Root-Expressed Rice PAP3b Enhances Secreted APase Activity and Helps Utilize Organic Phosphate.

Phosphate (Pi) deficiency leads to the induction of purple acid phosphatases (PAPs) in plants, which dephosphorylate organic phosphorus (P) complexes in the rhizosphere and intracellular compartments to release Pi. In this study, we demonstrate that OsPAP3b belongs to group III low-molecular weight PAP and is low Pi-responsive, preferentially in roots. The expression of OsPAP3b is negatively regulated with Pi resupply. Interestingly, OsPAP3b was found to be dual localized to the nucleus and secretome. Furthermore, OsPAP3b is transcriptionally regulated by OsPHR2 as substantiated by DNA-protein binding assay. Through in vitro biochemical assays, we further demonstrate that OsPAP3b is a functional acid phosphatase (APase) with broad substrate specificity. The overexpression (OE) of OsPAP3b in rice led to increased secreted APase activity and improved mineralization of organic P sources, which resulted in better growth of transgenics compared to the wild type when grown on organic P as an exogenous P substrate. Under Pi deprivation, OsPAP3b knock-down and knock-out lines showed no significant changes in total P content and dry biomass. However, the expression of other phosphate starvation-induced genes and the levels of metabolites were found to be altered in the OE and knock-down lines. In addition, in vitro pull-down assay revealed multiple putative interacting proteins of OsPAP3b. Our data collectively suggest that OsPAP3b can aid in organic P utilization in rice. The APase isoform behavior and nuclear localization indicate its additional role, possibly in stress signaling. Considering its important roles, OsPAP3b could be a potential target for improving low Pi adaptation in rice.

Bacterial distribution in Twilight zone of the Indian sector of Southern Ocean: V3- V4 rDNA hypervariable region data.

Twilight zones in oceans represent the oceanic waters between 200 m to 1000 m in depth, wherein sunlight is diffused and intensity is <1% of surface value. The activities and diversity of marine micro-organisms in this unique zone are understudied, especially in the Indian Sector of the Southern Ocean. For a better understanding of the microbial environment and diversity in the twilight zone of the Indian sector of Southern Ocean, samples were collected from 200m depth in eddy-influenced waters of Subtropical Front (STF), Sub-Antarctic Front (SAF), Polar Front (PF), waters off Kerguelen (Kw), and Prydz Bay (Pb) waters. In this article, next-generation sequencing (NGS) based amplicon data of 16s rDNA bacterial samples are presented. Hypervariable V3-V4 regions were sequenced using Hiseq platform, and data was processed using Mothur v 1.48.0, and database Silva 138.1nr. Total of nine different phyla is reported from the Southern Ocean at 200m, whereas at order level Synechococcales was found in STF waters only and SAR 11_ Clades were present in all stations.

Bacterial distribution in the Equatorial Indian Ocean using Amplicon sequencing of V3-V4 rDNA hypervariable region data.

The Equatorial Indian Ocean (EIO) is a complex system strongly influenced by Indian Monsoon. During a RAMA (Research Moored Array for African-Asian-Australian Monsoon Analysis and Prediction) mooring maintenance expedition during the Southwest monsoon (August-September 2016) onboard ORV Sagar Kanya, seawater samples from the surface, deep chlorophyll maxima (DCM) and 200m were collected for bacterioplankton community structure. Herein we document our amplicon data of the bacterial community at 4 stations (4.01°S, 1.60°S, 0.36°N and 1.78°N) along the 67°00' E transect. The samples were subjected to next-generation sequencing (NGS), followed by processing with Mothur v 1.48.0, and the taxonomic classification prepared with Silva 138.1nr reference database. Our data indicates Alphaproteobacteria (48 %) and Cyanobacteria (33 %) dominance in the surface and DCM samples.

Finding a breather for Oryza sativa: Understanding hormone signalling pathways involved in rice plants to submergence stress.

During the course of evolution, different ecotypes of rice (Oryza sativa L.) have evolved distinct strategies to cope with submergence stress. Such contrasting responses are mediated by plant hormones that are principle regulators of growth, development and responses to various biotic and abiotic stresses. These hormones act cooperatively and show extensive crosstalk which is mediated by key regulatory genes that serve as nodes of molecular communication. The presence or absence of such genes leads to significant changes in hormone signalling pathways and hence, governs the type of response that the plant will exhibit. As flooding is one of the leading causes of crop loss across all the major rice-producing countries, it is crucial to deeply understand the molecular nexus governing the response to submergence to produce flood resilient varieties. This review focuses on the hormonal signalling pathways that mediate two contrasting responses of the rice plant to submergence stress namely, rapid internode elongation to escape flood waters and quiescence response that enables the plant to survive under complete submergence. The significance of several key genes such as Sub1A-1, SLR1, SD1 and SK1/SK2, in defining the ultimate response to submergence has also been discussed.

Effects of growth conditions on siderophore producing bacteria and siderophore production from Indian Ocean sector of Southern Ocean.

Iron is an important element for growth and metabolism of all marine organisms, including bacteria. Most (99.9%) of iron in oceans are bound to organic ligands like siderophores and siderophore-like compounds. Distribution of bioavailable iron mainly depends on pH and temperature of the ocean. Due to global warming and ocean acidification, bioavailability of iron may alter and in turn effect the response of marine bacteria. In this study, we investigated the effect of growth conditions like pH, temperature, and iron (III) concentrations on growth and siderophore production in selected heterotrophic bacteria isolated from waters around Kerguelen Islands (KW) and Prydz Bay (PB). Microcosm experiments were carried out on two KW-isolates (Enterococcus casseliflavus and Psychrobacter piscatorii) and five PB-isolates (Pseudoalteromonas tetraodonis, Bacillus cereus, Psychrobacter pocilloporae, Micrococcus aloeverae, and Pseudomonas weihenstephanensis) which produced either hydroxamate-type or catecholate-type siderophores. Increasing iron concentrations (10 nM to 50 µM) increased the growth rate of all isolates while siderophore production (% siderophore) generally reduced at higher iron concentration. Siderophore production peaked at early log phase, probably in response to higher iron-demand. Temperature and pH experiments showed that most isolates produced more siderophore at 15 and 25 °C temperature and pH 8.5. These results reveal that in future ocean conditions (warmer and acidified waters), bacterial growth and siderophore production may get affected and thereby influencing iron uptake and associated biogeochemical processes.

Traversing the Links between Heavy Metal Stress and Plant Signaling.

Plants confront multifarious environmental stresses widely divided into abiotic and biotic stresses, of which heavy metal stress represents one of the most damaging abiotic stresses. Heavy metals cause toxicity by targeting crucial molecules and vital processes in the plant cell. One of the approaches by which heavy metals act in plants is by over production of reactive oxygen species (ROS) either directly or indirectly. Plants act against such overdose of metal in the environment by boosting the defense responses like metal chelation, sequestration into vacuole, regulation of metal intake by transporters, and intensification of antioxidative mechanisms. This response shown by plants is the result of intricate signaling networks functioning in the cell in order to transmit the extracellular stimuli into an intracellular response. The crucial signaling components involved are calcium signaling, hormone signaling, and mitogen activated protein kinase (MAPK) signaling that are discussed in this review. Apart from signaling components other regulators like microRNAs and transcription factors also have a major contribution in regulating heavy metal stress. This review demonstrates the key role of MAPKs in synchronously controlling the other signaling components and regulators in metal stress. Further, attempts have been made to focus on metal transporters and chelators that are regulated by MAPK signaling.

Regulation of WRKY46 Transcription Factor Function by Mitogen-Activated Protein Kinases in Arabidopsis thaliana.

Mitogen-activated protein kinase (MAPK) cascades are central signaling pathways activated in plants after sensing internal developmental and external stress cues. Knowledge about the downstream substrate proteins of MAPKs is still limited in plants. We screened Arabidopsis WRKY transcription factors as potential targets downstream of MAPKs, and concentrated on characterizing WRKY46 as a substrate of the MAPK, MPK3. Mass spectrometry revealed in vitro phosphorylation of WRKY46 at amino acid position S168 by MPK3. However, mutagenesis studies showed that a second phosphosite, S250, can also be phosphorylated. Elicitation with pathogen-associated molecular patterns (PAMPs), such as the bacterial flagellin-derived flg22 peptide led to in vivo destabilization of WRKY46 in Arabidopsis protoplasts. Mutation of either phosphorylation site reduced the PAMP-induced degradation of WRKY46. Furthermore, the protein for the double phosphosite mutant is expressed at higher levels compared to wild-type proteins or single phosphosite mutants. In line with its nuclear localization and predicted function as a transcriptional activator, overexpression of WRKY46 in protoplasts raised basal plant defense as reflected by the increase in promoter activity of the PAMP-responsive gene, NHL10, in a MAPK-dependent manner. Thus, MAPK-mediated regulation of WRKY46 is a mechanism to control plant defense.

ROS mediated MAPK signaling in abiotic and biotic stress- striking similarities and differences.

Plants encounter a number of environmental stresses throughout their life cycles, most of which activate mitogen activated protein kinase (MAPK) pathway. The MAPKs show crosstalks at several points but the activation and the final response is known to be specific for particular stimuli that in-turn activates specific set of downstream targets. Interestingly, reactive oxygen species (ROS) is an important and common messenger produced in various environmental stresses and is known to activate many of the MAPKs. ROS activates a similar MAPK in different environmental stimuli, showing different downstream targets with different and specific responses. In animals and yeast, the mechanism behind the specific activation of MAPK by different concentration and species of ROS is elaborated, but in plants this aspect is still unclear. This review mainly focuses on the aspect of specificity of ROS mediated MAPK activation. Attempts have been made to review the involvement of ROS in abiotic stress mediated MAPK signaling and how it differentiates with that of biotic stress.

MicroRNA biogenesis factor DRB1 is a phosphorylation target of mitogen activated protein kinase MPK3 in both rice and Arabidopsis.

MicroRNA (miRNA) biogenesis requires AtDRB1 (double-stranded RNA binding protein)/HYL1 (Hyponastic Leaves1) protein for processing and maturation of miRNA precursors. The AtDRB1/HYL1 protein associates with AtDCL1 (Dicer-Like1) and accurately processes primary-miRNAs (pri-mRNAs) first to precursor-miRNAs (pre-miRNAs) and finally to mature miRNAs. The dephosphorylation of AtDRB1/HYL1 protein is very important for the precise processing of miRNA precursors. The monocot model crop plant Oryza sativa encodes four orthologues of AtDRB1/HYL1 protein, the only one encoded by Arabidopsis thaliana. The present study focuses on the functionality of the O. sativa DRBs as the orthologues of AtDRB1/HYL1 by using RNA binding assays and in planta protein-protein interaction analysis. Further, mitogen-activated protein kinase MPK3 is established as the kinase phosphorylating DRB1 protein in both the model plants, O. sativa and Arabidopsis. MicroRNA microarray analysis in atmpk3 and atmpk6 mutants indicate the importance of AtMPK3 in maintaining the level of miRNAs in the plant.

Transcriptome analysis of Catharanthus roseus for gene discovery and expression profiling.

The medicinal plant, Catharanthus roseus, accumulates wide range of terpenoid indole alkaloids, which are well documented therapeutic agents. In this study, deep transcriptome sequencing of C. roseus was carried out to identify the pathways and enzymes (genes) involved in biosynthesis of these compounds. About 343 million reads were generated from different tissues (leaf, flower and root) of C. roseus using Illumina platform. Optimization of de novo assembly involving a two-step process resulted in a total of 59,220 unique transcripts with an average length of 1284 bp. Comprehensive functional annotation and gene ontology (GO) analysis revealed the representation of many genes involved in different biological processes and molecular functions. In total, 65% of C. roseus transcripts showed homology with sequences available in various public repositories, while remaining 35% unigenes may be considered as C. roseus specific. In silico analysis revealed presence of 11,620 genic simple sequence repeats (excluding mono-nucleotide repeats) and 1820 transcription factor encoding genes in C. roseus transcriptome. Expression analysis showed roots and leaves to be actively participating in bisindole alkaloid production with clear indication that enzymes involved in pathway of vindoline and vinblastine biosynthesis are restricted to aerial tissues. Such large-scale transcriptome study provides a rich source for understanding plant-specialized metabolism, and is expected to promote research towards production of plant-derived pharmaceuticals.

Interaction between two rice mitogen activated protein kinases and its possible role in plant defense.

BACKGROUND: The canonical mitogen activated protein kinase (MAPK) signaling pathway plays a vital role in carrying out the normal growth and development of the plant. The pathway, connecting the upstreams signal with the downstream target is considered to be linear, mostly starting with a MAPKKK and ending in a MAPK. RESULTS: Here we report a novel interaction between two rice MAPKs, OsMPK20-4 and OsMPK3 suggesting the complex nature of the pathway rather than a linear one at individual steps. The interaction between OsMPK20-4 and OsMPK3 found by yeast two-hybrid analysis was confirmed in planta by co-immunoprecipitation and fluorescence resonance energy transfer (FRET) assays. The interaction is specific and is phosphorylation independent. The results suggest a role of the interaction between OsMPK20-4 and OsMPK3 in basic plant defense. CONCLUSIONS: The current novel work showing the physical interaction between two plant MAPKs, OsMPK20-4 and OsMPK3 is the diversion from the dogma of a typical MAPK cascade thereby opening a new dimension to the MAPK signal transduction.

Post-translational derepression of invertase activity in source leaves via down-regulation of invertase inhibitor expression is part of the plant defense response.

There is increasing evidence that pathogens do not only elicit direct defense responses, but also cause pronounced changes in primary carbohydrate metabolism. Cell-wall-bound invertases belong to the key regulators of carbohydrate partitioning and source-sink relations. Whereas studies have focused so far only on the transcriptional induction of invertase genes in response to pathogen infection, the role of post-translational regulation of invertase activity has been neglected and was the focus of the present study. Expression analyses revealed that the high mRNA level of one out of three proteinaceous invertase inhibitors in source leaves of Arabidopsis thaliana is strongly repressed upon infection by a virulent strain of Pseudomonas syringae pv. tomato DC3000. This repression is paralleled by a decrease in invertase inhibitor activity. The physiological role of this regulatory mechanism is revealed by the finding that in situ invertase activity was detectable only upon infection by P. syringae. In contrast, a high invertase activity could be measured in vitro in crude and cell wall extracts prepared from both infected and non-infected leaves. The discrepancy between the in situ and in vitro invertase activity of control leaves and the high in situ invertase activity in infected leaves can be explained by the pathogen-dependent repression of invertase inhibitor expression and a concomitant reduction in invertase inhibitor activity. The functional importance of the release of invertase from post-translational inhibition for the defense response was substantiated by the application of the competitive chemical invertase inhibitor acarbose. Post-translational inhibition of extracellular invertase activity by infiltration of acarbose in leaves was shown to increase the susceptibility to P. syringae. The impact of invertase inhibition on spatial and temporal dynamics of the repression of photosynthesis and promotion of bacterial growth during pathogen infection supports a role for extracellular invertase in plant defense. The acarbose-mediated increase in susceptibility was also detectable in sid2 and cpr6 mutants and resulted in slightly elevated levels of salicylic acid, demonstrating that the effect is independent of the salicylic acid-regulated defense pathway. These findings provide an explanation for high extractable invertase activity found in source leaves that is kept inhibited in situ by post-translational interaction between invertase and the invertase inhibitor proteins. Upon pathogen infection, the invertase activity is released by repression of invertase inhibitor expression, thus linking the local induction of sink strength to the plant defense response.

Tomato mitogen activated protein kinases regulate the expression of extracellular invertase Lin6 in response to stress related stimuli.

Activation of mitogen-activated protein kinases (MAPKs) is a common reaction of plant cells in defence-related signal transduction pathways. Since the downstream events after the activation of MAPKs are largely unknown in plants, the role of MAPKs in the coordinate regulation of defence reactions and primary carbon metabolism by stress related stimuli has been analysed in tomato (Lycopersicon peruvianum Mill.). Thus, the relationship between MAPK, LpMPK2 and LpMPK3 and extracellular invertase Lin6, as the key enzyme of an apoplasmic phloem unloading pathway, has been analysed. It was observed that the mRNAs of LpMPK3 and Lin6 are sequentially induced by the same set of stress related stimuli, wounding, a fungal elicitor derived from Fusarium oxysporum lycopersici, the endogenous plant derived elicitor PGA and salt stress, while LpMPK2 transcripts are constitutively expressed. In a gain of function approach, a His-tagged version of LpMPK2 and a HA-tagged version of LpMPK3 were transiently and functionally expressed in leaves of transgenic tobacco (Nicotiana tabacum L.) plants expressing the ß-glucuronidase reporter gene under control of the Lin6 promoter via agro-infection. The induction of the Lin6 promoter, as revealed by an increase in ß-glucuronidase activity after 24 h, was dependent both on the expression and activation of both LpMPK2 and LpMPK3. These data suggest that the induction of extracellular invertase Lin6 by stress-related stimuli requires LpMPK2 and LpMPK3, and thus demonstrate that MAPK signalling might be involved in the regulation of primary carbon metabolism in general and sink metabolism in particular.

Cloning, characterization and localization of a novel basic peroxidase gene from Catharanthus roseus.

Catharanthus roseus (L.) G. Don produces a number of biologically active terpenoid indole alkaloids via a complex terpenoid indole alkaloid biosynthetic pathway. The final dimerization step of this pathway, leading to the synthesis of a dimeric alkaloid, vinblastine, was demonstrated to be catalyzed by a basic peroxidase. However, reports of the gene encoding this enzyme are scarce for C. roseus. We report here for the first time the cloning, characterization and localization of a novel basic peroxidase, CrPrx, from C. roseus. A 394 bp partial peroxidase cDNA (CrInt1) was initially amplified from the internodal stem tissue, using degenerate oligonucleotide primers, and cloned. The full-length coding region of CrPrx cDNA was isolated by screening a leaf-specific cDNA library with CrInt1 as probe. The CrPrx nucleotide sequence encodes a deduced translation product of 330 amino acids with a 21 amino acid signal peptide, suggesting that CrPrx is secretory in nature. The molecular mass of this unprocessed and unmodified deduced protein is estimated to be 37.43 kDa, and the pI value is 8.68. CrPrx was found to belong to a 'three intron' category of gene that encodes a class III basic secretory peroxidase. CrPrx protein and mRNA were found to be present in specific organs and were regulated by different stress treatments. Using a beta-glucuronidase-green fluorescent protein fusion of CrPrx protein, we demonstrated that the fused protein is localized in leaf epidermal and guard cell walls of transiently transformed tobacco. We propose that CrPrx is involved in cell wall synthesis, and also that the gene is induced under methyl jasmonate treatment. Its potential involvement in the terpenoid indole alkaloid biosynthetic pathway is discussed.

Plant physiology meets phytopathology: plant primary metabolism and plant-pathogen interactions.

Phytopathogen infection leads to changes in secondary metabolism based on the induction of defence programmes as well as to changes in primary metabolism which affect growth and development of the plant. Therefore, pathogen attack causes crop yield losses even in interactions which do not end up with disease or death of the plant. While the regulation of defence responses has been intensively studied for decades, less is known about the effects of pathogen infection on primary metabolism. Recently, interest in this research area has been growing, and aspects of photosynthesis, assimilate partitioning, and source-sink regulation in different types of plant-pathogen interactions have been investigated. Similarly, phytopathological studies take into consideration the physiological status of the infected tissues to elucidate the fine-tuned infection mechanisms. The aim of this review is to give a summary of recent advances in the mutual interrelation between primary metabolism and pathogen infection, as well as to indicate current developments in non-invasive techniques and important strategies of combining modern molecular and physiological techniques with phytopathology for future investigations.

Mechanistic investigation and implications of photodynamic therapy induction of vascular endothelial growth factor in prostate cancer.

Photodynamic therapy (PDT) is now an approved therapeutic modality, and induction of vascular endothelial growth factor (VEGF) following subcurative PDT is of concern as VEGF may provide a survival stimulus to tumors. The processes that limit the efficacy of PDT warrant investigation so that mechanism-based interventions may be developed. This study investigates VEGF increase following subcurative PDT using the photosensitizer benzoporphyrin derivative (BPD) both in an in vitro and in an orthotopic model of prostate cancer using the human prostate cancer cell line LNCaP. The two subcurative doses used, 0.25 and 0.5 J/cm(2), mimicked subcurative PDT and elicited a 1.6- and 2.1-fold increase, respectively, in secreted VEGF 24 hours following PDT. Intracellular VEGF protein measurement and VEGF mRNA showed a 1.4- and 1.6-fold increase only at 0.5 J/cm(2). In vivo subcurative PDT showed an increase in VEGF by both immunohistochemistry and ELISA. In vitro analysis showed no activation of hypoxia-inducible factor-1alpha (HIF-1alpha) or cyclooxygenase-2 (COX-2) following subcurative PDT; furthermore, small interfering RNA inhibition of HIF-1alpha and COX-2 inhibitor treatment had no effect on PDT induction of VEGF. PDT in the presence of phosphatidylinositol 3-kinase/AKT inhibitor or mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase inhibitor still induced VEGF. However, subcurative PDT increased phosphorylated p38 and stress-activated protein kinase/c-Jun NH(2)-terminal kinase. The p38 MAPK inhibitor abolished PDT induction of VEGF. The results establish the importance of VEGF in subcurative BPD-PDT of prostate cancer and suggest possible molecular pathways for its induction. These findings should provide the basis for the development of molecular-based interventions for enhancing PDT and merit further studies.

Cyclopentenone isoprostanes induced by reactive oxygen species trigger defense gene activation and phytoalexin accumulation in plants.

Lipid peroxidation may be initiated either by lipoxygenases or by reactive oxygen species (ROS). Enzymatic oxidation of alpha-linolenate can result in the biosynthesis of cyclic oxylipins of the jasmonate type while free-radical-catalyzed oxidation of alpha-linolenate may yield several classes of cyclic oxylipins termed phytoprostanes in vivo. Previously, we have shown that one of these classes, the E1-phytoprostanes (PPE1), occurs ubiquitously in plants. In this work, it is shown that PPE1 are converted to novel cyclopentenone A1- and B1-phytoprostanes (PPA1 and PPB1) in planta. Enhanced formation of PPE1, PPA1, and PPB1 is observed after peroxide stress in tobacco cell cultures as well as after infection of tomato plants with a necrotrophic fungus, Botrytis cinerea. PPA1 and PPB1 display powerful biologic activities including activation of mitogen-activated protein kinase (MAPK) and induction of glutathione-S-transferase (GST), defense genes, and phytoalexins. Data collected so far infer that enhanced phytoprostane formation is a general consequence of oxidative stress in plants. We propose that phytoprostanes are components of an oxidant-injury-sensing, archaic signaling system that serves to induce several plant defense mechanisms.

A heat-activated MAP kinase in tomato: a possible regulator of the heat stress response.

Adaptation to elevated temperatures is of major importance for the survival of plants. The role of kinases in heat stress response was studied in tomato by in gel and in solution kinase assays using myelin basic protein as substrate. The application of heat stress in a naturally occurring temperature range resulted in a fast and transient activation of a 50 kDa mitogen-activated protein (MAP) kinase both in a photoautotrophic cell suspension culture and in leaves of mature plants. The heat activation of the MAP kinase was shown to be calcium-dependent. The specific phosphorylation of tomato heat stress transcription factor HsfA3 by a partially purified preparation of the heat-activated MAP kinase supports a physiological role of the identified kinase activity in transducing the heat stress signal.

Metabolizable and non-metabolizable sugars activate different signal transduction pathways in tomato.

To gain insight into the regulatory mechanisms of sugar signaling in plants, the effect of derivatives of the transport sugar sucrose (Suc), the Suc isomers palatinose and turanose, and the Suc analog fluoro-Suc were tested. Photo-autotrophic suspension culture cells of tomato (Lycopersicon peruvianum) were used to study their effect on the regulation of marker genes of source and sink metabolism, photosynthesis, and the activation of mitogen-activated protein kinases (MAPKs). Suc and glucose (Glc) resulted in reverse regulation of source and sink metabolism. Whereas the mRNA level of extracellular invertase (Lin6) was induced, the transcript level of small subunit of ribulose bisphosphate carboxylase (RbcS) was repressed. In contrast, turanose, palatinose, and fluoro-Suc only rapidly induced Lin6 mRNA level, whereas the transcript level of RbcS was not affected. The differential effect of the metabolizable and non-metabolizable sugars on RbcS mRNA regulation was reflected by the fact that only Suc and Glc inhibited photosynthesis and chlorophyll fluorescence. The activation of different signal transduction pathways by sugars was further supported by the analysis of the activation of MAPKs. MAPK activity was found to be strongly activated by turanose, palatinose, and fluoro-Suc, but not by Suc and Glc. To analyze the role of sugars in relation to pathogen perception, an elicitor preparation of Fusarium oxysporum lycopersici was used. The strong activation of MAPKs and the fast and transient induction of Lin6 expresssion by the fungal elicitor resembles the effect of turanose, palatinose, and fluoro-Suc and indicates that non-metabolizable sugars are sensed as stress-related stimuli.