RESUMO
Plants growing under natural conditions experience high light (HL) intensities that are often accompanied by elevated temperatures. These conditions could affect photosynthesis, reduce yield, and negatively impact agricultural productivity. The combination of different abiotic challenges creates a new type of stress for plants by generating complex environmental conditions that often exceed the impact of their individual parts. Transcription factors (TFs) play a key role in integrating the different molecular signals generated by multiple stress conditions, orchestrating the acclimation response of plants to stress. In this study, we show that the TF WRKY48 negatively controls the acclimation of Arabidopsis thaliana plants to a combination of HL and heat stress (HL + HS), and its expression is attenuated by jasmonic acid under HL + HS conditions. Using comparative physiological and transcriptomic analyses between wild-type and wrky48 mutants, we further demonstrate that under control conditions, WRKY48 represses the expression of a set of transcripts that are specifically required for the acclimation of plants to HL + HS, hence its suppression during the HL + HS stress combination contributes to plant survival under these conditions. Accordingly, mutants that lack WRKY48 are more resistant to HL + HS, and transgenic plants that overexpress WRKY48 are more sensitive to it. Taken together, our findings reveal that WRKY48 is a negative regulator of the transcriptomic response of Arabidopsis to HL + HS and provide new insights into the complex regulatory networks of plant acclimation to stress combination.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Resposta ao Choque Térmico , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Arabidopsis/metabolismo , Aclimatação , Luz , Plantas/metabolismo , Regulação da Expressão Gênica de Plantas , Estresse FisiológicoRESUMO
After perception of vegetation proximity by phytochrome photoreceptors, shade-avoider plants initiate a set of responses known as the Shade Avoidance Syndrome (SAS). Shade perception by the phytochrome B (phyB) photoreceptor unleashes the PHYTOCHROME INTERACTING FACTORs (PIFs) and initiates SAS responses. In Arabidopsis (Arabidopsis thaliana) seedlings, shade perception involves rapid and massive changes in gene expression, increases auxin production, and promotes hypocotyl elongation. Other components, such as phyA and ELONGATED HYPOCOTYL 5 (HY5), also participate in the shade regulation of the hypocotyl elongation response by repressing it. However, why and how so many regulators with either positive or negative activities modulate the same response remain unclear. Our physiological, genetic, cellular, and transcriptomic analyses showed that (1) these components are organized into two main branches or modules and (2) the connection between them is dynamic and changes with the time of shade exposure. We propose a model for the regulation of shade-induced hypocotyl elongation in which the temporal and spatial functional importance of the various SAS regulators analyzed here helps to explain the co-existence of differentiated regulatory branches with overlapping activities.
RESUMO
Composite generalist herbivores are comprised of host-adapted populations that retain the ability to shift hosts. The degree and overlap of mechanisms used by host-adapted generalist and specialist herbivores to overcome the same host plant defenses are largely unknown. Tetranychidae mites are exceptionally suited to address the relationship between host adaptation and specialization in herbivores as this group harbors closely related species with remarkably different host ranges-an extreme generalist the two-spotted spider mite (Tetranychus urticae Koch [Tu]) and the Solanaceous specialist Tetranychus evansi (Te). Here, we used tomato-adapted two-spotted spider mite (Tu-A) and Te populations to compare mechanisms underlying their host adaptation and specialization. We show that both mites attenuate induced tomato defenses, including protease inhibitors (PIs) that target mite cathepsin L digestive proteases. While Te solely relies on transcriptional attenuation of PI induction, Tu and Tu-A have elevated constitutive activity of cathepsin L proteases, making them less susceptible to plant anti-digestive proteins. Tu-A and Te also rely on detoxification of tomato constitutive defenses. Te uses esterase and P450 activities, while Tu-A depends on the activity of all major detoxification enzymatic classes to disarm tomato defensive compounds to a lesser extent. Thus, even though both Tu-A and Te use similar mechanisms to counteract tomato defenses, Te can better cope with them. This finding is congruent with the ecological and evolutionary times required to establish mite adaptation and specialization states, respectively.
Assuntos
Tetranychidae , Animais , Adaptação ao Hospedeiro , Catepsina L , Plantas , Evolução Biológica , HerbivoriaRESUMO
Climate change induces significant abiotic stresses that adversely affect crop yields. One promising solution to improve plant resilience under adverse conditions is the application of exogenous salicylic acid (SA). However, its negative effects on growth and development are a concern. Encapsulation with protective materials like amorphous silica and chitosan has demonstrated a controlled release of SA, minimizing the detrimental impacts. In this work, we elucidate the physiological mechanisms behind this protective mechanism. We employed in vitro cultivation of Arabidopsis, comparing plant responses to both free and encapsulated SA under conditions of salt or mannitol stress, combined or not with high temperature (30°C). Plants treated with encapsulated SA displayed an enhanced tolerance to these stresses that was due, at least in part, to the maintenance of physiological endogenous SA levels, which in turn regulate indole-3-acetic acid (IAA) homeostasis. The activity of the Arabidopsis "DR5::GFP" reporter line supported this finding. Unlike plants treated with free SA (with altered DR5 activity under stress), those treated with encapsulated SA maintained similar activity levels to control plants. Moreover, stressed plants treated with free SA overexpressed genes involved in the SA biosynthesis pathway, leading to increased SA accumulation in roots and rosettes. In contrast, plants treated with encapsulated SA under stress did not exhibit increased expression of EDS1, PAL1, and NPR1 in roots, or of PAL1, PBS3, and NPR1 in rosettes. This indicates that these plants likely experienced lower stress levels, possibly because the encapsulated SA provided sufficient defense activation without triggering pleiotropic effects.
Assuntos
Arabidopsis , Homeostase , Reguladores de Crescimento de Plantas , Ácido Salicílico , Estresse Fisiológico , Ácido Salicílico/farmacologia , Ácido Salicílico/metabolismo , Arabidopsis/efeitos dos fármacos , Arabidopsis/genética , Arabidopsis/fisiologia , Arabidopsis/metabolismo , Homeostase/efeitos dos fármacos , Reguladores de Crescimento de Plantas/metabolismo , Reguladores de Crescimento de Plantas/farmacologia , Estresse Fisiológico/efeitos dos fármacos , Ácidos Indolacéticos/metabolismo , Ácidos Indolacéticos/farmacologia , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Proteínas de Arabidopsis/metabolismo , Proteínas de Arabidopsis/genéticaRESUMO
Environmental conditions are an important factor driving pathogens' evolution. Here, we explore the effects of drought stress in plant virus evolution. We evolved turnip mosaic potyvirus in well-watered and drought conditions in Arabidopsis thaliana accessions that differ in their response to virus infection. Virus adaptation occurred in all accessions independently of watering status. Drought-evolved viruses conferred a significantly higher drought tolerance to infected plants. By contrast, nonsignificant increases in tolerance were observed in plants infected with viruses evolved under standard watering. The magnitude of this effect was dependent on the plant accessions. Differences in tolerance were correlated to alterations in the expression of host genes, some involved in regulation of the circadian clock, as well as in deep changes in the balance of phytohormones regulating defense and growth signaling pathways. Our results show that viruses can promote host survival in situations of abiotic stress, with the magnitude of such benefit being a selectable trait.
Assuntos
Arabidopsis/genética , Interações Hospedeiro-Patógeno/genética , Doenças das Plantas/genética , Vírus de Plantas/genética , Simbiose/genética , Adaptação Fisiológica , Arabidopsis/virologia , Brassica napus/genética , Brassica napus/virologia , Secas , Evolução Molecular , Regulação da Expressão Gênica de Plantas/genética , Doenças das Plantas/virologia , Reguladores de Crescimento de Plantas/genética , Vírus de Plantas/patogenicidade , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/virologia , Potyvirus/genética , Potyvirus/patogenicidade , Estresse Fisiológico/genéticaRESUMO
BACKGROUND: Plants growing in the field are subjected to combinations of abiotic stresses. These conditions pose a devastating threat to crops, decreasing their yield and causing a negative economic impact on agricultural production. Metabolic responses play a key role in plant acclimation to stress and natural variation for these metabolic changes could be key for plant adaptation to fluctuating environmental conditions. RESULTS: Here we studied the metabolomic response of two Arabidopsis ecotypes (Columbia-0 [Col] and Landsberg erecta-0 [Ler]), widely used as genetic background for Arabidopsis mutant collections, subjected to the combination of high salinity and increased irradiance. Our findings demonstrate that this stress combination results in a specific metabolic response, different than that of the individual stresses. Although both ecotypes displayed reduced growth and quantum yield of photosystem II, as well as increased foliar damage and malondialdehyde accumulation, different mechanisms to tolerate the stress combination were observed. These included a relocation of amino acids and sugars to act as potential osmoprotectants, and the accumulation of different stress-protective compounds such as polyamines or secondary metabolites. CONCLUSIONS: Our findings reflect an initial identification of metabolic pathways that differentially change under stress combination that could be considered in studies of stress combination of Arabidopsis mutants that include Col or Ler as genetic backgrounds.
Assuntos
Arabidopsis , Arabidopsis/genética , Ecótipo , Salinidade , Metabolômica , AclimataçãoRESUMO
Plants are frequently subjected to different combinations of abiotic stresses, such as high light (HL) intensity, and elevated temperatures. These environmental conditions pose a threat to agriculture production, affecting photosynthesis, and decreasing yield. Metabolic responses of plants, such as alterations in carbohydrates and amino acid fluxes, play a key role in the successful acclimation of plants to different abiotic stresses, directing resources toward stress responses, and suppressing growth. Here we show that the primary metabolic response of Arabidopsis (Arabidopsis thaliana) plants to HL or heat stress (HS) is different from that of plants subjected to a combination of HL and HS (HL+HS). We further demonstrate that the combined stress results in a unique metabolic response that includes increased accumulation of sugars and amino acids coupled with decreased levels of metabolites participating in the tricarboxylic acid cycle. Among the amino acids exclusively accumulated during HL+HS, we identified the nonproteinogenic amino acid γ-aminobutyric acid (GABA). Analysis of different mutants deficient in GABA biosynthesis (GLUTAMATE DESCARBOXYLASE 3 [gad3]) as well as mutants impaired in autophagy (autophagy-related proteins 5 and 9 [atg5 and atg9]), revealed that GABA plays a key role in the acclimation of plants to HL+HS, potentially by promoting autophagy. Taken together, our findings identify a role for GABA in regulating plant responses to combined stress.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Aclimatação , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Regulação da Expressão Gênica de Plantas , Resposta ao Choque Térmico , Estresse Fisiológico , Ácido gama-Aminobutírico/metabolismoRESUMO
Plant transpiration is a fundamental process that determines plant water use efficiency (WUE), thermoregulation, nutrition, and growth. How transpiration impacts on such essential physiological aspects and how the environment modulates these effects are fundamental questions about which little is known. We investigated the genetic and environmental factors underlying natural variation in plant transpiration and water use efficiency in a population of natural Arabidopsis thaliana accessions grown under homogeneous conditions. As expected, we observed large variation of total transpiration capacity, transpiration per surface unit, and WUE among A. thaliana accessions. Despite the variation of stomatal density and ABA content in the population, WUE did not correlate with any of these parameters. On the contrary, a surprising direct correlation was found between WUE and projected leaf area, with bigger plants displaying a more efficient use of water. Importantly, genome-wide association studies further supported our observations through the identification of several loci involved in WUE variation, mutations in which caused a simultaneous reduction in plant size and a decrease in WUE. Altogether, our results strongly suggest that, although WUE depends on many parameters, plant size is an adaptive trait with respect to water use in A. thaliana.
Assuntos
Arabidopsis , Arabidopsis/fisiologia , Água , Estudo de Associação Genômica Ampla , Folhas de Planta/genética , Plantas/genética , Transpiração Vegetal/fisiologia , Estômatos de Plantas/fisiologiaRESUMO
Polyamines are small aliphatic polycations present in all living organisms. In plants, the most abundant polyamines are putrescine (Put), spermidine (Spd) and spermine (Spm). Polyamine levels change in response to different pathogens, including Pseudomonas syringae pv. tomato DC3000 (Pst DC3000). However, the regulation of polyamine metabolism and their specific contributions to defence are not fully understood. Here we report that stimulation of Put biosynthesis by Pst DC3000 is dependent on coronatine (COR) perception and jasmonic acid (JA) signalling, independently of salicylic acid (SA). Conversely, lack of Spm in spermine synthase (spms) mutant stimulated galactolipids and JA biosynthesis, and JA signalling under basal conditions and during Pst DC3000 infection, whereas compromised SA-pathway activation and defence outputs through SA-JA antagonism. The dampening of SA responses correlated with COR and Pst DC3000-inducible deregulation of ANAC019 expression and its key SA-metabolism gene targets. Spm deficiency also led to enhanced disease resistance to the necrotrophic fungal pathogen Botrytis cinerea and stimulated endoplasmic reticulum (ER) stress signalling in response to Pst DC3000. Overall, our findings provide evidence for the integration of polyamine metabolism in JA- and SA-mediated defence responses, as well as the participation of Spm in buffering ER stress during defence.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/genética , Espermina , Ácido Salicílico/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Ciclopentanos/metabolismo , Oxilipinas/metabolismo , Doenças das Plantas/microbiologia , Pseudomonas syringae/fisiologia , Regulação da Expressão Gênica de PlantasRESUMO
Heat waves occurring during droughts can have a devastating impact on yield, especially if they happen during the flowering and seed set stages of the crop cycle. Global warming and climate change are driving an alarming increase in the frequency and intensity of combined drought and heat stress episodes, critically threatening global food security. Because high temperature is detrimental to reproductive processes, essential for plant yield, we measured the inner temperature, transpiration, sepal stomatal aperture, hormone concentrations and transcriptomic response of closed soybean flowers developing on plants subjected to a combination of drought and heat stress. Here, we report that, during a combination of drought and heat stress, soybean plants prioritize transpiration through flowers over transpiration through leaves by opening their flower stomata, while keeping their leaf stomata closed. This acclimation strategy, termed 'differential transpiration', lowers flower inner temperature by about 2-3°C, protecting reproductive processes at the expense of vegetative tissues. Manipulating stomatal regulation, stomatal size and/or stomatal density of flowers could serve as a viable strategy to enhance the yield of different crops and mitigate some of the current and future impacts of global warming and climate change on agriculture.
Assuntos
Secas , Estômatos de Plantas , Produtos Agrícolas , Flores , Folhas de Planta/fisiologia , Estômatos de Plantas/fisiologia , Transpiração Vegetal/fisiologia , Estresse FisiológicoRESUMO
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.
Assuntos
Adaptação Biológica , Arabidopsis/fisiologia , Proteínas de Artrópodes/genética , Sistema Enzimático do Citocromo P-450/genética , Herbivoria , Phaseolus/fisiologia , Tetranychidae/fisiologia , Animais , Proteínas de Artrópodes/metabolismo , Cadeia Alimentar , Tetranychidae/genéticaRESUMO
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.
Assuntos
Arabidopsis/fisiologia , Glucosinolatos/metabolismo , Glicosídeo Hidrolases/metabolismo , Herbivoria , Indóis/metabolismo , Defesa das Plantas contra Herbivoria , Proteínas de Plantas/metabolismo , Animais , Arabidopsis/enzimologia , Tetranychidae/fisiologiaRESUMO
The reasons underlying the differential tolerance of Actinidia spp. to the pandemic pathogen Pseudomonas syringae pv. actinidiae (Psa) have not yet been elucidated. We hypothesized that differential plant-defence strategies linked to transcriptome regulation, phytohormones and primary metabolism might be key and that Actinidia chinensis susceptibility results from an inefficient activation of defensive mechanisms and metabolic impairments shortly following infection. Here, 48 h postinoculation bacterial density was 10-fold higher in A. chinensis var. deliciosa than in Actinidia arguta, accompanied by significant increases in glutamine, ornithine, jasmonic acid (JA) and salicylic acid (SA) (up to 3.2-fold). Actinidia arguta showed decreased abscisic acid (ABA) (0.7-fold), no changes in primary metabolites, and 20 defence-related genes that were only differentially expressed in this species. These include GLOX1, FOX1, SN2 and RBOHA, which may contribute to its higher tolerance. Results suggest that A. chinensis' higher susceptibility to Psa is due to an inefficient activation of plant defences, with the involvement of ABA, JA and SA, leading to impairments in primary metabolism, particularly the ammonia assimilation cycle. A schematic overview on the interaction between Psa and genotypes with distinct tolerance is provided, highlighting the key transcriptomic and metabolomic aspects contributing to the different plant phenotypes after infection.
Assuntos
Actinidia/fisiologia , Interações entre Hospedeiro e Microrganismos , Doenças das Plantas/microbiologia , Reguladores de Crescimento de Plantas/metabolismo , Pseudomonas syringae/fisiologia , Actinidia/microbiologia , Imunidade Vegetal/fisiologiaRESUMO
The synthetic auxin 2,4-dichlorophenoxyacetic acid (2,4-D) functions as an agronomic weed control herbicide. High concentrations of 2,4-D induce plant growth defects, particularly leaf epinasty and stem curvature. Although the 2,4-D triggered reactive oxygen species (ROS) production, little is known about its signalling. In this study, by using a null mutant in peroxisomal acyl CoA oxidase 1 (acx1-2), we identified acyl-coenzyme A oxidase 1 (ACX1) as one of the main sources of ROS production and, in part, also causing the epinastic phenotype following 2,4-D application. Transcriptomic analyses of wild type (WT) plants after treatment with 2,4-D revealed a ROS-related peroxisomal footprint in early plant responses, while other organelles, such as mitochondria and chloroplasts, are involved in later responses. Interestingly, a group of 2,4-D-responsive ACX1-dependent transcripts previously associated with epinasty is related to auxin biosynthesis, metabolism, and signalling. We found that the auxin receptor auxin signalling F-box 3 (AFB3), a component of Skp, Cullin, F-box containing complex (SCF) (ASK-cullin-F-box) E3 ubiquitin ligase complexes, which mediates auxin/indole acetic acid (AUX/IAA) degradation by the 26S proteasome, acts downstream of ACX1 and is involved in the epinastic phenotype induced by 2,4-D. We also found that protein degradation associated with ubiquitin E3-RING and E3-SCF-FBOX in ACX1-dependent signalling in plant responses to 2,4-D is significantly regulated over longer treatment periods.
Assuntos
Ácido 2,4-Diclorofenoxiacético/efeitos adversos , Arabidopsis/efeitos dos fármacos , Herbicidas/efeitos adversos , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais/efeitos dos fármacos , Transcriptoma/efeitos dos fármacos , Arabidopsis/fisiologiaRESUMO
Climate change is predicted to increase the frequency and intensity of abiotic stress combinations that negatively impact plants and pose a serious threat to crop yield and food supply. Plants respond to episodes of stress combination by activating specific physiological and molecular responses, as well as by adjusting different metabolic pathways, to mitigate the negative effects of the stress combination on plant growth, development, and reproduction. Plants synthesize a wide range of metabolites that regulate many aspects of plant growth and development, as well as plant responses to stress. Although metabolic responses to individual abiotic stresses have been studied extensively in different plant species, recent efforts have been directed at understanding metabolic responses that occur when different abiotic factors are combined. In this review we examine recent studies of metabolomic changes under stress combination in different plants and suggest new avenues for the development of stress combination-resilient crops based on metabolites as breeding targets.
Assuntos
Mudança Climática , Melhoramento Vegetal , Produtos Agrícolas/fisiologia , Desenvolvimento Vegetal , Estresse FisiológicoRESUMO
Plants use light as energy for photosynthesis but also as a signal of competing vegetation. Using different concentrations of norflurazon and lincomycin, we found that the response to canopy shade in Arabidopsis (Arabidopsis thaliana) was repressed even when inhibitors only caused a modest reduction in the level of photosynthetic pigments. High inhibitor concentrations resulted in albino seedlings that were unable to elongate when exposed to shade, in part due to attenuated light perception and signaling via phytochrome B and phytochrome-interacting factors. The response to shade was further repressed by a retrograde network with two separate nodes represented by the transcription factor LONG HYPOCOTYL 5 and the carotenoid-derived hormone abscisic acid. The unveiled connection among chloroplast status, light (shade) signaling, and developmental responses should contribute to achieve optimal photosynthetic performance under light-changing conditions.
Assuntos
Ácido Abscísico/metabolismo , Arabidopsis/metabolismo , Cloroplastos/metabolismo , Proteínas de Arabidopsis/metabolismo , Regulação da Expressão Gênica de Plantas , Hipocótilo/metabolismo , Fitocromo/metabolismo , Fitocromo B/metabolismoRESUMO
Plants have evolved two major ways to deal with nearby vegetation or shade: avoidance and tolerance. Moreover, some plants respond to shade in different ways; for example, Arabidopsis (Arabidopsis thaliana) undergoes an avoidance response to shade produced by vegetation, but its close relative Cardamine hirsuta tolerates shade. How plants adopt opposite strategies to respond to the same environmental challenge is unknown. Here, using a genetic strategy, we identified the C. hirsuta slender in shade1 mutants, which produce strongly elongated hypocotyls in response to shade. These mutants lack the phytochrome A (phyA) photoreceptor. Our findings suggest that C. hirsuta has evolved a highly efficient phyA-dependent pathway that suppresses hypocotyl elongation when challenged by shade from nearby vegetation. This suppression relies, at least in part, on stronger phyA activity in C. hirsuta; this is achieved by increased ChPHYA expression and protein accumulation combined with a stronger specific intrinsic repressor activity. We suggest that modulation of photoreceptor activity is a powerful mechanism in nature to achieve physiological variation (shade tolerance versus avoidance) for species to colonize different habitats.
Assuntos
Arabidopsis/fisiologia , Cardamine/fisiologia , Luz , Fitocromo/metabolismo , Plântula/metabolismo , Arabidopsis/genética , Arabidopsis/efeitos da radiação , Proteínas de Arabidopsis , Cardamine/genética , Cardamine/efeitos da radiação , Regulação da Expressão Gênica de Plantas/efeitos da radiação , Genes de Plantas/genética , Hipocótilo/metabolismo , Fitocromo/genética , Fitocromo/efeitos da radiação , Fitocromo A/genética , Fitocromo A/metabolismo , Fitocromo B/genética , Fitocromo B/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Plântula/genética , Plântula/crescimento & desenvolvimento , Plântula/efeitos da radiaçãoRESUMO
Drought, heat and high irradiance are abiotic stresses that negatively affect plant development and reduce crop productivity. The confluence of these three factors is common in nature, causing extreme situations for plants that compromise their viability. Drought and heat stresses increase the saturation of the photosystem reaction centers, increasing sensitivity to high irradiance. In addition, these stress conditions affect photosystem II (PSII) integrity, alter redox balance of the electron transport chain and decrease the photosynthetic rate. Here, we studied the effect of the stress combinations on the photosynthetic apparatus of two citrus genotypes, Carrizo citrange (Citrus sinensis × Poncirus trifoliata) and Cleopatra mandarin (Citrus reshni). Results obtained showed that physiological responses, such as modulation of stomatal aperture and transpiration rate, aimed to reduce leaf temperature, are key to diminishing heat impact on photosynthetic apparatus and increasing tolerance to double and triple combinations of drought, high irradiance and high temperatures. By using transcriptomic and proteomic analyses, we have demonstrated that under these abiotic stress combinations, Carrizo plants were able to increase expression of genes and proteins related to the photosystem repairing machinery (which better maintained the integrity of PSII) and other components of the photosynthetic apparatus. Our findings reveal crucial physiological and genetic responses in citrus to increase tolerance to the combination of multiple abiotic stresses that could be the basis for breeding programs that ensure a sustainable citrus production.
Assuntos
Citrus , Citrus/genética , Complexo de Proteína do Fotossistema II/metabolismo , Proteômica , Resposta ao Choque Térmico , Estresse Fisiológico , SecasRESUMO
KEY MESSAGE: The activation of the antioxidant system under stress combination is a transmissible trait from the rootstock to the scion. Therefore, rootstock selection is key to improve crop performance and a sustainable production under changing climate conditions. Climate change is altering weather conditions such as mean temperatures and precipitation patterns. Rising temperatures, especially in certain regions, accelerates soil water depletion and increases drought risk, which affects agriculture yield. Previously, our research demonstrated that the citrus rootstock Carrizo citrange (Citrus sinensis × Poncirus trifoliata) is more tolerant than Cleopatra mandarin (C. reshni) to drought and heat stress combination, in part, due to a higher activation of the antioxidant system that alleviated damage produced by oxidative stress. Here, by using reciprocal grafts of both genotypes, we studied the importance of the rootstock on scion performance and antioxidant response under this stress combination. Carrizo rootstock, under stress combination, positively influenced Cleopatra scion by reducing H2O2 accumulation, increasing superoxide dismutase (SOD) and ascorbate peroxidase (APX) enzymatic activities and inducing SOD1, APX2 and catalase (CAT) protein accumulations. On the contrary, Cleopatra rootstock induced decreases in APX2 expression, CAT activity and SOD1, APX2 and CAT contents on Carrizo scion. Taken together, our findings indicate that the activation of the antioxidant system under stress combination is a transmissible trait from the rootstock to the scion and highlight the importance of the rootstock selection to improve crop performance and maintain citrus yield under the current scenario of climate change.
Assuntos
Citrus , Antioxidantes/metabolismo , Citrus/metabolismo , Secas , Resposta ao Choque Térmico , Peróxido de Hidrogênio/metabolismo , Superóxido Dismutase-1/metabolismoRESUMO
The role of salicylic acid (SA) on plant responses to biotic and abiotic stresses is well documented. However, the mechanism by which exogenous SA protects plants and its interactions with other phytohormones remains elusive. SA effect, both free and encapsulated (using silica and chitosan capsules), on Arabidopsis thaliana development was studied. The effect of SA on roots and rosettes was analysed, determining plant morphological characteristics and hormone endogenous levels. Free SA treatment affected length, growth rate, gravitropic response of roots and rosette size in a dose-dependent manner. This damage was due to the increase of root endogenous SA concentration that led to a reduction in auxin levels. The encapsulation process reduced the deleterious effects of free SA on root and rosette growth and in the gravitropic response. Encapsulation allowed for a controlled release of the SA, reducing the amount of hormone available and the uptake by the plant, mitigating the deleterious effects of the free SA treatment. Although both capsules are suitable as SA carrier matrices, slightly better results were found with chitosan. Encapsulation appears as an attractive technology to deliver phytohormones when crops are cultivated under adverse conditions. Moreover, it can be a good tool to perform basic experiments on phytohormone interactions.