Publications by authors named "Thomas Roitsch"

81 Publications

Elevated CO2 modulates the effect of heat stress responses in Triticum aestivum by differential expression of isoflavone reductase-like (IRL) gene.

J Exp Bot 2021 May 29. Epub 2021 May 29.

Crop science, Department of Plant and Environmental Sciences, University of Copenhagen, Højbakkegård Allé, Taastrup, Denmark.

Two wheat genotypes forming high and low biomass (HB and LB), exhibiting differential expression of an isoflavone reductase-like (IRL) gene, and resulting in contrasting grain yield under heat stress field conditions, were analyzed in detail for their responses under controlled heat and elevated CO2 conditions. Significant differences in IRL expression between the two lines were hypothesized to be the basis of their differential performance under the tested conditions and their stress tolerance potential. By a holistic approach integrating advanced cell physiological phenotyping of the antioxidative and phytohormone system in spikes and leaves with measurements of ecophysiological and agronomic traits, the genetic differences of the genotypes in IRL expression were assessed. In response to heat and elevated CO2, the two genotypes showed opposite regulation of IRL expression, which was associated with cytokinin concentration, total flavonoid contents, activity of superoxide dismutase, antioxidant capacity and photosynthetic rate in leaves and cytokinin concentration and ascorbate peroxidase activity in spikes. Our study showed that IRL expression is associated with wheat yield performance under heat stress at anthesis, mediated by diverse physiological mechanisms. Hence, based on our results, the IRL gene is a promising candidate for developing genetic markers for breeding heat-tolerant wheat.
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http://dx.doi.org/10.1093/jxb/erab247DOI Listing
May 2021

Differential Response of Grapevine to Infection with ' Phytoplasma solani' in Early and Late Growing Season through Complex Regulation of mRNA and Small RNA Transcriptomes.

Int J Mol Sci 2021 Mar 29;22(7). Epub 2021 Mar 29.

National Institute of Biology, 1000 Ljubljana, Slovenia.

Bois noir is the most widespread phytoplasma grapevine disease in Europe. It is associated with ' Phytoplasma solani', but molecular interactions between the causal pathogen and its host plant are not well understood. In this work, we combined the analysis of high-throughput RNA-Seq and sRNA-Seq data with interaction network analysis for finding new cross-talks among pathways involved in infection of grapevine cv. Zweigelt with '. P. solani' in early and late growing seasons. While the early growing season was very dynamic at the transcriptional level in asymptomatic grapevines, the regulation at the level of small RNAs was more pronounced later in the season when symptoms developed in infected grapevines. Most differentially expressed small RNAs were associated with biotic stress. Our study also exposes the less-studied role of hormones in disease development and shows that hormonal balance was already perturbed before symptoms development in infected grapevines. Analysis at the level of communities of genes and mRNA-microRNA interaction networks revealed several new genes (e.g., expansins and cryptdin) that have not been associated with phytoplasma pathogenicity previously. These novel actors may present a new reference framework for research and diagnostics of phytoplasma diseases of grapevine.
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http://dx.doi.org/10.3390/ijms22073531DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8037961PMC
March 2021

New Cross-Talks between Pathways Involved in Grapevine Infection with ' Phytoplasma solani' Revealed by Temporal Network Modelling.

Plants (Basel) 2021 Mar 29;10(4). Epub 2021 Mar 29.

National Institute of Biology, 1000 Ljubljana, Slovenia.

Understanding temporal biological phenomena is a challenging task that can be approached using network analysis. Here, we explored whether network reconstruction can be used to better understand the temporal dynamics of bois noir, which is associated with ' Phytoplasma solani', and is one of the most widespread phytoplasma diseases of grapevine in Europe. We proposed a methodology that explores the temporal network dynamics at the community level, i.e., densely connected subnetworks. The methodology offers both insights into the functional dynamics via enrichment analysis at the community level, and analyses of the community dissipation, as a measure that accounts for community degradation. We validated this methodology with cases on experimental temporal expression data of uninfected grapevines and grapevines infected with '. P. solani'. These data confirm some known gene communities involved in this infection. They also reveal several new gene communities and their potential regulatory networks that have not been linked to '. P. solani' to date. To confirm the capabilities of the proposed method, selected predictions were empirically evaluated.
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http://dx.doi.org/10.3390/plants10040646DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8065506PMC
March 2021

Identification of Root-Associated Bacteria That Influence Plant Physiology, Increase Seed Germination, or Promote Growth of the Christmas Tree Species .

Front Microbiol 2020 17;11:566613. Epub 2020 Nov 17.

Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Frederiksberg, Denmark.

is used for Christmas tree production but poor seed germination and slow growth represent challenges for the growers. We addressed the plant growth promoting potential of root-associated bacteria isolated from . Laboratory screenings of a bacterial strain collection yielded several and strains that improved seed germination and produced indole-3-acetic acid. The impact of three of these strains on seed germination, plant growth and growth-related physiological parameters was then determined in greenhouse and field trials after seed inoculation, and their persistence was assessed by 16S rRNA gene-targeted bacterial community analysis. Two strains showed distinct and significant effects. sp. s50 enhanced seed germination in the greenhouse but did not promote shoot or root growth. In accordance, this strain did not increase the level of soluble hexoses needed for plant growth but increased the level of storage carbohydrates. Moreover, strain s50 increased glutathione reductase and glutathione-S-transferase activities in the plant, which may indicate induction of systemic resistance during the early phase of plant development, as the strain showed poor persistence in the root samples (rhizosphere soil plus root tissue). sp. s37 increased plant root growth, especially by inducing secondary root formation, under in greenhouse conditions, where it showed high persistence in the root samples. Under these conditions, it further it increased the level of soluble carbohydrates in shoots, and the levels of starch and non-structural carbohydrates in roots, stem and shoots. Moreover, it increased the chlorophyll level in the field trial. These findings indicate that this strain improves plant growth and vigor through effects on photosynthesis and plant carbohydrate reservoirs. The current results show that the two strains s37 and s50 could be considered for growth promotion programs of in greenhouse nurseries, and even under field conditions.
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http://dx.doi.org/10.3389/fmicb.2020.566613DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7705201PMC
November 2020

Photoprotection and optimization of sucrose usage contribute to faster recovery of photosynthesis after water deficit at high temperatures in wheat.

Physiol Plant 2021 Jun 26;172(2):615-628. Epub 2020 Oct 26.

BioISI-Biosystems and Integrative Sciences Institute, Faculdade de Ciências da Universidade de Lisboa, Lisbon, Portugal.

Plants are increasingly exposed to events of elevated temperature and water deficit, which threaten crop productivity. Understanding the ability to rapidly recover from abiotic stress, restoring carbon assimilation and biomass production, is important to unravel crop climate resilience. This study compared the photosynthetic performance of two Triticum aestivum L. cultivars, Sokoll and Paragon, adapted to the climate of Mexico and UK, respectively, exposed to 1-week water deficit and high temperatures, in isolation or combination. Measurements included photosynthetic assimilation rate, stomatal conductance, in vitro activities of Rubisco (EC 4.1.1.39) and invertase (INV, EC 3.2.1.26), antioxidant capacity and chlorophyll a fluorescence. In both genotypes, under elevated temperatures and water deficit (WD38°C), the photosynthetic limitations were mainly due to stomatal restrictions and to a decrease in the electron transport rate. Chlorophyll a fluorescence parameters clearly indicate differences between the two genotypes in the photoprotection when subjected to WD38°C and showed faster recovery of Paragon after stress relief. The activity of the cytosolic invertase (CytINV) under these stress conditions was strongly related to the fast photosynthesis recovery of Paragon. Taken together, the results suggest that optimal sucrose export/utilization and increased photoprotection of the electron transport machinery are important components to limit yield fluctuations due to water shortage and elevated temperatures.
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http://dx.doi.org/10.1111/ppl.13227DOI Listing
June 2021

Activities of leaf and spike carbohydrate-metabolic and antioxidant enzymes are linked with yield performance in three spring wheat genotypes grown under well-watered and drought conditions.

BMC Plant Biol 2020 Aug 31;20(1):400. Epub 2020 Aug 31.

Crop Science, Department of Plant and Environmental Sciences, University of Copenhagen, Højbakkegård Allé 13, 2630, Taastrup, Denmark.

Background: To improve our understanding about the physiological mechanism of grain yield reduction at anthesis, three spring wheat genotypes [L (advanced line), L (Vorobey) and L (Punjab-11)] having contrasting yield potential under drought in field were investigated under controlled greenhouse conditions, drought stress was imposed at anthesis stage by withholding irrigation until all plant available water was depleted, while well-watered control plants were kept at 95% pot water holding capacity.

Results: Compared to genotype L and L, pronounced decrease in grain number (NGS), grain yield (GY) and harvest index (HI) were found in genotype L, mainly due to its greater kernel abortion (KA) under drought. A significant positive correlation of leaf monodehydroascorbate reductase (MDHAR) with both NGS and HI was observed. In contrast, significant negative correlations of glutathione S-transferase (GST) and vacuolar invertase (vacInv) both within source and sink were found with NGS and HI. Likewise, a significant negative correlation of leaf abscisic acid (ABA) with NGS was noticed. Moreover, leaf aldolase and cell wall peroxidase (cwPOX) activities were significantly and positively associated with thousand kernel weight (TKW).

Conclusion: Distinct physiological markers correlating with yield traits and higher activity of leaf aldolase and cwPOX may be chosen as predictive biomarkers for higher TKW. Also, higher activity of MDHAR within the leaf can be selected as a predictive biomarker for higher NGS in wheat under drought. Whereas, lower activity of vacInv and GST both within leaf and spike can be selected as biomarkers for higher NGS and HI. The results highlighted the role of antioxidant and carbohydrate-metabolic enzymes in the modulation of source-sink balance in wheat crops, which could be used as bio-signatures for breeding and selection of drought-resilient wheat genotypes for a future drier climate.
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http://dx.doi.org/10.1186/s12870-020-02581-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7457523PMC
August 2020

Early-stage sugar beet taproot development is characterized by three distinct physiological phases.

Plant Direct 2020 Jul 1;4(7):e00221. Epub 2020 Aug 1.

Department of Crop Sciences UFT Tulln University of Natural Resources and Life Sciences (BOKU) Tulln Austria.

Despite the agronomic importance of sugar beet ( L.), the early-stage development of its taproot has only been poorly investigated. Thus, the mechanisms that determine growth and sugar accumulation in sugar beet are largely unknown. In the presented study, a physiological characterization of early-stage sugar beet taproot development was conducted. Activities were analyzed for fourteen key enzymes of carbohydrate metabolism in developing taproots over the first 80 days after sowing. In addition, we performed in situ localizations of selected carbohydrate-metabolic enzyme activities, anatomical investigations, and quantifications of soluble carbohydrates, hexose phosphates, and phytohormones. Based on the accumulation dynamics of biomass and sucrose, as well as on anatomical parameters, the early phase of taproot development could be subdivided into three stages-prestorage, transition, secondary growth and sucrose accumulation stage-each of which was characterized by distinct metabolic and phytohormonal signatures. The enzyme activity signatures corresponding to these stages were also shown to be robustly reproducible in experiments conducted in two additional locations. The results from this physiological phenotyping approach contribute to the identification of the key regulators of sugar beet taproot development and open up new perspectives for sugar beet crop improvement concerning both physiological marker-based breeding and biotechnological approaches.
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http://dx.doi.org/10.1002/pld3.221DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7395582PMC
July 2020

PsJN Stimulate Growth and Yield of Quinoa under Salinity Stress.

Plants (Basel) 2020 May 26;9(6). Epub 2020 May 26.

Quinoa Quality ApS, DK-4420 Regstrup, Denmark.

One of the major challenges in agriculture is to ensure sufficient and healthy food availability for the increasing world population in near future. This requires maintaining sustainable cultivation of crop plants under varying environmental stresses. Among these stresses, salinity is the second most abundant threat worldwide after drought. One of the promising strategies to mitigate salinity stress is to cultivate halotolerant crops such as quinoa. Under high salinity, performance can be improved by plant growth promoting bacteria (PGPB). Among PGPB, endophytic bacteria are considered better in stimulating plant growth compared to rhizosphere bacteria because of their ability to colonize both in plant rhizosphere and plant interior. Therefore, in the current study, a pot experiment was conducted in a controlled greenhouse to investigate the effects of endophytic bacteria i.e., PsJN on improving growth, physiology and yield of quinoa under salinity stress. At six leaves stage, plants were irrigated with saline water having either 0 (control) or 400 mM NaCl. The results indicated that plants inoculated with PsJN mitigated the negative effects of salinity on quinoa resulting in increased shoot biomass, grain weight and grain yield by 12%, 18% and 41% respectively, over un-inoculated control. Moreover, inoculation with PsJN improved osmotic adjustment and ion homeostasis ability. In addition, leaves were also characterized for five key reactive oxygen species (ROS) scavenging enzyme in response to PsJN treatment. This showed higher activity of catalase (CAT) and dehydroascobate reductase (DHAR) in PsJN-treated plants. These findings suggest that inoculation of quinoa seeds with PsJN could be used for stimulating growth and yield of quinoa in highly salt-affected soils.
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http://dx.doi.org/10.3390/plants9060672DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7355930PMC
May 2020

FMCH001 Increases Water Use Efficiency via Growth Stimulation in Both Normal and Drought Conditions.

Front Plant Sci 2020 7;11:297. Epub 2020 Apr 7.

Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Taastrup, Denmark.

Increasing agricultural losses due to biotic and abiotic stresses caused by climate change challenge food security worldwide. A promising strategy to sustain crop productivity under conditions of limited water availability is the use of plant growth promoting rhizobacteria (PGPR). Here, the effects of spore forming (FMCH001) on growth and physiology of maize ( L. cv. Ronaldinho) under well-watered and drought stressed conditions were investigated. Pot experiments were conducted in the automated high-throughput phenotyping platform PhenoLab and under greenhouse conditions. Results of the PhenoLab experiments showed that plants inoculated with FMCH001 exhibited increased root dry weight (DW) and plant water use efficiency (WUE) compared to uninoculated plants. In greenhouse experiments, root and shoot DW significantly increased by more than 15% in inoculated plants compared to uninoculated control plants. Also, the WUE increased in FMCH001 plants up to 46% in both well-watered and drought stressed plants. Root and shoot activities of 11 carbohydrate and eight antioxidative enzymes were characterized in response to FMCH001 treatments. This showed a higher antioxidant activity of catalase (CAT) in roots of FMCH001 treated plants compared to uninoculated plants. The higher CAT activity was observed irrespective of the water regime. These findings show that seed coating with Gram positive spore forming could be used as biostimulants for enhancing plant WUE under both normal and drought stress conditions.
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http://dx.doi.org/10.3389/fpls.2020.00297DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7155768PMC
April 2020

Simple semi-high throughput determination of activity signatures of key antioxidant enzymes for physiological phenotyping.

Plant Methods 2020 21;16:42. Epub 2020 Mar 21.

2Department of Plant and Environmental Sciences, Section of Crop Science, Copenhagen University, Højbakkegård Allé 13, 2630 Tåstrup, Denmark.

Background: Reactive oxygen species (ROS) such as hydrogen peroxide and superoxide anions significantly accumulate during biotic and abiotic stress and cause oxidative damage and eventually cell death. There is accumulating evidence that ROS are also involved in regulating beneficial plant-microbe interactions, signal transduction and plant growth and development. Due to the relevance of ROS throughout the life cycle and for interaction with the multifactorial environment, the physiological phenotyping of the mechanisms controlling ROS homeostasis is of general importance.

Results: In this study, we have developed a robust and resource-efficient experimental platform that allows the determination of the activities of the nine key ROS scavenging enzymes from a single extraction that integrates posttranscriptional and posttranslational regulations. The assays were optimized and adapted for a semi-high throughput 96-well assay format. In a case study, we have analyzed tobacco leaves challenged by pathogen infection, drought and salt stress. The three stress factors resulted in distinct activity signatures with differential temporal dynamics.

Conclusions: This experimental platform proved to be suitable to determine the antioxidant enzyme activity signature in different tissues of monocotyledonous and dicotyledonous model and crop plants. The universal enzymatic extraction procedure combined with the 96-well assay format demonstrated to be a simple, fast and semi-high throughput experimental platform for the precise and robust fingerprinting of nine key antioxidant enzymatic activities in plants.
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http://dx.doi.org/10.1186/s13007-020-00583-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7085164PMC
March 2020

Under the Christmas Tree: Belowground Bacterial Associations With Across Production Systems and Plant Development.

Front Microbiol 2020 4;11:198. Epub 2020 Mar 4.

Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Frederiksberg, Denmark.

is an economically important tree crop widely used for Christmas tree production. After initial growth in nurseries, seedlings are transplanted to the field. Rhizosphere bacterial communities generally impact the growth and health of the host plant. However, the dynamics of these communities during growth in nurseries, and during transplanting, has not previously been addressed. By a 16S rRNA gene amplicon sequencing approach, we characterized the composition and dynamics of bacterial communities in the rhizosphere during early plant growth in field and greenhouse nurseries and for plants transplanted from the greenhouse to the field. Moreover, the N-cycling potential of rhizosphere bacteria across plant age was addressed in both nurseries. Overall, a rhizosphere core microbiome of , comprising 19.9% of the taxa at genus level, was maintained across plant age, nursery production systems, and even during the transplantation of plants from the greenhouse to the field. The core microbiome included the bacterial genera , , , , , , and , which harbor several N-fixing and plant growth-promoting taxa. Nevertheless, both plant age and production system caused significant changes in the rhizosphere bacterial communities. Concerning community composition, the relative abundance of Rhizobiales (genera , , and ) was higher in the rhizosphere of field-grown , whereas the relative abundance of Enterobacteriales and Pseudomonadales (genus ) was higher in the greenhouse. Analysis of community dynamics across plant age showed that in the field nursery, the most abundant bacterial orders showed more dynamic changes in their relative abundance in the rhizosphere than in the bulk soil. In the greenhouse, age-dependent dynamics even occurred but affected different taxa than for the field-grown plants. The N-cycling potential of rhizosphere bacterial communities showed an increase of the relative abundance of genes involved in nitrogen fixation and denitrification by plant age. Similarly, the relative abundance of reported nitrogen-fixing or denitrifying bacteria increased by plant age. However, different community structures seemed to lead to an increased potential for nitrogen fixation and denitrification in the field versus greenhouse nurseries.
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http://dx.doi.org/10.3389/fmicb.2020.00198DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7064441PMC
March 2020

Role of Cytokinins for Interactions of Plants With Microbial Pathogens and Pest Insects.

Front Plant Sci 2019 19;10:1777. Epub 2020 Feb 19.

Department of Plant and Environmental Sciences, University of Copenhagen, Copenhagen, Denmark.

It has been recognized that cytokinins are plant hormones that influence not only numerous aspects of plant growth, development and physiology, including cell division, chloroplast differentiation and delay of senescence but the interaction with other organisms, including pathogens. Cytokinins are not only produced by plants but are also by other prokaryotic and eukaryotic organism such as bacteria, fungi, microalgae and insects. Notably, cytokinins are produced both by pathogenic and also beneficial microbes and are known to induce resistance in plants against pathogen infections. In this review the contrasting role of cytokinin for the defence and susceptibility of plants against bacterial and fungal pathogen and pest insects is assessed. We also discuss the cross talk of cytokinins with other phytohormones and the underlying mechanism involved in enhancing plant immunity against pathogen infections and explore possible practical applications in crop plant production.
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http://dx.doi.org/10.3389/fpls.2019.01777DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7042306PMC
February 2020

Noninvasive Phenotyping of Plant-Pathogen Interaction: Consecutive Imaging of Fluorescing , Plant Phenolic Fluorescence, and Chlorophyll Fluorescence in Leaves.

Front Plant Sci 2019 15;10:1239. Epub 2019 Oct 15.

Department of Pharmaceutical Biology, University of Würzburg, Würzburg, Germany.

Plant-pathogen interactions have been widely studied, but mostly from the site of the plant secondary defense. Less is known about the effects of pathogen infection on plant primary metabolism. The possibility to transform a fluorescing protein into prokaryotes is a promising phenotyping tool to follow a bacterial infection in plants in a noninvasive manner. In the present study, virulent and avirulent strains were transformed with green fluorescent protein (GFP) to follow the spread of bacteria by imaging Pulse-Amplitude-Modulation (PAM) fluorescence and conventional binocular microscopy. The combination of various wavelengths and filters allowed simultaneous detection of GFP-transformed bacteria, PAM chlorophyll fluorescence, and phenolic fluorescence from pathogen-infected plant leaves. The results show that fluorescence imaging allows spatiotemporal monitoring of pathogen spread as well as phenolic and chlorophyll fluorescence , thus providing a novel means to study complex plant-pathogen interactions and relate the responses of primary and secondary metabolism to pathogen spread and multiplication. The study establishes a deeper understanding of imaging data and their implementation into disease screening.
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http://dx.doi.org/10.3389/fpls.2019.01239DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6803544PMC
October 2019

Physiological phenotyping of mammalian cell lines by enzymatic activity fingerprinting of key carbohydrate metabolic enzymes: a pilot and feasibility study.

BMC Res Notes 2019 Oct 22;12(1):682. Epub 2019 Oct 22.

Department of Science and Environment, Roskilde University, Universitetsvej 1, 4000, Roskilde, Denmark.

Objective: Enzymatic fingerprinting of key enzymes of glucose metabolism is a valuable analysis tool in cell physiological phenotyping of plant samples. Yet, a similar approach for mammalian cell line samples is missing. In this study, we applied semi-high throughput enzyme activity assays that were originally designed for plant samples and tested their feasibility in extracts of six frequently used mammalian cell lines (Caco2, HaCaT, C2C12, HEK293, HepG2 and INS-1E).

Results: Enzyme activities for aldolase, hexokinase, glucose-6-phosphate dehydrogenase, phosphoglucoisomerase, phosphoglucomutase, phosphofructokinase could be detected in samples of one or more mammalian cell lines. We characterized effects of sample dilution, assay temperature and repeated freeze-thaw cycles causing potential biases. After careful selection of experimental parameters, the presented semi-high throughput methods could be established as useful tool for physiological phenotyping of cultured mammalian cells.
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http://dx.doi.org/10.1186/s13104-019-4697-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6805439PMC
October 2019

Accumulation of and Response to Auxins in Roots and Nodules of the Actinorhizal Plant Compared to the Model Legume .

Front Plant Sci 2019 24;10:1085. Epub 2019 Sep 24.

Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden.

Actinorhizal nodules are structurally different from legume nodules and show a greater similarity to lateral roots. Because of the important role of auxins in lateral root and nodule formation, auxin profiles were examined in roots and nodules of the actinorhizal species and the model legume . The auxin response in roots and nodules of both species was analyzed in transgenic root systems expressing a beta-glucuronidase gene under control of the synthetic auxin-responsive promoter . The effects of two different auxin on root development were compared for both species. The auxin present in nodules at the highest levels was phenylacetic acid (PAA). No differences were found between the concentrations of active auxins of roots nodules, while levels of the auxin conjugate indole-3-acetic acid-alanine were increased in nodules compared to roots of both species. Because auxins typically act in concert with cytokinins, cytokinins were also quantified. Concentrations of -zeatin and some glycosylated cytokinins were dramatically increased in nodules compared to roots of , but not of . The ratio of active auxins to cytokinins remained similar in nodules compared to roots in both species. The auxin response, as shown by the activation of the promoter, seemed significantly reduced in nodules compared to roots of both species, suggesting the accumulation of auxins in cell types that do not express the signal transduction pathway leading to activation. Effects on root development were analyzed for the synthetic auxin naphthaleneacetic acid (NAA) and PAA, the dominant auxin in nodules. Both auxins had similar effects, except that the sensitivity of roots to PAA was lower than to NAA. However, while the effects of both auxins on primary root growth were similar for both species, effects on root branching were different: both auxins had the classical positive effect on root branching in , but a negative effect in . Such a negative effect of exogenous auxin on root branching has previously been found for a cucurbit that forms lateral root primordia in the meristem of the parental root; however, root branching in does not follow that pattern.
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http://dx.doi.org/10.3389/fpls.2019.01085DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6773980PMC
September 2019

Root-Associated Microbial Communities of : Insights Into Interactions of Microbial Communities With Antioxidative Enzymes and Plant Growth.

Front Microbiol 2019 22;10:1937. Epub 2019 Aug 22.

Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Frederiksberg, Denmark.

is a major Christmas tree species in Europe, but their uneven and prolonged growth slows down their production. By a 16S and 18S rRNA gene amplicon sequencing approach, we performed a characterization of root-associated bacterial and fungal communities for three-year-old plants collected from two nurseries in Denmark and Germany and displaying different growth patterns (small versus tall plants). Proteobacteria had the highest relative abundance at both sampling sites and plant sizes, and Ascomycota was the most abundant fungal phylum. At the order level, Acidobacteriales, Actinomycetales, Burkholderiales, Rhizobiales, and Xanthomonadales represented the bacterial core microbiome of , independently of the sampling site or plant size, while the fungal core microbiome included members of the Agaricales, Hypocreales, and Pezizales. Principal Coordinate Analysis indicated that both bacterial and fungal communities clustered according to the sampling site pointing to the significance of soil characteristics and climatic conditions for the composition of root-associated microbial communities. Major differences between communities from tall and small plants were a dominance of the potential pathogen (Hypocreales) in the small plants from Germany, while Agaricales, that includes reported beneficial ectomycorrhizal fungi, dominated in the tall plants. An evaluation of plant root antioxidative enzyme profiles showed higher levels of the antioxidative enzymes ascorbate peroxidase, peroxidase, and superoxide dismutase in small plants compared to tall plants. We suggest that the higher antioxidative enzyme activities combined with the growth arrest phenotype indicate higher oxidative stress levels in the small plants. Additionally, the correlations between the relative abundances of specific taxa of the microbiome with the plant antioxidative enzyme profiles were established. The main result was that many more bacterial taxa correlated positively than negatively with one or more antioxidative enzyme activity. This may suggest that the ability of bacteria to increase plant antioxidative enzyme defenses is widespread.
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http://dx.doi.org/10.3389/fmicb.2019.01937DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6714061PMC
August 2019

Noninvasive determination of toxic stress biomarkers by high-throughput screening of photoautotrophic cell suspension cultures with multicolor fluorescence imaging.

Plant Methods 2019 24;15:100. Epub 2019 Aug 24.

Department of Adaptive Biotechnologies, Global Change Research Institute, CAS, 603 00 Brno, Czech Republic.

Background: With increasing pollution, herbicide application and interest in plant phenotyping, sensors capturing early responses to toxic stress are demanded for screening susceptible or resistant plant varieties. Standard toxicity tests on plants are laborious, demanding in terms of space and material, and the measurement of growth-inhibition based endpoints takes relatively long time. The aim of this work was to explore the potential of photoautotrophic cell suspension cultures for high-throughput early toxicity screening based on imaging techniques. The investigation of the universal potential of fluorescence imaging methods involved testing of three toxicants with different modes of action (DCMU, glyphosate and chromium).

Results: The increased pace of testing was achieved by using non-destructive imaging methods-multicolor fluorescence (MCF) and chlorophyll fluorescence (ChlF). These methods detected the negative effects of the toxicants earlier than it was reflected in plant growth inhibition (decrease in leaf area and final dry weight). Moreover, more subtle and transient effects not resulting in growth inhibition could be detected by fluorescence. The pace and sensitivity of stress detection was further enhanced by using photoautotrophic cell suspension cultures. These reacted sooner, more pronouncedly and to lower concentrations of the tested toxicants than the plants. Toxicant-specific stress signatures were observed as a combination of MCF and ChlF parameters and timing of the response. Principal component analysis was found to be useful for reduction of the collected multidimensional data sets to a few informative parameters allowing comparison of the toxicant signatures.

Conclusions: Photoautotrophic cell suspension cultures have proved to be useful for rapid high-throughput screening of toxic stress and display a potential for employment as an alternative to tests on whole plants. The MCF and ChlF methods are capable of distinguishing early stress signatures of at least three different modes of action.
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http://dx.doi.org/10.1186/s13007-019-0484-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6708129PMC
August 2019

Amylopectin Chain Length Dynamics and Activity Signatures of Key Carbon Metabolic Enzymes Highlight Early Maturation as Culprit for Yield Reduction of Barley Endosperm Starch after Heat Stress.

Plant Cell Physiol 2019 Dec;60(12):2692-2706

Carlsberg Research Laboratory, J.C, Jacobsens Gade 4, 1799 Copenhagen V, Denmark.

Abiotic environmental stresses have a negative impact on the yield and quality of crops. Understanding these stresses is an essential enabler for mitigating breeding strategies and it becomes more important as the frequency of extreme weather conditions increases due to climate change. This study analyses the response of barley (Hordeum vulgare L.) to a heat wave during grain filling in three distinct stages: the heat wave itself, the return to a normal temperature regime, and the process of maturation and desiccation. The properties and structure of the starch produced were followed throughout the maturational stages. Furthermore, the key enzymes involved in the carbohydrate supply to the grain were monitored. We observed differences in starch structure with well-separated effects because of heat stress and during senescence. Heat stress produced marked effects on sucrolytic enzymes in source and sink tissues. Early cessation of plant development as an indirect consequence of the heat wave was identified as the major contributor to final yield loss from the stress, highlighting the importance for functional stay-green traits for the development of heat-resistant cereals.
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http://dx.doi.org/10.1093/pcp/pcz155DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6896705PMC
December 2019

Review: New sensors and data-driven approaches-A path to next generation phenomics.

Plant Sci 2019 May 12;282:2-10. Epub 2019 Jan 12.

National Institute of Agricultural Botany (NIAB), Huntingdon Road, Cambridge, CB3 0LE, UK. Electronic address:

At the 4th International Plant Phenotyping Symposium meeting of the International Plant Phenotyping Network (IPPN) in 2016 at CIMMYT in Mexico, a workshop was convened to consider ways forward with sensors for phenotyping. The increasing number of field applications provides new challenges and requires specialised solutions. There are many traits vital to plant growth and development that demand phenotyping approaches that are still at early stages of development or elude current capabilities. Further, there is growing interest in low-cost sensor solutions, and mobile platforms that can be transported to the experiments, rather than the experiment coming to the platform. Various types of sensors are required to address diverse needs with respect to targets, precision and ease of operation and readout. Converting data into knowledge, and ensuring that those data (and the appropriate metadata) are stored in such a way that they will be sensible and available to others now and for future analysis is also vital. Here we are proposing mechanisms for "next generation phenomics" based on our learning in the past decade, current practice and discussions at the IPPN Symposium, to encourage further thinking and collaboration by plant scientists, physicists and engineering experts.
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http://dx.doi.org/10.1016/j.plantsci.2019.01.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6483971PMC
May 2019

Screening of Barley Resistance Against Powdery Mildew by Simultaneous High-Throughput Enzyme Activity Signature Profiling and Multispectral Imaging.

Front Plant Sci 2018 23;9:1074. Epub 2018 Jul 23.

Institute for Crop Science and Resource Conservation-Plant Diseases and Plant Protection, University of Bonn, Bonn, Germany.

Molecular marker analysis allow for a rapid and advanced pre-selection and resistance screenings in plant breeding processes. During the phenotyping process, optical sensors have proved their potential to determine and assess the function of the genotype of the breeding material. Thereby, biomarkers for specific disease resistance traits provide valuable information for calibrating optical sensor approaches during early plant-pathogen interactions. In this context, the combination of physiological, metabolic phenotyping and phenomic profiles could establish efficient identification and quantification of relevant genotypes within breeding processes. Experiments were conducted with near-isogenic lines of (susceptible, mildew locus o and Mildew locus a resistant). Multispectral imaging of barley plants was daily conducted 0-8 days after inoculation (dai) in a high-throughput facility with 10 wavelength bands from 400 to 1,000 nm. In parallel, the temporal dynamics of the activities of invertase isoenzymes, as key sink specific enzymes that irreversibly cleave the transport sugar sucrose into the hexose monomers, were profiled in a semi high-throughput approach. The activities of cell wall, cytosolic and vacuole invertase revealed specific dynamics of the activity signatures for susceptible genotypes and genotypes with and based resistances 0-120 hours after inoculation (hai). These patterns could be used to differentiate between interaction types and revealed an early influence of f.sp. conidia on the specific invertase activity already 0.5 hai. During this early powdery mildew pathogenesis, the reflectance intensity increased in the blue bands and at 690 nm. The resistant plants showed an increased reflectance at 680 and 710 nm and a decreased reflectance in the near infrared bands from 3 dai. Applying a Support Vector Machine classification as a supervised machine learning approach, the pixelwise identification and quantification of powdery mildew diseased barley tissue and hypersensitive response spots were established. This enables an automatic identification of the barley-powdery mildew interaction. The study established a proof-of-concept for plant resistance phenotyping with multispectral imaging in high-throughput. The combination of invertase analysis and multispectral imaging showed to be a complementing validation system. This will provide a deeper understanding of optical data and its implementation into disease resistance screening.
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http://dx.doi.org/10.3389/fpls.2018.01074DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6065056PMC
July 2018

A transnational and holistic breeding approach is needed for sustainable wheat production in the Baltic Sea region.

Physiol Plant 2018 Dec 25;164(4):442-451. Epub 2018 Apr 25.

Department of Crop Production Ecology, SLU, Uppsala, Sweden.

The Baltic Sea is one of the largest brackish water bodies in the world. Eutrophication is a major concern in the Baltic Sea due to the leakage of nutrients to the sea with agriculture being the primary source. Wheat (Triticum aestivum L.) is the most widely grown crop in the countries surrounding the Baltic Sea and thus promoting sustainable agriculture practices for wheat cultivation will have a major impact on reducing pollution in the Baltic Sea. This approach requires identifying and addressing key challenges for sustainable wheat production in the region. Implementing new technologies for climate-friendly breeding and digital farming across all surrounding countries should promote sustainable intensification of agriculture in the region. In this review, we highlight major challenges for wheat cultivation in the Baltic Sea region and discuss various solutions integrating transnational collaboration for pre-breeding and technology sharing to accelerate development of low input wheat cultivars with improved host plant resistance to pathogen and enhanced adaptability to the changing climate.
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http://dx.doi.org/10.1111/ppl.12726DOI Listing
December 2018

Integration of multi-omics techniques and physiological phenotyping within a holistic phenomics approach to study senescence in model and crop plants.

J Exp Bot 2018 02;69(4):825-844

Department of Plant and Environmental Sciences, Copenhagen Plant Science Centre, University of Copenhagen, Højbakkegård Allé, Taastrup, Denmark.

The study of senescence in plants is complicated by diverse levels of temporal and spatial dynamics as well as the impact of external biotic and abiotic factors and crop plant management. Whereas the molecular mechanisms involved in developmentally regulated leaf senescence are very well understood, in particular in the annual model plant species Arabidopsis, senescence of other organs such as the flower, fruit, and root is much less studied as well as senescence in perennials such as trees. This review addresses the need for the integration of multi-omics techniques and physiological phenotyping into holistic phenomics approaches to dissect the complex phenomenon of senescence. That became feasible through major advances in the establishment of various, complementary 'omics' technologies. Such an interdisciplinary approach will also need to consider knowledge from the animal field, in particular in relation to novel regulators such as small, non-coding RNAs, epigenetic control and telomere length. Such a characterization of phenotypes via the acquisition of high-dimensional datasets within a systems biology approach will allow us to systematically characterize the various programmes governing senescence beyond leaf senescence in Arabidopsis and to elucidate the underlying molecular processes. Such a multi-omics approach is expected to also spur the application of results from model plants to agriculture and their verification for sustainable and environmentally friendly improvement of crop plant stress resilience and productivity and contribute to improvements based on postharvest physiology for the food industry and the benefit of its customers.
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http://dx.doi.org/10.1093/jxb/erx333DOI Listing
February 2018

Differential Effects of Carbohydrates on Arabidopsis Pollen Germination.

Plant Cell Physiol 2017 04;58(4):691-701

Lehrstuhl für Pharmazeutische Biologie, Universität Würzburg, Würzburg, Germany.

Pollen germination as a crucial process in plant development strongly depends on the accessibility of carbon as energy source. Carbohydrates, however, function not only as a primary energy source, but also as important signaling components. In a comprehensive study, we analyzed various aspects of the impact of 32 different sugars on in vitro germination of Arabidopsis pollen comprising about 150 variations of individual sugars and combinations. Twenty-six structurally different mono-, di- and oligosaccharides, and sugar analogs were initially tested for their ability to support pollen germination. Whereas several di- and oligosaccharides supported pollen germination, hexoses such as glucose, fructose and mannose did not support and even considerably inhibited pollen germination when added to germination-supporting medium. Complementary experiments using glucose analogs with varying functional features, the hexokinase inhibitor mannoheptulose and the glucose-insensitive hexokinase-deficient Arabidopsis mutant gin2-1 suggested that mannose- and glucose-mediated inhibition of sucrose-supported pollen germination depends partially on hexokinase signaling. The results suggest that, in addition to their role as energy source, sugars act as signaling molecules differentially regulating the complex process of pollen germination depending on their structural properties. Thus, a sugar-dependent multilayer regulation of Arabidopsis pollen germination is supported, which makes this approach a valuable experimental system for future studies addressing sugar sensing and signaling.
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http://dx.doi.org/10.1093/pcp/pcx020DOI Listing
April 2017

Modulating the Levels of Plant Hormone Cytokinins at the Host-Pathogen Interface.

Methods Mol Biol 2017 ;1569:141-150

Department of Plant and Environmental Sciences, Copenhagen Plant Science Centre, University of Copenhagen, Taastrup, Denmark.

Cytokinins are adenine and non-adenine derived heterogeneous class of regulatory molecules that participate in almost every aspect of plant biology. They also affect plant defense responses as well as help microbial pathogens to establish pathogenesis. The functional approaches that ensure desired and subtle modulations in the levels of plant cytokinins are highly instrumental in assessing their functions in plant immunity. Here, we describe a detailed working protocol regarding the enhanced production of cytokinins from plants that harbor isopentenyltransferase (IPT) enzyme gene under the control of 4xJERE (jasmonic acid and elicitor-responsive element) pathogen-inducible promoter. Our devised expression system is a context-dependent solution when it comes to investigating host-pathogen interactions under the modulated conditions of plant cytokinins.
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http://dx.doi.org/10.1007/978-1-4939-6831-2_11DOI Listing
February 2018

Determination of the Activity Signature of Key Carbohydrate Metabolism Enzymes in Phenolic-rich Grapevine Tissues.

Acta Chim Slov 2016 12;63(4):757-762

Physiological studies in plants often require enzyme extraction from tissues containing high concentrations of phenols and polyphenols. Unless removed or neutralized, such compounds may hinder extraction, inactivate enzymes, and interfere with enzyme detection. The following protocol for activity assays for enzymes of primary carbohydrate metabolism, while based on our recently published one for quantitative measurement of activities using coupled spectrophotometric assays in a 96-well format, is tailored to the complexities of phenolic- and anthocyanin-rich extracts from grapevine leaf. As a case study we applied the protocol to grapevine leaf samples infected with plant pathogenic bacteria 'Candidatus Phytoplasma solani', known to alter carbohydrate metabolism in grapevine. The described adaptations may be useful for determination of metabolic fingerprints for physiological phenotyping of other plant species with inherently high levels of phenolic compounds.
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http://dx.doi.org/10.17344/acsi.2016.2484DOI Listing
December 2016

Metabolic Control of Tobacco Pollination by Sugars and Invertases.

Plant Physiol 2017 02 6;173(2):984-997. Epub 2016 Dec 6.

Institut für Zellbiologie und Pflanzenphysiologie, Universität Regensburg, 93053 Regensburg, Germany (M.G., T.R.);

Pollination in flowering plants is initiated by germination of pollen grains on stigmas followed by fast growth of pollen tubes representing highly energy-consuming processes. The symplastic isolation of pollen grains and tubes requires import of Suc available in the apoplast. We show that the functional coupling of Suc cleavage by invertases and uptake of the released hexoses by monosaccharide transporters are critical for pollination in tobacco (Nicotiana tabacum). Transcript profiling, in situ hybridization, and immunolocalization of extracellular invertases and two monosaccharide transporters in vitro and in vivo support the functional coupling in supplying carbohydrates for pollen germination and tube growth evidenced by spatiotemporally coordinated expression. Detection of vacuolar invertases in maternal tissues by these approaches revealed metabolic cross talk between male and female tissues and supported the requirement for carbohydrate supply in transmitting tissue during pollination. Tissue-specific expression of an invertase inhibitor and addition of the chemical invertase inhibitor miglitol strongly reduced extracellular invertase activity and impaired pollen germination. Measurements of (competitive) uptake of labeled sugars identified two import pathways for exogenously available Suc into the germinating pollen operating in parallel: direct Suc uptake and via the hexoses after cleavage by extracellular invertase. Reduction of extracellular invertase activity in pollen decreases Suc uptake and severely compromises pollen germination. We further demonstrate that Glc as sole carbon source is sufficient for pollen germination, whereas Suc is supporting tube growth, revealing an important regulatory role of both the invertase substrate and products contributing to a potential metabolic and signaling-based multilayer regulation of pollination by carbohydrates.
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http://dx.doi.org/10.1104/pp.16.01601DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5291038PMC
February 2017

Structure of a Berberine Bridge Enzyme-Like Enzyme with an Active Site Specific to the Plant Family Brassicaceae.

PLoS One 2016 8;11(6):e0156892. Epub 2016 Jun 8.

Institute of Biochemistry, Graz University of Technology, Graz, Austria.

Berberine bridge enzyme-like (BBE-like) proteins form a multigene family (pfam 08031), which is present in plants, fungi and bacteria. They adopt the vanillyl alcohol-oxidase fold and predominantly show bi-covalent tethering of the FAD cofactor to a cysteine and histidine residue, respectively. The Arabidopsis thaliana genome was recently shown to contain genes coding for 28 BBE-like proteins, while featuring four distinct active site compositions. We determined the structure of a member of the AtBBE-like protein family (termed AtBBE-like 28), which has an active site composition that has not been structurally and biochemically characterized thus far. The most salient and distinguishing features of the active site found in AtBBE-like 28 are a mono-covalent linkage of a histidine to the 8α-position of the flavin-isoalloxazine ring and the lack of a second covalent linkage to the 6-position, owing to the replacement of a cysteine with a histidine. In addition, the structure reveals the interaction of a glutamic acid (Glu426) with an aspartic acid (Asp369) at the active site, which appear to share a proton. This arrangement leads to the delocalization of a negative charge at the active site that may be exploited for catalysis. The structure also indicates a shift of the position of the isoalloxazine ring in comparison to other members of the BBE-like family. The dioxygen surrogate chloride was found near the C(4a) position of the isoalloxazine ring in the oxygen pocket, pointing to a rapid reoxidation of reduced enzyme by dioxygen. A T-DNA insertional mutant line for AtBBE-like 28 results in a phenotype, that is characterized by reduced biomass and lower salt stress tolerance. Multiple sequence analysis showed that the active site composition found in AtBBE-like 28 is only present in the Brassicaceae, suggesting that it plays a specific role in the metabolism of this plant family.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0156892PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4898691PMC
July 2017

Metabolic Consequences of Infection of Grapevine (Vitis vinifera L.) cv. "Modra frankinja" with Flavescence Dorée Phytoplasma.

Front Plant Sci 2016 23;7:711. Epub 2016 May 23.

Department of Biotechnology and Systems Biology, National Institute of Biology Ljubljana, Slovenia.

Flavescence dorée, caused by the quarantine phytoplasma FDp, represents the most devastating of the grapevine yellows diseases in Europe. In an integrated study we have explored the FDp-grapevine interaction in infected grapevines of cv. "Modra frankinja" under natural conditions in the vineyard. In FDp-infected leaf vein-enriched tissues, the seasonal transcriptional profiles of 14 genes selected from various metabolic pathways showed an FDp-specific plant response compared to other grapevine yellows and uncovered a new association of the SWEET17a vacuolar transporter of fructose with pathogens. Non-targeted metabolome analysis from leaf vein-enriched tissues identified 22 significantly changed compounds with increased levels during infection. Several metabolites corroborated the gene expression study. Detailed investigation of the dynamics of carbohydrate metabolism revealed significant accumulation of sucrose and starch in the mesophyll of FDp-infected leaves, as well as significant up-regulation of genes involved in their biosynthesis. In addition, infected leaves had high activities of ADP-glucose pyrophosphorylase and, more significantly, sucrose synthase. The data support the conclusion that FDp infection inhibits phloem transport, resulting in accumulation of carbohydrates and secondary metabolites that provoke a source-sink transition and defense response status.
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http://dx.doi.org/10.3389/fpls.2016.00711DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4876132PMC
May 2016

Cytokinin production by Pseudomonas fluorescens G20-18 determines biocontrol activity against Pseudomonas syringae in Arabidopsis.

Sci Rep 2016 Mar 17;6:23310. Epub 2016 Mar 17.

Department of Plant and Environmental Sciences, Copenhagen Plant Science Centre, University of Copenhagen, Højbakkegård Allé 13, 2630 Taastrup, Denmark.

Plant beneficial microbes mediate biocontrol of diseases by interfering with pathogens or via strengthening the host. Although phytohormones, including cytokinins, are known to regulate plant development and physiology as well as plant immunity, their production by microorganisms has not been considered as a biocontrol mechanism. Here we identify the ability of Pseudomonas fluorescens G20-18 to efficiently control P. syringae infection in Arabidopsis, allowing maintenance of tissue integrity and ultimately biomass yield. Microbial cytokinin production was identified as a key determinant for this biocontrol effect on the hemibiotrophic bacterial pathogen. While cytokinin-deficient loss-of-function mutants of G20-18 exhibit impaired biocontrol, functional complementation with cytokinin biosynthetic genes restores cytokinin-mediated biocontrol, which is correlated with differential cytokinin levels in planta. Arabidopsis mutant analyses revealed the necessity of functional plant cytokinin perception and salicylic acid-dependent defence signalling for this biocontrol mechanism. These results demonstrate microbial cytokinin production as a novel microbe-based, hormone-mediated concept of biocontrol. This mechanism provides a basis to potentially develop novel, integrated plant protection strategies combining promotion of growth, a favourable physiological status and activation of fine-tuned direct defence and abiotic stress resilience.
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http://dx.doi.org/10.1038/srep23310DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4794740PMC
March 2016

Exogenous Classic Phytohormones Have Limited Regulatory Effects on Fructan and Primary Carbohydrate Metabolism in Perennial Ryegrass (Lolium perenne L.).

Front Plant Sci 2015 20;6:1251. Epub 2016 Jan 20.

Institute of Plant Sciences, Karl-Franzens-Universität Graz Graz, Austria.

Fructans are polymers of fructose and one of the main constituents of water-soluble carbohydrates in forage grasses and cereal crops of temperate climates. Fructans are involved in cold and drought resistance, regrowth following defoliation and early spring growth, seed filling, have beneficial effects on human health and are used for industrial processes. Perennial ryegrass (Lolium perenne L.) serves as model species to study fructan metabolism. Fructan metabolism is under the control of both synthesis by fructosyltransferases (FTs) and breakdown through fructan exohydrolases (FEHs). The accumulation of fructans can be triggered by high sucrose levels and abiotic stress conditions such as drought and cold stress. However, detailed studies on the mechanisms involved in the regulation of fructan metabolism are scarce. Since different phytohormones, especially abscisic acid (ABA), are known to play an important role in abiotic stress responses, the possible short term regulation of the enzymes involved in fructan metabolism by the five classical phytohormones was investigated. Therefore, the activities of enzymes involved in fructan synthesis and breakdown, the expression levels for the corresponding genes and levels for water-soluble carbohydrates were determined following pulse treatments with ABA, auxin (AUX), ethylene (ET), gibberellic acid (GA), or kinetin (KIN). The most pronounced fast effects were a transient increase of FT activities by AUX, KIN, ABA, and ET, while minor effects were evident for 1-FEH activity with an increased activity in response to KIN and a decrease by GA. Fructan and sucrose levels were not affected. This observed discrepancy demonstrates the importance of determining enzyme activities to obtain insight into the physiological traits and ultimately the plant phenotype. The comparative analyses of activities for seven key enzymes of primary carbohydrate metabolism revealed no co-regulation between enzymes of the fructan and sucrose pool.
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http://dx.doi.org/10.3389/fpls.2015.01251DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4719101PMC
February 2016