Understanding the systems-level actions of transcriptional responses to hormones provides insight into how the genome is reprogrammed in response to environmental stimuli. Here, we investigated the ...signalling pathway of the hormone jasmonic acid (JA), which controls a plethora of critically important processes in plants and is orchestrated by the transcription factor MYC2 and its closest relatives in Arabidopsis thaliana. We generated an integrated framework of the response to JA, which spans from the activity of master and secondary regulatory transcription factors, through gene expression outputs and alternative splicing, to protein abundance changes, protein phosphorylation and chromatin remodelling. We integrated time-series transcriptome analysis with (phospho)proteomic data to reconstruct gene regulatory network models. These enabled us to predict previously unknown points of crosstalk of JA to other signalling pathways and to identify new components of the JA regulatory mechanism, which we validated through targeted mutant analysis. These results provide a comprehensive understanding of how a plant hormone remodels cellular functions and plant behaviour, the general principles of which provide a framework for analyses of cross-regulation between other hormone and stress signalling pathways.
The phytohormone 7-iso-(+)-jasmonoyl-L-isoleucine (JA-Ile) mediates plant defense responses against herbivore and pathogen attack, and thus increases plant resistance against foreign invaders. ...However, JA-Ile also causes growth inhibition; and therefore JA-Ile is not a practical chemical regulator of plant defense responses. Here, we describe the rational design and synthesis of a small molecule agonist that can upregulate defense-related gene expression and promote pathogen resistance at concentrations that do not cause growth inhibition in Arabidopsis. By stabilizing interactions between COI1 and JAZ9 and JAZ10 but no other JAZ isoforms, the agonist leads to formation of JA-Ile co-receptors that selectively activate the JAZ9-EIN3/EIL1-ORA59 signaling pathway. The design of a JA-Ile agonist with high selectivity for specific protein subtypes may help promote the development of chemical regulators that do not cause a tradeoff between growth and defense.
Abstract
The evolution of adaptive interactions with beneficial, neutral and detrimental microbes was one of the key features enabling plant terrestrialization. Extensive studies have revealed ...conserved and unique molecular mechanisms underlying plant–microbe interactions across different plant species; however, most insights gleaned to date have been limited to seed plants. The liverwort Marchantia polymorpha, a descendant of early diverging land plants, is gaining in popularity as an advantageous model system to understand land plant evolution. However, studying evolutionary molecular plant–microbe interactions in this model is hampered by the small number of pathogens known to infect M. polymorpha. Here, we describe four pathogenic fungal strains, Irpex lacteus Marchantia-infectious (MI)1, Phaeophlebiopsis peniophoroides MI2, Bjerkandera adusta MI3 and B. adusta MI4, isolated from diseased M. polymorpha. We demonstrate that salicylic acid (SA) treatment of M. polymorpha promotes infection of the I. lacteus MI1 that is likely to adopt a necrotrophic lifestyle, while this effect is suppressed by co-treatment with the bioactive jasmonate in M. polymorpha, dinor-cis-12-oxo-phytodienoic acid (dn-OPDA), suggesting that antagonistic interactions between SA and oxylipin pathways during plant–fungus interactions are ancient and were established already in liverworts.
The cytokinin response factors (CRFs) are a group of related AP2/ERF transcription factors that are transcriptionally induced by cytokinin. Here we explore the role of the CRFs in Arabidopsis ...thaliana growth and development by analyzing lines with decreased and increased CRF function. While single crf mutations have no appreciable phenotypes, disruption of multiple CRFs results in larger rosettes, delayed leaf senescence, a smaller root apical meristem (RAM), reduced primary and lateral root growth, and, in etiolated seedlings, shorter hypocotyls. In contrast, overexpression of CRFs generally results in the opposite phenotypes. The crf1,2,5,6 quadruple mutant is embryo lethal, indicating that CRF function is essential for embryo development. Disruption of the CRFs results in partially insensitivity to cytokinin in a root elongation assay and affects the basal expression of a significant number of cytokinin‐regulated genes, including the type‐A ARRs, although it does not impair the cytokinin induction of the type‐A ARRs. Genes encoding homeobox transcription factors are mis‐expressed in the crf1,3,5,6 mutant, including STIMPY/WOX9 that is required for root and shoot apical meristem maintenance roots and which has previously been linked to cytokinin. These results indicate that the CRF transcription factors play important roles in multiple aspects of plant growth and development, in part through a complex interaction with cytokinin signaling.
Summary
Infection of a plant by a pathogen induces a variety of defense responses that imply the action of several signaling molecules, including salicylic acid (SA), jasmonic acid (JA) and ethylene ...(E). Here we describe the role of ETHYLENE‐RESPONSE‐FACTOR1 (ERF1) as a regulator of ethylene responses after pathogen attack in Arabidopsis. The ERF1 transcript is induced on infection by Botrytis cinerea, and overexpression of ERF1 in Arabidopsis is sufficient to confer resistance to necrotrophic fungi such as B. cinerea and Plectosphaerella cucumerina. A positive co‐operation between E and SA pathways was observed in the plant response to P. cucumerina. Infection by Pseudomonas syringae tomato DC3000, however, does not affect ERF1 expression, and activation of ethylene responses by ERF1 overexpression in Arabidopsis plants reduces tolerance against this pathogen, suggesting negative crosstalk between E and SA signaling pathways, and demonstrating that positive and negative interactions between both pathways can be established depending on the type of pathogen.
Existing roads require periodic evaluation in order to ensure safe transportation. Estimations of the available sight distance (ASD) are fundamental to make sure motorists have sufficient visibility ...to perform basic driving tasks. Mobile LiDAR Systems (MLS) can provide these evaluations with accurate three-dimensional models of the road and surroundings. Similarly, Geographic Information System (GIS) tools have been employed to obtain ASD. Due to the fact that widespread GIS formats used to store digital surface models handle elevation as an attribute of location, the presented methodology has separated the representation of ground and aboveground elements. The road geometry and surrounding ground are stored in digital terrain models (DTM). Correspondingly, abutting vegetation, manmade structures, road assets and other roadside elements are stored in 3D objects and placed on top of the DTM. Both the DTM and 3D objects are accurately obtained from a denoised and classified LiDAR point cloud. Based on the consideration that roadside utilities and most manmade structures are well-defined geometric elements, some visual obstructions are extracted and/or replaced with 3D objects from online warehouses. Different evaluations carried out with this method highlight the tradeoff between the accuracy of the estimations, performance and geometric complexity as well as the benefits of the individual consideration of road assets.
Analyses of Arabidopsis thaliana defense response to the damping-off oomycete pathogen Pythium irregulare show that resistance to P. irregulare requires a multicomponent defense strategy. Penetration ...represents a first layer, as indicated by the susceptibility of pen2 mutants, followed by recognition, likely mediated by ERECTA receptor-like kinases. Subsequent signaling of inducible defenses is predominantly mediated by jasmonic acid (JA), with insensitive coi1 mutants showing extreme susceptibility. In contrast with the generally accepted roles of ethylene and salicylic acid cooperating with or antagonizing, respectively, JA in the activation of defenses against necrotrophs, both are required to prevent disease progression, although much less so than JA. Meta-analysis of transcriptome profiles confirmed the predominant role of JA in activation of P. irregulare-induced defenses and uncovered abscisic acid (ABA) as an important regulator of defense gene expression. Analysis of cis-regulatory sequences also revealed an unexpected overrepresentation of ABA response elements in promoters of P. irregulare-responsive genes. Subsequent infections of ABA-related and callose-deficient mutants confirmed the importance of ABA in defense, acting partly through an undescribed mechanism. The results support a model for ABA affecting JA biosynthesis in the activation of defenses against this oomycete.
UPb geochronology along a north-south transect from central Sonora to northern Sinaloa in northwestern Mexico indicates several changes in provenance sources through time and space. Lower Cambrian ...arenites of the Proveedora Quartzite yield a single main age peak at 1075 Ma with minor Paleoproterozoic contribution. Arenites from the Sonobari Complex of southwestern Sonora-northwestern Sinaloa, purportedly assigned to the early Paleozoic, yield main peaks at 1424, 1662, and 1736 Ma, probably derived from the Yavapai and Mazatzal provinces, which are pervasively intruded by early Mesoproterozoic granites coeval to those forming the Granite-Rhyolite Province. Lower to Upper Ordovician units deposited on shelf, slope, and abyssal environments display very similar zircon age patterns, with main peaks ca. 2700 and 1850 Ma, indicating a large drainage system arising from the Archean cratons of Laurentia such as the Wyoming or Superior Provinces, and Paleoproterozoic sources similar to the Trans-Hudsonian orogen, which are older than the Yavapai Province. The Río Fuerte quartzites from southern Sonora-northern Sinaloa contain main peaks at 534, 542, and 637 Ma whose sources may be peri-Gondwanan blocks similar to Avalonia or Carolina terranes. A minor peak at 475 Ma suggests input from igneous suites reported from the Acatlán Complex in southern Mexico. UPb geochronology permit inference of a late Paleozoic collisional orogen in northwestern Mexico that was originated by the collision of Gondwanan blocks against southern Laurentia and outline the boundary between terranes related to continental blocks in the Pangaea supercontinent.
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•Cambrian Shelf and off-shelf sedimentary sequences mainly derive from Paleoproterozoic sources.•Mid-Late Ordovician shelf, slope, and abyssal sequences derive from Arquean and Paleoproterozoic.•The metamorphic Río Fuerte Formation main sources are Peri-Gondwanan and Grenvillian rocks.
Root-knot nematodes differentiate highly specialized feeding cells in roots (giant cells, GCs), through poorly characterized mechanisms that include extensive transcriptional changes. While global ...transcriptome analyses have used galls, which are complex root structures that include GCs and surrounding tissues, no global gene expression changes specific to GCs have been described. We report on the differential transcriptome of GCs versus root vascular cells, induced in Arabidopsis by Meloidogyne javanica at a very early stage of their development, 3 days after infection (d.p.i.). Laser microdissection was used to capture GCs and root vascular cells for microarray analysis, which was validated through qPCR and by a promoter-GUS fusion study. Results show that by 3 d.p.i., GCs exhibit major gene repression. Although some genes showed similar regulation in both galls and GCs, the majority had different expression patterns, confirming the molecular distinctiveness of the GCs within the gall. Most of the differentially regulated genes in GCs have no previously assigned function. Comparisons with other transcriptome analyses revealed similarities between GCs and cell suspensions differentiating into xylem cells. This suggests a molecular link between GCs and developing vascular cells, which represent putative GC stem cells. Gene expression in GCs at 3 d.p.i. was also found to be similar to crown galls induced by Agrobacterium tumefaciens, a specialized root biotroph.
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