Arabidopsis thaliana is able to sense tomato Systemin promoting defense against fungal pathogens

Pòster presentat al Symposium on Small Molecules in Plant Research: Chemistry and Biology Come Together (Valencia, Spain, 10-11 December 2019).Systemin is a small tomato peptide that regulates the plant response against herbivores and pathogenic fungi. It is released from a larger precursor upon wounding or pathogen attack and binds to a membrane receptor of the adjacent cell inducing a cascade of plant defences, including JA-related responses, that lead to the accumulation of protease inhibitors in local and systemic tissue. Although the tomato Systemin has been the focus of many recent studies, very little is known about the perception and function of Systemin in heterologous species

Systemic resistance in citrus to Tetranychus urticae induced by conspecifics is transmitted by grafting and mediated by mobile amino acids

Recent research suggests that systemic signalling and communication between roots and leaves plays an important role in plant defence against herbivores. In the present study, we show that the oviposition of the two-spotted spider mite Tetranychus urticae in the systemic leaves of citrus rootstock Citrus aurantium (sour orange) was reduced by 50% when a lower leaf was previously infested with conspecifics. Metabolomic and gene expression analysis of the root efflux revealed a strong accumulation of glutamic acid (Glu) that triggered the expression of the citrus putative glutamate receptor ( GRL ) in the shoots. Additionally, uninfested sour orange systemic leaves showed increased expression of glutamate receptors and higher amounts of jasmonic acid (JA) and 12-oxo-phytodienoic acid in plants that were previously infested. Glu perception in the shoots induced the JA pathway, which primed LOX-2 gene expression when citrus plants were exposed to a second infestation. The spider mite- susceptible citrus rootstock Cleopatra mandarin ( C. unshiu ) also expressed systemic resistance, although the resistance was less effective than the resistance in sour orange. Surprisingly, the mobile signal in Cleopatra mandarin was not Glu, which suggests a strong genotype-dependency for systemic signalling in citrus. When the cultivar Clemenules ( C. clementina ) was grafted onto sour orange, there was a reduction in symptomatic leaves and T. urticae populations compared to the same cultivar grafted onto Cleopatra mandarin. Thus, systemic resistance is transmitted from the roots to the shoots in citrus and is dependent on rootstock resistance

Metabolomics of cereals under biotic stress: current knowledge and techniques

Prone to attacks by pathogens and pests, plants employ intricate chemical defense mechanisms consisting of metabolic adaptations. However, many plant attackers are manipulating the host metabolism to counteract defense responses and to induce favorable nutritional conditions. Advances in analytical chemistry have allowed the generation of extensive metabolic profiles during plant-pathogen and pest interactions. Thereby, metabolic processes were found to be highly specific for given tissues, species, and plantpathogen/pest interactions. The clusters of identified compounds not only serve as base in the quest of novel defense compounds, but also as markers for the characterization of the plants’ defensive state. The latter is especially useful in agronomic applications where meaningful markers are essential for crop protection. Cereals such as maize make use of their metabolic arsenal during both local and systemic defense responses, and the chemical response is highly adapted to specific attackers. Here, we summarize highlights and recent findings of metabolic patterns of cereals under pathogen and pest attack.National Centre of Competence in Research (NCCR) 'Plant Survival' SNF 31003A_140593 Swiss National Science Foundation Plan de Promocion de la Investigacion de la Universitat Jaume I P1.1B2010-0

Systemic resistance in citrus to Tetranychus urticae induced by conspecifics is transmitted by grafting and mediated by mobile amino acids

Recent research suggests that systemic signalling and communication between roots and leaves plays an important role in plant defence against herbivores. In the present study, we show that the oviposition of the two-spotted spider mite Tetranychus urticae in the systemic leaves of citrus rootstock Citrus aurantium (sour orange) was reduced by 50% when a lower leaf was previously infested with conspecifics. Metabolomic and gene expression analysis of the root efflux revealed a strong accumulation of glutamic acid (Glu) that triggered the expression of the citrus putative glutamate receptor (GRL) in the shoots. Additionally, uninfested sour orange systemic leaves showed increased expression of glutamate receptors and higher amounts of jasmonic acid (JA) and 12-oxo-phytodienoic acid in plants that were previously infested. Glu perception in the shoots induced the JA pathway, which primed LOX-2 gene expression when citrus plants were exposed to a second infestation. The spider mite-susceptible citrus rootstock Cleopatra mandarin (C. unshiu) also expressed systemic resistance, although the resistance was less effective than the resistance in sour orange. Surprisingly, the mobile signal in Cleopatra mandarin was not Glu, which suggests a strong genotype-dependency for systemic signalling in citrus. When the cultivar Clemenules (C. clementina) was grafted onto sour orange, there was a reduction in symptomatic leaves and T. urticae populations compared to the same cultivar grafted onto Cleopatra mandarin. Thus, systemic resistance is transmitted from the roots to the shoots in citrus and is dependent on rootstock resistance

Preparing to fight back: generation and storage of priming compounds

Immune-stimulated plants are able to respond more rapidly and adequately to various biotic stresses allowing them to efficiently combat an infection. During the priming phase, plant are stimulated in absence of a challenge, and can accumulate and store conjugates or precursors of molecules as well as other compounds that play a role in defense. These molecules can be released during the defensive phase following stress. These metabolites can also participate in the first stages of the stress perception. Here, we report the metabolic changes occuring in primed plants during the priming phase. β-aminobutyric acid (BABA) causes a boost of the primary metabolism through the tricarboxylic acids (TCA) such as citrate, fumarate, (S)-malate and 2-oxoglutarate, and the potentiation of phenylpropanoid biosynthesis and the octodecanoic pathway. On the contrary, Pseudomonas syringae pv tomato (PstAvrRpt2) represses the same pathways. Both systems used to prime plants share some common signals like the changes in the synthesis of amino acids and the production of SA and its glycosides, as well as IAA. Interestingly, a product of the purine catabolism, xanthosine, was found to accumulate following both BABA- and PstAvrRpt2-treatement. The compounds that are strongly affected in this stage are called priming compounds, since their effect on the metabolism of the plant is to induce the production of primed compounds that will help to combat the stress. At the same time, additional identified metabolites suggest the possible defense pathways that plants are using to get ready for the battle

The RNA Silencing Enzyme RNA Polymerase V Is Required for Plant Immunity

RNA–directed DNA methylation (RdDM) is an epigenetic control mechanism driven by small interfering RNAs (siRNAs) that influence gene function. In plants, little is known of the involvement of the RdDM pathway in regulating traits related to immune responses. In a genetic screen designed to reveal factors regulating immunity in Arabidopsis thaliana, we identified NRPD2 as the OVEREXPRESSOR OF CATIONIC PEROXIDASE 1 (OCP1). NRPD2 encodes the second largest subunit of the plant-specific RNA Polymerases IV and V (Pol IV and Pol V), which are crucial for the RdDM pathway. The ocp1 and nrpd2 mutants showed increases in disease susceptibility when confronted with the necrotrophic fungal pathogens Botrytis cinerea and Plectosphaerella cucumerina. Studies were extended to other mutants affected in different steps of the RdDM pathway, such as nrpd1, nrpe1, ago4, drd1, rdr2, and drm1drm2 mutants. Our results indicate that all the mutants studied, with the exception of nrpd1, phenocopy the nrpd2 mutants; and they suggest that, while Pol V complex is required for plant immunity, Pol IV appears dispensable. Moreover, Pol V defective mutants, but not Pol IV mutants, show enhanced disease resistance towards the bacterial pathogen Pseudomonas syringae DC3000. Interestingly, salicylic acid (SA)–mediated defenses effective against PsDC3000 are enhanced in Pol V defective mutants, whereas jasmonic acid (JA)–mediated defenses that protect against fungi are reduced. Chromatin immunoprecipitation analysis revealed that, through differential histone modifications, SA–related defense genes are poised for enhanced activation in Pol V defective mutants and provide clues for understanding the regulation of gene priming during defense. Our results highlight the importance of epigenetic control as an additional layer of complexity in the regulation of plant immunity and point towards multiple components of the RdDM pathway being involved in plant immunity based on genetic evidence, but whether this is a direct or indirect effect on disease-related genes is unclear

Accurate and easy method for systemin quantifcation and examining metabolic changes under diferent endogenous levels

Background: Systemin has been extensively studied since it was discovered and is described as a peptidic hormone in tomato plants and other Solanaceae. Jasmonic acid and systemin are proposed to act through a positive feedback loop with jasmonic acid, playing synergistic roles in response to both wounding and insect attack. Despite its biological relevance, most studies regarding the function of systemin in defence have been studied via PROSYSTEMIN (PROSYS) gene expression, which encodes the propeptide prosystemin that is later cleaved to systemin (SYS). Interest‑ ingly, hardly any studies have been based on quantifcation of the peptide. Results: In this study, a simple and accurate method for systemin quantifcation was developed to understand its impact on plant metabolism. The basal levels of systemin were found to be extremely low. To study the role of endogenous systemin on plant metabolism, systemin was quantifed in a transgenic line overexpressing the PROSYS gene (PS+) and in a silenced antisense line (PS−). We evaluated the relevance of systemin in plant metabolism by analysing the metabolomic profles of both lines compared to wildtype plants through untargeted metabolomic profling. Compounds within the lignan biosynthesis and tyrosine metabolism pathways strongly accumulated in PS+compared to wild-type plants and to plants from the PS− line. The exogenous treatments with SYS enhanced accumulation of lignans, which confrms the role of SYS in cell wall reinforcement. Unexpectedly, PS+plants displayed wild-type levels of jasmonic acid (JA) but elevated accumulation of 12-oxo-phytodienoic acid (OPDA), suggesting that PS+should not be used as an over-accumulator of JA in experimental setups. Conclusions: A simple method, requiring notably little sample manipulation to quantify the peptide SYS, is described. Previous studies were based on genetic changes. In our study, SYS accumulated at extremely low levels in wild-type tomato leaves, showed slightly higher levels in the PROSYSTEMIN-overexpressing plants and was absent in the silenced lines. These small changes have a signifcant impact on plant metabolism. SA and OPDA, but not JA, were higher in the PROSYS-overexpressing plants

Small Signals Lead to Big Changes: The Potential of Peptide-Induced Resistance in Plants

The plant immunity system is being revisited more and more and new elements and roles are attributed to participating in the response to biotic stress. The new terminology is also applied in an attempt to identify different players in the whole scenario of immunity: Phytocytokines are one of those elements that are gaining more attention due to the characteristics of processing and perception, showing they are part of a big family of compounds that can amplify the immune response. This review aims to highlight the latest findings on the role of phytocytokines in the whole immune response to biotic stress, including basal and adaptive immunity, and expose the complexity of their action in plant perception and signaling events

Effect of grafting on phenology, susceptibility to Phytophthora cinnamomi and hormone profile of chestnut

Ink disease caused by the root-rot pathogen P. cinnamomi (Pc) threatens European sweet chestnut (Castanea sativa Mill.) orchards, and growers increasingly graft susceptible C. sativa traditional varieties on Pc-resistant hybrid commercial rootstocks. The influence of the scion, the rootstock, and grafting per se on the vegetative budburst, growth, susceptibility to Pc and defence-related hormone profile of Castanea spp. are unknown. In a greenhouse experiment, these effects were evaluated by reciprocally grafting two Pc resistant C. crenata x C. sativa clones and two Pc susceptible C. sativa clones. Resistance to Pc and the hormone content of leaves and roots were rootstock-dependent, and survival rates of susceptible chestnuts strongly increased when grafted on resistant rootstocks. The scion had no effect on the resistance to Pc and the hormone profile of leaves and roots of grafted trees, but influenced vegetative budburst and primary growth. Grafting per se increased susceptibility to Pc and altered the defence-related phytohormone content of trees, especially in resistant rootstocks, but did not influence budburst and growth of trees. Grafting-induced alteration of the constitutive defense-related hormone profile could explain the increased susceptibility of resistant rootstocks to Pc. Nine days after infection, a dynamic hormonal response consisting of decreased jasmonates (JA and JA-Ile) in leaves and increased ABA and JA-Ile in roots was observed in resistant chestnuts. This is the first study addressing the role of grafting in modulating resistance to the soil-borne pathogen Pc in chestnut trees

Defensive plats responses induced by Nesidiocoris tenuis (Hemiptera:Miridae) on tomato plants

In the last decade, biological control programs for greenhouse tomatoes and other crops have been successfully implemented using zoophytophagous plant bugs (Miridae), which can feed on both plant tissues and insect prey. It is well known that plants respond to herbivore attacks by releasing volatile compounds through diverse pathways triggered by phytohormones. These herbivore-induced plant volatiles can alert neighboring plants, repel or attract herbivores, and attract natural enemies of these herbivores. Nevertheless, the possible benefits of induced plant responses by zoophytophagous predators that could add to their usefulness as biocontrol agents have not been studied until now. Here we show that the zoophytophagous predator Nesidiocoris tenuis activated abscisic acid and jasmonic acid (JA) signaling pathways in tomato plants, which made them less attractive to the whitefly Bemisia tabaci, a major tomato pest worldwide, and more attractive to the whitefly parasitoid, Encarsia formosa. We also found that intact tomato plants exposed to volatiles from N. tenuis-punctured plants activated the JA pathway, and as a consequence, E. formosa was also attracted to these intact plants with activated defense systems. Thus, our results demonstrate that N. tenuis not only benefits tomato plants directly by entomophagy but also indirectly by phytophagy, which induces a physiological response in the tomato plant.The research leading to these results was funded by the European Union Seventh Framework Programme (FP7/2007–2013) under grant agreement no. 265865, the Spanish Ministry of Science and Innovation (AGL2011-30538-C03) and the Conselleria d’Agricultura, Pesca i Alimentació de la Generalitat Valenciana. The authors thank Virginia Pedroche (IVIA) and Blas Agut (UJI) for their technical assistance, Javier Calvo (KOPPERT BS) for the supply of insects, Universitat Jaume I-SCIC for technical support and two anonymous reviewers for their valuable comments on a previous version of this manuscript