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SUMMARYCrops often have to face several abiotic stresses simultaneously, and under these conditions, the plant’s response significantly differs from that observed under a single stress. Nevertheless, most of the molecular markers identified for increasing plant stress tolerance have been characterized under single abiotic stresses, explaining their unexpected results when they are tested under real field conditions. One important regulator of the plant’s responses to abiotic stresses is ABA. The ABA signaling system engages many stress-responsive genes, however, many others do not respond to ABA treatments. Thus, the ABA-independent pathway, which is still largely unknown, involve multiple signaling pathways and important molecular components necessary for the plant’s adaptation to climate change.In the present study, tomato ABA-deficient mutants (flacca, flc) were subjected to salinity, heat, or their combination. A deep RNA-seq analysis revealed that the combination of salinity and heat induced an important reprogramming of the tomato transcriptome, and from the 685 genes that were specifically regulated under this combination in our flc mutants, 463 genes were regulated by ABA-independent systems. Among these genes, we identified 6 transcription factors (TFs) belonging to the R2R3MYB family that were significantly upregulated. A protein-protein interaction network showed that the TFs SlMYB50 and SlMYB86 were directly involved in the upregulation of the flavonol biosynthetic pathway-related genes. This is the first time that some important ABA-independent TFs involved in the specific plant response to abiotic stress combination have been identified. Considering that ABA levels dramatically change in response to environmental factors, the study of ABA-independent genes that are specifically regulated under stress combination may provide a marvelous tool for increasing plant resilience to climate change.SIGNIFICANCE STATEMENTThis study in tomato Wt and ABA-deficient mutant plants reveals a specific and unique ABA-independent transcriptome reprogramming under abiotic stress combination, with the identification of some key TFs that were induced under these specific conditions. Taking into account that ABA levels dramatically change in all crops in response to environmental factors, the study of ABA-independent genes that are specifically regulated under stress combination may provide a marvelous tool for increasing plant resilience to climate change.

During the last years, a great effort has been dedicated at the development and employment of diverse approaches for achieving more stress-tolerant and climate-flexible crops and sustainable yield increases to meet the food and energy demands of the future. The ongoing climate change is in fact leading to more frequent extreme events with a negative impact on food production, such as increased temperatures, drought, soil salinization as well as invasive arthropod pests and diseases. In this review, diverse "green strategies" (e.g., chemical priming, root-associated microorganisms), and advanced technologies (e.g., genome editing, high-throughput phenotyping) are described on the basis of the most recent research evidence. Particularly, attention has been focused on the potential use in a context of sustainable and climate-smart agriculture (the so called "next agriculture generation") to improve plant tolerance and resilience to abiotic and biotic stresses. In addition, the gap between the results obtained in controlled experiments and those from application of these technologies in real field conditions (lab to field step) is also discussed. This article is protected by copyright. All rights reserved.

La citricultura actual esta amenacada pel canvi climatic. L’increment de les temperatures, junt amb l’aparicio d’altres fenomens climatics adversos, modifica les condicions ambientals de les regions on s’han desenvolupat les varietats citricoles actuals. Els efectes perjudicials sobre la fisiologia i produccio dels citrics que tenen aquests factors ambientals adversos, com la sequera o la salinitat del sol, s’incrementaran a causa de les altes temperatures, la qual cosa posara en risc la produccio del cultiu i, en casos extrems, fins i tot la supervivencia de les plantes. L’estudi de les respostes de tolerancia dels citrics al canvi climatic pot mostrar-nos les claus per a desenvolupar noves varietats de citrics capacos de resistir les futures condicions ambientals i mantenir la produccio.

Arabidopsis (Arabidopsis thaliana) defenses against herbivores are regulated by the jasmonate (JA) hormonal signaling pathway, which leads to the production of a plethora of defense compounds. Arabidopsis defense compounds include tryptophan-derived metabolites, which limit Arabidopsis infestation by the generalist herbivore two-spotted spider mite, Tetranychus urticae. However, the phytochemicals responsible for Arabidopsis protection against T. urticae are unknown. Here, we used Arabidopsis mutants disrupted in the synthesis of tryptophan-derived secondary metabolites to identify phytochemicals involved in the defense against T. urticae. We show that of the three tryptophan-dependent pathways found in Arabidopsis, the indole glucosinolate (IG) pathway is necessary and sufficient to assure tryptophan-mediated defense against T. urticae. We demonstrate that all three IGs can limit T. urticae herbivory, but that they must be processed by myrosinases to hinder T. urticae oviposition. Putative IG breakdown products were detected in mite-infested leaves, suggesting in planta processing by myrosinases. Finally, we demonstrate that besides IGs, there are additional JA-regulated defenses that control T. urticae herbivory. Together, our results reveal the complexity of Arabidopsis defenses against T. urticae that rely on multiple IGs, specific myrosinases, and additional JA-dependent defenses.

Cadmium (Cd) pollution of agricultural soils is a growing global problem. Plant growth restriction is the main visible symptom of Cd toxicity, and this metal may be particularly harmful to the preformed, seminal root during the pre-emergence stage. In the present study, we focused on Cd phytotoxicity on seminal root growth, nutrient composition, redox status, and hormone homeostasis during the pre-emergence stage, distinguishing between the root apex and the remaining root tissue. After 72 h of metal exposure (50 and 100 µM CdCl2), root length and biomass was diminished, as well as Ca, Fe, Mg, and Mn contents. A redox imbalance was evidenced by changes in peroxidase activities and decreased ascorbate-dehydroascorbate ratio in both root parts. There was less accumulation of carbonylated proteins in both root fractions upon exposition to 50 µM Cd, compared to 100 µM Cd, and this was related to increased 20S proteasome activities. Cd incremented ABA, IAA, and SA contents, but drastically reduced the biologically active gibberellin GA4 and the conjugate jasmonoyl isoleucine (JA-Ile). We demonstrated that the whole root tissue is involved in maize response to Cd stress, which entails redox and hormonal rearrangements, probably directed to widen plant defense lines at the expense of root growth.

Water-deficit stress is the most important abiotic stress restricting plant growth, development and yield. The effects of this stress, however, depend on genotypes, among other factors. This study assembles morpho-physiological and metabolic approaches to assess hormonal and metabolic profile changes, upon water-deficit stress, in the shoot and roots of two contrasting sunflower inbred lines, B59 (water-deficit stress sensitive) and B71 (water-deficit stress tolerant). The analyses were carried out using mass spectrometry and performing a multivariate statistical analysis to identify relationships between the analyzed variables. Water-deficit stress reduced all morpho-physiological parameters, except for root length in the tolerant inbred line. The hormonal pathways were active in mediating the seedling performance to imposed water-deficit stress in both lines, although with some differences between lines at the organ level. B59 displayed a diverse metabolite battery, including organic acids, organic compounds as well as sugars, mainly in the shoot, whereas B71 showed primary amino acids, organic acids and organic compounds predominantly in its roots. The discrimination between control and water-deficit stress conditions was possible thanks to potential biomarkers of stress treatment, e.g., proline, maleic acid and malonic acid. This study indicated that the studied organs of sunflower seedlings have different mechanisms of regulation under water-deficit stress. These findings could help to better understand the physio-biochemical pathways underlying stress tolerance in sunflower at early-growth stage.

[EN] Amblyseius swirskii is a predatory mite widely used for the control of very important pest species, such as whiteflies and thrips, in organic farming and conventional agriculture. However, this species cannot establish on tomato crops, probably due to the toxic effects of plant trichomes and their exudates. We evaluated tomato plants for effects on: a) A. swirskii preference mediated by plant volatiles, b) A. swirskii development, predation capacity and reproductive performance, c) the dispersal and survival of mites as affected by stem trichomes, and d) mite survival as a function of secondary metabolites secreted by tomato trichomes. The results showed that A. swirskii mites which gained experience foraging on tomato plants, tend to avoid them. The survival of A. swirskii eggs and juveniles on tomato leaves was not different from that on sweet pepper. However, adult survival was significantly lower when tested on whole plants. This was ostensibly due to the impact of trichomes and their secondary metabolites that are abundant on the stems and which negatively impacted mite dispersal on the plant. Among the secondary metabolites detected in tomato trichomes, the strongest negative effects were associated with acyl sugars. Acyl sugars were highly toxic to the mites and also, physically accumulated on their bodies after walking on tomato stems. Altogether, our results reveal why A. swirskii is not an efficient biocontrol agent on tomato crops., This work was funded by the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 641456. JGC was supported by the Spanish Ministry of Economy and Competitiveness, Ramon y Cajal Program (RYC-2013-13834). JLR was supported by the Spanish Ministry of Economy and Competitiveness through a "Juan de la Cierva-Formacion" grant (FJCI-2016-28601). Mass spectrometric determinations were carried out at Servei Central d'Instrumentacio Cientifica (SCIC) from Universitat Jaume I.

Cadmium is one of the most important contaminants and it induces severe plant growth restriction. In this study, we analyzed the metabolic changes associated with root growth restriction caused by cadmium in the early seminal root apex of wheat. Our study included two genotypes: the commercial variety ProINTA Federal (WT) and the PSARK::IPT (IPT) line which exhibit high-grade yield performance under water deficit. Root tips of seedlings grown for 72 h without or with 10 μM CdCl2 (Cd-WT and Cd-IPT) were compared. Root length reduction was more severe in Cd-WT than Cd-IPT. Cd decreased superoxide dismutase activity in both lines and increased catalase activity only in the WT. In Cd-IPT, ascorbate and guaiacol peroxidase activities raised compared to Cd-WT. The hormonal homeostasis was altered by the metal, with significant decreases in abscisic acid, jasmonic acid, 12-oxophytodienoic acid, gibberellins GA20, and GA7 levels. Increases in flavonoids and phenylamides were also found. Root growth impairment was not associated with a decrease in expansin (EXP) transcripts. On the contrary, TaEXPB8 expression increased in the WT treated by Cd. Our findings suggest that the line expressing the PSARK::IPT construction increased the homeostatic range to cope with Cd stress, which is visible by a lesser reduction of the root elongation compared to WT plants. The decline of root growth produced by Cd was associated with hormonal imbalance at the root apex level. We hypothesize that activation of phenolic secondary metabolism could enhance antioxidant defenses and contribute to cell wall reinforcement to deal with Cd toxicity.

[EN] Modern agricultural policies across the globe are committed to a significant reduction in chemical pesticide dependency; however, pest management strategies are still based on the use of synthetic pesticides. There is an urgent need to find new, sustainable and biorational tools for pest management programs. Plants communicate with each other and activate defense mechanisms against pests using herbivore-induced plant volatiles (HIPVs). The use of such HIPVs could be an ecologically sustainable alternative. However, as of now, there have been no comprehensive studies on HIPVs, from selection to practical use in industry production. Here, we describe the first case of an HIPV successfully implemented for pest control under commercial greenhouse conditions. In this research, tomato plants induced with (Z)-3-hexenyl propanoate [(Z)-3-HP] were less susceptible to the attack of economically important tomato pests. We designed and calibrated polymeric dispensers for the constant release of (Z)-3-HP. These dispensers maintained commercial tomato plant defenses activated for more than two months reducing herbivore pest damage without reducing plant productivity. Transcriptomic and metabolomic analyses of plants induced with (Z)-3-HP confirmed that genes involved in specialized anti-herbivore defense were up-regulated, resulting in an increased production of fatty acid-derived compounds, activation of the lipoxygenase pathway and accumulation of specific defense compounds. Our work demonstrates under commercial greenhouse conditions how the release of HIPVs as elicitors of plant defenses via designed polymeric dispensers can be successfully integrated as a new biorational and sustainable tool for pest control, The research leading to these results was partially funded by the Spanish Ministry of Economy and Competitiveness MINECO (AGL2014-55616-C3 and RTA2017-00073-00-00), by EU through the project HARNESSTOM (Horizon 2020 program; contract 101000716) and the Conselleria d'Agricultura, Pesca i Alimentacio de la Generalitat Valenciana. The authors thank Dr. Alejandro Tena (IVIA) and Alice Mockford (University of Worcester) for helpful comments on earlier versions of the manuscript and Julio Marco for letting us conduct this research in his greenhouse and for his selfless support throughout project. JLR was supported by the Spanish Ministry of Economy and Competitiveness through a "Juan de la Cierva-Formacion" grant (FJCI-2016-28601).

Drought is one of the most important constraints to crop productivity worldwide. Control of plant responses to drought is very complex. The mechanisms and their intensity may differ between species and/or genotypes ultimately conditioning tolerance or susceptibility. We explore here the strategy set up by two oat cultivars to cope with drought based on root morphological, anatomical, physiological and molecular studies. A dramatic and rapid abscisic acid increase in the susceptible genotype resulted in a tight and rapid reduction of stomatal conductance. Despite of this, leaf water potential decreased concomitantly due to a decrease in root hydraulic conductivity. By contrast, the resistant genotype, showed a mild and slow increase in abscisic acid that allowed maintaining transpiration longer. This response was linked to an increase in root hydraulic conductance through an increase in total root length and in the length of the thinnest roots as well as a rise in root conductivity. This was also coupled with anatomical changes leading to a reduction of metabolic cost. These changes allowed the resistant genotype to maintain higher water potential reducing drought symptoms and promoting growth under water deficit conditions., This work was supported by the Spanish Ministry of Economy and Competitiveness [AGL2016-78965AGR], (AEI/FEDER, UE), Spanish Ministry of Science and Innovation [PID2019-104518RB-100], and regional government through the AGR-253 group, the European Regional and Social Development Funds. FJC is holder of a FPI fellowship from the Spanish Ministry of Economy and Competitiveness [BES-2014-071044].

DORMANCY-ASSOCIATED MADS-BOX (DAM) genes have recently emerged as key potential regulators of the dormancy cycle and climate adaptation in perennial species. Particularly, PpeDAM6 has been proposed to act as a major repressor of bud dormancy release and bud break in peach (Prunus persica). PpeDAM6 expression is downregulated concomitantly with the perception of a given genotype-dependent accumulation of winter chilling time, and the coincident enrichment in H3K27me3 chromatin modification at a specific genomic region. We have identified three peach BASIC PENTACYSTEINE PROTEINs (PpeBPCs) interacting with two GA-repeat motifs present in this H3K27me3-enriched region. Moreover, PpeBPC1 represses PpeDAM6 promoter activity by transient expression experiments. On the other hand, the heterologous overexpression of PpeDAM6 in European plum (Prunus domestica) alters plant vegetative growth, resulting in dwarf plants tending toward shoot meristem collapse. These alterations in vegetative growth of transgenic lines associate with impaired hormone homeostasis due to the modulation of genes involved in jasmonic acid, cytokinin, abscisic acid, and gibberellin pathways, and the downregulation of shoot meristem factors, specifically in transgenic leaf and apical tissues. The expression of many of these genes is also modified in flower buds of peach concomitantly with PpeDAM6 downregulation, which suggests a role of hormone homeostasis mechanisms in PpeDAM6-dependent maintenance of floral bud dormancy and growth repression.

Cadmium (Cd) pollution of agricultural soils is a growing global concern. Plant growth restriction is the main visible symptom of Cd toxicity, and this metal may be particularly harmful to the preformed, seminal root during the pre-emergence stage. In the present study, we focused on Cd phytotoxicity in seminal root growth, nutrient composition, redox status, and hormone homeostasis during the pre-emergence stage of maize (Zea mays L) plants, distinguishing between the root apex and the remaining root tissue. After 72 h of metal exposure (50 and 100 µM CdCl2), root length and biomass, as well as Ca, Fe, Mg, and Mn contents, were diminished. A redox imbalance was evidenced by changes in peroxidase activities and the ascorbate–dehydroascorbate ratio decreased in both root parts. There were fewer carbonylated proteins in both root fractions after exposure to 50 µM Cd, compared to 100 µM Cd, which was related to increased 20S proteasome activities. Cd incremented ABA, IAA, and SA contents, but drastically reduced the biologically active gibberellin GA4 and the conjugate jasmonoyl-isoleucine (JA-Ile). We demonstrated that the whole root tissue is involved in the maize response to Cd stress, which entails redox and hormonal rearrangements, probably directed to widen the plant defense lines at the expense of root growth.

Soil flooding is a compound abiotic stress that alters soil properties and limits atmospheric gas diffusion (O2 and CO2) to the roots. The involvement of abscisic acid (ABA) in the regulation of soil flooding-specific genetic and metabolic responses has been scarcely studied despite its key importance as regulator in other abiotic stress conditions. To attain this objective, wild type and ABA-deficient tomatoes were subjected to short-term (24 h) soil waterlogging. After this period, gas exchange parameters were reduced in the wild type but not in ABA-deficient plants that always had higher E and gs. Transcript and metabolite alterations were more intense in waterlogged tissues, with genotype-specific variations. Waterlogging reduced the ABA levels in the roots while inducing PYR/PYL/RCAR ABA receptors and ABA-dependent transcription factor transcripts, of which induction was less pronounced in the ABA-deficient genotype. Ethylene/O2-dependent genetic responses (ERFVIIs, plant anoxia survival responses, and genes involved in the N-degron pathway) were induced in hypoxic tissues independently of the genotype. Interestingly, genes encoding a nitrate reductase and a phytoglobin involved in NO biosynthesis and scavenging and ERFVII stability were induced in waterlogged tissues, but to a lower extent in ABA-deficient tomato. At the metabolic level, flooding-induced accumulation of Ala was enhanced in ABA-deficient lines following a differential accumulation of Glu and Asp in both hypoxic and aerated tissues, supporting their involvement as sources of oxalacetate to feed the tricarboxylic acid cycle in waterlogged tissues and constituting a potential advantage upon long periods of soil waterlogging. The promoter analysis of upregulated genes indicated that the production of oxalacetate from Asp via Asp oxidase, energy processes such as acetyl-CoA, ATP, and starch biosynthesis, and the lignification process were likely subjected to ABA regulation. Taken together, these data indicate that ABA depletion in waterlogged tissues acts as a positive signal, inducing several specific genetic and metabolic responses to soil flooding., This work was supported by the Spanish Ministerio de Economía y Competitividad, Universitat Jaume I and Generalitat Valenciana/Fondo Europeo de Desarrollo Regional (FEDER), co-funded through grant nos. AGL2016-76574-R, UJI-B2016-23, UJI-B2016-24, IDIFEDER/2018/010, and UJI-B2019-24 to AG-C, VA, and MG-G, respectively. CD was supported by UJI PICD program. MG-G and JM were supported by Ramon y Cajal contracts from Spanish Ministerio de Economía y Competitividad (RYC-2016-19325 and RYC-2017-23645, respectively). JR was supported by a Juan de la Cierva-Formación contract from the Spanish Ministerio de Economía y Competitividad (FJCI-2016-28601).

Interaction between plants and their environment is changing as a consequence of the climate change and global warming, increasing the performance and dispersal of some pest species which become invasive species. Tetranychus evansi also known as the tomato red spider mite, is an invasive species which has been reported to increase its performance when feeding in the tomato cultivar Moneymaker (MM) under water deficit conditions. In order to clarify the underlying molecular events involved, we examined early plant molecular changes occurring on MM during T. evansi infestation alone or in combination with moderate drought stress. Hormonal profiling of MM plants showed an increase in abscisic acid (ABA) levels in drought-stressed plants while salicylic acid (SA) levels were higher in drought-stressed plants infested with T. evansi, indicating that SA is involved in the regulation of plant responses to this stress combination. Changes in the expression of ABA-dependent DREB2, NCED1, and RAB18 genes confirmed the presence of drought-dependent molecular responses in tomato plants and indicated that these responses could be modulated by the tomato red spider mite. Tomato metabolic profiling identified 42 differentially altered compounds produced by T. evansi attack, moderate drought stress, and/or their combination, reinforcing the idea of putative manipulation of tomato plant responses by tomato red spider mite. Altogether, these results indicate that the tomato red spider mite acts modulating plant responses to moderate drought stress by interfering with the ABA and SA hormonal responses, providing new insights into the early events occurring on plant biotic and abiotic stress interaction., This work was supported by a Young Investigator project (AGL2015-73235-JIN) and a Ramon y Cajal contract (RYC-2016-19325) from the Ministerio de Economía y Competitividad (MINECO) and Fondo Europeo de Desarrollo Regional (FEDER), and Universitat Jaume grant (UJI-B2019-24) to MG-G; by a Grant from INIA (GENOMITE, Proposal No. 618105 FACCE Era Net Plus-Food security, Agriculture, Climate Change) to FO; by MINECO, FEDER, Generalitat Valenciana and Universitat Jaume I through grants nos. AGL201676574-R, IDIFEDER 2018-10 and UJI-B2016- 23/UJI-B2016-24 to AG-C and VA. We are grateful to Maria Navajas for kindly providing the T. evansi population used in this study. The authors greatly acknowledge the central facilities (Servei Central d’Instrumentació Científica, SCIC) of the Universitat Jaume I where the phytohormone and metabolic profiling measurements were carried out.

Genetic adaptation, occurring over a long evolutionary time, enables host-specialized herbivores to develop novel resistance traits and to efficiently counteract the defenses of a narrow range of host plants. In contrast, physiological acclimation, leading to the suppression and/or detoxification of host defenses, is hypothesized to enable broad generalists to shift between plant hosts. However, the host adaptation mechanisms used by generalists composed of host-adapted populations are not known. Two-spotted spider mite (TSSM; Tetranychus urticae) is an extreme generalist herbivore whose individual populations perform well only on a subset of potential hosts. We combined experimental evolution, Arabidopsis thaliana genetics, mite reverse genetics, and pharmacological approaches to examine mite host adaptation upon the shift of a bean (Phaseolus vulgaris)-adapted population to Arabidopsis. We showed that cytochrome P450 monooxygenases are required for mite adaptation to Arabidopsis. We identified activities of two tiers of P450s: general xenobiotic-responsive P450s that have a limited contribution to mite adaptation to Arabidopsis and adaptation-associated P450s that efficiently counteract Arabidopsis defenses. In approximately 25 generations of mite selection on Arabidopsis plants, mites evolved highly efficient detoxification-based adaptation, characteristic of specialist herbivores. This demonstrates that specialization to plant resistance traits can occur within the ecological timescale, enabling the TSSM to shift to novel plant hosts., Mites can evolve highly efficient detoxification-based adaptation in approximately 25 generations on an initially unfavorable plant host, revealing that specialization can occur within the ecological timescale.

Copper (Cu) interferes with numerous biological functions in plants, including plant growth, which is partly governed by plant hormones. In the present study, Cu stress effect on the roots of pre-emerging maize seedlings in terms of growth, nutrient composition, protein modifications, and root hormone homeostasis was investigated, focusing on possible metabolic differences between the root apex and the rest of the root tissues. Significant decreases in root length and root biomass after 72 h of Cu exposure (50 and 100 μM CuCl2), accompanied by reductions in Ca, Mg, and P root contents, were found. Cu also generated cell redox imbalance in both root tissues and revealed by altered enzymatic and non-enzymatic antioxidant defenses. Oxidative stress was evidenced by an increased protein carbonylation level in both tissues. Copper also induced protein ubiquitylation and SUMOylation and affected 20S proteasome peptidase activities in both tissues. Drastic reductions in ABA, IAA, JA (both free and conjugated), GA3, and GA4 levels in the root apex were detected under Cu stress. Our results show that Cu exposure generated oxidative damage and altered root hormonal homeostasis, mainly at the root apex, leading to a strong root growth inhibition. Severe protein post-translational modifications upon Cu exposure occurred in both tissues, suggesting that even when hormonal adjustments to cope with Cu stress occurred mainly at the root apex, the entire root is compromised in the protein turnover that seems to be necessary to trigger and/or to sustain defense mechanisms against Cu toxicity.

19 páginas.- 3 figuras.- referencias, Introduction: Citrus is a subtropical crop and, therefore, is poorly tolerant to water deficit and salt stress conditions. Its cultivation has been extended to different climatic regions between 40° north-south latitudes, where citrus production is particularly high in arid and semiarid regions. In major citrus-producing regions such as the Mediterranean Basin, Southern California (USA), South Africa, and Australia, where summer weather is usually dry and hot, and available water is of low quality due to excessive concentrations of soluble salts, water deficit and salinity become limiting to citrus productivity (revised in Maas, 1993; Storey and Walker, 1999; Gómez-Cadenas et al., 2003). Furthermore, climate change in citrus-producing regions is expected to amplify the effects of drought and salinity stress (see Chapter 13).....

Citrus is adequately adapted to production conditions in three major climate types. Climate change is expected to affect each in different ways. In this chapter, we discuss the mechanisms of tolerance and sensitivity to stresses associated with soil and air moisture, salinity, air temperature, and ambient carbon dioxide. Variations in most of these conditions are expected to pose challenges to citrus production. Increased ambient carbon dioxide is expected to partially mitigate growth losses due to most other environmental stresses. Access to sufficient quality and quantity of irrigation water is the major hurdle for future production. Opportunities for germplasm improvement exist in selecting or developing commercial cultivars with increased tolerance to soil water deficit, flooding, salinity, and high and low temperatures, as well as genotypes with improved growth responses to elevated carbon dioxide.

[EN] The presence of antibiotics in soils could be due to natural production by soil microorganisms or to the effect of anthropogenic activities. However, the impact of these compounds on plant physiology has not been thoroughly investigated. To evaluate the effect of beta-lactam antibiotics (carbenicillin and penicillin) on the growth and development of Arabidopsis thaliana roots, plants were grown in the presence of different amounts and we found a reduction in root size, an increase in the size of root hairs as well as an abnormal position closer to the tip of the roots. Those phenomena were dependent on the accumulation of both antibiotics inside root tissues and also correlated with a decrease in size of the root apical meristem not related to an alteration in cell division but to a decrease in cell expansion. Using an RNA sequencing analysis, we detected an increase in the expression of genes related to the response to oxidative stress, which would explain the increase in the levels of endogenous reactive oxygen species found in the presence of those antibiotics. Moreover, some auxin-responsive genes were misregulated, especially an induction of CYP79B3, possibly explaining the increase in auxin levels in the presence of carbenicillin and the decrease in the amount of indole glucosinolates, involved in the control of fungal infections. Accordingly, penicillin-treated plants were hypersensitive to the endophyte fungus Colletotrichum tofieldiae. These results underscore the risks for plant growth of beta-lactam antibiotics in agricultural soils, and suggest a possible function for these compounds as fungus-produced signaling molecules to modify plant behavior., This work has been financed by the Spanish Ministerio de Medio Ambiente Rural y Marino [MMA 022/PC08/3-04.2] and the Spanish Agencia Estatal de Investigación [BFU2016-80621-P]. M.E.G. is a fellow of the program Convocatoria Abierta 2013 - Fase I (Instituto de Fomento de Talento Humano (IFTH), Secretaría Nacional de Educación Superior Ciencia y Tecnología (SENESCYT) (Ecuador). N.B-T is a recipient of a MINECO FPI Fellowship (BES-2014-068868).

Plant survival depends on the optimal use of resources under variable environmental conditions. Among the mechanisms that mediate the balance between growth, differentiation, and stress responses, the regulation of transcriptional activity by DELLA proteins stands out. In angiosperms, DELLA accumulation promotes defense against biotic and abiotic stress and represses cell division and expansion, while the loss of DELLA function is associated with increased plant size and sensitivity toward stress.1 Given that DELLA protein stability is dependent on gibberellin (GA) levels2 and GA metabolism is influenced by the environment,3 this pathway is proposed to relay environmental information to the transcriptional programs that regulate growth and stress responses in angiosperms.4,5 However, DELLA genes are also found in bryophytes, whereas canonical GA receptors have been identified only in vascular plants.6, 7, 8, 9, 10 Thus, it is not clear whether these regulatory functions of DELLA predated or emerged with typical GA signaling. Here, we show that, as in vascular plants, the only DELLA in the liverwort Marchantia polymorpha also participates in the regulation of growth and key developmental processes and promotes oxidative stress tolerance. Moreover, part of these effects is likely caused by the conserved physical interaction with the MpPIF transcription factor. Therefore, we suggest that the role in the coordination of growth and stress responses was already encoded in the DELLA protein of the common ancestor of land plants, and the importance of this function is underscored by its conservation over the past 450 million years., Work in the authors’ laboratories has been funded by the Spanish Agencia Estatal de Investigación and FEDER (grants BFU2016-80621-P and PID2019-110717GB to M.A.B.) and JSPS/MEXT KAKENHI (JP17H07424 and JP19H05675 to T.K.; 20H04884 to R.N.). J.H.-G. and A.S.-M. were supported by a predoctoral fellowship from the Spanish Ministry of Education, Culture and Sport (FPU15/01756) and an MSCA Individual Fellowship (H2020-MSCA-IF-2016-746396), respectively. R.S. was supported by the Japanese Government (MEXT) Scholarship Program.

The root system is the main organ involved in the water uptake and it is assumed that it perceives soil dehydration, triggering water stress responses at the entire plant level, including abscisic acid (ABA) accumulation. However, several lines of evidence demonstrate that leaves directly adjust their water status (and induce increases in ABA levels) in response to changes in the evaporative demand. To evaluate the influence of leaf water status on ABA accumulation in roots, the canopy of citrus plants was kept at high humidity while roots were dehydrated. Leaves and roots of completely dehydrated plants increased levels of ABA whereas plants with turgid leaves did not accumulate ABA either in leaves or in roots. Furthermore, in dehydrated roots, the expression of several key genes involved in carotenoid and ABA biosynthetic pathways such as CsβCHX1 and CsNCED1 was strongly affected by the water status of leaves whereas water availability in roots showed a marginal influence. Overall, results confirm that leaves are a relevant source of ABA for roots during dehydration and also demonstrate that leaf-dehydration is required to trigger ABA-induced responses in roots.

Plant viral infections alter gene expression and metabolism in infected host. To study the molecular responses of Mexican lime to CTV infection, an analysis of plant metabolome in response to infection with severe (T318) or mild (T385) isolates of CTV was performed. Healthy plants and those infected with any of the two virus strains showed different metabolite profiles, at different stages of new sprout development. Proline content increased in plants infected with CTV, proportionally to the virulence of the virus strain. Abscisic acid content decreased after virus infection whereas jasmonic and salicylic acid levels increased. CTV infection had an impact on plant secondary metabolism, by stimulating the synthesis of different metabolites such as l-methylhistidine, phenylpropanoid derivatives. These metabolites are common responses of different organisms, including higher mammals, to viral diseases, and its presence in this system points to the existence of universal responses to virus infection among different kingdoms.

Primary and secondary metabolite profiles were analyzed in roots and leaves of the halophytic shrub Prosopis strombulifera in response to control plants (no salt added in the growing media) and to lowering the osmotic potential to 1.0, 1.9, and 2.6 MPa generated by NaCl, Na2SO4, and the iso-osmotic combination of them at 24 h after reaching such potential. A rapid production of metabolites in response to sodium salt was found, which was correlated with modifications in growth parameters. Analysis of polar metabolite profiles by GC-MS rendered a total of 108 significantly altered compounds including 18 amino acids, 19 secondary metabolites, 23 carbohydrates, 13 organic acids, 4 indole acids, among others. Primary metabolites showed a differential response under the salt treatments, which was dependent on salt type and concentration, organ and age of plants. Most of identified compounds showed the strongest accumulation at the highest salt concentration assayed for Na2SO4-treated plants, which was correlated with damaging effects of sulfate anion on plant growth. Roots of NaCl-treated plants showed a higher number of altered metabolites (analyzed by UPLC-ESI-QqTOF-MS) compared to other treatments, while leaves of Na2SO4-treated plants showed the highest number of altered signals. A low degree of overlapping between secondary metabolites altered in roots and leaves of NaCl and Na2SO4-treated plants was found. However, when both NaCl and Na2SO4 salts were present plants always showed a lower number of altered metabolites. Three compounds were tentatively identified: tryptophan, lysophosphatidylcoline and 13-hydroxyoctadecadienoic acid. Increasing knowledge on P. strombulifera metabolism will contribute to unravel the underlying biochemical mechanism of salt tolerance.