Root Signal Research Articles

In vivo and in vitro 31P-NMR Study of the Phosphate Transport and Polyphosphate Metabolism in Hebeloma cylindrosporum in Response to Plant Roots Signals.

We used in vivo and in vitro phosphorus-31 nuclear magnetic resonance (31P-NMR) spectroscopy to follow the change in transport, compartmentation and metabolism of phosphate in the ectomycorrhizal fungus Hebeloma cylindrosporum in response to root signals originating from host (Pinus pinaster) or non-host (Zea mays) plants. A device was developed for the in vivo studies allowing the circulation of a continuously oxygenated mineral solution in an NMR tube containing the mycelia. The in vitro studies were performed on fungal material after several consecutive treatment steps (freezing in liquid nitrogen; crushing with perchloric acid; elimination of perchloric acid; freeze-drying; dissolution in an appropriate liquid medium).

Chemotaxis responses of Meloidogyne incognita towards tomato roots depends on concentration gradient of root exudates in vitro assay

Nematodes respond differently to various host-derived odorants which can be either an attractant or a repellent. However, nematodes require suitable concentration gradient of the host cues to respond. In the present study, we have systematically assessed the distance and optimum incubation time at which Meloidogyne incognita second stage juveniles (J2s) respond to tomato root exudates and invasion via an in vitro assay using PF-127 medium. In vitro assay is highly suitable to investigate the nematode's host finding and invasion behaviour under stringent laboratory conditions. Tomato roots incubated for 2 hrs in pluoronic gel followed by exposure to M. incognita J2s gave significant attraction with directional movement and penetration after 8 hrs as compared to the roots incubated for 0 hr, ½ hr, 1 hr and 1½ hrs. In addition, response of J2s to host root signals was confirmed in terms of stylet movement or thrusting which was significantly increased by exposure to tomato root exudates and neurotransmitter resorcinol that is known to induce stylet thrusting along with accumulation of esophageal gland secretions. Similar stylet thrusting was not seen in water. Thus, the present study indicates that nematodes require proper gradient of host signals during the host recognition. These findings can be utilized for understanding the intricate plant nematode interactions which in turn beneficial for the development of novel nematode control strategies.

Research Advances on Tall Fescue Salt Tolerance: From Root Signaling to Molecular and Metabolic Adjustment

Soil salinity is one of the major abiotic stress factors that constrain plant growth and limit crop productivity. About a quarter of the global land area is affected by salinity; therefore, there is increased need to develop salt-tolerant crops. Tall fescue (Festuca arundinacea) is one of the most important cool-season turfgrasses, which has medium tolerance to salinity and has a promising potential to be used as a turfgrass under saline conditions. However, up to now, the maximum use of tall fescue under salinity stress is still limited by inadequate scientific literature. Recent studies have attempted to identify various adaptive responses to salinity stress at molecular, cellular, metabolic, and physiological levels in tall fescue. The successful integration of information concerning signal sensing, molecular tools with recent advances in -omics would certainly provide a clue for creating salt-tolerant tall fescue. Because salinity limits water availability to plants via hindering water absorption, and by inducing physiological drought, here we review and propose a probable mechanism of tall fescue response to salinity stress and to similar effects induced by drought based on published literature.

MicroRNA-mediated responses to long-term magnesium-deficiency in Citrus sinensis roots revealed by Illumina sequencing

BackgroundMagnesium (Mg)-deficiency occurs most frequently in strongly acidic, sandy soils. Citrus are grown mainly on acidic and strong acidic soils. Mg-deficiency causes poor fruit quality and low fruit yield in some Citrus orchards. For the first time, we investigated Mg-deficiency-responsive miRNAs in ‘Xuegan’ (Citrus sinensis) roots using Illumina sequencing in order to obtain some miRNAs presumably responsible for Citrus Mg-deficiency tolerance.ResultsWe obtained 101 (69) miRNAs with increased (decreased) expression from Mg-starved roots. Our results suggested that the adaptation of Citrus roots to Mg-deficiency was related to the several aspects: (a) inhibiting root respiration and related gene expression via inducing miR158 and miR2919; (b) enhancing antioxidant system by down-regulating related miRNAs (miR780, miR6190, miR1044, miR5261 and miR1151) and the adaptation to low-phosphorus (miR6190); (c) activating transport-related genes by altering the expression of miR6190, miR6485, miR1044, miR5029 and miR3437; (d) elevating protein ubiquitination due to decreased expression levels of miR1044, miR5261, miR1151 and miR5029; (e) maintaining root growth by regulating miR5261, miR6485 and miR158 expression; and (f) triggering DNA repair (transcription regulation) by regulating miR5176 and miR6485 (miR6028, miR6190, miR6485, miR5621, miR160 and miR7708) expression. Mg-deficiency-responsive miRNAs involved in root signal transduction also had functions in Citrus Mg-deficiency tolerance.ConclusionsWe obtained several novel Mg-deficiency-responsive miRNAs (i.e., miR5261, miR158, miR6190, miR6485, miR1151 and miR1044) possibly contributing to Mg-deficiency tolerance. These results revealed some novel clues on the miRNA-mediated adaptation to nutrient deficiencies in higher plants.

Investigation of root signaling under heterogeneous salt stress: A case study for Cucumis sativus L.

To sense, respond and adapt to the constantly changing environmental conditions, plants have developed sophisticated signaling mechanisms. In this study, plant signaling under heterogeneous salt conditions was investigated. A split root system was established in which one half of the root apparatus (HR1) was treated with salt. The impact of the salt on the electrical signals as the initial response of the plant to exterior stimulus was measured in the other half of the root system (HR2) with a Multi Electrode Array (MEA) system. Duration and amplitude of the recorded electrical signals increased compared to the control. In order to identify the nature of the signal traveling from HR1 to HR2, H+ and K+ fluxes were measured in HR2 by using ion-selective microelectrodes (vibrating probe technique). A net potassium influx was observed after the treatment while no change in proton flux was detected. By corona sodium green and confocal microscopy we confirmed that changes in electrical signals and fluxes are not simply associated with apoplastic diffusion of sodium from HR1 to HR2. The activation of salt stress marker genes was also examined: the modulation of CsGOL-like expression seems to have systemic response, while ERF109 and aspartate oxidase showed localized responses.

Analysis of DNA methylation during spontaneous rooting from the stem apex in Rubus idaeus

Rubus idaeus L. is of great economic value. Some varieties of Rubus idaeus have a unique feature of spontaneous rooting from the stem apex. To determine whether DNA methylation is associated with the spontaneous rooting process, variations in the methylation at stem apex during four root developmental stages were investigated, using the methylation-sensitive amplification polymorphism (MSAP) technique and the bisulfite sequencing analysis (BSA). The results showed that the DNA methylation levels and patterns were significantly different between the four developmental stages. A total of 824 CCGG amplified sites were detected by MSAP. MSAP screening revealed that the level of DNA methylation at stages I to IV was 34.95, 36.04, 36.29, and 37.50%, respectively. The number of methylated sites and their methylation levels tended to decrease at stages III and IV (root differentiation and elongation) compared with those at stage I (stem elongation). After cloning and sequencing of the 16 polymorphic differentially methylated DNA fragments, BLAST search results indicated that they might be involved in differentiation of the lateral root primordium, plant defense, signal transduction, and energy metabolism. Results of the qRT-PCR and BSA analyses confirmed that methylation of some key genes was closely associated with their expression at the different developmental stages. These findings could be useful for future studies on the potential role of DNA methylation in spontaneous rooting from the stem apex, implying its importance in rooting regulation and rapid expansion of raspberry populations.

Simultaneous but spatially different regulation of non-photosynthetic callus formation and photosynthetic root development after shoot removal

ABSTRACTPlants coordinate plastid differentiation and cellular differentiation during tissue development. Recently, we reported a mechanism of chloroplast development and photosynthetic improvement in Arabidopsis roots after shoot removal. Shoot removal induces the expression of WOUND INDUCED DEDIFFERENTIATION (WIND) transcription factors at the wound site, which activates type-B ARABIDOPSIS RESPONSE REGULATOR (ARR)-mediated cytokinin signaling in roots. The type-B ARR signaling upregulates chloroplast-related transcription factors along with photosynthesis-associated genes, thereby inducing chloroplast development in detached roots. However, at the wound site, WINDs promote the development of non-green callus cells in a type-B ARR-dependent manner. Thus, in shoot-removed roots, WIND-mediated cytokinin signaling has spatially distinct roles: it represses chloroplast development at the wound site while activating the development in adjacent regions. Because WINDs are strong inducers of cell dedifferentiation, spatial differences in their expression levels between the wound site and other areas may determine the fate of chloroplast development.

Identification of root-preferential transcription factors in rice by analyzing GUS expression patterns of T-DNA tagging lines

T-DNA tagging lines are useful for analyzing the functions of genes and regulatory elements. We have previously generated approximately 100,000 insertional mutants in japonica rice (Oryza sativa), using T-DNA vectors carrying the promoter-less GUS reporter gene. In this study, we conducted GUS assays of seedlings from 430 lines in which TDNA was inserted into transcription factor genes. Among the 75 lines that showed GUS signals, nine displayed an endospermpreferential expression pattern; two lines demonstrated GUS signals in both endosperm and roots; 21 lines had GUS expression mainly in leaves; 19 lines showed GUS signal in both leaves and roots; and 24 lines expressed GUS predominantly in the roots. Co-segregation analyses of 49 homozygous lines indicated that the GUS expression patterns observed from 38 lines were due to the T-DNA insertion. We also identified fusion transcripts between tagged genes and the GUS reporter in six lines. Quantitative RT-PCR confirmed that the GUS expression patterns of those tagged lines indeed represent organ- and tissue-preferential expression of the tagged genes. The GUS-tagged transcription factor lines identified here will be useful for functional analysis of these candidates.

Broadband signal response of thermo-acoustic devices and its applications.

Thermo-acoustic (TA) transducers are generation of sound speakers without any mechanical vibration system which exhibit an extremely wide frequency response range. In this paper, acoustic field responses to broadband input signals applied to both free-standing and nano-thinfilm-substrate thermo-acoustic devices are developed theoretically by using the Fourier transformation. A series of signals, including single-frequency signal, square root signal, periodic triangle wave signal, and periodic rectangular pulse signal, are applied to these TA devices in simulations and the acoustic pressure responses are investigated. The reproducibility of input signals is predicted. The single frequency results show good agreement with previously published experimental results. Alternative methods for reproducing the original signals with small distortion and low power consumption are introduced. The excellent performance of the TA devices on broadband signal responses will provide a design approach for sound parametric array and underwater communication equipment.

Using Barkhausen noise to measure coating depth of coated high-speed steel

Coated high-speed steel tools are widely used in machining processes as they offer an excellent tool life to cost ratio, but they quickly need replacing once the coated layer is worn away. It would be therefore useful to be able to measure the tool life remaining non-destructively and cheaply. To achieve this, the work presented here aims to measure the thickness of the coated layer of high-speed cutting tools by using Barkhausen noise (BHN) techniques. Coated high-speed steel specimens coated with two different materials (chromium nitride (CrN), titanium nitride (TiN)) were tested using a cost-effective measuring system developed for this study. Sensory features were extracted from the signal received from a pick-up coil and the signal features, Root mean square, peak count, and signal energy, were successfully correlated with the thickness of the coating layer on high-speed steel (HSS) specimens. The results suggest that the Barkhausen noise measuring system developed in this study can successfully indicate the different thickness of the coating layer on CrN/TiN coated HSS specimens.

Depletion of abscisic acid levels in roots of flooded Carrizo citrange (Poncirus trifoliata L. Raf. × Citrus sinensis L. Osb.) plants is a stress-specific response associated to the differential expression of PYR/PYL/RCAR receptors.

Soil flooding reduces root abscisic acid (ABA) levels in citrus, conversely to what happens under drought. Despite this reduction, microarray analyses suggested the existence of a residual ABA signaling in roots of flooded Carrizo citrange seedlings. The comparison of ABA metabolism and signaling in roots of flooded and water stressed plants of Carrizo citrange revealed that the hormone depletion was linked to the upregulation of CsAOG, involved in ABA glycosyl ester (ABAGE) synthesis, and to a moderate induction of catabolism (CsCYP707A, an ABA 8'-hydroxylase) and buildup of dehydrophaseic acid (DPA). Drought strongly induced both ABA biosynthesis and catabolism (CsNCED1, 9-cis-neoxanthin epoxycarotenoid dioxygenase 1, and CsCYP707A) rendering a significant hormone accumulation. In roots of flooded plants, restoration of control ABA levels after stress release was associated to the upregulation of CsBGLU18 (an ABA β-glycosidase) that cleaves ABAGE. Transcriptional profile of ABA receptor genes revealed a different induction in response to soil flooding (CsPYL5) or drought (CsPYL8). These two receptor genes along with CsPYL1 were cloned and expressed in a heterologous system. Recombinant CsPYL5 inhibited ΔNHAB1 activity in vitro at lower ABA concentrations than CsPYL8 or CsPYL1, suggesting its better performance under soil flooding conditions. Both stress conditions induced ABA-responsive genes CsABI5 and CsDREB2A similarly, suggesting the occurrence of ABA signaling in roots of flooded citrus seedlings. The impact of reduced ABA levels in flooded roots on CsPYL5 expression along with its higher hormone affinity reinforce the role of this ABA receptor under soil-flooding conditions and explain the expression of certain ABA-responsive genes.

Diffusion of the maize root signal (E)-β-caryophyllene in soils of different textures and the effects on the migration of the entomopathogenic nematode Heterorhabditis megidis

Maize roots respond to feeding by larvae of the beetle Diabrotica virgifera virgifera by releasing (E)-β-caryophyllene (Eβc). This insect-induced root volatile attracts entomopathogenic nematodes (EPN) and thereby helps to protect the roots against herbivore damage. Previous studies suggest that diffusion of Eβc occurs through the gaseous rather than the aqueous phase in sand and its diffusion is best at low levels of humidity. However, it remains largely unknown how Eβc diffuses in typical natural and agricultural soils. To fully understand the function and efficiency of root-produced Eβc as a belowground signal it is important to know how it spreads in real soils and how soil properties affect its diffusion. Using gas chromatography-mass spectrometry analyses, the diffusion of two doses of synthetic Eβc (200 ng and 20,000 ng) injected in sand was compared with the diffusion of Eβc injected in clay, clay-loam and sandy-loam soils, at 3 moisture levels (5, 10 and 20% water), and at two distances (5 and 10cm) from the Eβc injection point. The diffusion of the compound was measured with a Solid Phase Micro Extraction (SPME) fiber every 30minutes over a period of 9 hours. We found that, in contrast to the pattern observed for pure sand, Eβc diffused best when humidity was high in the three agricultural soils. In subsequent experiments we used glass-trays to create two types of mesocosms to assess the effect of synthetic or root-produced Eβc on the dispersal of the EPN Heterorhabditis megidis and its infection of sentinel hosts in the trays. The presence of synthetic Eβc did not affect the ability of H. megidis to infect the sentinel host. However, under the test conditions, Eβc released from maize roots influenced the migration behaviour of H. megidis depending on soil type. The results suggest that D. virgifera-damaged maize plants may recruit H. megidis more efficiently in clay loam soils than in other types of soil. These new insights into the diffusion dynamics and attraction efficiency of the root-produced signal Eβc may help efforts to develop novel strategies for the sustainable management of the maize pest D. virgifera.

Growth of street trees in urban ecosystems: structural cells and structural soil

Samanea saman and Peltophorum pterocarpum common to the Singapore streetscape were planted in structural soil and structural cell. These were installed with the intention of observing medium to long term plant responses to the various designed soil and cell systems. To verify root colonization in these systems under the sidewalk, root presence was measured using the ground-penetrating radar (GPR) in the fifth year following installation. GPR data indicated widespread colonization of roots in the designed soil and cell system. The highest root signal counts were concentrated deeper in the profile. Trees grown in open spaces were characterized by shallow root systems. Tree physical data identified that trees grown in structural cells had significantly greater growth performances. The observations here provided evidence that these systems served as an acceptable rooting environment when confronted with limited space and soil volumes common to urban environments.

Na2CO3-responsive mechanisms in halophyte Puccinellia tenuiflora roots revealed by physiological and proteomic analyses.

Soil alkalization severely affects crop growth and agricultural productivity. Alkali salts impose ionic, osmotic, and high pH stresses on plants. The alkali tolerance molecular mechanism in roots from halophyte Puccinellia tenuiflora is still unclear. Here, the changes associated with Na2CO3 tolerance in P. tenuiflora roots were assessed using physiological and iTRAQ-based quantitative proteomic analyses. We set up the first protein dataset in P. tenuiflora roots containing 2,671 non-redundant proteins. Our results showed that Na2CO3 slightly inhibited root growth, caused ROS accumulation, cell membrane damage, and ion imbalance, as well as reduction of transport and protein synthesis/turnover. The Na2CO3-responsive patterns of 72 proteins highlighted specific signaling and metabolic pathways in roots. Ca2+ signaling was activated to transmit alkali stress signals as inferred by the accumulation of calcium-binding proteins. Additionally, the activities of peroxidase and glutathione peroxidase, and the peroxiredoxin abundance were increased for ROS scavenging. Furthermore, ion toxicity was relieved through Na+ influx restriction and compartmentalization, and osmotic homeostasis reestablishment due to glycine betaine accumulation. Importantly, two transcription factors were increased for regulating specific alkali-responsive gene expression. Carbohydrate metabolism-related enzymes were increased for providing energy and carbon skeletons for cellular metabolism. All these provide new insights into alkali-tolerant mechanisms in roots.

Two spatially and temporally distinct Ca2+ signals convey Arabidopsis thaliana responses to K+ deficiency

In plants, potassium (K+ ) homeostasis is tightly regulated and established against a concentration gradient to the environment. Despite the identification of Ca2+ -regulated kinases as modulators of K+ channels, the immediate signaling and adaptation mechanisms of plants to low-K+ conditions are only partially understood. To assess the occurrence and role of Ca2+ signals in Arabidopsis thaliana roots, we employed ratiometric analyses of Ca2+ dynamics in plants expressing the Ca2+ reporter YC3.6 in combination with patch-clamp analyses of root cells and two-electrode voltage clamp (TEVC) analyses in Xenopus laevis oocytes. K+ deficiency triggers two successive and distinct Ca2+ signals in roots exhibiting spatial and temporal specificity. A transient primary Ca2+ signature arose within 1min in the postmeristematic stelar tissue of the elongation zone, while a secondary Ca2+ response occurred after several hours as sustained Ca2+ elevation in defined tissues of the elongation and root hair differentiation zones. Patch-clamp and TEVC analyses revealed Ca2+ dependence of the activation of the K+ channel AKT1 by the CBL1-CIPK23 Ca2+ sensor-kinase complex. Together, these findings identify a critical role of cell group-specific Ca2+ signaling in low K+ responses and indicate an essential and direct role of Ca2+ signals for AKT1K+ channel activation in roots.

Calcium-Mediated Abiotic Stress Signaling in Roots.

Roots are subjected to a range of abiotic stresses as they forage for water and nutrients. Cytosolic free calcium is a common second messenger in the signaling of abiotic stress. In addition, roots take up calcium both as a nutrient and to stimulate exocytosis in growth. For calcium to fulfill its multiple roles must require strict spatio-temporal regulation of its uptake and efflux across the plasma membrane, its buffering in the cytosol and its sequestration or release from internal stores. This prompts the question of how specificity of signaling output can be achieved against the background of calcium’s other uses. Threats to agriculture such as salinity, water availability and hypoxia are signaled through calcium. Nutrient deficiency is also emerging as a stress that is signaled through cytosolic free calcium, with progress in potassium, nitrate and boron deficiency signaling now being made. Heavy metals have the capacity to trigger or modulate root calcium signaling depending on their dose and their capacity to catalyze production of hydroxyl radicals. Mechanical stress and cold stress can both trigger an increase in root cytosolic free calcium, with the possibility of membrane deformation playing a part in initiating the calcium signal. This review addresses progress in identifying the calcium transporting proteins (particularly channels such as annexins and cyclic nucleotide-gated channels) that effect stress-induced calcium increases in roots and explores links to reactive oxygen species, lipid signaling, and the unfolded protein response.

The systemic nodule number regulation kinase SUNN in Medicago truncatula interacts with MtCLV2 and MtCRN.

Autoregulation of nodulation (AON), a systemic signaling pathway in legumes, limits the number of nodules formed by the legume in its symbiosis with rhizobia. Recent research suggests a model for the systemic regulation in Medicago truncatula in which root signaling peptides are translocated to the shoot where they bind to a shoot receptor complex containing the leucine-rich repeat receptor-like kinase SUNN, triggering signal transduction which terminates nodule formation in roots. Here we show that a tagged SUNN protein capable of rescuing the sunn-4 phenotype is localized to the plasma membrane and is associated with the plasmodesmata. Using bimolecular fluorescence complementation analysis we show that, like its sequence ortholog Arabidopsis CLV1, SUNN interacts with homologous CLV1-interacting proteins MtCLAVATA2 and MtCORYNE. All three proteins were also able to form homomers and MtCRN and MtCLV2 also interact with each other. A crn Tnt1 insertion mutant of M. truncatula displayed a shoot controlled increased nodulation phenotype, similar to the clv2 mutants of pea and Lotus japonicus. Together these data suggest that legume AON signaling could occur through a multi-protein complex and that both MtCRN and MtCLV2 may play roles in AON together with SUNN.

Salinity and osmotic stress trigger different antioxidant responses related to cytosolic ascorbate peroxidase knockdown in rice roots

Salinity and osmotic stress trigger distinct signals in roots, which might induce differences in antioxidant responses. To clarify these relationships, transgenic rice plants silenced in both cytosolic ascorbate peroxidases (apx1/2) and non-transformed (NT) were exposed to iso-osmotic concentrations of NaCl and mannitol. Under both stress conditions, apx1/2 roots did not suffer oxidative stress, revealing that cytosolic APXs were not crucial to oxidative protection. Silenced and non-transformed roots triggered different responses to high salinity and osmotic stress and these stressful factors induced also distinct antioxidant changes. High salinity up-regulated expression of important OsAPX isoforms and these changes were related to increased APX activity, especially in NT roots. Intriguingly, salt stress triggered up-regulation of OsCAT isoforms but CAT activity did not change in both genotypes. In contrast, mannitol trigged very low increment in expression of OsAPX isoforms but induced substantial up-regulation in APX activity in NT roots. Mannitol also remarkably up-regulated OsCATB expression in parallel to CAT activity, in both apx1/2 and NT roots. POD and GPX (glutathione peroxidases) activities were strongly increased by high salinity but did not change in response to mannitol, in both genotypes. The two stress types as well as apx1/2 and NT roots displayed different response in terms of modulation in the H2O2 levels but lipid peroxidation did not change. Membrane integrity was drastically affected by both stressful factors and similarly in both genotypes, whereas root fresh matter was affected only by salt stress. Altogether, the obtained data reveal that high salinity and osmotic stress trigger different antioxidant responses and these strategies were genotype-dependent. The different antioxidant molecular-biochemical mechanisms employed by cytosolic APX knockdown and non-transformed roots allowed reaching similar physiological performance.

Small Molecule DFPM Derivative-Activated Plant Resistance Protein Signaling in Roots Is Unaffected by EDS1 Subcellular Targeting Signal and Chemical Genetic Isolation of victr R-Protein Mutants.

The small molecule DFPM ([5-(3,4-dichlorophenyl)furan-2-yl]-piperidine-1-ylmethanethione) was recently shown to trigger signal transduction via early effector-triggered immunity signaling genes including EDS1 and PAD4 in Arabidopsis thaliana accession Col-0. Chemical genetic analyses of A. thaliana natural variants identified the plant Resistance protein-like Toll/Interleukin1 Receptor (TIR)-Nucleotide Binding (NB)-Leucine-Rich Repeat (LRR) protein VICTR as required for DFPM-mediated root growth arrest. Here a chemical genetic screen for mutants which disrupt DFPM-mediated root growth arrest in the Col-0 accession identified new mutant alleles of the TIR-NB-LRR gene VICTR. One allele, victr-6, carries a Gly216-to-Asp mutation in the Walker A domain supporting an important function of the VICTR nucleotide binding domain in DFPM responses consistent with VICTR acting as a canonical Resistance protein. The essential nucleo-cytoplasmic regulator of TIR-NB-LRR-mediated effector-triggered immunity, EDS1, was reported to have both nuclear and cytoplasmic actions in pathogen resistance. DFPM was used to investigate the requirements for subcellular EDS1 localization in DFPM-mediated root growth arrest. EDS1-YFP fusions engineered to localize mainly in the cytoplasm or the nucleus by tagging with a nuclear export signal (NES) or a nuclear localization signal (NLS), respectively, were tested. We found that wild-type EDS1-YFP and both the NES and NLS-tagged EDS1 variants were induced by DFPM treatments and fully complemented eds1 mutant plants in root responses to DFPM, suggesting that enrichment of EDS1 in either compartment could confer DFPM-mediated root growth arrest. We further found that a light and O2-dependent modification of DFPM is necessary to mediate DFPM signaling in roots. Chemical analyses including Liquid Chromatography-Mass Spectrometry and High-Resolution Atmospheric Pressure Chemical Ionization Mass Spectrometry identified a DFPM modification product that is likely responsible for bioactivity mediating root growth arrest. We propose a chemical structure of this product and a possible reaction mechanism for DFPM modification.

Development of marker genes for jasmonic acid signaling in shoots and roots of wheat

ABSTRACTThe jasmonic acid (JA) signaling pathway plays key roles in a diverse array of plant development, reproduction, and responses to biotic and abiotic stresses. Most of our understanding of the JA signaling pathway derives from the dicot model plant Arabidopsis thaliana, while corresponding knowledge in wheat is somewhat limited. In this study, the expression of 41 genes implicated in the JA signaling pathway has been assessed on 10 day-old bread wheat seedlings, 24 h, 48 h, and 72 h after methyl-jasmonate (MeJA) treatment using quantitative real-time PCR. The examined genes have been previously reported to be involved in JA biosynthesis and catabolism, JA perception and signaling, and pathogen defense in wheat shoots and roots. This study provides evidence to suggest that the effect of MeJA treatment is more prominent in shoots than roots of wheat seedlings, and substantial regulation of the JA pathway-dependent defense genes occurs at 72 h after MeJA treatment. Results show that the expression of 22 genes was significantly affected by MeJA treatment in wheat shoots. However, only PR1.1 and PR3 were significantly differentially expressed in wheat roots, both at 24 h post-MeJA treatment, with other genes showing large variation in their gene expression in roots. While providing marker genes on JA signaling in wheat, future work may focus on elucidating the regulatory function of JA-modulated transcription factors, some of which have well-studied potential orthologs in Arabidopsis.