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Leaf-cutting ants (Formicidae; Atta spp., Acromyrmex spp.) cut off pieces of leaves and other plant tissue and feed it to their symbiotic fungi. As this foraging behavior poses an imminent threat to agriculture, leaf-cutting ants are considered as pests of huge ecologically and economically importance. Consequently, research on leaf-cutting ants focused on their foraging decisions and interactions with their cultivated symbiotic fungi, whereas their effect on the attacked plants, apart from the loss of plant tissue, remains largely unknown. In this study, we investigated the consequences of an attack by leaf-cutting ants and analyzed the plants' defense responses in comparison to chewing caterpillars and mechanical damage. We found that an attack by leaf-cutting ants induces the production of jasmonates in several host and non-host plant species (Arabidopsis thaliana, Vicia faba, Phaseolus lunatus, Tococa quadrialata). Additionally, we showed in the natural host plant lima bean (P. lunatus) that leaf-cutting ant damage immediately leads to the emission of typical herbivory-induced plant volatiles, including green leaf volatiles and terpenoids. Further data exploration revealed clear differences in the defense-related phytohormone profile in plant species of Neotropical and Eurasian origin. Taken together, we show that leaf-cutting ant infestation and their way of clipping the plants' tissues induce jasmonate and jasmonates-mediated responses and do not differ from those to mechanical injury or larval feeding.
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This study investigated the accumulation of phenlyacetaldoxime (PAOx) and PAOx-Glc in Tococa quadrialata leaves in response to herbivore infestation and mechanical wounding. Results show that PAOx levels peaked at 24 h post-infestation, while PAOx-Glc remained present for several days. The accumulation of PAOx began as early as 3 h after herbivory, with PAOx-Glc significantly increased after 6 h. Mechanical wounding induced similar responses in PAOx and PAOx-Glc accumulation as herbivory, suggesting that continuous tissue damage triggers the production of these compounds. Interestingly, SpitWorm-treated leaves showed the highest levels of both PAOx and PAOx-Glc, indicating that herbivore-derived oral secretions (OS) play a role in the induction of these compounds. Additionally, JA-independent PAOx production was found to be associated with tissue damage rather than specific known signaling compounds. Emission of benzyl cyanide and 2-phenylethanol, PAOx-derived plant volatiles, was observed in response to herbivory and SpitWorm treatment providing plant-derived OS, further highlighting the role of herbivore cues in plant defense responses.
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Herbivoria , Folhas de Planta , Herbivoria/fisiologia , Folhas de Planta/metabolismo , AnimaisRESUMO
Plants assimilate inorganic nitrogen (N) to glutamine. Glutamine is the most abundant amino acid in most plant species, the N-supplying precursor of all N-containing compounds in the cell and the first organic nitrogen molecule formed from inorganic nitrogen taken up by the roots. In addition to its role in plant nutrition, glutamine most likely also has a function as a signaling molecule in the regulation of nitrogen metabolism. We investigated whether glutamine influences the high-affinity transporter system for nitrate uptake. Therefore, we analyzed the expression of the nitrate transporter NRT2.4, which is inducible by N deficiency, in Arabidopsis thaliana grown under different nitrogen starvation scenarios, comparing nitrate or glutamine as the sole nitrogen source. Using the reporter line ProNRT2.4:GFP and two independent knockout lines, nrt2.4-1 and nrt2.4-2, we analyzed gene expression and amino acid profiles. We showed that the regulation of NRT2.4 expression depends on available nitrogen in general, for example on glutamine as a nitrogen source, and not specifically on nitrate. In contrast to high nitrate concentrations, amino acid profiles changed to an accumulation of amino acids containing more than one nitrogen during growth in high glutamine concentrations, indicating a switch to nitrogen storage metabolism. Furthermore, we demonstrated that the nrt2.4-2 line shows unexpected effects on NRT2.5 gene expression and the amino acids profile in shoots under high glutamine supply conditions compared to Arabidopsis wild type and nrt2.4-1, suggesting non-NRT2.4-related metabolic consequences in this knockout line.
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The degradation of cellulose generates cellooligomers, which function as damage-associated molecular patterns and activate immune and cell wall repair responses via the CELLOOLIGOMER RECEPTOR KINASE1 (CORK1). The most active cellooligomer for the induction of downstream responses is cellotriose, while cellobiose is around 100 times less effective. These short-chain cellooligomers are also metabolized after uptake into the cells. In this study, we demonstrate that CORK1 is mainly expressed in the vascular tissue of the upper, fully developed part of the roots. Cellooligomer/CORK1-induced responses interfere with chitin-triggered immune responses and are influenced by BRASSINOSTEROID INSENSITIVE 1-ASSOCIATED RECEPTOR KINASE1 and the receptor kinase FERONIA. The pathway also controls sugar transporter and metabolism genes and the phosphorylation state of these proteins. Furthermore, cellotriose-induced ROS production and WRKY30/40 expression are controlled by the sugar transporters SUCROSE-PROTON SYMPORTER1, SUGARS WILL EVENTUALLY BE EXPORTED TRANSPORTER11 (SWEET11), and SWEET12. Our data demonstrate that cellooligomer/CORK1 signaling is integrated into the pattern recognition receptor network and coupled to the primary sugar metabolism in Arabidopsis roots.
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Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas de Arabidopsis/metabolismo , Imunidade Vegetal/genética , Açúcares/metabolismo , Proteínas de Membrana Transportadoras/metabolismoRESUMO
In plant-microbe-insect systems, plant-mediated responses involve the regulation and interactions of plant defense signaling pathways of phytohormones jasmonic acid (JA), ethylene (ET), and salicylic acid (SA). Phytoplasma subgroup 16SrI is the causal agent of Aster Yellows (AY) disease and is primarily transmitted by populations of aster leafhoppers (Macrosteles quadrilineatus Forbes). Aster Yellows infection in plants is associated with the downregulation of the JA pathway and increased leafhopper oviposition. The extent to which the presence of intact phytohormone-mediated defensive pathways regulates aster leafhopper behavioral responses, such as oviposition or settling preferences, remains unknown. We conducted no-choice and two-choice bioassays using a selection of Arabidopsis thaliana lines that vary in their defense pathways and repeated the experiments using AY-infected aster leafhoppers to evaluate possible differences associated with phytoplasma infection. While nymphal development was similar among the different lines and groups of AY-uninfected and AY-infected insects, the number of offspring and individual female egg load of AY-uninfected and AY-infected insects differed in lines with mutated components of the JA and SA signaling pathways. In most cases, AY-uninfected insects preferred to settle on wild-type (WT) plants over mutant lines; no clear pattern was observed in the settling preference of AY-infected insects. These findings support previous observations in other plant pathosystems and suggest that plant signaling pathways and infection with a plant pathogen can affect insect behavioral responses in more than one manner. Potential differences with previous work on AY could be related to the specific subgroup of phytoplasma involved in each case.
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Arabidopsis , Ciclopentanos , Hemípteros , Oviposição , Oxilipinas , Phytoplasma , Doenças das Plantas , Transdução de Sinais , Animais , Phytoplasma/fisiologia , Hemípteros/fisiologia , Hemípteros/microbiologia , Ciclopentanos/metabolismo , Oxilipinas/metabolismo , Arabidopsis/microbiologia , Arabidopsis/metabolismo , Arabidopsis/fisiologia , Arabidopsis/imunologia , Feminino , Doenças das Plantas/microbiologia , Ácido Salicílico/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Etilenos/metabolismoRESUMO
Date palm (Phoenix dactylifera L.) is able to grow and complete its life cycle while being rooted in highly saline soils. Which of the many well-known salt-tolerance strategies are combined to fine-tune this remarkable resilience is unknown. The precise location, whether in the shoot or the root, where these strategies are employed remains uncertain, leaving us unaware of how the various known salt-tolerance mechanisms are integrated to fine-tune this remarkable resilience. To address this shortcoming, we exposed date palm to a salt stress dose equivalent to seawater for up to 4 weeks and applied integrative multi-omics analyses followed by targeted metabolomics, hormone, and ion analyses. Integration of proteomic into transcriptomic data allowed a view beyond simple correlation, revealing a remarkably high degree of convergence between gene expression and protein abundance. This sheds a clear light on the acclimatization mechanisms employed, which depend on reprogramming of protein biosynthesis. For growth in highly saline habitats, date palm effectively combines various salt-tolerance mechanisms found in both halophytes and glycophytes: "avoidance" by efficient sodium and chloride exclusion at the roots, and "acclimation" by osmotic adjustment, reactive oxygen species scavenging in leaves, and remodeling of the ribosome-associated proteome in salt-exposed root cells. Combined efficiently as in P. dactylifera L., these sets of mechanisms seem to explain the palm's excellent salt stress tolerance.
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Phoeniceae , Phoeniceae/genética , Plantas Tolerantes a Sal/genética , Multiômica , Proteômica , Água do MarRESUMO
Non-mycorrhizal but beneficial fungi often mitigate (a)biotic stress-related traits in host plants. The underlying molecular mechanisms are mostly still unknown, as in the interaction between the endophytic growth-promoting soil fungus Mortierella hyalina and Arabidopsis thaliana. Here, abiotic stress in the form of nitrogen (N) deficiency was used to investigate the effects of the fungus on colonized plants. In particular, the hypothesis was investigated that fungal infection could influence N deficiency via an interaction with the high-affinity nitrate transporter NRT2.4, which is induced by N deficiency. For this purpose, Arabidopsis wild-type nrt2.4 knock-out and NRT2.4 reporter lines were grown on media with different nitrate concentrations with or without M. hyalina colonization. We used chemical analysis methods to determine the amino acids and phytohormones. Experimental evidence suggests that the fungus does not modulate NRT2.4 expression under N starvation. Instead, M. hyalina alleviates N starvation in other ways: The fungus supplies nitrogen (15N) to the N-starved plant. The presence of the fungus restores the plants' amino acid homeostasis, which was out of balance due to N deficiency, and causes a strong accumulation of branched-chain amino acids. We conclude that the plant does not need to invest in defense and resources for growth are maintained, which in turn benefits the fungus, suggesting that this interaction should be considered a mutualistic symbiosis.
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Proteínas de Arabidopsis , Arabidopsis , Mortierella , Proteínas de Arabidopsis/genética , Nitrogênio/metabolismo , Mortierella/metabolismo , Nitratos/metabolismo , Aminoácidos/metabolismo , Homeostase , Regulação da Expressão Gênica de Plantas , Proteínas de Transporte de Ânions/metabolismo , Raízes de Plantas/metabolismoRESUMO
Host jumps are a major factor for the emergence of new fungal pathogens. In the evolution of smut fungi, a putative host jump occurred in Sporisorium reilianum that today exists in two host-adapted formae speciales, the sorghum-pathogenic S. reilianum f. sp. reilianum and maize-pathogenic S. reilianum f. sp. zeae. To understand the molecular host-specific adaptation to maize, we compared the transcriptomes of maize leaves colonized by both formae speciales. We found that both varieties induce many common defense response-associated genes, indicating that both are recognized by the plant as pathogens. S. reilianum f. sp. reilianum additionally induced genes involved in systemic acquired resistance. In contrast, only S. reilianum f. sp. zeae induced expression of chorismate mutases that function in reducing the level of precursors for generation of the defense compound salicylic acid (SA), as well as oxylipin biosynthesis enzymes necessary for generation of the SA antagonist jasmonic acid (JA). In accordance, we found reduced SA levels as well as elevated JA and JA-Ile levels in maize leaves inoculated with the maize-adapted variety. These findings support a model of the emergence of the maize-pathogenic variety from a sorghum-specific ancestor following a recent host jump.
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Basidiomycota , Ustilaginales , Zea mays/genética , Ustilaginales/fisiologia , Plantas , Doenças das Plantas/microbiologiaRESUMO
Co-infestations by herbivores, a common situation found in natural settings, can distinctly affect induced plant defenses compared to single infestations. Related tritrophic interactions might be affected through the emission of changed blends of herbivore-induced plant volatiles (HIPVs). In a previous study, we observed that the infestation by red spider mite (Oligonychus ilicis) on coffee plants facilitated the infestation by white mealybug (Planococcus minor), whereas the reverse sequence of infestation did not occur. Here, we examined the involvement of the jasmonate and salicylate pathways in the plant-mediated asymmetrical facilitation between red spider mites and white mealybugs as well as the effect of multiple herbivory on attractiveness to the predatory mite Euseius concordis and the ladybug Cryptolaemus montrouzieri. Both mite and mealybug herbivory led to the accumulation of JA-Ile, JA, and cis-OPDA in plants, although the catabolic reactions of JA-Ile were specifically regulated by each herbivore. Infestation by mites or mealybugs induced the release of novel volatiles by coffee plants, which selectively attracted their respective predators. Even though the co-infestation by mites and mealybugs resulted in a stronger accumulation of JA-Ile, JA and SA than the single infestation treatments, the volatile emission was similar to that of mite-infested or mealybug-infested plants. However, multiple infestation had a negative impact on the attractiveness of HIPVs to the predators, making them less attractive to the predatory mite and a repellent to the ladybug. We discuss the potential underlying mechanisms of the susceptibility induced by mites, and the effect of multiple infestation on each predator.
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Coffea , Tetranychidae , Animais , Herbivoria , Café , Ciclopentanos/metabolismoRESUMO
BACKGROUND: Though many abiotic factors are constantly changing, the photoperiod is a predictable factor that enables plants to time many physiological responses. This timing is regulated by the circadian clock, yet little is known about how the clock adapts to the differences in photoperiod between mid-latitudes and high latitudes. The primary objective of this study was to compare how clock gene expression is modified in four woodland strawberry (Fragaria vesca L.) accessions originating from two different populations in Italy (IT1: Tenno, Italy, 45°N, IT4: Salorno, Italy, 46°N) and two in Northern Norway (NOR2: Alta, Norway, 69°N, NOR13: Indre Nordnes, Norway 69°N) when grown under simulated daylength conditions of an Arctic or mid-latitude photoperiod. The second objective was to investigate whether population origin or the difference in photoperiod influenced phytohormone accumulation. RESULTS: The Arctic photoperiod induced lower expression in IT4 and NOR13 for six clock genes (FvLHY, FvRVE8, FvPRR9, FvPRR7, FvPRR5, and FvLUX), in IT1 for three genes (FvLHY, FvPRR9, and FvPRR5) and in NOR2 for one gene (FvPRR9). Free-running rhythms for FvLHY in IT1 and IT4 were higher after the Arctic photoperiod, while the free-running rhythm for FvLUX in IT4 was higher after the mid-latitude photoperiod. IT1 showed significantly higher expression of FvLHY and FvPRR9 than all other accessions, as well as significantly higher expression of the circadian regulated phytohormone, abscisic acid (ABA), but low levels of salicylic acid (SA). NOR13 had significantly higher expression of FvRVE8, FvTOC1, and FvLUX than all other accessions. NOR2 had extremely low levels of auxin (IAA) and high levels of the jasmonate catabolite, hydroxyjasmonic acid (OH-JA). CONCLUSIONS: Our study shows that circadian rhythms in Fragaria vesca are driven by both the experienced photoperiod and genetic factors, while phytohormone levels are primarily determined by specific accessions' genetic factors rather than the experienced photoperiod.
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Relógios Circadianos , Fragaria , Fotoperíodo , Fragaria/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Ritmo Circadiano/genética , AclimataçãoRESUMO
Aldoximes are well-known metabolic precursors for plant defense compounds such as cyanogenic glycosides, glucosinolates, and volatile nitriles. They are also defenses themselves produced in response to herbivory; however, it is unclear whether aldoximes can be stored over a longer term as defense compounds and how plants protect themselves against the potential autotoxic effects of aldoximes. Here, we show that the Neotropical myrmecophyte tococa (Tococa quadrialata, recently renamed Miconia microphysca) accumulates phenylacetaldoxime glucoside (PAOx-Glc) in response to leaf herbivory. Sequence comparison, transcriptomic analysis, and heterologous expression revealed that 2 cytochrome P450 enzymes, CYP79A206 and CYP79A207, and the UDP-glucosyltransferase UGT85A123 are involved in the formation of PAOx-Glc in tococa. Another P450, CYP71E76, was shown to convert PAOx to the volatile defense compound benzyl cyanide. The formation of PAOx-Glc and PAOx in leaves is a very local response to herbivory but does not appear to be regulated by jasmonic acid signaling. In contrast to PAOx, which was only detectable during herbivory, PAOx-Glc levels remained high for at least 3 d after insect feeding. This, together with the fact that gut protein extracts of 3 insect herbivore species exhibited hydrolytic activity toward PAOx-Glc, suggests that the glucoside is a stable storage form of a defense compound that may provide rapid protection against future herbivory. Moreover, the finding that herbivory or pathogen elicitor treatment also led to the accumulation of PAOx-Glc in 3 other phylogenetically distant plant species suggests that the formation and storage of aldoxime glucosides may represent a widespread plant defense response.
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Glucosídeos , Herbivoria , Glucosídeos/metabolismo , Nitrilas/metabolismo , Sistema Enzimático do Citocromo P-450/genética , Sistema Enzimático do Citocromo P-450/metabolismo , Oximas/metabolismo , Folhas de Planta/metabolismoRESUMO
Sweet potato (Ipomoea batatas) is an important tuber crop, but also target of numerous insect pests. Intriguingly, the abundant storage protein in tubers, sporamin, has intrinsic trypsin protease inhibitory activity. In leaves, sporamin is induced by wounding or a volatile homoterpene and enhances insect resistance. While the signalling pathway leading to sporamin synthesis is partially established, the initial event, perception of a stress-related signal is still unknown. Here, we identified an IbLRR-RK1 that is induced upon wounding and herbivory, and related to peptide-elicitor receptors (PEPRs) from tomato and Arabidopsis. We also identified a gene encoding a precursor protein comprising a peptide ligand (IbPep1) for IbLRR-RK1. IbPep1 represents a distinct signal in sweet potato, which might work in a complementary and/or parallel pathway to the previously described hydroxyproline-rich systemin (HypSys) peptides to strengthen insect resistance. Notably, an interfamily compatibility in the Pep/PEPR system from Convolvulaceae and Solanaceae was identified.
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Ipomoea batatas , Ipomoea batatas/genética , Ipomoea batatas/metabolismo , Ligantes , Proteínas de Plantas/metabolismo , Regulação da Expressão Gênica de Plantas , Peptídeos/metabolismoRESUMO
N-acyl homoserine lactones (AHLs) are important players in plant-bacteria interactions. Different AHL-producing bacteria can improve plant growth and resistance against plant pathogens. In nature, plants may host a variety of AHL-producing bacteria and frequently experience numerous AHLs at the same time. Therefore, a coordinated response to combined AHL molecules is necessary. The purpose of this study was to explore the mechanism of AHL-priming using combined AHL molecules including N-(3-oxo-hexanoyl)-L-homoserine lactone, N-3-oxo-octanoyl-L-homoserine lactone, N-3-oxo-dodecanoyl-L-homoserine lactone, and N-3-oxo-tetradecanoyl-L-homoserine lactone and AHL-producing bacteria including Serratia plymuthica HRO-C48, Rhizobium etli CFN42, Burkholderia graminis DSM17151, and Ensifer meliloti (Sinorhizobium meliloti) Rm2011. We used transcriptome analysis, phytohormone measurements, as well as genetic and microbiological approaches to assess how the combination of structurally diverse AHL molecules influence Arabidopsis (Arabidopsis thaliana). Our findings revealed a particular response to a mixture of AHL molecules (AHL mix). Different expression patterns indicated that the reaction of plants exposed to AHL mix differs from that of plants exposed to single AHL molecules. In addition, different content of jasmonic acid (JA) and derivatives revealed that jasmonates play an important role in AHL mix-induced priming. The fast and stable decreased concentration of COOH-JA-Ile after challenge with the flagellin-derived peptide flg22 indicated that AHL mix modifies the metabolism of jasmonates. Study of various JA- and salicylic acid-related Arabidopsis mutants strengthened the notion that JA homeostasis is involved in AHL-priming. Understanding how the combination of AHLs primes plants for enhanced resistance has the potential to broaden our approaches in sustainable agriculture and will help to effectively protect plants against pathogens.
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Arabidopsis , Acil-Butirolactonas/farmacologia , Percepção de Quorum/genética , Bactérias , PlantasRESUMO
Phloridzin is the most abundant polyphenolic compound in apple (Malus × domestica Borkh.), which results from the action of a key phloretin-specific UDP-2'-O-glucosyltransferase (MdPGT1). Here, we simultaneously assessed the effects of targeting MdPGT1 by conventional transgenesis and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9)-mediated genome editing. To this end, we conducted transcriptomic and metabolic analyses of MdPGT1 RNA interference knockdown and genome-edited lines. Knockdown lines exhibited characteristic impairment of plant growth and leaf morphology, whereas genome-edited lines exhibited normal growth despite reduced foliar phloridzin. RNA-sequencing analysis identified a common core of regulated genes, involved in phenylpropanoid and flavonoid pathways. However, we identified genes and processes differentially modulated in stunted and genome-edited lines, including key transcription factors and genes involved in phytohormone signalling. Therefore, we conducted a phytohormone profiling to obtain insight into their role in the phenotypes observed. We found that salicylic and jasmonic acid were increased in dwarf lines, whereas auxin and ABA showed no correlation with the growth phenotype. Furthermore, bioactive brassinosteroids were commonly up-regulated, whereas gibberellin GA4 was distinctively altered, showing a sharp decrease in RNA interference knockdown lines. Expression analysis by reverse transcriptase-quantitative polymerase chain reaction expression analysis further confirmed transcriptional regulation of key factors involved in brassinosteroid and gibberellin interaction. These findings suggest that a differential modulation of phytohormones may be involved in the contrasting effects on growth following phloridzin reduction. The present study also illustrates how CRISPR/Cas9 genome editing can be applied to dissect the contribution of genes involved in phloridzin biosynthesis in apple.
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Malus , Malus/genética , Malus/metabolismo , Sistemas CRISPR-Cas , Florizina/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Giberelinas/metabolismo , Edição de Genes/métodosRESUMO
Infection with the necrotrophic fungus Diplodia sapinea (Fr.) Fuckel is among the economically and ecologically most devastating diseases of conifers in the northern hemisphere and is accelerated by global climate change. This study aims to characterize the changes mediated by D. sapinea infection on its pine host (Pinus sylvestris L.) that lead to the death of its needles. For this purpose, we performed an indoor infection experiment and inoculated shoot tips of pine seedlings with virulent D. sapinea. The consequences for foliar traits, including the phytohormone profile, were characterized at both the metabolite and transcriptome level. Our results showed that D. sapinea infection strongly affected foliar levels of most phytohormones and impaired a multitude of other metabolic and structural foliar traits, such as reactive oxygen species scavenging. Transcriptome analysis revealed that these changes are partially mediated via modified gene expression by fungal exposure. Diplodia sapinea appears to overcome the defense reactions of its pine host by reprogramming gene expression and post-transcriptional controls that determine essential foliar metabolic traits such as the phytohormone profile, cell wall composition and antioxidative system.
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Pinus sylvestris , Pinus , Reguladores de Crescimento de Plantas , Doenças das Plantas/microbiologia , Pinus/genética , Pinus/microbiologiaRESUMO
Global warming is predicted to change the growth conditions for plants and crops in regions at high latitudes (>60° N), including the Arctic. This will be accompanied by alterations in the composition of natural plant and pest communities, as herbivorous arthropods will invade these regions as well. Interactions between previously non-overlapping species may occur and cause new challenges to herbivore attack. However, plants growing at high latitudes experience less herbivory compared to plants grown at lower latitudes. We hypothesize that this finding is due to a gradient of constitutive chemical defense towards the Northern regions. We further hypothesize that higher level of defensive compounds is mediated by higher level of the defense-related phytohormone jasmonate. Because its biosynthesis is light dependent, Arctic summer day light conditions can promote jasmonate accumulation and, hence, downstream physiological responses. A pilot study with bilberry (Vaccinium myrtillus) plants grown under different light regimes supports the hypothesis.
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Ant-plant defensive mutualism is a widely studied phenomenon, where ants protect their host plants (myrmecophytes) against herbivores in return for the provision of nesting sites and food. However, few studies addressed the influence of ant colonization and herbivory on the plant's metabolism. We chose the Amazonian plant Tococa quadrialata, living in association with Azteca cf. tonduzi ants for an ant-exclusion study to reveal the chemistry behind this symbiosis. We found that colonized plants did not only benefit from protection but also from increased amino acid and nitrogen content, enabling better performance even in an herbivore-free environment. In contrast, ant-deprived T. quadrialata plants accumulated more ellagitannins, a major class of constitutive defense compounds. Moreover, herbivory-induced jasmonate-mediated defense responses, including the upregulation of signaling and defense genes and the emission of volatiles irrespective of colonization status. Altogether, we show how ant-colonization can influence the general and defense-related metabolism and performance of myrmecophytes.
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General volatile anesthetic diethyl ether blocks sensation and responsive behavior not only in animals but also in plants. Here, using a combination of RNA-seq and proteomic LC-MS/MS analyses, we investigated the effect of anesthetic diethyl ether on gene expression and downstream consequences in plant Arabidopsis thaliana. Differential expression analyses revealed reprogramming of gene expression under anesthesia: 6,168 genes were upregulated, 6,310 genes were downregulated, while 9,914 genes were not affected in comparison with control plants. On the protein level, out of 5,150 proteins identified, 393 were significantly upregulated and 227 were significantly downregulated. Among the highest significantly downregulated processes in etherized plants were chlorophyll/tetrapyrrole biosynthesis and photosynthesis. However, measurements of chlorophyll a fluorescence did not show inhibition of electron transport through photosystem II. The most significantly upregulated process was the response to heat stress (mainly heat shock proteins, HSPs). Using transgenic A. thaliana expressing APOAEQUORIN, we showed transient increase of cytoplasmic calcium level [Ca2+]cyt in response to diethyl ether application. In addition, cell membrane permeability for ions also increased under anesthesia. The plants pre-treated with diethyl ether, and thus with induced HSPs, had increased tolerance of photosystem II to subsequent heat stress through the process known as cross-tolerance or priming. All these data indicate that diethyl ether anesthesia may partially mimic heat stress in plants through the effect on plasma membrane.
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Plants use secondary metabolites such as polyphenols for chemical defense against pathogens and herbivores. Despite their importance in plant pathogen interactions and tolerance to diseases, it remains challenging to detect polyphenols in complex plant tissues. Here, we create molecular sensors for plant polyphenol imaging that are based on near-infrared (NIR) fluorescent single-wall carbon nanotubes (SWCNTs). We identified polyethylene glycol-phospholipids that render (6,5)-SWCNTs sensitive (Kd =90â nM) to plant polyphenols (tannins, flavonoids, ), which red-shift (up to 20â nm) and quench their emission (ca. 1000â nm). These sensors report changes in total polyphenol level after herbivore or pathogen challenge in crop plant systems (Soybean Glycine max) and leaf tissue extracts (Tococa spp.). We furthermore demonstrate remote chemical imaging of pathogen-induced polyphenol release from roots of soybean seedlings over the time course of 24â h. This approach allows in situ visualization and understanding of the chemical plant defense in real time and paves the way for plant phenotyping for optimized polyphenol secretion.
Assuntos
PolifenóisRESUMO
KEY MESSAGE: Calmodulin-like-proteins (CML) belong to a family of calcium-sensing proteins that are unique for plants and involved in many different developmental and stress-related reactions. In defense against herbivory, some pathogens and drought, CML37 acts as a positive and CML42 as a negative regulator, respectively. We provide evidence that both CMLs act antagonistically in the regulation of induced defense responses. A double knock-out line, cml37 x cml42, thus shows wild-type phenotypes upon all kind of stresses we used. A transient increase in the cytosolic calcium concentration is one of the first reactions that can be measured in plant cells upon abiotic as well as biotic stress treatments. These calcium signals are sensed by calcium binding proteins such as calmodulin-like proteins (CMLs), which transduce the sensed information into appropriate stress responses by interacting with downstream target proteins. In previous studies, CML37 has been shown to positively regulate the plants' defense against both the insect herbivore Spodoptera littoralis and the response to drought stress. In contrast, CML42 is known to negatively regulate those two stress responses. Here, we provide evidence that these two CMLs act antagonistically in the regulation of induced responses directed against drought and herbivory stress as well as in the defense against the necrotrophic pathogen Alternaria brassicicola. Both CMLs shape the plant reactions by altering the phytohormone signaling. Consequently, the phytohormone-regulated production of defensive compounds like glucosinolates is also antagonistically mediated by both CMLs. The finding that CML37 and CML42 have antagonistic roles in diverse stress-related responses suggests that these calcium sensor proteins represent important tools for the plant to balance and fine-tune the signaling and downstream reactions upon environmental stress.