram menor porcentagem de desfolha. Na safra 2010/11, a aplicação na detecção da doença apresentou incremento na produtividade. O controle mais eficaz da doença ocorreu quando a primeira aplicação de fungicidas foi realizada mais próxima da detecção do patógeno na área. Palavras-chave: Glycine max, Phakopsora pachyrhizi, doenças da sojaAbstract: Asian soybean rust is the main disease of soybeans in Brazil. Our objective was to evaluate the effect of the strobilurin + triazole fungicides applied at and after pathogen detection in the experimental area. A second fungicide spray was done three weeks later. The experiments were carried out in, 2008/09, 2009/10 and 2010/11 crop seasons. The experiments were carried out in a randomized block design, with five replications. In the four crop seasons, disease levels were negatively affected by fungicide sprays, regardless of the application time. In 2009/10 crop season fungicide did not affect crop yield. The efficacy of chemical control was greater as the first fungicide was sprayed closer to the pathogen detection. Key-words: Glycine max, Phakopsora pachyrhizi, soybean diseases IntroduçãoA principal doença da soja é a ferrugem asiática da soja (FAS), causada por Phakopsora pachyrhizi. No campo, o fungo infecta o tecido foliar de uma ampla gama de hospedeiros, alem disto,seus uredinosporos são liberados por um ostíolo na urédia (Goellner et al. 2010). No início da doença são observadas pequenas lesões de coloração castanho. Entre 5 a 8 dias após infecção inicial, pústulas de ferrugem tornam-se visíveis, e desenvolvem-se na parte inferior do limbo foliar.A ferrugem asiática é a mais destrutiva doença foliar da soja, e perdas de rendimento superiores a 50% são comuns sob condições ambientais favoráveis para o desenvolvimento da doença. Temperaturas de 15ºC a 25ºC e o mínimo de seis horas de molh...
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