Search

It is well known that plants respond to various stresses by releasing volatile organic compounds (VOCs). Green leaf volatiles (GLVs), which are commonly produced across different plant species after tissue damage, comprise an important group within VOCs. Among them, (Z)-3-hexenyl butyrate (HB) was described as a natural stomatal closure inducer, playing an important role in stomatal immunity, although its mechanism of action is still unknown. Here, through different genetic, pharmacological, and biochemical approaches we uncover that HB perception initiates different defense signaling events such as activation of Ca2+ permeable channels, mitogen-activated protein kinases (MPKs) and production of NADPH oxidase-mediated reactive oxygen species (ROS). Furthermore, HB-mediated stomata closure resulted to be independent of abscisic acid (ABA) biosynthesis and signaling. Additionally, exogenous treatments with this volatile alleviate water stress and improve fruit productivity in tomato plants. HB efficacy was also tested under open field conditions, leading to enhanced resistance against Phytophthora spp. and Pseudomonas syringae infection in potato and tomato plants, respectively. Collectively, our results provide insights into HB signaling transduction pathway, confirming its role in stomatal closure and plant immune system activation, and proposing HB as a new phytoprotector for the sustainable control of biotic and abiotic stresses in agriculture.

SummaryCarotenoids are photoprotectant pigments and precursors of the hormones abscisic acid (ABA) and strigolactones (SL). Carotenoids are produced in plastids from geranylgeranyl diphosphate (GGPP), which is diverted to the carotenoid pathway by phytoene synthase (PSY). In tomato (Solanum lycopersicum), 3 genes encode plastid-targeted GGPP synthases (SlG1 to 3) and 3 genes encode PSY isoforms (PSY1 to 3).Here we investigated the function of SlG1 by generating loss-of-function lines and combining their metabolic and physiological phenotypes with gene co-expression and co-immunoprecipitation analyses.Leaves and fruits ofslg1lines showed a wild-type phenotype in terms of isoprenoid accumulation, photosynthesis and development. Consistently,SlG1is co-expressed withPSY3and other genes involved in the production of carotenoids and SL (but not ABA) only in roots. SlG1 was also found to physically interact with the root-specific PSY3 isoform (and not with PSY1 and PSY2). Root SL (but not ABA) levels were reduced inslg1lines.Our results confirm a specific role of SlG1 in SL production in combination with PSY3. This role appears to be restricted to roots asslg1plants do not exhibit the shoot phenotype displayed by other SL-deficient mutants.

Cutin and suberin are lipid polyesters deposited in specific apoplastic compartments. Their fundamental roles in plant biology include controlling the movement of gases, water and solutes, and conferring pathogen resistance. Both cutin and suberin have been shown to be present in the Arabidopsis seed coat where they regulate seed dormancy and longevity. In this study, we use accelerated and natural ageing seed assays, glutathione redox potential measures, optical and transmission electron microscopy and gas chromatography-mass spectrometry to demonstrate that increasing the accumulation of lipid polyesters in the seed coat is the mechanism by which the AtHB25 transcription factor regulates seed permeability and longevity. Chromatin immunoprecipitation during seed maturation revealed that the lipid polyester biosynthetic gene long-chain acyl-CoA synthetase 2 (LACS2) is a direct AtHB25 binding target. Gene transfer of this transcription factor to wheat and tomato demonstrated the importance of apoplastic lipid polyesters for the maintenance of seed viability. Our work establishes AtHB25 as a trans-species regulator of seed longevity and has identified the deposition of apoplastic lipid barriers as a key parameter to improve seed longevity in multiple plant species.

[EN] Background and aims: Morphological and biochemical traits of four halophytes of the genus Limonium were analysed in plants sampled from salt marshes in SE Spain. This work aimed to explore the mechanism(s) behind the adaptation of these species to stressful habitats, with particular emphasis on responses to drought. Methods: Plants of each species together with soil samples were collected in summer, which is the most stressful season in the Mediterranean. Soil parameters and plant morphological traits were determined, and the levels of several biochemical stress markers in plants were measured using spectrophotometric assays. A multivariate analysis was performed to correlate soil and plant data. Results: Morphological characteristics regarding the underground system topology and several biochemical traits (higher foliar Ca2+, sucrose and glucose, and lower proline, glycine-betaine and fructose) clearly separate L. santapolense individuals from plants of the other three species. Conclusions: Drought tolerance of L. santapolense in the field is mostly dependent on morphological adaptations: when growing in an arid location, plants of this species develop long taproots that can extract water from the deep, moist layers of the soil., This research was partly supported by the project AICO/2017/039 from Generalitat Valenciana. We are indebted to Dr. Inmaculada Bautista (Universitat Politècnica de Valencia, Spain) for her useful suggestions for improving the manuscript.

Summary RNA interference (RNAi)‐based tools are used in multiple organisms to induce antiviral resistance through the sequence‐specific degradation of target RNAs by complementary small RNAs. In plants, highly specific antiviral RNAi‐based tools include artificial microRNAs (amiRNAs) and synthetic trans‐acting small interfering RNAs (syn‐tasiRNAs). syn‐tasiRNAs have emerged as a promising antiviral tool allowing for the multi‐targeting of viral RNAs through the simultaneous expression of several syn‐tasiRNAs from a single precursor. Here, we compared in tomato plants the effects of an amiRNA construct expressing a single amiRNA and a syn‐tasiRNA construct expressing four different syn‐tasiRNAs against Tomato spotted wilt virus (TSWV), an economically important pathogen affecting tomato crops worldwide. Most of the syn‐tasiRNA lines were resistant to TSWV, whereas the majority of the amiRNA lines were susceptible and accumulated viral progenies with mutations in the amiRNA target site. Only the two amiRNA lines with higher amiRNA accumulation were resistant, whereas resistance in syn‐tasiRNA lines was not exclusive of lines with high syn‐tasiRNA accumulation. Collectively, these results suggest that syn‐tasiRNAs induce enhanced antiviral resistance because of the combined silencing effect of each individual syn‐tasiRNA, which minimizes the possibility that the virus simultaneously mutates all different target sites to fully escape each syn‐tasiRNA., Significance Statement This work represents the successful application of syn‐tasiRNAs in a crop to induce high resistance against an economically important virus. Syn‐tasiRNAs outcompete amiRNAs in antiviral resistance: the possibility of co‐expressing multiple syn‐tasiRNAs from a single precursor allows for the simultaneous multi‐targeting of viral RNAs, which limits the ability of the virus to mutate target sites.

[EN] Viroids are naked RNAs that do not code for any known protein and yet are able to infect plants causing severe diseases. Because of their RNA nature, many studies have focused on the involvement of viroids in RNA-mediated gene silencing as being their pathogenesis mechanism. Here, the alterations caused by the Citrus exocortis viroid (CEVd) on the tomato translation machinery were studied as a new aspect of viroid pathogenesis. The presence of viroids in the ribosomal fractions of infected tomato plants was detected. More precisely, CEVd and its derived viroid small RNAs were found to co-sediment with tomato ribosomes in vivo, and to provoke changes in the global polysome profiles, particularly in the 40S ribosomal subunit accumulation. Additionally, the viroid caused alterations in ribosome biogenesis in the infected tomato plants, affecting the 18S rRNA maturation process. A higher expression level of the ribosomal stress mediator NAC082 was also detected in the CEVd-infected tomato leaves. Both the alterations in the rRNA processing and the induction of NAC082 correlate with the degree of viroid symptomatology. Taken together, these results suggest that CEVd is responsible for defective ribosome biogenesis in tomato, thereby interfering with the translation machinery and, therefore, causing ribosomal stress., Spanish Ministry of Science, Innovation and Universities [BIO2009-11818, BIO2015-70483-R to A.F.]; Spanish Ministry of Science, Innovation and Universities [BFU2009-11958]; Generalitat Valenciana (Valencia, Spain) [AICO/2017/048]; Natural Sciences and Engineering Research Council of Canada [155219-17 to J.-P.P.]; The RNA group is supported by a grant from the Universite de Sherbrooke; J.-P.P. holds the Research Chair of the Universite de Sherbrooke in RNA Structure and Genomics, and is a member of the Centre de Recherche du CHUS; B.B.-P. was a recipient of a VALi+d postdoctoral contract of the Generalitat Valenciana [APOSTD/2017/039]; Schleiff group is funded through the Deutsche Forschungsgemeinschaft [SFB 902]. Funding for open access charge: Spanish Ministry of Science, Innovation and Universities.

New strategies of control need to be developed with the aim of economic and environmental sustainability in plant and crop protection. Metabolomics is an excellent platform for both understanding the complex plant–pathogen interactions and unraveling new chemical control strategies. GC-MS-based metabolomics, along with a phytohormone analysis of a compatible and incompatible interaction between tomato plants and Fusarium oxysporum f. sp. lycopersici, revealed the specific volatile chemical composition and the plant signals associated with them. The susceptible tomato plants were characterized by the over-emission of methyl- and ethyl-salicylate as well as some fatty acid derivatives, along with an activation of salicylic acid and abscisic acid signaling. In contrast, terpenoids, benzenoids, and 2-ethylhexanoic acid were differentially emitted by plants undergoing an incompatible interaction, together with the activation of the jasmonic acid (JA) pathway. In accordance with this response, a higher expression of several genes participating in the biosynthesis of these volatiles, such as MTS1, TomloxC,TomloxD, and AOS, as well as JAZ7, a JA marker gene, was found to be induced by the fungus in these resistant plants. The characterized metabolome of the immune tomato plants could lead to the development of new resistance inducers against Fusarium wilt treatment.

This article belongs to the Section Molecular Plant Sciences., Infectious viroid clones consist of dimeric cDNAs used to generate transcripts which mimic the longer-than-unit replication intermediates. These transcripts can be either generated in vitro or produced in vivo by agro-inoculation. We have designed a new plasmid, which allows both inoculation methods, and we have compared them by infecting Solanum lycopersicum and Solanum melongena with clones of Citrus exocortis virod (CEVd), Tomato chlorotic dwarf viroid (TCDVd), and Potato spindle tuber viroid (PSTVd). Our results showed more uniform and severe symptoms in agro-inoculated plants. Viroid accumulation and the proportion of circular and linear forms were different depending on the host and the inoculation method and did not correlate with the symptoms, which correlated with an increase in PR1 induction, accumulation of the defensive signal molecules salicylic (SA) and gentisic (GA) acids, and ribosomal stress in tomato plants. The alteration in ribosome biogenesis was evidenced by both the upregulation of the tomato ribosomal stress marker SlNAC082 and the impairment in 18S rRNA processing, pointing out ribosomal stress as a novel signature of the pathogenesis of nuclear-replicating viroids. In conclusion, this updated binary vector has turned out to be an efficient and reproducible method that will facilitate the studies of viroid–host interactions., This work was supported by the Spanish Ministry of Economy and Competitiveness (co-supported by FEDER) Grants BIO2017-88321-R (V.P.) and PID2019-104126RB-I00 (G.G.).

[EN] Higher education is continuously evolving to keep up with the challenges posed by the introduction of information and communication technologies (ICT) to education. In this sense, distance learning is booming, with an increasing number of higher education students taking advantage of the flexibility remote learning provides. The School of Agricultural Engineering and Environment (ETSIAMN) of Universitat Politècnica de València (UPV) has been gradually incorporating ICT tools in its bachelor and master degrees for the last two decades. As a result, many college students and university instructors are familiar with ICT techniques. However, the unprecedented COVID-19 crisis has put distance learning in the spotlight like never before, forcing students, faculty, and staff to adapt to the new situation with hardly any preparation time. For that reason, it is convenient to analyse in depth the results and impact of the teaching and evaluation methodologies developed and applied during this critical period, as a way to detect and amend potential inefficiencies in the learning process. The specific goal of this study was to analyse the teaching period during the COVID-19 crisis in ETSIAMN, which covered the spring semester of the academic year 2019-2020. To this purpose, 114 instructors and 274 students were surveyed in July 2020, belonging to four bachelor degrees (agricultural and biological engineering; forestry engineering; food engineering; and biotechnology), and three master degrees (agricultural and biological engineering; forestry engineering, and oenology). Regarding the experimental design for the survey, three main blocks were identified: the first block corresponds to teaching methodologies, comparing students and faculty preferences for distance lecturing; the second block focuses on evaluation modalities and exam configurations; and the final block centers on the difficulties found by both students and lecturers along the adaptation process from conventional to distance teaching. Results showed that instructors and students preferred a combination of live streaming with recorded lectures, being multiple choice the favourite examination type, although many students rated first a project-based evaluation. Overall, students rejected tests with no possibilities to go back on already answered questions, and instructors mostly preferred limiting the time to complete the on-line tests. The lack of motivation was the main barrier encountered by students to achieve an effective learning. Finally, a set of counterweighting measures to improve and promote the successful implementation of distance learning in engineering colleges is proposed.

[ES] Los consumidores son conscientes del peligro derivado del uso de antioxidantes y antimicrobianos sintéticos en la industria agroalimentaria, demandando alternativas más seguras y ecológicas. En este estudio, se ha determinado la actividad antioxidante de aceites esenciales comerciales mediante el método DPPH y su efecto antimicrobiano frente a la bacteria Pseudomonas syringae y el hongo fitopatógeno Fusarium oxysporum a través del empleo del método estandarizado de disco. Los aceites esenciales de clavo, ajedrea, canela y orégano, así como carvacrol, mostraron la máxima actividad antioxidante, comparable a antioxidantes establecidos. El aceite esencial de gaulteria fue el más potente inhibidor del crecimiento de P. syringae en las dosis más altas (20 y 10 µL) ensayadas. El aceite esencial de orégano, así como su componente principal carvacrol, detuvieron el crecimiento de la bacteria incluso a la dosis más baja ensayada (1 µL). Los aceites esenciales de canela, orégano y menta inhibieron el desarrollo de F. oxysporum en todas las dosis (20, 10 y 5 µL) aplicadas. En general, la mayoría de aceites esenciales mostraron más actividad antifúngica que antibacteriana y antioxidante., [EN] Consumers are aware of the dangers arising from the use of synthetic antioxidants and antimicrobials in the agrifood industry, demanding safer and "greener" alternatives. In this study, the antioxidant activity of commercial essential oils through DPPH method, their antimicrobial effects against the bacterium Pseudomonas syringae and the phytopathogenic fungus Fusarium oxysporum by means of the standardized disk method were determined. Clove along with winter savory, cinnamon and oregano essential oils as well as carvacrol showed the highest antioxidant activity comparable to reference standards. Wintergreen essential oil was the most potent inhibitor against P. syringae growth at the highest doses (20 and 10 µL). Oregano essential oil and its main component carvacrol were able to stop the bacterium growth even at the lowest treatment (1 µL). Cinnamon, oregano and peppermint essential oils inhibited F. oxysporum development at all doses (20, 10 and 5 µL) assayed. In general, most of the essential oils displayed more antifungal than antibacterial and antioxidant activities.

© 2020 by the authors., Citrus exocortis viroid (CEVd) is known to cause different symptoms in citrus trees, and its mechanism of infection has been studied in tomato as an experimental host, producing ribosomal stress on these plants. Some of the symptoms caused by CEVd in tomato plants resemble those produced by the phytohormone ethylene. The present study is focused on elucidating the relationship between CEVd infection and ethylene on disease development. To this purpose, the ethylene insensitive Never ripe (Nr) tomato mutants were infected with CEVd, and several aspects such as susceptibility to infection, defensive response, ethylene biosynthesis and ribosomal stress were studied. Phenotypic characterization revealed higher susceptibility to CEVd in these mutants, which correlated with higher expression levels of both defense and ethylene biosynthesis genes, as well as the ribosomal stress marker SlNAC082. In addition, Northern blotting revealed compromised ribosome biogenesis in all CEVd infected plants, particularly in Nr mutants. Our results indicate a higher ethylene biosynthesis in Nr mutants and suggest an important role of this phytohormone in disease development and ribosomal stress caused by viroid infection.

[EN] Background: Secondary metabolites play an important role in the plant defensive response. They are produced as a defence mechanism against biotic stress by providing plants with antimicrobial and antioxidant weapons. In higher plants, the majority of secondary metabolites accumulate as glycoconjugates. Glycosylation is one of the commonest modifications of secondary metabolites, and is carried out by enzymes called glycosyltransferases. Results: Here we provide evidence that the previously described tomato wound and pathogen-induced glycosyltransferase Twi1 displays in vitro activity toward the coumarins scopoletin, umbelliferone and esculetin, and the flavonoids quercetin and kaempferol, by uncovering a new role of this gene in plant glycosylation. To test its activity in vivo, Twi1-silenced transgenic tomato plants were generated and infected with Tomato spotted wilt virus. The Twi1- silenced plants showed a differential accumulation of Twi1 substrates and enhanced susceptibility to the virus. Conclusions: Biochemical in vitro assays and transgenic plants generation proved to be useful strategies to assign a role of tomato Twi1 in the plant defence response. Twi1 glycosyltransferase showed to regulate quercetin and kaempferol levels in tomato plants, affecting plant resistance to viral infection., This work was supported by grant BIO2012-33419 from the Direccion General de Programas y Transferencia de Conocimiento, Spanish Ministry of Science and Innovation, and grant AICO/2017/048 from the Valencian Local Government (Generalitat Valenciana, Spain). LC was supported by a predoctoral fellowship (ACIF/2010/231) from the Valencian Local Government (Generalitat Valenciana, Spain). None of the funding bodies was involved in the design of the study, the collection, analysis, and interpretation of the data, nor in the writing of the manuscript, which was made entirely by the authors.

© The Author(s)., Benzothiadiazole (BTH) is a functional analogue of the phytohormone salycilic acid (SA) involved in the plant immune response. NahG tomato plants are unable to accumulate SA, which makes them hypersusceptible to several pathogens. Treatments with BTH increase the resistance to bacterial, fungal, viroid, or viral infections. In this study, metabolic alterations in BTH-treated Money Maker and NahG tomato plants infected by citrus exocortis viroid (CEVd) were investigated by nuclear magnetic resonance spectroscopy. Using multivariate data analysis, we have identified defence metabolites induced after viroid infection and BTH-treatment. Glycosylated phenolic compounds include gentisic and ferulic acid accumulated in CEVd-infected tomato plants, as well as phenylalanine, tyrosine, aspartate, glutamate, and asparagine. Besides, an increase of γ-aminobutyric acid (GABA), glutamine, adenosine, and trigonelline, contributed to a clear discrimination between the metabolome of BTH-treated tomato leaves and their corresponding controls. Among them, GABA was the only metabolite significantly accumulated in both genotypes after the chemical treatment. In view of these results, the addition of GABA was performed on tomato plants infected by CEVd, and a reversion of the NahG hypersusceptibility to CEVd was observed, indicating that GABA could regulate the resistance to CEVd induced by BTH., This research was funded by Dirección General de Programas y Transferencia de Conocimiento, from the Spanish Ministry of Science and Innovation, Grant BIO2012-33419. MP. López-Gresa was the recipient of a postdoctoral fellowship JC2008-00432 Spanish Ministry of Science and Innovation.

© 2020 by the authors., Agronomy solutions for modifying pre-harvest grape ripening are needed for a more sustainable viticulture. Field experiments were performed in Vitis vinifera L. vines to study the effect of the previously described stomata-closing compound (Z)-3-hexenyl butyrate (HB). Exogenous treatments at different doses were periodically carried out using a randomized block design. Firstly, we observed that HB was able to induce stomatal closure in grapevine plants. Under field conditions, the application of HB around veraison induced a higher color intensity in berries, and vines treated at higher doses reached this stage earlier than the un-treated controls. There was also a clear increase in both grape anthocyanin concentration and total soluble solids without having a negative impact on total yield. We therefore, confirm the role of HB as a universal natural stomatal closure compound and propose a new use for HB in viticulture as a ripening inducer, by accelerating anthocyanin accumulation., This research was funded by Grant INNVAL10/18/005 from the Agència Valenciana de la Innovació (Spain). C.P. was a recipient of a predoctoral contract of the Generalitat Valenciana (ACIF/2019/187). D.S.I. is supported by AEI-FEDER grant AGL2017-83738-C3-3-R.

The authors acknowledge funding by MINECO BIO2015-70483-R to AF, by CAM S2013/ABI-2734 and by ERC GA260468 to MMC, by the Deutsche Forschungsgemeinschaft (DFG, grant TRR175-C05) to DL, by NSF IOS 1444561 and NSF IOS PAPM-EAGER 1650139 to AS, and by Bio4Energy, a Strategic Research Environment appointed by the Swedish government to JH.

[EN] Volatile organic compounds (VOCs) emitted by plants are secondary metabolites that mediate the plant interaction with pathogens and herbivores. These compounds may perform direct defensive functions, i. e., acting as antioxidant, antibacterial, or antifungal agents, or indirectly by signaling the activation of the plant's defensive responses. Using a non-targeted GC-MS metabolomics approach, we identified the profile of the VOCs associated with the differential immune response of the Rio Grande tomato leaves infected with either virulent or avirulent strains of Pseudomonas syringae DC3000 pv. tomato. The VOC profile of the tomato leaves infected with avirulent bacteria is characterized by esters of (Z)-3-hexenol with acetic, propionic, isobutyric or butyric acids, and several hydroxylated monoterpenes, e. g., linalool, a -terpineol, and 4-terpineol, which defines the profile of an immunized plant response. In contrast, the same tomato cultivar infected with the virulent bacteria strain produced a VOC profile characterized by monoterpenes and SA derivatives. Interestingly, the differential VOCs emission correlated statistically with the induction of the genes involved in their biosynthetic pathway. Our results extend plant defense system knowledge and suggest the possibility for generating plants engineered to over-produce these VOCs as a complementary strategy for resistance., This work was funded by Grant BIO2012-33419 from the Spanish Ministry of Economy and Competitiveness.

Capítulo 10., Many hypotheses have been advanced to explain how viroid infection might alter host gene expression to produce the symptoms seen on diseased plants. Only recently, however, has a series of technological advances allowed these hypotheses to be tested experimentally. The first section of this chapter describes changes in the host proteome following viroid infection. Next, we describe changes at the transcriptional level as measured by microarray analysis and other genomics-based approaches and evidence for both pre- and posttranscriptional regulation. Interactions between proteins and nucleic acids result in formation of molecular networks, and identification of these “interactomes” allows integration of results obtained by transcriptomic and proteomic approaches. The final section describes interactions between viroids and several host proteins, outlining possible directions for future systems-based research.

[EN] We describe the efficacy of Bacillus subtilis strain IAB/BS03 in reducing disease incidence of B. subtilis IAB/BS03 as a foliar treatment against Botrytis cinerea and Pseudomonas syringae on greenhouse-grown tomato (Solanum lycopersicon) plants. We also tested the effect of foliar treatments on lettuce (Lactuca sativa) against lettuce downy mildew caused by Bremia lactucae in multiple trials under different field conditions. All the assays indicated that B. subtilis IAB/BS03 reduced disease. To ascertain the mechanism of action, the induction of pathogenesis-related (PR) proteins, the accumulation of salicylic acid and the activation of peroxidase caused by foliar or root treatments with B. subtilis IAB/BS03 were studied in tomato. A salicylic acid-independent induction of the antifungal protein PR1 was observed after treatment with B. subtilis IAB/BS03, with the strongest induction due to root treatment compared with foliar application. A metabolic analysis of B. subtilis IAB/BS03 culture broth using Ultra Performance Liquid Chromatography coupled with ultraviolet and mass spectrometric detection determined surfactin and iturin A isomers. These compounds have been described as antifungal and antibiotic lipopeptides. The results indicated that B. subtilis IAB/BS03 could be effectively used as a biocontrol agent., This work was funded by IAB S. L. (Investigaciones y Aplicaciones Biotecnologicas, S. L.), and by grant BIO2012-33419 from the Spanish Ministry of Economy and Competitiveness. Mayte Castellano was the recipient of a research grant also funded by IAB S. L. The authors would like to thank Cristina Torres (IBMCP, UPV-CSIC) for her excellent technical assistance.

[EN] Tomato plants expressing the NahG transgene, which prevents accumulation of endogenous salicylic acid (SA), were used to study the importance of the SA signalling pathway in basal defence against Citrus Exocortis Viroid (CEVd) or Tomato Spotted Wilt Virus (TSWV). The lack of SA accumulation in the CEVd- or TSWV-infected NahG tomato plants led to an early and dramatic disease phenotype, as compared to that observed in the corresponding parental Money Maker. Addition of acibenzolar-S-methyl, a benzothiadiazole (BTH), which activates the systemic acquired resistance pathway downstream of SA signalling, improves resistance of NahG tomato plants to CEVd and TSWV. CEVd and TSWV inoculation induced the accumulation of the hydroxycinnamic amides p-coumaroyltyramine, feruloyltyramine, caffeoylputrescine, and feruloylputrescine, and the defence related proteins PR1 and P23 in NahG plants earlier and with more intensity than in Money Maker plants, indicating that SA is not essential for the induction of these plant defence metabolites and proteins. In addition, NahG plants produced very high levels of ethylene upon CEVd or TSWV infection when compared with infected Money Maker plants, indicating that the absence of SA produced additional effects on other metabolic pathways. This is the first report to show that SA is an important component of basal resistance of tomato plants to both CEVd and TSWV, indicating that SA-dependent defence mechanisms play a key role in limiting the severity of symptoms in CEVd- and TSWV-infected NahG tomato plants., This work was supported by grant BIO2012-33419 from the Spanish Ministry of Economy and Competitiveness received by JMB. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

[EN] The importance of salicylic acid (SA) in the signal transduction pathway of plant disease resistance has been well documented in many incompatible plant-pathogen interactions, but less is known about signalling in compatible interactions. In this type of interaction, tomato plants have been found to accumulate high levels of 2,5-dihydroxybenzoic acid (gentisic acid, GA), a metabolic derivative of SA. Exogenous GA treatments induce in tomato plants a set of PR proteins that differ from those induced by salicylic acid. While SA accumulates in tomato plants mainly as 2-O-beta-D-glucoside, GA has only been found as 5-O-beta-D-xyloside. To characterize this step of the GA signalling pathway further, the present work focuses on the study of the GA-conjugating activity in tomato plants. A gentisate glycosyltransferase (GAGT) cDNA has been isolated and overexpressed in Pichia pastoris, and GA-conjugating activity was confirmed by detecting the xylosylated GA. The purified plant protein is highly specific for GA, showing no activity toward many other phenolic compounds, including SA. In addition, it shows an outstanding selectivity for UDP-xylose as the sugar donor, which differentiates this enzyme from most glycosyltransferases. Both the GA-conjugating activity and the corresponding mRNA show a strong, rapid, and transient induction upon treatment of tomato plants with GA or SA. Furthermore, its expression is rapidly induced by compatible infections. However, neither the gene nor the activity seems to respond to incompatible infections or wounding. The unique properties of this new glycosyltransferase suggest a specific role in regulating the free GA levels in compatible plant-pathogen interactions., This work has been supported by the Spanish Ministry of Science and Innovation (grant numbers BMC2003-07837 and BFU2006-11546).

Proteinaceous aspartic proteinase inhibitors are rare in nature and are described in only a few plant species. One of them corresponds to a family of cathepsin D inhibitors (CDIs) described in potato (Solanum tuberosum), involving up to 15 isoforms with a high sequence similarity. In this work, we describe a tomato (Solanum lycopersicum) wound-inducible protein called jasmonic-induced protein 21 (JIP21). Sequence analysis of its cDNA predicted a putative function as a CDI. The JIP21 gene, whose protein has been demonstrated to be glycosylated, is constitutively expressed in flowers, stem, and fruit, and is inducible to high levels by wounding and methyl jasmonate in leaves of tomato plants. The genomic sequence of JIP21 shows that the gene is intronless and reveals the presence of both a methyl jasmonate box (TGACT) and a G-box (CACGT) in the promoter. In contrast to the presumed role of JIP21 based on sequence analysis, a detailed biochemical characterization of the purified protein uncovers a different function as a strong chymotrypsin inhibitor, which questions the previously predicted inhibitory activity against aspartic proteinases. Moreover, Egyptian cotton worm (Spodoptera littoralis) larvae fed on transgenic tomato plants overexpressing JIP21 present an increase in mortality and a delay in growth when compared with larvae fed on wild-type plants. These larvae belong to the Lepidoptera family whose main digestive enzymes have been described as being Ser proteases. All these results support the notion that tomato JIP21 should be considered as a chymotrypsin inhibitor belonging to the Ser proteinase inhibitors rather than a CDI. Therefore, we propose to name this protein tomato chymotrypsin inhibitor 21 (TCI21).

[EN] Hydroxycinnamic acid amides (HCAA) are secondary metabolites involved in plant development and defense that have been widely reported throughout the plant kingdom. These phenolics show antioxidant, antiviral, antibacterial, and antifungal activities. Hydroxycinnamoyl-CoA: tyramine N-hydroxycinnamoyl transferase (THT) is the key enzyme in HCAA synthesis and is induced in response to pathogen infection, wounding, or elicitor treatments, preceding HCAA accumulation. We have engineered transgenic tomato plants overexpressing tomato THT. These plants displayed an enhanced THT gene expression in leaves as compared with wild type (WT) plants. Consequently, leaves of THT-over-expressing plants showed a higher constitutive accumulation of the amide coumaroyltyramine (CT). Similar results were found in flowers and fruits. Moreover, feruloyltyramine (FT) also accumulated in these tissues, being present at higher levels in transgenic plants. Accumulation of CT, FT and octopamine, and noradrenaline HCAA in response to Pseudomonas syringae pv. tomato infection was higher in transgenic plants than in the WT plants. Transgenic plants showed an enhanced resistance to the bacterial infection. In addition, this HCAA accumulation was accompanied by an increase in salicylic acid levels and pathogenesis-related gene induction. Taken together, these results suggest that HCAA may play an important role in the defense of tomato plants against P. syringae infection., The authors are grateful to C. Torres, A. Sauri, and T. Caballero for technical support. We also thank C. Gomez-Mena for her assistance in tomato flower sampling. This work was supported by Grant BIO2012-33419 from the Direccion General de Programas y Transferencia de Conocimiento, from the Spanish Ministry of Science and Innovation. L. Campos was the recipient of a predoctoral fellowship ACIF/2010/231 from Generalitat Valenciana (Spain). The work presented here was carried out in collaboration between all authors. J. M. Belles defined the research theme. L. Campos, L. Zacares and M. P. Lopez-Gresa carried out the laboratory experiments. P. Lison and I. Rodrigo contributed to the experimental design and the interpretation of the data. L. Campos drafted the article. M. P. Lopez-Gresa, P. Lison and I. Rodrigo participated in revising it critically for important intellectual content. J. M. Belles and V. Conejero gave the final approval of the version to be published. Each author has participated sufficiently in the work to take public responsibility for the content.

[EN] We have observed that treatments with salicylic acid (SA) or gentisic acid (GA) induced resistance to RNA pathogens such as ToMV and CEVd in tomato and Gynura auriantiaca, respectively. Accumulation of SA and GA has been found to occur in plants infected by these pathogens, thus pointing out a possible defence role of both molecules. To study the molecular basis of the observed induced resistance to RNA pathogens the induction of silencing-related genes by SA and GA was considered. For that purpose, we searched for tomato genes which were orthologous to those described in Arabidopsis thaliana, such as AtDCL1, AtDCL2, AtDCL4, AtRDR1, AtRDR2 and AtRDR6, and we tracked their induction in tomato along virus and viroid infections. We observed that CEVd significantly induced all these genes in tomato, with the exception of ToRDR6, being the induction of ToDCL4 the most outstanding. Regarding the ToMV asymptomatic infection, with the exception of ToRDR2, we observed a significant induction of all the indicated silencing-related genes, being ToDCL2 the most induced gene. Subsequently, we analyzed their transcriptional activation by SA and at the time when ToMV was inoculated on plants. ToDCL2, ToRDR1 and ToRDR2 were significantly induced by both SA and GA, whereas ToDCL1 was only induced by SA. Such an induction resulted more effective by SA treatment, which is in agreement with the stronger SAinduced resistance observed. Our results suggest that the observed delay in the RNA pathogen accumulation could be due to the pre-induction of RNA silencing-related genes by SA or GA. 2014 Elsevier Masson SAS. All rights reserved, The authors are grateful to Cristina Torres and Asuncion Sauri for technical support. This work was supported by Grant BFU2009-11958 from Direccion General de Programas y Transferencia de Conocimiento, from Spanish Ministry of Science and Innovation, and Grants PAID-06-08-3295 and SP20120576 from Universitat Politecnica de Valencia (UPV). Laura Campos was the recipient of a predoctoral fellowship ACIF/2010/231 from Generalitat Valenciana (Spain). Ma Pilar Lopez Gresa held a postdoctoral fellowship JAE-Doc_08_00402 from the Consejo Superior de Investigaciones Cientificas (Spain).

A proteomic analysis of buds from mandarin trees with contrasting fruit load (on- and off-crop trees) was carried out during the onset of low-temperature induction. The aim of the study was to find out more about the molecular mechanism relating to alternate bearing in Citrus and its relationship with flowering. The 'Moncada' variety (Clementine 'Oroval' x 'Kara' mandarin), displaying remarkable behaviour in alternate production, was used in this study. From 2D DICE gel, 192 spots were isolated: 97 showed increased expression in the off-crop buds as compared to the on-crop buds, while 95 exhibited enhanced expression in the on-crop buds versus the off-crop buds. These spots were identified by MALDI-MS or LC -MS-MS. The largest groups of proteins up-expressed in the off-crop buds were the proteins involved in carbohydrate and amino acid metabolism, and the proteins expressed in response to stimuli such as reactive oxygen species. The largest groups of proteins up-expressed in the on-crop buds were related to primary metabolism, oxidative stress and defence responses. Depending on their function, some of these proteins can stimulate the flowering, such as fructose-bisphosphate aldolase or leucine-rich repeat transmembrane protein kinase, while others can inhibit it, such as cytochrome c oxidase subunit II. Twenty-two other proteins with unknown functions were up-expressed in the on- or off-crop buds. (C) 2013 Elsevier Masson SAS. All rights reserved., M.C. Gonzalez-Mas was the recipient of a contract by the Fundacion AgroAlimed (Conselleria d'Agricultura, Pesca i Alimentacio, Generalitat Valenciana). This work has been supported by grants from the Instituto Nacional de Investigaciones Agrarias, Spain (RTA2009-00147, RTA2011-00114-00-00). The DIGE were performed by the Proteomic Service of the Instituto de Biologia Molecular y Celular de Plantas (UPV-Valencia). Mass analyses were carried out in the Proteomic Laboratory of CIPF (a ProteoRed_ISCIII member; the Spanish Proteomics Network); special thanks are due to Dr. L. Valero and E. Dionis for assistance and advice on mass analyses.

Viroids are single-stranded, circular, noncoding RNAs that infect plants, causing devastating diseases. In this work, we employed 2D DIGE, followed by MS identification, to analyze the response of tomato plants infected by Citrus exocortis viroid (CEVd). Among the differentially expressed proteins detected, 45 were successfully identified and classified into different functional categories. Validation results by RT-PCR allowed us to classify the proteins into two expression groups. First group included genes with changes at the transcriptional level upon CEVd infection, such as an endochitinase, a β-glucanase, and pathogenesis-related proteins, PR10 and P69G. All these defense proteins were also induced by gentisic acid, a pathogen-induced signal in compatible interactions. The second group of proteins showed no changes at the transcriptional level and included several ribosomal proteins and translation factors, such as the elongation factors 1 and 2 and the translation initiation factor 5-alpha. These results were validated by 2D Western blot, and possible PTMs caused by CEVd infection were detected. Moreover, an interaction between eukaryotic elongation factor 1 and CEVd was observed by 2D Northwestern. The present study provides new protein-related information on the mechanisms of plant resistance to pathogens., We would like to thank the Proteomic Service of the IBMCP (Instituto de Biologia Molecular y Celular de Plantas, Valencia, Spain) for the technical assistance. We also thank Dr. Alejandro Ferrando (Instituto de Biologia Molecular y Celular de Plantas UPV-CSIC) for critical reading of the manuscript, discussions, and for kindly providing us with the eIF5A antisera. We are also grateful to Dr. Brenda Hunter (University of Arizona) for both eEF1A and eEF2 antiserum. This work was supported by Grant BFU2009-11958 from Direccion General de Programas y Transferencia de Conocimiento, from Spanish Ministry of Science and Innovation. Laura Campos was the recipient of a predoctoral fellowship ACIF/2010/231 from Generalitat Valenciana (Spain). M. Pilar Lopez-Gresa held a postdoctoral fellowship JAEDoc_08_ 00402 from the Consejo Superior de Investigaciones Cientificas (Spain).

[EN] 1H nuclear magnetic resonance (NMR)-based metabolomics has been applied to study the compatible interaction between tomato plants and Tomato Mosaic Virus (ToMV). A detailed time course of metabolic fingerprinting of ToMV-inoculated and non-inoculated systemically infected tomato leaves has provided a fundamental understanding of the metabolic state of the plant not only in response to ToMV infection, but also under various physiological conditions. By this analytical platform a total of 32 metabolites including amino/organic acids, sugars, phenylpropanoids, flavonoids and other miscellaneous compounds were detected. Using multivariate data analysis, we have identified a subset of metabolites induced during the plant defence response and metabolites whose accumulation was dependent on the developmental stage, the position of the leaf on the stem, and the harvesting time. Specifically, a general time-dependent decrease in organic acids, amino acids (excluding asparagine), phenylpropanoids and rutin was observed in individual leaves. In addition, metabolite alterations were also found to correlate with the developmental stage of the leaf: high levels of organic acids, some amino acids, phenylpropanoids, and flavonoids were found in lower leaves while elevated amounts of sugars were present in the upper ones. Moreover, a marked variation in the content of some metabolites was also observed to be associated to the asymptomatic ToMV infection both in inoculated and systemically infected leaves. While flavonoids accumulated in virus-inoculated leaves, increased levels of phenylpropanoids were observed in non-inoculated leaves where ToMV actively replicates. Finally, diurnal changes in the metabolite content were also observed: an increase of amino acids and organic acids (except glutamic acid) were observed in the samples collected in the morning, whereas sugars and secondary metabolite levels increased in the tomato leaves harvested in the evening, The authors are grateful to Cristina Torres Vidal for technical support and Dr. Lynne Yenush for critical reading of the manuscript and exciting intellectual discussions. This work was supported by Grant BFU 2009-11958 from Secretaria de Estado de Investigacion from Spanish Ministry of Science and Innovation. M.P.L.G held a postdoctoral fellowship JAEDoc 08 00402 from the Consejo Superior de Investigaciones Cientificas (Spain) and was recipient of a postdoctoral fellowship (BEST/2010/111) from Generalitat Valencia (Spain).

[EN] In the present work, we aimed to define the chemical nature of the phenylpropanoids induced during the interaction of the tomato plant. cultivar Rutgers, with the bacterial pathogen Pseudomonas syringae pv. tomato. Using LC-MS and NMR spectroscopy, we determined the chemical structures of this class of metabolites, which accumulated in response to exposure to the pathogen. A rapid accumulation of phytoalexin hydroxycinnamic acid amides (HCAA) of noradrenaline (cis/trans N-p-coumaroylnoradrenaline and cis/trans N-feruloylnoradrenline) and octopamine (cis/trans N-p-coumaroyloctopamine and cis/trans N-feruloyloctopamine), chlorogenic acid (CGA), and the flavonoid rutin was detected after bacterial infiltration. Among them, cis N-p-coumaroylnoradrenaline, cis N-p-coumaroyloctopamine, and isomers cis/trans of N-feruloylnoradrenaline have never been described in the literature. Moreover, cis/trans isomers of N-feruloyloctopamine are identified for the first time as being associated with the tomato/P. syringae interaction. Inhibition of the P. syringae-induced ethylene by 2-aminoethoxyvinylglycine, markedly impaired the accumulation of HCAA in inoculated tomato leaves, but it had no effect on CGA or rutin synthesis. On the other hand, the lack of accumulation of SA in NahG transgenic tomato plants, overexpressing a bacterial salicylic hydroxylase, did not prevent the enhancing of HCAA produced by P. syringae infection. Taken together, our results indicate that ethylene, but not SA, is essential for the synthesis of HCAA in response to bacterial infection of tomato leaves. Antibiotic activities of the induced metabolites were also studied. CGA induced a notable expression of the defence-related genes PR1 and P23. Moreover, trans-HCAA of noradrenaline and octopamine showed a potent free radical scavenging competence. In particular, trans N-feruloylnoradrenaline presented a very outstanding antioxidant activity, thus indicating that these compounds may play a role in the defence response of tomato plants against bacterial infection. (C) 2011 Elsevier B.V. All rights reserved., The authors want to thank Dr. Lynne Yenush for critical reading of the manuscript and exciting intellectual discussions. Dominique Melck, Estrella Mateos (ICB and ITQ NMR Service) for recording NMR spectra and Letizia Ciavatta for interpretation of the 600-MHz NMR spectra. This work was supported by Grant BFU2006-11546 from Direccion General de Programas y Transferencia de Conocimiento, from Spanish Ministry of Science and Innovation. M.P.L.G. was the recipient of a postdoctoral fellowship APOSTD/2007/128 from Generalitat Valencia (Spain).

SummaryIn Arabidopsis, the flagellin-derived peptide flg22 elevates antibacterial resistance [1] and inhibits growth [2] upon perception via the leucine-rich repeat receptor-like kinase Flagellin-Sensitive 2 (FLS2) [3]. DELLA proteins are plant growth repressors whose degradation is promoted by the phytohormone gibberellin [4]. Here, we show that DELLA stabilization contributes to flg22-induced growth inhibition. In addition, we show that DELLAs promote susceptibility to virulent biotrophs and resistance to necrotrophs, partly by altering the relative strength of salicylic acid and jasmonic acid (JA) signaling. A quadruple-DELLA mutant (which lacks four out of the five Arabidopsis DELLA proteins [5]) was partially insensitive to gene induction by Methyl-Jasmonate (MeJA), whereas the constitutively active dominant DELLA mutant gai [6] was sensitized for JA-responsive gene induction, implicating DELLAs in JA-signaling and/or perception. Accordingly, the elevated resistance of gai to the necrotrophic fungus Alternaria brassicicola and susceptibility to the hemibiotroph Pseudomonas syringae pv. tomato strain DC3000 (Pto DC3000) was attenuated in the JA-insensitive coi1-16 mutant [7]. These findings suggest an explanation for why the necrotrophic fungus Gibberella fujikuroi, causal agent of the foolish-seedling disease of rice, makes gibberellin.