Plant hormones and signaling peptides
26.6K views | +2 today
Follow
Plant hormones and  signaling peptides
Your new post is loading...
Your new post is loading...
Scooped by Christophe Jacquet
Scoop.it!

A ligand-independent origin of abscisic acid perception | PNAS

A ligand-independent origin of abscisic acid perception | PNAS | Plant hormones and  signaling peptides | Scoop.it
Land plants are considered monophyletic, descending from a single successful colonization of land by an aquatic algal ancestor. The ability to survive dehydration to the point of desiccation is a key adaptive trait enabling terrestrialization. In extant land plants, desiccation tolerance depends on the action of the hormone abscisic acid (ABA) that acts through a receptor-signal transduction pathway comprising a PYRABACTIN RESISTANCE 1-like (PYL)–PROTEIN PHOSPHATASE 2C (PP2C)–SNF1-RELATED PROTEIN KINASE 2 (SnRK2) module. Early-diverging aeroterrestrial algae mount a dehydration response that is similar to that of land plants, but that does not depend on ABA: Although ABA synthesis is widespread among algal species, ABA-dependent responses are not detected, and algae lack an ABA-binding PYL homolog. This raises the key question of how ABA signaling arose in the earliest land plants. Here, we systematically characterized ABA receptor-like proteins from major land plant lineages, including a protein found in the algal sister lineage of land plants. We found that the algal PYL-homolog encoded by Zygnema circumcarinatum has basal, ligand-independent activity of PP2C repression, suggesting this to be an ancestral function. Similarly, a liverwort receptor possesses basal activity, but it is further activated by ABA. We propose that co-option of ABA to control a preexisting PP2C-SnRK2-dependent desiccation-tolerance pathway enabled transition from an all-or-nothing survival strategy to a hormone-modulated, competitive strategy by enabling continued growth of anatomically diversifying vascular plants in dehydrative conditions, enabling them to exploit their new environment more efficiently.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Negative gravitropic response of roots directs auxin flow to control root gravitropism - Ge - 2019 - Plant, Cell & Environment

Negative gravitropic response of roots directs auxin flow to control root gravitropism - Ge - 2019 - Plant, Cell & Environment | Plant hormones and  signaling peptides | Scoop.it
Root tip is capable of sensing and adjusting its growth direction in response to gravity, a phenomenon known as root gravitropism. Previously, we have shown that negative gravitropic response of roots (NGR) is essential for the positive gravitropic response of roots. Here, we show that NGR, a plasma membrane protein specifically expressed in root columella and lateral root cap cells, controls the positive root gravitropic response by regulating auxin efflux carrier localization in columella cells and the direction of lateral auxin flow in response to gravity. Pharmacological and genetic studies show that the negative root gravitropic response of the ngr mutants depends on polar auxin transport in the root elongation zone. Cell biology studies further demonstrate that polar localization of the auxin efflux carrier PIN3 in root columella cells and asymmetric lateral auxin flow in the root tip in response to gravistimulation is reversed in the atngr1;2;3 triple mutant. Furthermore, simultaneous mutations of three PIN genes expressed in root columella cells impaired the negative root gravitropic response of the atngr1;2;3 triple mutant. Our work revealed a critical role of NGR in root gravitropic response and provided an insight of the early events and molecular basis of the positive root gravitropism.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

The missing link in jasmonic acid biosynthesis

The missing link in jasmonic acid biosynthesis | Plant hormones and  signaling peptides | Scoop.it
Jasmonic acid biosynthesis starts in chloroplasts and is finalized in peroxisomes. The required export of a crucial intermediate out of the chloroplast is now shown to be mediated by a protein from the outer envelope called JASSY.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Jasmonate-mediated wound signalling promotes plant regeneration

Jasmonate-mediated wound signalling promotes plant regeneration | Plant hormones and  signaling peptides | Scoop.it
Wounding is the first event triggering regeneration1,2,3,4. However, the molecular basis of wound signalling pathways in plant regeneration is largely unclear. We previously established a method to study de novo root regeneration (DNRR) in Arabidopsis thaliana5,6, which provides a platform for analysing wounding. During DNRR, auxin is biosynthesized after leaf detachment and promotes cell fate transition to form the root primordium5,6,7. Here, we show that jasmonates (JAs) serve as a wound signal during DNRR. Within 2 h of leaf detachment, JA is produced in leaf explants and activates ETHYLENE RESPONSE FACTOR109 (ERF109). ERF109 upregulates ANTHRANILATE SYNTHASE α1 (ASA1)—a tryptophan biosynthesis gene in the auxin production pathway8,9,10—dependent on the pre-deposition of SET DOMAIN GROUP8 (SDG8)-mediated histone H3 lysine 36 trimethylation (H3K36me3)11 on the ASA1 locus. After 2 h, ERF109 activity is inhibited by direct interaction with JASMONATE-ZIM-DOMAIN (JAZ) proteins to prevent hypersensitivity to wounding. Our results suggest that a dynamic JA wave cooperates with histone methylation to upregulate a pulse of auxin production and promote DNRR in response to wounding.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Ectopic expression of ARGOS8 reveals a role for ethylene in root‐lodging resistance in maize - Shi - 2019 - The Plant Journal -

Ectopic expression of ARGOS8 reveals a role for ethylene in root‐lodging resistance in maize - Shi - 2019 - The Plant Journal - | Plant hormones and  signaling peptides | Scoop.it
Ethylene plays a critical role in many diverse processes in plant development. Recent studies have demonstrated that overexpression of the maize ARGOS8 gene reduces the plant's response to ethylene by decreasing ethylene signaling and enhances grain yield in transgenic maize plants. The objective of this study was to determine the effects of ethylene on the development of nodal roots, which are primarily responsible for root‐lodging resistance in maize. Exogenous application of the ethylene precursor 1‐aminocyclopropane‐1‐carboxylic acid (ACC) was found to promote the emergence of nodal roots. Transcriptome analysis of nodal tissues revealed that the expression of genes involved in metabolic processes and cell wall biogenesis was upregulated in response to ACC treatment, supporting the notion that ethylene is a positive regulator for the outgrowth of young root primordia. In BSV::ARGOS8 transgenic plants with reduced ethylene sensitivity due to constitutive overexpression of ARGOS8, nodal root emergence was delayed and the promotional effect of ACC on nodal root emergence decreased. Field tests showed that the BSV::ARGOS8 plants had higher root lodging relative to non‐transgenic controls. When ARGOS8 expression was controlled by the developmentally regulated promoter FTM1, which conferred ARGOS8 overexpression in adult plants but not in the nodal roots and nodes in juvenile plants, the FTM1::ARGOS8 plants had no significant difference in root lodging compared with the wild type but produced a higher grain yield. These results suggest that ethylene has a role in promoting nodal root emergence and that a delay in nodal root development has a negative effect on root‐lodging resistance in maize.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Microbial modulation of plant ethylene signaling: ecological and evolutionary consequences | Microbiome | Full Text

Microbial modulation of plant ethylene signaling: ecological and evolutionary consequences | Microbiome | Full Text | Plant hormones and  signaling peptides | Scoop.it
The plant hormone ethylene is one of the central regulators of plant development and stress resistance. Optimal ethylene signaling is essential for plant fitness and is under strong selection pressure. Plants upregulate ethylene production in response to stress, and this hormone triggers defense mechanisms. Due to the pleiotropic effects of ethylene, adjusting stress responses to maximize resistance, while minimizing costs, is a central determinant of plant fitness. Ethylene signaling is influenced by the plant-associated microbiome. We therefore argue that the regulation, physiology, and evolution of the ethylene signaling can best be viewed as the interactive result of plant genotype and associated microbiota. In this article, we summarize the current knowledge on ethylene signaling and recapitulate the multiple ways microorganisms interfere with it. We present ethylene signaling as a model system for holobiont-level evolution of plant phenotype: this cascade is tractable, extremely well studied from both a plant and a microbial perspective, and regulates fundamental components of plant life history. We finally discuss the potential impacts of ethylene modulation microorganisms on plant ecology and evolution. We assert that ethylene signaling cannot be fully appreciated without considering microbiota as integral regulatory actors, and we more generally suggest that plant ecophysiology and evolution can only be fully understood in the light of plant-microbiome interactions.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Multifaceted activity of cytokinin in leaf development shapes its size and structure in Arabidopsis - Skalák - 2019 - The Plant Journal -

Multifaceted activity of cytokinin in leaf development shapes its size and structure in Arabidopsis - Skalák - 2019 - The Plant Journal - | Plant hormones and  signaling peptides | Scoop.it
The phytohormone cytokinin has been shown to affect many aspects of plant development ranging from the regulation of the shoot apical meristem to leaf senescence. However, some studies have reported contradictory effects of cytokinin on leaf physiology. Therefore cytokinin treatments cause both chlorosis and increased greening and both lead to decrease or increase in cell size. To elucidate this multifaceted role of cytokinin in leaf development, we have employed a system of temporal controls over the cytokinin pool and investigated the consequences of modulated cytokinin levels in the third leaf of Arabidopsis. We show that, at the cell proliferation phase, cytokinin is needed to maintain cell proliferation by blocking the transition to cell expansion and the onset of photosynthesis. Transcriptome profiling revealed regulation by cytokinin of a gene suite previously shown to affect cell proliferation and expansion and thereby a molecular mechanism by which cytokinin modulates a molecular network underlying the cellular responses. During the cell expansion phase, cytokinin stimulates cell expansion and differentiation. Consequently, a cytokinin excess at the cell expansion phase results in an increased leaf and rosette size fueled by higher cell expansion rate, yielding higher shoot biomass. Proteome profiling revealed the stimulation of primary metabolism by cytokinin, in line with an increased sugar content that is expected to increase turgor pressure, representing the driving force of cell expansion. Therefore, the developmental timing of cytokinin content fluctuations, together with a tight control of primary metabolism, is a key factor mediating transitions from cell proliferation to cell expansion in leaves.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Frontiers | Jasmonate Zim-Domain Protein 9 Interacts With Slender Rice 1 to Mediate the Antagonistic Interaction Between Jasmonic and Gibberellic Acid Signals in Rice | Plant Science

Frontiers | Jasmonate Zim-Domain Protein 9 Interacts With Slender Rice 1 to Mediate the Antagonistic Interaction Between Jasmonic and Gibberellic Acid Signals in Rice | Plant Science | Plant hormones and  signaling peptides | Scoop.it
The jasmonic acid (JA) and gibberellic acid (GA) signaling pathways interact to coordinate stress responses and developmental processes. This coordination affects plant growth and yield, and is mediated by interactions between the repressors of each pathway, the JASMONATE ZIM-DOMAIN PROTEIN (JAZ) and DELLA proteins. In this study we attempted to identify rice (Oryza sativa) JAZs that interact with rice DELLAs such as SLENDER RICE 1 (SLR1). Analysis of protein–protein interactions showed that OsJAZ8 and OsJAZ9 interact with SLR1; OsJAZ9 also interacted with the SLR1-LIKE (SLRL) protein SLRL2. Based on this broader interaction, we explored the function of OsJAZ9 in JA and GA responses by analyzing transcript levels of the JA-responsive gene OsbHLH148 and the GA-responsive gene OsPIL14 in OsJAZ9-overexpressing (OsJAZ9-Ox) and osjaz9 mutant plants. OsbHLH148 and OsPIL14 encode key transcription factors controlling JA and GA responses, respectively, and JA and GA antagonistically regulate their expression. In OsJAZ9-Ox, the expression of OsbHLH148 was downregulated and the expression of OsPIL14 was upregulated. By contrast, in osjaz9 mutants, the expression of OsbHLH148 was upregulated and the expression of OsPIL14 was downregulated. These observations indicated that OsJAZ9 regulates both JA and GA responses in rice, and this finding was supported by the opposite expression patterns of OsDREB1s, downstream targets of OsbHLH148 and OsPIL14, in the OsJAZ9-Ox and osjaz9 plants. Together, these findings indicate that OsJAZ9 suppresses JA responses and promotes GA responses in rice, and the protein–protein interaction between OsJAZ9 and SLR1 is involved in the antagonistic interplay between JA and GA.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Sulfate is Incorporated into Cysteine to Trigger ABA Production and Stomatal Closure

Sulfate is Incorporated into Cysteine to Trigger ABA Production and Stomatal Closure | Plant hormones and  signaling peptides | Scoop.it
Plants close stomata when root water availability becomes limiting. Recent studies have demonstrated that soil-drying induces root-to-shoot sulfate transport via the xylem and that sulfate closes stomata. Here we provide evidence for a physiologically relevant signaling pathway that underlies sulfate-induced stomatal closure in Arabidopsis (Arabidopsis thaliana). We uncovered that, in the guard cells, sulfate activates NADPH oxidases to produce reactive oxygen species (ROS) and that this ROS induction is essential for sulfate-induced stomata closure. In line with the function of ROS as the second-messenger of abscisic acid (ABA) signaling, sulfate does not induce ROS in the ABA-synthesis mutant, aba3-1, and sulfate-induced ROS were ineffective at closing stomata in the ABA-insensitive mutant abi2-1 and a SLOW ANION CHANNEL1 loss-of-function mutant. We provided direct evidence for sulfate-induced accumulation of ABA in the cytosol of guard cells by application of the ABAleon2.1 ABA sensor, the ABA signaling reporter ProRAB18:GFP, and quantification of endogenous ABA marker genes. In concordance with previous studies, showing that ABA DEFICIENT3 uses Cys as the substrate for activation of the ABSCISIC ALDEHYDE OXIDASE3 (AAO3) enzyme catalyzing the last step of ABA production, we demonstrated that assimilation of sulfate into Cys is necessary for sulfate-induced stomatal closure and that sulfate-feeding or Cys-feeding induces transcription of NINE-CIS-EPOXYCAROTENOID DIOXYGENASE3, limiting the synthesis of the AAO3 substrate. Consequently, Cys synthesis-depleted mutants are sensitive to soil-drying due to enhanced water loss. Our data demonstrate that sulfate is incorporated into Cys and tunes ABA biosynthesis in leaves, promoting stomatal closure, and that this mechanism contributes to the physiological water limitation response.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

DOF2.1 Controls Cytokinin-Dependent Vascular Cell Proliferation Downstream of TMO5/LHW - ScienceDirect

DOF2.1 Controls Cytokinin-Dependent Vascular Cell Proliferation Downstream of TMO5/LHW - ScienceDirect | Plant hormones and  signaling peptides | Scoop.it
To create a three-dimensional structure, plants rely on oriented cell divisions and cell elongation. Oriented cell divisions are specifically important in procambium cells of the root to establish the different vascular cell types [1, 2]. These divisions are in part controlled by the auxin-controlled TARGET OF MONOPTEROS5 (TMO5) and LONESOME HIGHWAY (LHW) transcription factor complex [3, 4, 5, 6, 7]. Loss-of-function of tmo5 or lhw clade members results in strongly reduced vascular cell file numbers, whereas ectopic expression of both TMO5 and LHW can ubiquitously induce periclinal and radial cell divisions in all cell types of the root meristem. TMO5 and LHW interact only in young xylem cells, where they promote expression of two direct target genes involved in the final step of cytokinin (CK) biosynthesis, LONELY GUY3 (LOG3) and LOG4 [8, 9] Therefore, CK was hypothesized to act as a mobile signal from the xylem to trigger divisions in the neighboring procambium cells [3, 6]. To unravel how TMO5/LHW-dependent cytokinin regulates cell proliferation, we analyzed the transcriptional responses upon simultaneous induction of both transcription factors. Using inferred network analysis, we identified AT2G28510/DOF2.1 as a cytokinin-dependent downstream target gene. We further showed that DOF2.1 controls specific procambium cell divisions without inducing other cytokinin-dependent effects such as the inhibition of vascular differentiation. In summary, our results suggest that DOF2.1 and its closest homologs control vascular cell proliferation, thus leading to radial expansion of the root.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Salicylic acid activates poplar defense against the biotrophic rust fungus Melampsora larici‐populina via increased biosynthesis of catechin and proanthocyanidins - Ullah - 2019 - New Phytologist -...

Salicylic acid activates poplar defense against the biotrophic rust fungus Melampsora larici‐populina via increased biosynthesis of catechin and proanthocyanidins - Ullah - 2019 - New Phytologist -... | Plant hormones and  signaling peptides | Scoop.it
Poplar trees synthesize flavan‐3‐ols (catechin and proanthocyanidins) as a defense against foliar rust fungi, but the regulation of this defense response is poorly understood. Here, we investigated the role of hormones in regulating flavan‐3‐ol accumulation in poplar during rust infection.
We profiled levels of defense hormones, signaling genes, and flavan‐3‐ol metabolites in black poplar leaves at different stages of rust infection. Hormone levels were manipulated by external sprays, genetic engineering, and drought to reveal their role in rust fungal defenses.
Levels of salicylic acid (SA), jasmonic acid, and abscisic acid increased in rust‐infected leaves and activated downstream signaling, with SA levels correlating closely with those of flavan‐3‐ols. Pretreatment with the SA analog benzothiadiazole increased flavan‐3‐ol accumulation by activating the MYB–bHLH–WD40 complex and reduced rust proliferation. Furthermore, transgenic poplar lines overproducing SA exhibited higher amounts of flavan‐3‐ols constitutively via the same transcriptional activation mechanism. These findings suggest a strong association among SA, flavan‐3‐ol biosynthesis, and rust resistance in poplars. Abscisic acid also promoted poplar defense against rust infection, but likely through stomatal immunity independent of flavan‐3‐ols. Jasmonic acid did not confer any apparent defense responses to the fungal pathogen.
We conclude that SA activates flavan‐3‐ol biosynthesis in poplar against rust infection.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Archetypal Roles of an Abscisic Acid Receptor in Drought and Sugar Responses in Liverworts

Archetypal Roles of an Abscisic Acid Receptor in Drought and Sugar Responses in Liverworts | Plant hormones and  signaling peptides | Scoop.it
Abscisic acid (ABA) controls seed dormancy and stomatal closure through binding to the intracellular receptor Pyrabactin resistance1 (Pyr1)/Pyr1-like/regulatory components of ABA receptors (PYR/PYL/RCAR) in angiosperms. Genes encoding PYR/PYL/RCAR are thought to have arisen in the ancestor of embryophytes, but the roles of the genes in nonvascular plants have not been determined. In the liverwort Marchantia polymorpha, ABA reduces growth and enhances desiccation tolerance through increasing accumulation of intracellular sugars and various transcripts such as those of Late Embryogenesis Abundant (LEA)-like genes. In this study, we analyzed a gene designated MpPYL1, which is closely related to PYR/PYL/RCAR of angiosperms, in transgenic liverworts. Transgenic lines overexpressing MpPYL1-GFP showed ABA-hypersensitive growth with enhanced desiccation tolerance, whereas Mppyl1 generated by CRISPR-Cas9-mediated genome editing showed ABA-insensitive growth with reduced desiccation tolerance. Transcriptome analysis indicated that MpPYL1 is a major regulator of abiotic stress-associated genes, including all 35 ABA-induced LEA-like genes. Furthermore, these transgenic plants showed altered responses to extracellular Suc, suggesting that ABA and PYR/PYL/RCAR function in sugar responses. The results presented here reveal an important role of PYR/PYL/RCAR in the ABA response, which was likely acquired in the common ancestor of land plants. The results also indicate the archetypal role of ABA and its receptor in sugar response and accumulation processes for vegetative desiccation tolerance in bryophytes.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

HOMEOBOX PROTEIN52 Mediates the Crosstalk between Ethylene and Auxin Signaling during Primary Root Elongation by Modulating Auxin Transport-Related Gene Expression

HOMEOBOX PROTEIN52 Mediates the Crosstalk between Ethylene and Auxin Signaling during Primary Root Elongation by Modulating Auxin Transport-Related Gene Expression | Plant hormones and  signaling peptides | Scoop.it
The gaseous hormone ethylene participates in many physiological processes in plants. Ethylene-inhibited root elongation involves PIN-FORMED2 (PIN2)-mediated basipetal auxin transport, but the molecular mechanisms underlying the regulation of PIN2 function by ethylene (and therefore auxin distribution) are poorly understood. Here, we report that the plant-specific and ethylene-responsive HD-Zip gene HB52 is involved in ethylene-mediated inhibition of primary root elongation in Arabidopsis thaliana. Biochemical and genetic analyses demonstrated that HB52 is ethylene responsive and acts downstream of ETHYLENE-INSENSITIVE3 (EIN3). HB52 knockdown mutants displayed an ethylene-insensitive phenotype during primary root elongation, while its overexpression resulted in short roots, as observed in ethylene-treated plants. In addition, root auxin distribution and gravitropism were impaired in HB52 knockdown and overexpression lines. Consistent with these findings, in vitro and in vivo binding experiments showed that HB52 regulates the expression of auxin transport-related genes, including PIN2, WAVY ROOT GROWTH1 (WAG1), and WAG2 by physically binding to their promoter regions. These findings suggest that HB52 functions in the ethylene-mediated inhibition of root elongation by modulating the expression of auxin transport components downstream of EIN3, revealing a mechanism in which HB52 acts as an important node in the crosstalk between ethylene and auxin signaling during plant growth and development.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Systemic Root-Shoot Signaling Drives Jasmonate-Based Root Defense against Nematodes - ScienceDirect

Systemic Root-Shoot Signaling Drives Jasmonate-Based Root Defense against Nematodes - ScienceDirect | Plant hormones and  signaling peptides | Scoop.it
Shoot-root communication is crucial for plant adaptation to environmental changes. However, the extensive crosstalk between shoots and roots that controls the synthesis of jasmonates (JAs), in order to enhance defense responses against rhizosphere herbivores, remains poorly understood. Here, we report that the root-knot nematode (RKN) Meloidogyne incognita induces the systemic transmission of electrical and reactive oxygen species (ROS) signals from attacked tomato roots to the leaves, leading to an increased accumulation of JAs in the leaves. Grafting of 1.0-cm stem sections from mutants lacking GLUTAMATE RECEPTOR-LIKE 3.5 or the mutants deficient in RESPIRATORY BURST OXIDASE HOMOLOG 1 abolished the RKN-induced electrical signals and associated ROS and JA accumulation in the upper stems and leaves with attenuated resistance to RKN. Furthermore, the absence of systemic transmission of electrical and ROS signals compromised the activation of mitogen-activated protein kinases (MPKs) 1/2 in leaves. Silencing MPK1 or MPK2 abolished RKN-induced accumulation of JAs and associated resistance. These findings reveal a systemic signaling loop that integrates electrical, ROS, and JA signals to enhance the resistance in distal organs via root-shoot-root communication.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

A Cellular Insulator against CLE45 Peptide Signaling - ScienceDirect

A Cellular Insulator against CLE45 Peptide Signaling - ScienceDirect | Plant hormones and  signaling peptides | Scoop.it
OPS activity antagonizes CLE45 signaling in developing protophloem sieve elements

•Enhanced CLE45 signaling can be overcome by increased OPS dosage


•OPS dampens CLE45 sensing by direct interference with CLE45 signaling components


•OPS hyperactivity confers resistance to various root-active CLE peptides

No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Multiple Auxin-Response Regulators Enable Stability and Variability in Leaf Development - ScienceDirect

Multiple Auxin-Response Regulators Enable Stability and Variability in Leaf Development - ScienceDirect | Plant hormones and  signaling peptides | Scoop.it
Auxin-signal transduction is mediated by the antagonistic activity of transcriptional activators and repressors. Both activators and repressors belong to gene families, but the biological importance of this complexity is not clear. Here, we addressed this question using tomato leaf development as a model by generating and analyzing mutants in multiple auxin-response components. In developing compound tomato leaves, auxin promotes leaflet formation and blade growth, and in the intercalary regions between leaflets, auxin response is inhibited by the Aux/IAA protein ENTIRE (E). e mutants form simple leaves due to ectopic blade growth in the intercalary domain. Using this unique loss-of-function phenotype and genome editing of auxin-response factor (ARF) genes, encoding auxin-response activators, we identified the contribution of specific ARFs to the e phenotype. Mutations in the related ARFs SlMP, SlARF19A, and SlARF19B, but not SlARF7, reduced the leaf blade and suppressed the e phenotype in a dosage-dependent manner that correlated with their relative expression, leading to a continuum of shapes. While single e and slmp mutants affected blade growth in an opposite manner, leaves of e slmp double mutants were similar to those of the wild type. However, the leaf shape of e slmp was more variable than that of the wild type, and it showed increased sensitivity to auxin. Our findings demonstrate that the existence of multiple auxin-response repressors and activators stabilizes the developmental output of auxin and that tuning their activity enables shape variability. The increased complexity of the auxin response therefore balances stability and flexibility in leaf patterning.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

A novel gibberellin promotes seedling establishment

A novel gibberellin promotes seedling establishment | Plant hormones and  signaling peptides | Scoop.it
A previously unknown biologically active gibberellin present in seeds of Arabidopsis thaliana is formed by hydration of the gibberellin precursor GA12 through the action of GAS2, a 2-oxoglutarate-dependent dioxygenase that decreases sensitivity to abscisic acid and promotes seed germination and seedling establishment.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Frontiers | Nodulating Legumes Are Distinguished by a Sensitivity to Cytokinin in the Root Cortex Leading to Pseudonodule Development | Plant Science

Frontiers | Nodulating Legumes Are Distinguished by a Sensitivity to Cytokinin in the Root Cortex Leading to Pseudonodule Development | Plant Science | Plant hormones and  signaling peptides | Scoop.it
Root nodule symbiosis (RNS) is a feature confined to a single clade of plants, the Fabids. Among Fabids capable of RNS, legumes form root cortex-based nodules in symbioses with rhizobia, while actinorhizal species form lateral root-based nodules with actinomycetes. Cytokinin has previously been shown to be sufficient for “pseudonodule” initiation in model legumes. Here, we tested whether this response correlates with the ability to nodulate across a range of plant species. We analyzed the formation of pseudonodules in 17 nodulating and non-nodulating legume species, and 11 non-legumes, including nodulating actinorhizal species, using light and fluorescence microscopy. Cytokinin-induced pseudonodules arising from cortical cell divisions occurred in all nodulating legume species, but not in any of the other species, including non-nodulating legumes. Pseudonodule formation was dependent on the CRE1 cytokinin receptor in Medicago truncatula. Inhibition of root growth by cytokinin occurred across plant groups, indicating that pseudonodule development is the result of a specific cortical cytokinin response unique to nodulating legumes. Lack of a cortical cytokinin response from the Arabidopsis thaliana cytokinin reporter TCSn::GFP supported this hypothesis. Our results suggest that the ability to form cortical cell-derived nodules was gained in nodulating legumes, and likely lost in non-nodulating legumes, due to a specific root cortical response to cytokinin.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

The roles of jasmonate signalling in nitrogen uptake and allocation in rice (Oryza sativa L.) - Wu - 2019 - Plant, Cell & Environment -

The roles of jasmonate signalling in nitrogen uptake and allocation in rice (Oryza sativa L.) - Wu - 2019 - Plant, Cell & Environment - | Plant hormones and  signaling peptides | Scoop.it
Herbivore damage by chewing insects activates jasmonate (JA) signalling that can elicit systemic defense responses in rice. Few details are known, however, concerning the mechanism, whereby JA signalling modulates nutrient status in rice in response to herbivory. (15NH4)2SO4 labelling experiments, proteomic surveys, and RT‐qPCR analyses were used to identify the roles of JA signalling in nitrogen (N) uptake and allocation in rice plants. Exogenous applications of methyl jasmonate (MeJA) to rice seedlings led to significantly reduced N uptake in roots and reduced translocation of recently‐absorbed 15N from roots to leaves, likely occurring as a result of down‐regulation of glutamine synthetase cytosolic isozyme 1–2 and ferredoxin–nitrite reductase. Shoot MeJA treatment resulted in a remobilization of endogenous unlabelled 14N from leaves to roots, and root MeJA treatment also increased 14N accumulation in roots but did not affect 14N accumulation in leaves of rice. Additionally, proteomic and RT‐qPCR experiments showed that JA‐mediated plastid disassembly and dehydrogenases GDH2 up‐regulation contribute to N release in leaves to support production of defensive proteins/compounds under N‐limited condition. Collectively, our results indicate that JA signalling mediates large‐scale systemic changes in N uptake and allocation in rice plants.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Aberrant protein phosphatase 2C leads to abscisic acid insensitivity and high transpiration in parasitic Striga

Aberrant protein phosphatase 2C leads to abscisic acid insensitivity and high transpiration in parasitic Striga | Plant hormones and  signaling peptides | Scoop.it
Striga parasitizes major crops in arid regions, depriving the host crop of nutrients through the transpiration stream and causing vast agricultural damage. Here, we report on the mechanism underlying how Striga maintains high transpiration under drought conditions. We found that Striga did not respond to abscisic acid, the phytohormone responsible for controlling stomatal closure. Protein phosphatase 2C of Striga (ShPP2C1) is not regulated by abscisic acid receptors, and this feature is attributable to specific mutations in its amino acid sequence. Moreover, Arabidopsis transformed with ShPP2C1 showed an abscisic acid-insensitive phenotype, indicating that ShPP2C1 functions as a dominant negative regulator of abscisic acid signal transduction. These findings suggest that ShPP2C1 interrupts abscisic acid signalling in Striga, resulting in high transpiration and subsequent efficient absorption of host nutrients under drought conditions.
No comment yet.
Rescooped by Christophe Jacquet from LRSV Publications
Scoop.it!

New Phytologist - Auxin‐mediated Aux/IAA‐ARF‐HB signaling cascade regulates secondary xylem development in Populus

New Phytologist - Auxin‐mediated Aux/IAA‐ARF‐HB signaling cascade regulates secondary xylem development in Populus | Plant hormones and  signaling peptides | Scoop.it
Wood development is strictly regulated by various phytohormones and auxin plays a central regulatory role in this process. However, how the auxin signaling is transducted in developing secondary xylem during wood formation in tree species remains unclear. Here, we identified an Aux/INDOLE‐3‐ACETIC ACID 9 (IAA9)‐AUXIN RESPONSE FACTOR 5 (ARF5) module in Populus tomentosa as a key mediator of auxin signaling to control early developing xylem development. PtoIAA9, a canonical Aux/IAA gene, is predominantly expressed in vascular cambium and developing secondary xylem and induced by exogenous auxin. Overexpression of PtoIAA9m encoding a stabilized IAA9 protein significantly represses secondary xylem development in transgenic poplar. We further showed that PtoIAA9 interacts with PtoARF5 homologs via the C‐terminal III/IV domains. The truncated PtoARF5.1 protein without the III/IV domains rescued defective phenotypes caused by PtoIAA9m. Expression analysis showed that the PtoIAA9‐PtoARF5 module regulated the expression of genes associated with secondary vascular development in PtoIAA9m‐ and PtoARF5.1‐overexpressing plants. Furthermore, PtoARF5.1 could bind to the promoters of two Class III homeodomain‐leucine zipper (HD‐ZIP III) genes, PtoHB7 and PtoHB8, to modulate secondary xylem formation. Taken together, our results suggest that the Aux/IAA9‐ARF5 module is required for auxin signaling to regulate wood formation via orchestrating the expression of HD‐ZIP III transcription factors in poplar.

Via LRSV
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

The role of KDEL-tailed cysteine endopeptidases of Arabidopsis (AtCEP2 and AtCEP1) in root development

The role of KDEL-tailed cysteine endopeptidases of Arabidopsis (AtCEP2 and AtCEP1) in root development | Plant hormones and  signaling peptides | Scoop.it
Plants encode a unique group of papain-type cysteine endopeptidases (CysEP) characterized by a C-terminal KDEL endoplasmic reticulum retention signal (KDEL-CysEP) and an unusually broad substrate specificity. The three Arabidopsis KDEL-CysEPs (AtCEP1, AtCEP2, and AtCEP3) are differentially expressed in vegetative and generative tissues undergoing programmed cell death (PCD). While KDEL-CysEPs have been shown to be implicated in the collapse of tissues during PCD, roles of these peptidases in processes other than PCD are unknown. Using mCherry-AtCEP2 and EGFP-AtCEP1 reporter proteins in wild type versus atcep2 or atcep1 mutant plants, we explored the participation of AtCEP in young root development. Loss of AtCEP2, but not AtCEP1 resulted in shorter primary roots due to a decrease in cell length in the lateral root (LR) cap, and impairs extension of primary root epidermis cells such as trichoblasts in the elongation zone. AtCEP2 was localized to root cap corpses adherent to epidermal cells in the rapid elongation zone. AtCEP1 and AtCEP2 are expressed in root epidermis cells that are separated for LR emergence. Loss of AtCEP1 or AtCEP2 caused delayed emergence of LR primordia. KDEL-CysEPs might be involved in developmental tissue remodeling by supporting cell wall elongation and cell separation.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

BES1 hinders ABSCISIC ACID INSENSITIVE5 and promotes seed germination in Arabidopsis - Zhao - 2019 - New Phytologist -

BES1 hinders ABSCISIC ACID INSENSITIVE5 and promotes seed germination in Arabidopsis - Zhao - 2019 - New Phytologist - | Plant hormones and  signaling peptides | Scoop.it
Proper regulation of seed germination is essential for the successful propagation of a plant. The transcription factor ABSCISIC ACID INSENSITIVE5 (ABI5) of the abscisic acid (ABA) signaling pathway plays a central role in the inhibition of seed germination. ABI5 is precisely regulated by the core ABA signaling components and multiple other factors. However, the complex regulatory network of ABI5 remains largely unknown.
In this study, we determined the biochemical interaction between ABI5 and the BRINSENSITIVE1 (BRI1)‐EMS‐SUPPRESSOR1 (BES1) transcription factor of the brassinosteroid (BR) signaling pathway, as well as the function of BES1 regulating ABI5 during seed germination in Arabidopsis.
BES1 directly interacts with ABI5 both in vitro and in vivo. The bZIP domain of ABI5, which is responsible for DNA binding, is critical for ABI5 binding to BES1. The interaction of BES1 with ABI5 significantly suppressed the binding of ABI5 to the promoter regions of downstream genes, which resulted in their reduced expression and consequently facilitated seed germination.
This study shed new light on the coordination of multiple signaling pathways during seed germination. In particular, BES1 directly binds to ABI5, which interferes with its transcriptional activity and suppresses ABA signaling output.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Canonical and noncanonical ethylene signaling pathways that regulate Arabidopsis susceptibility to the cyst nematode Heterodera schachtii - Piya - 2019 - New Phytologist -

Canonical and noncanonical ethylene signaling pathways that regulate Arabidopsis susceptibility to the cyst nematode Heterodera schachtii - Piya - 2019 - New Phytologist - | Plant hormones and  signaling peptides | Scoop.it
Plant‐parasitic cyst nematodes successfully exploit various phytohormone signaling pathways to establish a new hormonal equilibrium that facilitates nematode parasitism. Although it is largely accepted that ethylene regulates plant responses to nematode infection, a mechanistic understanding of how ethylene shapes plant–nematode interactions remains largely unknown.
In this study, we examined the involvement of various components regulating ethylene perception and signaling in establishing Arabidopsis susceptibility to the cyst nematode Heterodera schachtii using a large set of well‐characterized single and higher order mutants.
Our analyses revealed the existence of two pathways that separately engage ethylene with salicylic acid (SA) and cytokinin signaling during plant response to nematode infection. One pathway involves the canonical ethylene signaling pathway in which activation of ethylene signaling results in suppression of SA‐based immunity. The second pathway involves the ethylene receptor ETR1, which signals independently of SA acid to affect immunity, instead altering cytokinin‐mediated regulation of downstream components.
Our results reveal important mechanisms through which cyst nematodes exploit components of ethylene perception and signaling to affect the balance of hormonal signaling through ethylene interaction with SA and cytokinin networks. This hormonal interaction overcomes plant defense and provokes a susceptible response.
No comment yet.
Scooped by Christophe Jacquet
Scoop.it!

Frontiers | AP2/ERF Family Transcription Factors ORA59 and RAP2.3 Interact in the Nucleus and Function Together in Ethylene Responses | Plant Science

Frontiers | AP2/ERF Family Transcription Factors ORA59 and RAP2.3 Interact in the Nucleus and Function Together in Ethylene Responses | Plant Science | Plant hormones and  signaling peptides | Scoop.it
The gaseous plant hormone ethylene is a key signaling molecule regulating plant growth, development, and defense against pathogens. Octadecanoid-responsive arabidopsis 59 (ORA59) is an ethylene response factor (ERF) transcription factor and has been suggested to integrate ethylene and jasmonic acid signaling and regulate resistance to necrotrophic pathogens. Here we screened for ORA59 interactors using the yeast two-hybrid system to elucidate the molecular function of ORA59. This led to the identification of RELATED TO AP2.3 (RAP2.3), another ERF transcription factor belonging to the group VII ERF family. In binding assays, ORA59 and RAP2.3 interacted in the nucleus and showed ethylene-dependent nuclear localization. ORA59 played a positive role in ethylene-regulated responses, including the triple response, featured by short, thick hypocotyl and root, and exaggerated apical hook in dark-grown seedlings, and resistance to the necrotrophic pathogen Pectobacterium carotovorum, as shown by the increased and decreased ethylene sensitivity and disease resistance in ORA59-overexpressing (ORA59OE) and null mutant (ora59) plants, respectively. In genetic crosses, ORA59OE rap2.3 crossed lines lost ORA59-mediated positive effects and behaved like rap2.3 mutant. These results suggest that ORA59 physically interacts with RAP2.3 and that this interaction is important for the regulatory roles of ORA59 in ethylene responses.
No comment yet.