Does abscisic acid affect strigolactone biosynthesis?

Strigolactones are considered a novel class of plant hormones that, in addition to their endogenous signalling function, are exuded into the rhizosphere acting as a signal to stimulate hyphal branching of arbuscular mycorrhizal (AM) fungi and germination of root parasitic plant seeds. Considering the importance of the strigolactones and their biosynthetic origin (from carotenoids), we investigated the relationship with the plant hormone abscisic acid (ABA). Strigolactone production and ABA content in the presence of specific inhibitors of oxidative carotenoid cleavage enzymes and in several tomato ABA-deficient mutants were analysed by LC-MS/MS. In addition, the expression of two genes involved in strigolactone biosynthesis was studied. * • The carotenoid cleavage dioxygenase (CCD) inhibitor D2 reduced strigolactone but not ABA content of roots. However, in abamineSG-treated plants, an inhibitor of 9-cis-epoxycarotenoid dioxygenase (NCED), and the ABA mutants notabilis, sitiens and flacca, ABA and strigolactones were greatly reduced. The reduction in strigolactone production correlated with the downregulation of LeCCD7 and LeCCD8 genes in all three mutants. * • The results show a correlation between ABA levels and strigolactone production, and suggest a role for ABA in the regulation of strigolactone biosynthesis

Phosphorus availability drives mycorrhiza induced resistance in tomato

Arbuscular mycorrhizal (AM) symbiosis can provide multiple benefits to the host plant, including improved nutrition and protection against biotic stress. Mycorrhiza induced resistance (MIR) against pathogens and insect herbivores has been reported in different plant systems, but nutrient availability may influence the outcome of the interaction. Phosphorus (P) is a key nutrient for plants and insects, but also a regulatory factor for AM establishment and functioning. However, little is known about how AM symbiosis and P interact to regulate plant resistance to pests. Here, using the tomato-Funneliformis mosseae mycorrhizal system, we analyzed the effect of moderate differences in P fertilization on plant and pest performance, and on MIR against biotic stressors including the fungal pathogen Botrytis cinerea and the insect herbivore Spodoperta exigua. P fertilization impacted plant nutritional value, plant defenses, disease development and caterpillar survival, but these effects were modulated by the mycorrhizal status of the plant. Enhanced resistance of F. mosseae-inoculated plants against B. cinerea and S. exigua depended on P availability, as no protection was observed under the most P-limiting conditions. MIR was not directly explained by changes in the plant nutritional status nor to basal differences in defense-related phytohormones. Analysis of early plant defense responses to the damage associated molecules oligogalacturonides showed primed transcriptional activation of plant defenses occurring at intermediate P levels, but not under severe P limitation. The results show that P influences mycorrhizal priming of plant defenses and the resulting induced-resistance is dependent on P availability, and suggest that mycorrhiza fine-tunes the plant growth vs defense prioritization depending on P availability. Our results highlight how MIR is context dependent, thus unravel molecular mechanism based on plant defence in will contribute to improve the efficacy of mycorrhizal inoculants in crop protection

Intra and Inter-Spore Variability in Rhizophagus irregularis AOX Gene

Funding: This work was supported by the European Commission through the project AGRO-AMF-AOX within the program Industry-Academia Partnerships and Pathways (IAPP, FP7). Still in the frame of the AGRO-AMF-AOX project, JS further acknowledges his recruitment, and CC, HC, AN, CS and BAS appreciate the further support given in the form of a secondment. Inoq GmbH provided support in the form of salary for CS, but did not have any additional role in the study design, data collection and analyses, decision to publish, or preparation of the manuscript. The specific role of CS is articulated in the ‘author contributions’ section. Part of this work was also supported by grant AGL2012-39923 from the Spanish National R&D Plant of the Ministry of Science and Innovation (MICINN). TN was supported by a Marie Curie fellowship (FP7-PEOPLE-2012-CIG Project Reference 321725) and by the Portuguese Foundation for Science and Technology – FCT (SFRH/BCC/52187/2013). The authors further thank the program POPH—Operational Program for Human Potential—and Fundo Europeu de Desenvolvimento Regional (FEDER) funds through the Operational Program for Competitiveness Factors—COMPETE, and national funds through FCT under the strategic project PEst-C/AGR/UI0115/2011 and PEst-OE/AGR/UI0115/2014.Peer reviewe

Mycorrhiza induced resistance against pests: from the lab to the field

1 página - Conferencia invitada presentada en Iberian Plant Biology 2023. XVIII Portuguese-Spanish Congress on Plant Biology and the XXV Meeting of the Spanish Society of Plant Biology. 9-12 Julio 2023, Braga, PortugalArbuscular mycorrhizal fungi (AMF) can prime plant defences increasing their resistance against pathogens and insect herbivores. Using tomato as a model, we have shown that inoculation with different AMF reduces the performance of the chewing herbivore Spodoptera exigua and the leaf miner Tuta absoluta. Transcriptomic and metabolomics analyses revealed that this Mycorrhiza Induced Resistance (MIR) is associated to boosted activation of plant direct and indirect defences in response to the attackers. We found primed accumulation in attacked leaves of antiherbivore metabolites, including alkaloids and polyamine conjugates, and functional analyses demonstrated that some of the identified compounds significantly inhibit herbivore development. In addition, the symbiosis altered the volatile blends released by the plant, and enhanced the attraction of natural enemies of the pests (Nesidiocoris tenuis, commonly used in biocontrol programs). Finally, networks analyses allowed the identification of key regulators of the primed response within the jasmonic acid and ethylene signalling pathways. Despite the many studies showing induced resistance by microorganisms in different plant‐pest systems, the variability in the protection achieved under agronomic settings is hindering the application of this strategy in agriculture. Plant‐microbe‐herbivore interactions are highly context dependent, with multiple biotic and abiotic factors influencing the final output. Identifying such factors is essential to optimize the application of microbial inoculants for crop protection in agriculture. We found that the plant genotype and nutrient availability are important drivers of the context dependency of MIR in tomato. Despite of the variability, comparisons across different experimental scales, from controlled lab set‐ups to commercial production conditions, confirmed that MIR can be achieved under crop production conditions and is compatible with other biocontrol methods. Accordingly, MIR can be a relevant addition to current Integrated Pest Management Programs

Hormonal and transcriptional profiles highlight common and differential host responses to arbuscular mycorrhizal fungi and the regulation of the oxylipin pathway

Arbuscular mycorrhizal (AM) symbioses are mutualistic associations between soil fungi and most vascular plants. The symbiosis significantly affects the host physiology in terms of nutrition and stress resistance. Despite the lack of host range specificity of the interaction, functional diversity between AM fungal species exists. The interaction is finely regulated according to plant and fungal characters, and plant hormones are believed to orchestrate the modifications in the host plant. Using tomato as a model, an integrative analysis of the host response to different mycorrhizal fungi was performed combining multiple hormone determination and transcriptional profiling. Analysis of ethylene-, abscisic acid-, salicylic acid-, and jasmonate-related compounds evidenced common and divergent responses of tomato roots to Glomus mosseae and Glomus intraradices, two fungi differing in their colonization abilities and impact on the host. Both hormonal and transcriptional analyses revealed, among others, regulation of the oxylipin pathway during the AM symbiosis and point to a key regulatory role for jasmonates. In addition, the results suggest that specific responses to particular fungi underlie the differential impact of individual AM fungi on plant physiology, and particularly on its ability to cope with biotic stresses

Estrigolactonas: señales de "cry for help" en la rizosfera

Conferencia presentada en: Reunión de la Red de Investigación: Aprendiendo de la naturaleza: interacciones multitróficas para la protección de cultivos y bosques (Ref.: RED2018-102407-T) Madrid 18-20 mayo (2022

Editorial: The role of plant hormones in plant-microbe symbioses

descripción no proporcionada por scopusEF was supported by Australian Research Council Future Fellowship and Discovery Grants. JALR was supported by grants AGL2015-64990-C2-1R from the Spanish National R&D Plan of the Ministry of Economy and Competitiveness (MINECO) and the European Regional Development Fund (ERDF), and 201640I040 from the Spanish National Research Council (CSIC). JP would like to acknowledge the Australian Research Council for research funding (DE150100408). DR was supported by Danish National Research Foundation

Analyzing the effect of strigolactones on the motility behavior of Rhizobia

Edited by Prandi, C., Cardinale, F.In the Rhizobium–legume symbiosis, strigolactones (SLs) promote root nodule formation; however, the exact mechanism underlying this positive effect remains unknown. The recent finding that an SL receptor legume mutant shows a wild-type nodulation phenotype suggests that SLs influence the symbiosis by acting on the bacterial partner. In agreement with this, the application of the synthetic SL analog GR24 on the alfalfa symbiont Sinorhizobium (Ensifer) meliloti has been shown to stimulate swarming, a specialized bacterial surface motility, which could influence infection of legumes by Rhizobia. Surface motility assays for many bacteria, and particularly for Rhizobia, are challenging. The establishment of protocols to study bacterial surface motility is key to decipher the role of SLs as rhizosphere cues for rhizobacteria. In this chapter, we describe a set of protocols implemented to study the different types of motility exhibited by S. meliloti.This work was supported by grants PGC2018-096477-B-I00, RTI2018-094350-B-C31 and AGL2017-88-083-R from the Spanish National R&D Plan of the Ministry of Science, Innovation and Universities Economy and Competitiveness, and European Regional Development Funds (MCIU/AEI/FEDER, EU)

Histochemical and molecular quantification of arbuscular mycorrhiza symbiosis

Arbuscular mycorrhizae (AM) are one of the most widespread and studied plant associations with beneficial microorganisms. Indeed, more than 80% of land plants, including most agricultural and horticultural crop species, are able to establish this mutualistic symbiosis with AM fungi. Through this association the fungus helps the plant in the acquisition of water and mineral nutrients, especially under stress conditions. AM symbiosis affects other ecologically and economically important traits such as plant architecture, flowering, and fruit quality but also tolerance against biotic and abiotic stresses. As a consequence, AM fungi have a great potential as biofertilizers and bioprotection agents in sustainable agriculture. However, in order to take advantage of all these benefits, a good and functional symbiosis is required. Here we present methods for reliable quantification of colonization levels which should be useful not only for research but also from the agronomic point of view.This work was supported by grants AGL2015-64990-C2-1-R and BIO2017-90877-REDT from the Ministry of Economy and Competitiveness (MINECO) and 201640I040 from CSIC