Reversible phosphorylation is an essential mechanism regulating signal transduction during development and environmental stress responses. An important number of dephosphorylation events in the cell ...are catalyzed by type one protein phosphatases (PP1), which catalytic activity is driven by the binding of regulatory proteins that control their substrate specificity or subcellular localization. Plants harbor several PP1 isoforms accounting for large functional redundancies. While animal PP1s were reported to play relevant roles in controlling multiple cellular processes, plant orthologs remain poorly studied. To decipher the role of plant PP1s, we compared PP1 genes from three monocot species, Brachypodium, common wheat and rice at the genomic and transcriptomic levels. To gain more insight into the wheat PP1 proteins, we identified and characterized TdPP1a, the first wheat type one protein phosphatase from a Tunisian durum wheat variety Oum Rabiaa3. TdPP1a is highly conserved in sequence and structure when compared to mammalian, yeast and other plant PP1s. We demonstrate that TdPP1a is an active, metallo-dependent phosphatase in vitro and is able to interact with AtI2, a typical regulator of PP1 functions. Also, TdPP1a is capable to complement the heat stress sensitivity of the yeast mutant indicating that TdPP1a is functional also in vivo. Moreover, transient expression of TdPP1a::GFP in tobacco leaves revealed that it is ubiquitously distributed within the cell, with a strong accumulation in the nucleus. Finally, transcriptional analyses showed similar expression levels in roots and leaves of durum wheat seedlings. Interestingly, the expression in leaves is significantly induced following salinity stress, suggesting a potential role of TdPP1a in wheat salt stress response.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
An activation-tagged allele of activated disease resistance 1 (ADR1) has previously been shown to convey broad spectrum disease resistance. ADR1 was found to encode a coiled-coil ...(CC)-nucleotide-binding site (NBS)-leucine-rich repeat (LRR) protein, which possessed domains of homology with serine/threonine protein kinases. Here, we show that either constitutive or conditional enhanced expression of ADR1 conferred significant drought tolerance. This was not a general feature of defence-related mutants because cir (constitutive induced resistance) 1, cir2 and cpr (constitutive expressor of PR genes) 1, which constitutively express systemic acquired resistance (SAR), failed to exhibit this phenotype. Cross-tolerance was not a characteristic of adr1 plants, rather they showed increased sensitivity to thermal and salinity stress. Hence, adr1-activated signalling may antagonise some stress responses. Northern analysis of abiotic marker genes revealed that dehydration-responsive element (DRE)B2A but not DREB1A, RD (response to dehydration)29A or RD22 was expressed in adr1 plant lines. Furthermore, DREB2A expression was salicylic acid (SA) dependent but NPR (non-expressor of PR genes) 1 independent. In adr1/ADR1 nahG (naphthalene hydroxylase G), adr1/ADR1 eds (enhanced disease susceptibility) 1 and adr1/ADR1 abi1 double mutants, drought tolerance was significantly reduced. Microarray analyses of plants containing a conditional adr1 allele demonstrated that a significant number of the upregulated genes had been previously implicated in responses to dehydration. Therefore, biotic and abiotic signalling pathways may share multiple nodes and their outputs may have significant functional overlap.
Citizen science has shown great potential for bringing large groups of people closer to science, thanks in part to cooperation with universities and research centers. In this context, amateur weather ...networks played a major role in the last few decades thanks to a constant growth in technology. An example is given by the Meteonetwork association, born in 2002, and mainly composed by atmospheric science enthusiasts, who built up in time a huge weather station network in Italy. In recent years, they have enlarged their horizons over Europe, displaying real time observations and daily maps coming from both personal weather stations and official networks. This study described how Meteonetwork has set up an open crowdsourced weather data system, how data are validated, and which products are generated and freely accessible for scientists and stakeholders for their own purposes. Two concrete use cases were described as examples: the Weatherness Project, which selects a subnet of Meteonetwork data for biometeorological and health purposes and the data assimilation process implemented to improve the initial conditions into the WRF meteorological model for daily weather forecasts.
Plant adaptation, growth and development rely on the integration of many environmental and endogenous signals that collectively determine the overall plant phenotypic plasticity. Plant signaling ...molecules, also known as phytohormones, are fundamental to this process. These molecules act at low concentrations and regulate multiple aspects of plant fitness and development via complex signaling networks. By its nature, phytohormone research lies at the interface between chemistry and biology. Classically, the scientific community has always used synthetic phytohormones and analogs to study hormone functions and responses. However, recent advances in synthetic and combinational chemistry, have allowed a new field, plant chemical biology, to emerge and this has provided a powerful tool with which to study phytohormone function. Plant chemical biology is helping to address some of the most enduring questions in phytohormone research such as: Are there still undiscovered plant hormones? How can we identify novel signaling molecules? How can plants activate specific hormone responses in a tissue-specific manner? How can we modulate hormone responses in one developmental context without inducing detrimental effects on other processes? The chemical genomics approaches rely on the identification of small molecules modulating different biological processes and have recently identified active forms of plant hormones and molecules regulating many aspects of hormone synthesis, transport and response. We envision that the field of chemical genomics will continue to provide novel molecules able to elucidate specific aspects of hormone-mediated mechanisms. In addition, compounds blocking specific responses could uncover how complex biological responses are regulated. As we gain information about such compounds we can design small alterations to the chemical structure to further alter specificity, enhance affinity or modulate the activity of these compounds.
Redundancy and specificity in jasmonate signalling Chini, Andrea; Gimenez-Ibanez, Selena; Goossens, Alain ...
Current opinion in plant biology,
October 2016, 2016-10-00, 20161001, Letnik:
33
Journal Article
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•A single bioactive hormone regulates a myriad of JA-mediated physiological processes.•JA-output is determined by redundant and specific functions of signalling components.•Major ...sources of specificity are spatiotemporal expression and protein interactions.•Hormone thresholds and crosstalk with other signals also contribute to specificity.
Jasmonates (JAs) are essential phytohormones regulating plant development and environmental adaptation. Many components of the JA-signalling pathway have been identified. However, our insight into the mechanisms by which a single bioactive JA hormone can regulate a myriad of physiological processes and provide specificity in the response remains limited. Recent findings on molecular components suggest that, despite apparent redundancy, specificity is achieved by (1) distinct protein–protein interactions forming unique JAZ/transcription factor complexes, (2) discrete spatiotemporal expression of specific components, (3) variable hormone thresholds for the formation of multiple JA receptor complexes and (4) integration of several signals by JA-pathway components. The molecular modularity that is thereby created enables a single bioactive hormone to specifically modulate multiple JA-outputs in response to different environmental and developmental cues.
Significant progress has been recently made in our understanding of the evolution of jasmonates biosynthesis and signaling. The bioactive jasmonate activating COI1-JAZ co-receptor differs in ...bryophytes and vascular plants. Dinor-iso-12-oxo-phytodienoic acid (dn-iso-OPDA) is the bioactive hormone in bryophytes and lycophytes. However, further studies showed that the full activation of hormone signaling in Marchantia polymorpha requires additional unidentified hormones. Δ4-dn-OPDAs were previously identified as novel bioactive jasmonates in M. polymorpha. In this paper, we describe the major bioactive isomer of Δ4-dn-OPDAs as Δ4-dn-iso-OPDA through chemical synthesis, receptor binding assay, and biological activity in M. polymorpha. In addition, we disclosed that Δ4-dn-cis-OPDA is a biosynthetic precursor of Δ4-dn-iso-OPDA. We demonstrated that in planta cis-to-iso conversion of Δ4-dn-cis-OPDA occurs in the biosynthesis of Δ4-dn-iso-OPDA, defining a key biosynthetic step in the chemical evolution of hormone structure. We predict that these findings will facilitate further understanding of the molecular evolution of plant hormone signaling.
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•Δ4-dn-iso-OPDA is identified as the major bioactive isomer of Δ4-dn-OPDAs•Δ4-dn-iso-OPDA is biosynthesized through isomerization of Δ4-dn-cis-OPDA•Δ4-dn-OPDAs are distributed in bryophyte lineages
Biochemistry; Plant biochemistry; Plant biology
Severe genetic redundancy is particularly clear in gene families encoding plant hormone receptors, each subtype sharing redundant and specific functions. Genetic redundancy of receptor family members ...represents a major challenge for the functional dissection of each receptor subtype. A paradigmatic example is the perception of the hormone (+)-7-iso-jasmonoyl-L-isoleucine, perceived by several COI1-JAZ complexes; the specific role of each receptor subtype still remains elusive. Subtype-selective agonists of the receptor are valuable tools for analyzing the responses regulated by individual receptor subtypes. We constructed a stereoisomer library consisting of all stereochemical isomers of coronatine (COR), a mimic of the plant hormone (+)-7-iso-jasmonoyl-L-isoleucine, to identify subtype-selective agonists for COI1-JAZ co-receptors in Arabidopsis thaliana and Solanum lycopersicum. An agonist selective for the Arabidopsis COI1-JAZ9 co-receptor efficiently revealed that JAZ9 is not involved in most of the gene downregulation caused by COR, and the degradation of JAZ9-induced defense without inhibiting growth.
Jasmonic acid (JA) and its derivates, collectively known as jasmonates (JAs), are essential signalling molecules that coordinate the plant response to biotic and abiotic challenges, in addition to ...several developmental processes. The COI1 F-box and additional SCF modulators have long been known to have a crucial role in the JA-signalling pathway. Downstream JA-dependent transcriptional re-programming is regulated by a cascade of transcription factors and MYC2 plays a major role. Recently, JAZ family proteins have been identified as COI1 targets and repressors of MYC2, defining the 'missing link' in JA signalling. JA-Ile has been proposed to be the active form of the hormone, and COI1 is an essential component of the receptor complex. These recent discoveries have defined the core JA-signalling pathway as the module COI1/JAZs/MYC2.
A transgenic Arabidopsis line containing a chimeric PR-1luciferase (LUC) reporter gene was subjected to mutagenesis with activation tags. Screening of lines via high-throughput LUC imaging identified ...a number of dominant Arabidopsis mutants that exhibited enhanced PR-1 gene expression. Here, we report the characterization of one of these mutants, designated activated disease resistance (adr) 1. This line showed constitutive expression of a number of key defense marker genes and accumulated salicylic acid but not ethylene or jasmonic acid. Furthermore, adr1 plants exhibited resistance against the biotrophic pathogens Peronospora parasitica and Erysiphe cichoracearum but not the necrotrophic fungus Botrytis cinerea. Analysis of a series of adr1 double mutants suggested that adr1-mediated resistance against P. parasitica was salicylic acid (SA)-dependent, while resistance against E. cichoracearum was both SA-dependent and partially NPR1-dependent. The ADR1 gene encoded a protein possessing a number of key features, including homology to subdomains of protein kinases, a nucleotide binding domain, and leucine-rich repeats. The controlled, transient expression of ADR1 conveyed striking disease resistance in the absence of yield penalty, highlighting the potential utility of this gene in crop protection.
Biosynthesis of the phytohormone jasmonoyl-isoleucine (JA-Ile) requires reduction of the JA precursor 12-oxo-phytodienoic acid (OPDA) by OPDA reductase 3 (OPR3). Previous analyses of the opr3-1 ...Arabidopsis mutant suggested an OPDA signaling role independent of JA-Ile and its receptor COI1; however, this hypothesis has been challenged because opr3-1 is a conditional allele not completely impaired in JA-Ile biosynthesis. To clarify the role of OPR3 and OPDA in JA-independent defenses, we isolated and characterized a loss-of-function opr3-3 allele. Strikingly, opr3-3 plants remained resistant to necrotrophic pathogens and insect feeding, and activated COI1-dependent JA-mediated gene expression. Analysis of OPDA derivatives identified 4,5-didehydro-JA in wounded wild-type and opr3-3 plants. OPR2 was found to reduce 4,5-didehydro-JA to JA, explaining the accumulation of JA-Ile and activation of JA-Ile-responses in opr3-3 mutants. Our results demonstrate that in the absence of OPR3, OPDA enters the β-oxidation pathway to produce 4,5-ddh-JA as a direct precursor of JA and JA-Ile, thus identifying an OPR3-independent pathway for JA biosynthesis.
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