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The phytohormone jasmonate (JA) plays a central role in plant defenses against biotic stressors. However, our knowledge of the JA signaling pathway in rice (Oryza sativa) remains incomplete. Here, we integrated multi-omic data from three tissues to characterize the functional modules involved in organizing JA-responsive genes. In the core regulatory sector, MYC2 transcription factor transcriptional cascades are conserved. in different species but with distinct regulators (e.g. bHLH6 in rice)., in which genes are early expressed across all tissues. In the feedback sector, MYC2 also regulates the expression of JA repressor and catabolic genes, providing negative feedback that truncates the duration of JA responses. For example, the MYC2-regulated NAC (NAM, ATAF1/2 and CUC2) transcription factor genes NAC1, NAC3, and NAC4 encode proteins that repress JA signaling and herbivore resistance. In the tissue-specific sector, many late-expressed genes are associated with the biosynthesis of specialized metabolites that mediate particular defensive functions. For example, the terpene synthase gene TPS35 is specifically induced in the leaf sheath and TPS35 functions in defense against oviposition by brown planthoppers and the attraction of this herbivore's natural enemies. Thus, by characterizing core, tissue-specific, and feedback sectors of JA-elicited defense responses, this work provides a valuable resource for future discoveries of key JA components in this important crop.
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Plant defense against herbivores is costly and often associated with growth repression. The phytohormone jasmonate (JA) plays a central role in prioritizing defense over growth during herbivore attack, but the underlying mechanisms remain unclear. When brown planthoppers (BPH, Nilaparvata lugens) attack rice (Oryza sativa), growth is dramatically suppressed. BPH infestation also increases inactive gibberellin (GA) levels and transcripts of GA 2-oxidase (GA2ox) genes, 2 (GA2ox3 and GA2ox7) of which encode enzymes that catalyze the conversion of bioactive GAs to inactive GAs in vitro and in vivo. Mutation of these GA2oxs diminishes BPH-elicited growth restriction without affecting BPH resistance. Phytohormone profiling and transcriptome analyses revealed that GA2ox-mediated GA catabolism was enhanced by JA signaling. The transcript levels of GA2ox3 and GA2ox7 were significantly attenuated under BPH attack in JA biosynthesis (allene oxide cyclase [aoc]) or signaling-deficient (myc2) mutants. In contrast, GA2ox3 and GA2ox7 expression was increased in MYC2 overexpression lines. MYC2 directly binds to the G-boxes in the promoters of both GA2ox genes to regulate their expression. We conclude that JA signaling simultaneously activates defense responses and GA catabolism to rapidly optimize resource allocation in attacked plants and provides a mechanism for phytohormone crosstalk.
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When insect herbivores attack plants, elicitors from oral secretions and regurgitants (OS) enter wounds during feeding, eliciting defense responses. These generally require plant jasmonate (JA) signaling, specifically, a jasmonoyl-L-isoleucine (JA-Ile) burst, for their activation and are well studied in the native tobacco Nicotiana attenuata. We used intraspecific diversity captured in a 26-parent MAGIC population planted in nature and an updated genome assembly to impute natural variation in the OS-elicited JA-Ile burst linked to a mutation in the JA-Ile biosynthetic gene NaJAR4. Experiments revealed that NaJAR4 variants were associated with higher fitness in the absence of herbivores but compromised foliar defenses, with two NaJAR homologues (4 and 6) complementing each other spatially and temporally. From decade-long seed collections of natural populations, we uncovered enzymatically inactive variants occurring at variable frequencies, consistent with a balancing selection regime maintaining variants. Integrative analyses of OS-induced transcriptomes and metabolomes of natural accessions revealed that NaJAR4 is embedded in a nonlinear complex gene coexpression network orchestrating responses to OS, which we tested by silencing four hub genes in two connected coexpressed networks and examining their OS-elicited metabolic responses. Lines silenced in two hub genes (NaGLR and NaFB67) co-occurring in the NaJAR4/6 module showed responses proportional to JA-Ile accumulations; two from an adjacent module (NaERF and NaFB61) had constitutively expressed defenses with high resistance. We infer that mutations with large fitness consequences can persist in natural populations due to compensatory responses from gene networks, which allow for diversification in conserved signaling pathways and are generally consistent with predictions of an omnigene model.
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Redes Reguladoras de Genes , Herbivoria , Herbivoria/genética , MutaciónRESUMEN
Plants produce chemical defenses that poison insect herbivores or deter their feeding, but herbivores are also accompanied by microbial endosymbionts crucial for their nutrition, reproduction, and fitness. Hence, plant defenses could target a herbivore's beneficial endosymbionts, but this has not yet been demonstrated. Here, we studied flavonoids that are induced when rice is attacked by a phloem-feeding pest, the brown planthopper (BPH), which harbors beneficial yeast-like symbionts (YLS) essential for insect nutrition, such as by remedying deficiencies in sterols. BPH attack dramatically increased sakuranetin accumulations in leaf sheaths and phloem exudates. Sakuranetin is an antifungal phytoalexin derived from the antibacterial precursor, naringenin, via catalysis of naringenin-O-methyltransferase (NOMT). When added to artificial diets, sakuranetin decreased BPH survivorship, suggesting that it functions as an induced defense. Mutation of NOMT abolished sakuranetin accumulation and increased BPH oviposition and hatching rates. High-throughput amplicon sequencing revealed that BPH fed on sakuranetin-deficient nomt lines were enriched in YLS with only minor changes in the bacterial endosymbionts, compared to those feeding on sakuranetin-rich wild-type (WT) plants. In-vitro feeding of sakuranetin suggested that this flavonoid directly inhibited the growth of YLS. BPH feeding on nomt lines accumulated higher cholesterol levels, which might be attributed to increases in the supply of sterol precursors from the YLS, while nomt lines suffered more damage than WT plants did from BPH herbivory. BPH-elicited accumulation of sakuranetin requires intact jasmonate (JA) signaling. This study reveals that rice uses a JA-induced antifungal flavonoid phytoalexin in defense against BPH by inhibiting its beneficial endosymbionts.
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Hemípteros , Oryza , Animales , Femenino , Antifúngicos , Flavonoides/farmacología , Regulación de la Expresión Génica de las Plantas , Oryza/genéticaRESUMEN
The apocarotenoid strigolactones (SLs) facilitate pre-symbiotic communication between arbuscular mycorrhizal (AM) fungi and plants. Related blumenol-C-glucosides (blumenols), have also been associated with symbiosis, but the cues that are involved in the regulation of blumenol accumulation during AM symbiosis remain unclear. In rice, our analyses demonstrated a strict correlation between foliar blumenol abundance and intraradical fungal colonisation. More specifically, rice mutants affected at distinct stages of the interaction revealed that fungal cortex invasion was required for foliar blumenol accumulation. Plant phosphate status and D14L hormone signalling had no effect, contrasting their known role in induction of SLs. This a proportion of the SL biosynthetic enzymes, D27 and D17, are equally required for blumenol production. These results importantly clarify that, while there is a partially shared biosynthetic pathway between SL and blumenols, the dedicated induction of the related apocarotenoids occurs in response to cues acting at distinct stages during the root colonisation process. However, we reveal that neither SLs nor blumenols are essential for fungal invasion of rice roots.
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Lactonas , Micorrizas , Oryza , Simbiosis , Micorrizas/fisiología , Oryza/microbiología , Oryza/metabolismo , Oryza/genética , Oryza/fisiología , Lactonas/metabolismo , Raíces de Plantas/microbiología , Raíces de Plantas/metabolismo , Reguladores del Crecimiento de las Plantas/metabolismo , Glucósidos/metabolismo , Regulación de la Expresión Génica de las PlantasRESUMEN
Pentacyclic triterpenoids, recognized for their natural bioactivity, display complex spatiotemporal accumulation patterns within the ecological model plant Nicotiana attenuata. Despite their ecological importance, the underlying biosynthetic enzymes and functional attributes of triterpenoid synthesis in N. attenuata remain unexplored. Here, we show that three cytochrome P450 monooxygenases (NaCYP716A419, NaCYP716C87, and NaCYP716E107) from N. attenuata oxidize the pentacyclic triterpene skeleton, as evidenced by heterologous expression in Nicotiana benthamiana. NaCYP716A419 catalyzed a consecutive three-step oxidation reaction at the C28 position of ß-amyrin/lupeol/lupanediol, yielding the corresponding alcohol, aldehyde, and carboxylic acid. NaCYP716C87 hydroxylated the C2α position of ß-amyrin/lupeol/lupanediol/erythrodiol/oleanolic acid/betulinic acid, while NaCYP716E107 hydroxylated the C6ß position of ß-amyrin/oleanolic acid. The genes encoding these three CYP716 enzymes are highly expressed in flowers and respond to induction by ABA, MeJA, SA, GA3, and abiotic stress treatments. Using VIGS technology, we revealed that silencing of NaCYP716A419 affects the growth and reproduction of N. attenuata, suggesting the ecological significance of these specialized metabolite biosynthetic steps.
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Deploying toxins in complex mixtures is thought to be advantageous and is observed during antagonistic interactions in nature. Toxin mixtures are widely utilized in medicine and pest control, as they are thought to slow the evolution of detoxification counterresponses in the targeted organisms. Here we show that caterpillars rearrange key constituents of two distinct plant defense pathways to postingestively disable the defensive properties of both pathways. Specifically, phenolic esters of quinic acid, chlorogenic acids (CAs), potent herbivore and ultraviolet (UV) defenses, are reesterified to decorate particular sugars of 17-hydroxygeranyllinalool diterpene glycosides (HGL-DTGs) and prevent their respective antiherbivore defense functions. This was discovered through the employment of comparative metabolomics of the leaves of Nicotiana attenuata and the frass of this native tobacco's specialist herbivore, Manduca sexta larvae. Feeding caterpillars on leaves of transgenic plants abrogated in each of the two pathways, separately and together, revealed that one of the fully characterized frass conjugates, caffeoylated HGL-DTG, originated from ingested CA and HGL-DTGs and that both had negative effects on the defensive function of the other compound class, as revealed by rates of larval mass gain. This negative defensive synergy was further explored in 183 N. attenuata natural accessions, which revealed a strong negative covariance between the two defense pathways. Further mapping analyses in a biparental recombinant inbred line (RIL) population imputed quantitative trait loci (QTLs) for the two pathways at distinct genomic locations. The postingestive repurposing of defense metabolism constituents reveals a downside of deploying toxins in mixtures, a downside which plants in nature have evolved to counter.
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Manduca , Animales , Herbivoria , Insectos/metabolismo , Larva/metabolismo , Manduca/metabolismo , Proteínas de Plantas/metabolismo , Nicotiana/metabolismoRESUMEN
Nicotiana attenuata styles preferentially select pollen from among accessions with corresponding expression patterns of NaS-like-RNases (SLRs), and the postpollination ethylene burst (PPEB) is an accurate predictor of seed siring success. However, the ecological consequences of mate selection, its effect on the progeny, and the role of SLRs in the control of ethylene signaling remain unknown. We explored the link between the magnitude of the ethylene burst and expression of the SLRs in a set of recombinant inbred lines (RILs), dissected the genetic underpinnings of mate selection through genome-wide association study (GWAS), and examined its outcome for phenotypes in the next generation. We found that high levels of PPEB are associated with the absence of SLR2 in most of the tested RILs. We identified candidate genes potentially involved in the control of mate selection and showed that pollination of maternal genotypes with their favored pollen donors produces offspring with longer roots. When the maternal genotypes are only able to select against nonfavored pollen donors, the selection for such positive traits is abolished. We conclude that plants' ability of mate choice contributes to measurable changes in progeny phenotypes and is thus likely a target of selection.
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Regulación de la Expresión Génica de las Plantas , Fenotipo , Polen , Ribonucleasas , Polen/genética , Polen/fisiología , Ribonucleasas/genética , Ribonucleasas/metabolismo , Nicotiana/genética , Nicotiana/fisiología , Etilenos/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Polinización , Estudio de Asociación del Genoma Completo , Cigoto/metabolismo , Genotipo , EndogamiaRESUMEN
Laboratory studies have revealed that strigolatone (SL) and karrikin (KAR) signalling mediate responses to abiotic and biotic stresses, and reshape branching architecture that could increase reproductive performance and crop yields. To understand the ecological function of SL and KAR signalling, transgenic lines of wild tobacco Nicotiana attenuata, silenced in SL/KAR biosynthesis/signalling were grown in the glasshouse and in two field plots in the Great Basin Desert in Utah over four field seasons. Of the lines silenced in SL and KAR signalling components (irMAX2, irD14, irKAI2 and irD14 × irKAI2 plants), which exhibited the expected increases in shoot branching, only irMAX2 plants showed a strong leaf-bleaching phenotype when grown in the field. In the field, irMAX2 plants had lower sugar and higher leaf amino acid contents, lower lifetime fitness and were more susceptible to herbivore attack compared to wild-type plants. These irMAX2 phenotypes were not observed in glasshouse-grown plants. Transcriptomic analysis revealed dramatic responses to high-light intensity in irMAX2 leaves in the field: lutein contents decreased, and transcriptional responses to high-intensity light, singlet oxygen and hydrogen peroxide increased. PAR and UV-B manipulations in the field revealed that the irMAX2 bleaching phenotype is reversed by decreasing PAR, but not UV-B fluence. We propose that NaMAX2 functions in high-light adaptation and fitness optimisation by regulating high-light responses independently of its roles in the SL and KAR signalling pathways. The work provides another example of the value of studying the function of genes in the complex environments in which plants evolved, namely nature.
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Nicotiana , Hojas de la Planta , Nicotiana/metabolismo , Perfilación de la Expresión GénicaRESUMEN
The native diploid tobacco Nicotiana attenuata produces abundant, potent anti-herbivore defense metabolites known as 17-hydroxygeranyllinalool diterpene glycosides (HGL-DTGs) whose glycosylation and malonylation biosynthetic steps are regulated by jasmonate signaling. To characterize the biosynthetic pathway of HGL-DTGs, we conducted a genome-wide analysis of uridine diphosphate glycosyltransferases (UGTs) and identified 107 family-1 UGT members. The transcript levels of three UGTs were highly correlated with the transcript levels two key HGL-DTG biosynthetic genes: geranylgeranyl diphosphate synthase (NaGGPPS) and geranyllinalool synthase (NaGLS). NaGLS's role in HGL-DTG biosynthesis was confirmed by virus-induced gene silencing. Silencing the Uridine diphosphate (UDP)-rhamnosyltransferase gene UGT91T1 demonstrated its role in the rhamnosylation of HGL-DTGs. In vitro enzyme assays revealed that UGT74P3 and UGT74P4 use UDP-glucose for the glucosylation of 17-hydroxygeranyllinalool (17-HGL) to lyciumoside I. Plants with stable silencing of UGT74P3 and UGT74P5 were severely developmentally deformed, pointing to a phytotoxic effect of the aglycone. The application of synthetic 17-HGL and silencing of the UGTs in HGL-DTG-free plants confirmed this phytotoxic effect. Feeding assays with tobacco hornworm (Manduca sexta) larvae revealed the defensive functions of the glucosylation and rhamnosylation steps in HGL-DTG biosynthesis. Glucosylation of 17-HGL is therefore a critical step that contributes to the resulting metabolites' defensive function and solves the autotoxicity problem of this potent chemical defense.
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Monoterpenos Acíclicos/metabolismo , Diterpenos/metabolismo , Glicósidos/metabolismo , Nicotiana/metabolismo , Monoterpenos Acíclicos/química , Animales , Vías Biosintéticas , Silenciador del Gen , Glicosilación , Glicosiltransferasas/metabolismo , Herbivoria , Larva/fisiología , Manduca/fisiología , Metabolómica , Necrosis , Hojas de la Planta/metabolismo , Plantas Modificadas Genéticamente , Proteínas Recombinantes/metabolismoRESUMEN
Adsorption-based extracorporeal therapies have been subject to technical developments and clinical application for close to five decades. More recently, new technological developments in membrane and sorbent manipulation have made it possible to deliver more biocompatible extracorporeal adsorption therapies to patients with a variety of conditions. There are several key rationales based on physicochemical principles and clinical considerations that justify the application and investigation of such therapies as evidenced by multiple ex-vivo, experimental, and clinical observations. Accordingly, unspecific adsorptive extracorporeal therapies have now been applied to the treatment of a wide array of conditions from poisoning to drug overdoses, to inflammatory states and sepsis, and acute or chronic liver and kidney failure. In response to the rapidly expanding knowledge base and increased clinical evidence, we convened an Acute Disease Quality Initiative (ADQI) consensus conference dedicated to such treatment. The data show that hemoadsorption has clinically acceptable short-term biocompatibility and safety, technical feasibility, and experimental demonstration of specified target molecule removal. Pilot studies demonstrate potentially beneficial effects on physiology and larger studies of endotoxin-based hemoadsorption have identified possible target phenotypes for larger randomized controlled trials (RCTs). Moreover, in a variety of endogenous and exogenous intoxications, removal of target molecules has been confirmed in vivo. However, some studies have raised concerns about harm or failed to deliver benefits. Thus, despite many achievements, modern hemoadsorption remains a novel and experimental intervention with limited data, and a large research agenda.
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BACKGROUND: Historically IV and enteral fluids given during acute kidney injury (AKI) were restricted before the introduction of continuous renal replacement therapies (CRRTs) when more liberal fluids improved nutrition for the critically ill. However, fluid accumulation can occur when higher volumes each day are not considered in the fluid balance prescribing and the NET ultrafiltration (NUF) volume target. KEY MESSAGES: The delivered hours of CRRT each day are vital for achievement of fluid balance and time off therapy makes the task more challenging. Clinicians inexperienced with CRRT make this aspect of AKI management a focus of rounding with senior oversight, clear communication, and "precision" a clinical target. Sepsis-associated AKI can be a complex patient where resuscitation and admission days are with a positive fluid load and replacement mind set. Subsequent days in ICU requires fluid regulation, removal, with a comprehensive multilayered assessment before prescribing the daily fluid balance target and the required hourly NET plasma water removal rate (NUF rate). Future machines may include advanced software, new alarms - display metrics, messages and association with machine learning and "AKI models" for setting, monitoring, and guaranteeing fluid removal. This could also link to current hardware such as on-line blood volume assessment with continuous haematocrit measurement. SUMMARY: Fluid balance in the acutely ill is a challenge where forecasting and prediction are necessary. NUF rate and volume each hour should be tracked and adjusted to achieve the daily target. This requires human and machine connections.
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Lesión Renal Aguda , Terapia de Reemplazo Renal Continuo , Equilibrio Hidroelectrolítico , Humanos , Terapia de Reemplazo Renal Continuo/métodos , Lesión Renal Aguda/terapia , Fluidoterapia/métodos , Enfermedad Crítica , Sepsis/terapiaRESUMEN
INTRODUCTION: Hematocrit monitoring during continuous renal replacement therapy (CRRT) allows the continuous estimation of relative blood volume (RBV). This may enable early detection of intravascular volume depletion prior to clinical sequelae. We aimed to investigate the feasibility of extended RBV monitoring and its epidemiology during usual CRRT management by clinicians unaware of RBV. Moreover, we studied the association between changes in RBV and net ultrafiltration (NUF) rates. METHODS: In a cohort of adult intensive care unit patients receiving CRRT, we continuously monitored hematocrit and RBV using a pre-filter non-invasive optical sensor. We analyzed temporal changes in RBV and investigated the association between RBV change and NUF rates, using the classification of NUF rates into low, moderate, or high based on predefined cut-offs. RESULTS: We obtained >60,000 minute-by-minute measurements in >1,000 CRRT hours in 36 patients. The median RBV change was negative (decrease) in 69% of patients and the median peak change in RBV was -9.3% (IQR -3.9% to -14.3%). Moreover, the median RBV decreased from baseline by >5% in 40.2% of measurements and by >10% in 20.6% of measurements. Finally, RBV decreased significantly more when patients received a high NUF rate (>1.75 ml/kg/h) compared to low or moderate NUF rates (5.32% vs 1.93% or 1.97%, p<0.001). CONCLUSION: Continuous hematocrit and RBV monitoring during CRRT was feasible. RBV decreased significantly during CRRT, and decreases were greater with higher NUF rates. RBV monitoring may help optimize NUF management and prevent the occurrence of intravascular volume depletion.
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BACKGROUND: Continuous haemoglobin, venous blood oxygen saturation, and haematocrit (Hct) monitoring is currently not applied during continuous renal replacement therapy (CRRT). Such Hct monitoring enables estimation of changes in blood volume as percentage change (ΔBV%) from therapy start time and is incorporated into intermittent haemodialysis machines but not CRRT machines despite its potential to optimise fluid management in CRRT patients. METHODS: To overcome this problem, we used a standalone monitor (CRIT-LINE®IV, Fresenius Medical Care, Concord, USA) with an associated in-line blood chamber (CRIT-LINE®IV Blood Chamber, Fresenius Medical Care, Concord, USA) and designed our own adaptor connection piece (TekMed and Morriset, Melbourne and Brisbane, Australia) to allow these readings at the vascular access outflow and recorded data for estimated Hct and derived ΔBV% during CRRT. RESULTS: We report on this technique with an illustrative case example and 12 h of CRRT data on the fluid loss rate prescribed, hourly net patient fluid loss (range: 0-308 mL/h), mean arterial pressure, norepinephrine dose (range: 5-14 mcg/min), estimated continuous Hct and ΔBV%, and the otherwise undetected diagnosis of an approximate 15 % decrease in blood volume during the CRRT. CONCLUSION: We have described a technical CRRT circuit modification that can facilitate a previously unavailable assessment of fluid shifts during CRRT. Further application in clinical trials is now possible.
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Volumen Sanguíneo , Terapia de Reemplazo Renal Continuo , Humanos , Terapia de Reemplazo Renal Continuo/métodos , Hematócrito , Monitoreo Fisiológico/métodos , Determinación del Volumen Sanguíneo/métodos , Masculino , Lesión Renal Aguda/terapia , Lesión Renal Aguda/sangreRESUMEN
MAIN CONCLUSION: Nicotiana attenuata's capacity to interact with arbuscular mycorrhizal fungi influences its intraspecific competitive ability under field and glasshouse conditions, but not its overall community productivity. Arbuscular mycorrhizal (AM) fungi can alter the nutrient status and growth of plants, and they can also affect plant-plant, plant-herbivore, and plant-pathogen interactions. These AM effects are rarely studied in populations under natural conditions due to the limitation of non-mycorrhizal controls. Here we used a genetic approach, establishing field and glasshouse communities of AM-harboring Nicotiana attenuata empty vector (EV) plants and isogenic plants silenced in calcium- and calmodulin-dependent protein kinase expression (irCCaMK), and unable to establish AM symbioses. Performance and growth were quantified in communities of the same (monocultures) or different genotypes (mixed cultures) and both field and glasshouse experiments returned similar responses. In mixed cultures, AM-harboring EV plants attained greater stalk lengths, shoot and root biomasses, clearly out-competing the AM fungal-deficient irCCaMK plants, while in monocultures, both genotypes grew similarly. Competitive ability was also reflected in reproductive traits: EV plants in mixed cultures outperformed irCCaMK plants. When grown in monocultures, the two genotypes did not differ in reproductive performance, though total leaf N and P contents were significantly lower independent of the community type. Plant productivity in terms of growth and seed production at the community level did not differ, while leaf nutrient content of phosphorus and nitrogen depended on the community type. We infer that AM symbioses drastically increase N. attenuata's competitive ability in mixed communities resulting in increased fitness for the individuals harboring AM without a net gain for the community.
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Micorrizas , Micorrizas/fisiología , Raíces de Plantas , Plantas , Nicotiana/genética , Nicotiana/microbiología , Biomasa , Hongos/fisiología , Suelo , SimbiosisRESUMEN
Plants interact with arbuscular mycorrhizal fungi (AMF) and in doing so, change transcript levels of many miRNAs and their targets. However, the identity of an Argonaute (AGO) that modulates this interaction remains unknown, including in Nicotiana attenuata. We examined how the silencing of NaAGO1/2/4/7/and 10 by RNAi influenced plant-competitive ability under low-P conditions when they interact with AMF. Furthermore, the roles of seven miRNAs, predicted to regulate signaling and phosphate homeostasis, were evaluated by transient overexpression. Only NaAGO7 silencing by RNAi (irAGO7) significantly reduced the competitive ability under P-limited conditions, without changes in leaf or root development, or juvenile-to-adult phase transitions. In plants growing competitively in the glasshouse, irAGO7 roots were over-colonized with AMF, but they accumulated significantly less phosphate and the expression of their AMF-specific transporters was deregulated. Furthermore, the AMF-induced miRNA levels were inversely regulated with the abundance of their target transcripts. miRNA overexpression consistently decreased plant fitness, with four of seven-tested miRNAs reducing mycorrhization rates, and two increasing mycorrhization rates. Overexpression of Na-miR473 and Na-miRNA-PN59 downregulated targets in GA, ethylene, and fatty acid metabolism pathways. We infer that AGO7 optimizes competitive ability and colonization by regulating miRNA levels and signaling pathways during a plant's interaction with AMF.
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MicroARNs , Micorrizas , Nicotiana/metabolismo , Micorrizas/fisiología , Raíces de Plantas/metabolismo , MicroARNs/genética , MicroARNs/metabolismo , Fosfatos/metabolismoRESUMEN
Hydroxy- and carboxyblumenol C-glucosides specifically accumulate in roots and leaves of plants harboring arbuscular mycorrhizal fungi (AMF). To explore blumenol function in AMF relationships, we silenced an early key-gene in blumenol biosynthesis, CCD1 (carotenoid cleavage dioxygenase 1), in the ecological model plant, Nicotiana attenuata, and analyzed whole-plant performance in comparison with control and CCaMK-silenced plants, unable to form AMF associations. Root blumenol accumulations reflected a plant's Darwinian fitness, as estimated by capsule production, and were positively correlated with AMF-specific lipid accumulations in roots, with relationships that changed as plants matured when grown without competitors. When grown with wild-type competitors, transformed plants with decreased photosynthetic capacity or increased carbon flux to roots had blumenol accumulations that predicted plant fitness and genotype trends in AMF-specific lipids, but had similar levels of AMF-specific lipids between competing plants, likely reflecting AMF-networks. We propose that when grown in isolation, blumenol accumulations reflect AMF-specific lipid allocations and plant fitness. When grown with competitors, blumenol accumulations predict fitness outcomes, but not the more complicated AMF-specific lipid accumulations. RNA-seq analysis provided candidates for the final biosynthetic steps of these AMF-indicative blumenol C-glucosides; abrogation of these steps will provide valuable tools for understanding blumenol function in this context-dependent mutualism.
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Micorrizas , Raíces de Plantas/microbiología , Simbiosis , Plantas/microbiología , LípidosRESUMEN
In response to challenges from herbivores and competitors, plants use fitness-limiting resources to produce (auto)toxic defenses. Jasmonate signaling, mediated by MYC2 transcription factors (TF), is thought to reconfigure metabolism to minimize these formal costs of defense and optimize fitness in complex environments. To study the context-dependence of this metabolic reconfiguration, we cosilenced NaMYC2a/b by RNAi in Nicotiana attenuata and phenotyped plants in the field and increasingly realistic glasshouse setups with competitors and mobile herbivores. NaMYC2a/b had normal phytohormonal responses, and higher growth and fitness in herbivore-reduced environments, but were devastated in high herbivore-load environments in the field due to diminished accumulations of specialized metabolites. In setups with competitors and mobile herbivores, irMYC2a/b plants had lower fitness than empty vector (EV) in single-genotype setups but increased fitness in mixed-genotype setups. Correlational analyses of metabolic, resistance, and growth traits revealed the expected defense/growth associations for most sectors of primary and specialized metabolism. Notable exceptions were some HGL-DTGs and phenolamides that differed between single-genotype and mixed-genotype setups, consistent with expectations of a blurred functional trichotomy of metabolites. MYC2 TFs mediate the reconfiguration of primary and specialized metabolic sectors to allow plants to optimize their fitness in complex environments.
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Manduca , Nicotiana , Animales , Nicotiana/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Oxilipinas/metabolismo , Manduca/fisiología , Interferencia de ARN , Herbivoria/fisiología , Ciclopentanos/metabolismoRESUMEN
The phytohormones, jasmonates (JAs), mediate many plant developmental processes and their responses to important environmental stresses, such as herbivore attack. Bioactive JAs are perceived by CORONATINE INSENSITIVE (COI)-receptors, and associated JAZ proteins, to activate downstream responses. To date, the JA receptors of the important monocot crop plant, rice, remain to be explored. Here, we studied all three rice COI proteins, OsCOI1a, OsCOI1b, and OsCOI2, by ligand binding, genome editing, and phenotyping and examining some of the responsible mechanisms for the different responses. OsCOI2 binds to most individual OsJAZs in the presence of endogenous JA ligands, as OsCOI1a /1b do, albeit with greater partner selectivity. Single mutants of each OsCOI and OsCOI1a/1b double mutants were constructed by CRIPSR-Cas9-based genome editing and used to phenotype developmental and defense responses. OsCOI1b is involved in root growth and grain-size control and plays overlapping roles with OsCOI1a in spikelet development, while OsCOI2 regulates leaf senescence, male sterility, root growth, and grain size. All OsCOIs mediated resistance to the devastating rice pest, the brown planthopper. However, the defense sectors regulated by OsCOI1a/1b and OsCOI2 clearly differed. Our results revealed that all three OsCOIs are functional JA receptors that play diverse roles in regulating downstream JA responses.
Asunto(s)
Proteínas de Arabidopsis , Arabidopsis , Oryza , Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Oryza/metabolismo , Reguladores del Crecimiento de las Plantas/metabolismo , Plantas/metabolismo , Ciclopentanos/metabolismo , Oxilipinas/metabolismo , Regulación de la Expresión Génica de las PlantasRESUMEN
Plants are attacked by herbivores, which often specialize on different tissues, and in response, have evolved sophisticated resistance strategies that involve different types of chemical defenses frequently targeted to different tissues. Most known phytohormones have been implicated in regulating these defenses, with jasmonates (JAs) playing a pivotal role in complex regulatory networks of signaling interactions, often generically referred to as "cross talk." The newly identified class of phytohormones, strigolactones (SLs), known to regulate the shoot architecture, remain unstudied with regard to plant-herbivore interactions. We explored the role of SL signaling in resistance to a specialist weevil (Trichobaris mucorea) herbivore of the native tobacco, Nicotiana attenuata, that attacks the root-shoot junction (RSJ), the part of the plant most strongly influenced by alterations in SL signaling (increased branching). As SL signaling shares molecular components, such as the core F-box protein MORE AXILLARY GROWTH 2 (MAX2), with another new class of phytohormones, the karrikins (KARs), which promote seed germination and seedling growth, we generated transformed lines, individually silenced in the expression of NaMAX2, DWARF 14 (NaD14: the receptor for SL) and CAROTENOID CLEAVAGE DIOXYGENASE 7 (NaCCD7: a key enzyme in SL biosynthesis), and KARRIKIN INSENSITIVE 2 (NaKAI2: the KAR receptor). The mature stems of all transgenic lines impaired in the SL, but not the KAR signaling pathway, overaccumulated anthocyanins, as did the stems of plants attacked by the larvae of weevil, which burrow into the RSJs to feed on the pith of N. attenuata stems. T. mucorea larvae grew larger in the plants silenced in the SL pathway, but again, not in the KAI2-silenced plants. These phenotypes were associated with elevated JA and auxin (indole-3-acetic acid [IAA]) levels and significant changes in the accumulation of defensive compounds, including phenolamides and nicotine. The overaccumulation of phenolamides and anthocyanins in the SL pathway-silenced plants likely resulted from antagonism between the SL and JA pathway in N. attenuata. We show that the repressors of SL signaling, suppressor of max2-like (NaSMXL6/7), and JA signaling, jasmonate zim-domain (NaJAZs), physically interact, promoting NaJAZb degradation and releasing JASMONATE INSENSITIVE 1 (JIN1/MYC2) (NaMYC2), a critical transcription factor promoting JA responses. However, the increased performance of T. mucorea larvae resulted from lower pith nicotine levels, which were inhibited by increased IAA levels in SL pathway-silenced plants. This inference was confirmed by decapitation and auxin transport inhibitor treatments that decreased pith IAA and increased nicotine levels. In summary, SL signaling tunes specific sectors of specialized metabolism in stems, such as phenylpropanoid and nicotine biosynthesis, by tailoring the cross talk among phytohormones, including JA and IAA, to mediate herbivore resistance of stems. The metabolic consequences of the interplay of SL, JA, and IAA signaling revealed here could provide a mechanism for the commonly observed pattern of herbivore tolerance/resistance trade-offs.