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1.
Proc Natl Acad Sci U S A ; 118(43)2021 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-34675080

RESUMO

Plant secondary (or specialized) metabolites mediate important interactions in both the rhizosphere and the phyllosphere. If and how such compartmentalized functions interact to determine plant-environment interactions is not well understood. Here, we investigated how the dual role of maize benzoxazinoids as leaf defenses and root siderophores shapes the interaction between maize and a major global insect pest, the fall armyworm. We find that benzoxazinoids suppress fall armyworm growth when plants are grown in soils with very low available iron but enhance growth in soils with higher available iron. Manipulation experiments confirm that benzoxazinoids suppress herbivore growth under iron-deficient conditions and in the presence of chelated iron but enhance herbivore growth in the presence of free iron in the growth medium. This reversal of the protective effect of benzoxazinoids is not associated with major changes in plant primary metabolism. Plant defense activation is modulated by the interplay between soil iron and benzoxazinoids but does not explain fall armyworm performance. Instead, increased iron supply to the fall armyworm by benzoxazinoids in the presence of free iron enhances larval performance. This work identifies soil chemistry as a decisive factor for the impact of plant secondary metabolites on herbivore growth. It also demonstrates how the multifunctionality of plant secondary metabolites drives interactions between abiotic and biotic factors, with potential consequences for plant resistance in variable environments.

2.
J Chem Ecol ; 47(10-11): 889-906, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34415498

RESUMO

How climate change will modify belowground tritrophic interactions is poorly understood, despite their importance for agricultural productivity. Here, we manipulated the three major abiotic factors associated with climate change (atmospheric CO2, temperature, and soil moisture) and investigated their individual and joint effects on the interaction between maize, the banded cucumber beetle (Diabrotica balteata), and the entomopathogenic nematode (EPN) Heterorhabditis bacteriophora. Changes in individual abiotic parameters had a strong influence on plant biomass, leaf wilting, sugar concentrations, protein levels, and benzoxazinoid contents. Yet, when combined to simulate a predicted climate scenario (Representative Concentration Pathway 8.5, RCP 8.5), their effects mostly counter-balanced each other. Only the sharp negative impact of drought on leaf wilting was not fully compensated. In both current and predicted scenarios, root damage resulted in increased leaf wilting, reduced root biomass, and reconfigured the plant sugar metabolism. Single climatic variables modulated the herbivore performance and survival in an additive manner, although slight interactions were also observed. Increased temperature and CO2 levels both enhanced the performance of the insect, but elevated temperature also decreased its survival. Elevated temperatures and CO2 further directly impeded the EPN infectivity potential, while lower moisture levels improved it through plant- and/or herbivore-mediated changes. In the RCP 8.5 scenario, temperature and CO2 showed interactive effects on EPN infectivity, which was overall decreased by 40%. We conclude that root pest problems may worsen with climate change due to increased herbivore performance and reduced top-down control by biological control agents.

3.
Ecol Evol ; 11(9): 4182-4192, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33976802

RESUMO

Climate change will profoundly alter the physiology and ecology of plants, insect herbivores, and their natural enemies, resulting in strong effects on multitrophic interactions. Yet, manipulative studies that investigate the direct combined impacts of changes in CO2, temperature, and precipitation on the third trophic level remain rare. Here, we assessed how exposure to elevated CO2, increased temperature, and decreased precipitation directly affect the performance and predation success of species from four major groups of herbivore natural enemies: an entomopathogenic nematode, a wolf spider, a ladybug, and a parasitoid wasp. A four-day exposure to future climatic conditions (RCP 8.5), entailing a 28% decrease in precipitation, a 3.4°C raise in temperature, and a 400 ppm increase in CO2 levels, slightly reduced the survival of entomopathogenic nematodes, but had no effect on the survival of other species. Predation success was not negatively affected in any of the tested species, but it was even increased for wolf spiders and entomopathogenic nematodes. Factorial manipulation of climate variables revealed a positive effect of reduced soil moisture on nematode infectivity, but not of increased temperature or elevated CO2. These results suggest that natural enemies of herbivores may be well adapted to short-term changes in climatic conditions. These findings provide mechanistic insights that will inform future efforts to disentangle the complex interplay of biotic and abiotic factors that drive climate-dependent changes in multitrophic interaction networks.

4.
Insects ; 12(2)2021 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-33671118

RESUMO

The western corn rootworm, Diabrotica virgifera virgifera LeConte, is resistant to four separate classes of traditional insecticides, all Bacillius thuringiensis (Bt) toxins currently registered for commercial use, crop rotation, innate plant resistance factors, and even double-stranded RNA (dsRNA) targeting essential genes via environmental RNA interference (RNAi), which has not been sold commercially to date. Clearly, additional tools are needed as management options. In this review, we discuss the state-of-the-art knowledge about biotic factors influencing herbivore success, including host location and recognition, plant defensive traits, plant-microbe interactions, and herbivore-pathogens/predator interactions. We then translate this knowledge into potential new management tools and improved biological control.

5.
Plant Cell Environ ; 44(8): 2672-2686, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-33748996

RESUMO

Plant leaves that are exposed to herbivore-induced plant volatiles (HIPVs) respond by increasing their defenses, a phenomenon referred to as priming. Whether this phenomenon also occurs in the roots is unknown. Using maize plants, Zea mays, whose leaves respond strongly to leaf HIPVs, we measured the impact of belowground HIPVs, emanating from roots infested by the banded cucumber beetle, Diabrotica balteata, on constitutive and herbivore-induced levels of defense-related gene expression, phytohormones, volatile and non-volatile primary and secondary metabolites, growth and herbivore resistance in roots of neighbouring plants. HIPV exposure did not increase constitutive or induced levels of any of the measured root traits. Furthermore, HIPV exposure did not reduce the performance or survival of D. balteata on maize or its ancestor teosinte. Cross-exposure experiments between HIPVs from roots and leaves revealed that maize roots, in contrast to maize leaves, neither emit nor respond strongly to defense-regulating HIPVs. Together, these results demonstrate that volatile-mediated defense regulation is restricted to the leaves of maize. This finding is in line with the lower diffusibility of volatiles in the soil and the availability of other, potentially more efficient, information conduits below ground.

6.
PLoS Biol ; 19(2): e3001114, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33600420

RESUMO

Plants produce complex mixtures of primary and secondary metabolites. Herbivores use these metabolites as behavioral cues to increase their fitness. However, how herbivores combine and integrate different metabolite classes into fitness-relevant foraging decisions in planta is poorly understood. We developed a molecular manipulative approach to modulate the availability of sugars and benzoxazinoid secondary metabolites as foraging cues for a specialist maize herbivore, the western corn rootworm. By disrupting sugar perception in the western corn rootworm and benzoxazinoid production in maize, we show that sugars and benzoxazinoids act as distinct and dynamically combined mediators of short-distance host finding and acceptance. While sugars improve the capacity of rootworm larvae to find a host plant and to distinguish postembryonic from less nutritious embryonic roots, benzoxazinoids are specifically required for the latter. Host acceptance in the form of root damage is increased by benzoxazinoids and sugars in an additive manner. This pattern is driven by increasing damage to postembryonic roots in the presence of benzoxazinoids and sugars. Benzoxazinoid- and sugar-mediated foraging directly improves western corn rootworm growth and survival. Interestingly, western corn rootworm larvae retain a substantial fraction of their capacity to feed and survive on maize plants even when both classes of chemical cues are almost completely absent. This study unravels fine-grained differentiation and combination of primary and secondary metabolites into herbivore foraging and documents how the capacity to compensate for the lack of important chemical cues enables a specialist herbivore to survive within unpredictable metabolic landscapes.


Assuntos
Benzoxazinas/metabolismo , Besouros/fisiologia , Açúcares/metabolismo , Zea mays/metabolismo , Animais , Comportamento Apetitivo/fisiologia , Besouros/crescimento & desenvolvimento , Herbivoria , Larva/crescimento & desenvolvimento , Larva/fisiologia , Metaboloma , Raízes de Plantas/metabolismo , Zea mays/genética
7.
Plant Cell Environ ; 2020 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-33073385

RESUMO

The above article was published in error by the publisher before a final editorial decision had been reached. It has therefore been removed temporarily while the editorial process concludes. The publisher apologizes for the inconvenience.

9.
Sci Rep ; 10(1): 8257, 2020 05 19.
Artigo em Inglês | MEDLINE | ID: mdl-32427834

RESUMO

Natural enemies of herbivores are expected to adapt to the defence strategies of their preys or hosts. Such adaptations may also include their capacity to cope with plant metabolites that herbivores sequester as a defence. In this study, we evaluated the ability of Mexican entomopathogenic nematodes (EPN) to resist benzoxazinoids that are sequestered from maize roots by the western corn rootworm (WCR, Diabrotica virgifera virgifera; Coleoptera: Chrysomelidae), an important maize pest in America and Europe. From maize fields throughout Mexico, we retrieved 40 EPN isolates belonging to five different species, with a majority identified as Heterorhabditis bacteriophora. In the laboratory, all nematodes readily infected non-sequestering larvae of the banded cucumber beetle (D. balteata), while infectivity varied strongly for WCR larvae. While some H. bacteriophora isolates seemed negatively affected by benzoxazinoids, most showed to be resistant. Thus, EPN from Mexican maize fields can cope with these plant defence metabolites, but the results also indicate that WCR larvae possess other mechanisms that help to resist EPN. This work contributes to a better understanding of the capacity of herbivore natural enemies to resist plant defence metabolites. Furthermore, it identifies several benzoxazinoid-resistant EPN isolates that may be used to control this important maize pest.


Assuntos
Benzoxazinas/farmacologia , Besouros/efeitos dos fármacos , Besouros/parasitologia , Resistência a Inseticidas , Inseticidas/farmacologia , Nematoides/fisiologia , Doenças das Plantas/parasitologia , Zea mays/parasitologia , Animais , Besouros/fisiologia , Herbivoria/efeitos dos fármacos , Herbivoria/fisiologia , Larva/efeitos dos fármacos , Larva/parasitologia , Larva/fisiologia , México , Controle Biológico de Vetores
10.
Plant J ; 103(1): 308-322, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32130751

RESUMO

Circadian organ movements are ubiquitous in plants. These rhythmic outputs are thought to be regulated by the circadian clock and auxin signalling, but the underlying mechanisms have not been clarified. Flowers of Nicotiana attenuata change their orientation during the daytime through a 140° arc to balance the need for pollinators and the protection of their reproductive organs. This rhythmic trait is under the control of the circadian clock and results from bending and re-straightening movements of the pedicel, stems that connect flowers to the inflorescence. Using an explant system that allowed pedicel growth and curvature responses to be characterized with high spatial and temporal resolution, we demonstrated that this movement is organ autonomous and mediated by auxin. Changes in the growth curvature of the pedicel are accompanied by an auxin gradient and dorsiventral asymmetry in auxin-dependent transcriptional responses; application of auxin transport inhibitors influenced the normal movements of this organ. Silencing the expression of the circadian clock component ZEITLUPE (ZTL) arrested changes in the growth curvature of the pedicel and altered auxin signalling and responses. IAA19-like, an Aux/IAA transcriptional repressor that is circadian regulated and differentially expressed between opposite tissues of the pedicel, and therefore possibly involved in the regulation of changes in organ curvature, physically interacted with ZTL. Together, these results are consistent with a direct link between the circadian clock and the auxin signalling pathway in the regulation of this rhythmic floral movement.


Assuntos
Peptídeos e Proteínas de Sinalização do Ritmo Circadiano/fisiologia , Flores/fisiologia , Proteínas de Plantas/fisiologia , Tabaco/fisiologia , Ritmo Circadiano/fisiologia , Flores/metabolismo , Regulação da Expressão Gênica de Plantas , Ácidos Indolacéticos/metabolismo , Reguladores de Crescimento de Plantas/metabolismo , Reguladores de Crescimento de Plantas/fisiologia , Proteínas de Plantas/metabolismo , Tabaco/metabolismo
11.
Nat Biotechnol ; 38(5): 600-608, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32066956

RESUMO

The western corn rootworm (WCR) decimates maize crops worldwide. One potential way to control this pest is treatment with entomopathogenic nematodes (EPNs) that harbor bacterial symbionts that are pathogenic to insects. However, WCR larvae sequester benzoxazinoid secondary metabolites that are produced by maize and use them to increase their resistance to the nematodes and their symbionts. Here we report that experimental evolution and selection for bacterial symbionts that are resistant to benzoxazinoids improve the ability of a nematode-symbiont pair to kill WCR larvae. We isolated five Photorhabdus symbionts from different nematodes and increased their benzoxazinoid resistance through experimental evolution. Benzoxazinoid resistance evolved through multiple mechanisms, including a mutation in the aquaporin-like channel gene aqpZ. We reintroduced benzoxazinoid-resistant Photorhabdus strains into their original EPN hosts and identified one nematode-symbiont pair that was able to kill benzoxazinoid-sequestering WCR larvae more efficiently. Our results suggest that modification of bacterial symbionts might provide a generalizable strategy to improve biocontrol of agricultural pests.


Assuntos
Aquaporinas/genética , Benzoxazinas/farmacologia , Farmacorresistência Bacteriana , Nematoides/microbiologia , Photorhabdus/fisiologia , Zea mays/crescimento & desenvolvimento , Animais , Proteínas de Bactérias/genética , Evolução Molecular , Engenharia Genética , Mutação , Nematoides/patogenicidade , Controle Biológico de Vetores , Photorhabdus/efeitos dos fármacos , Photorhabdus/genética , Doenças das Plantas/prevenção & controle , Zea mays/parasitologia
12.
Proc Biol Sci ; 287(1921): 20192930, 2020 02 26.
Artigo em Inglês | MEDLINE | ID: mdl-32097589

RESUMO

A plant's offspring may escape unfavourable local conditions through seed dispersal. Whether plants use this strategy to escape insect herbivores is not well understood. Here, we explore how different dandelion (Taraxacum officinale agg.) populations, including diploid outcrossers and triploid apomicts, modify seed dispersal in response to root herbivore attack by their main root-feeding natural enemy, the larvae of the common cockchafer Melolontha melolontha. In a manipulative field experiment, root herbivore attack increased seed dispersal potential through a reduction in seed weight in populations that evolved under high root herbivore pressure, but not in populations that evolved under low pressure. This increase in dispersal potential was independent of plant cytotype, but associated with a reduction in germination rate, suggesting that adapted dandelions trade dispersal for establishment upon attack by root herbivores. Analysis of vegetative growth parameters suggested that the increased dispersal capacity was not the result of stress flowering. In summary, these results suggest that root herbivory selects for an induced increase in dispersal ability in response to herbivore attack. Induced seed dispersal may be a strategy that allows adapted plants to escape from herbivores.


Assuntos
Besouros/fisiologia , Germinação , Herbivoria , Taraxacum/fisiologia , Animais
13.
J Chem Ecol ; 46(1): 63-75, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31832894

RESUMO

Plants experience seasonal fluctuations in abiotic and biotic factors such as herbivore attack rates. If and how root defense expression co-varies with seasonal fluctuations in abiotic factors and root herbivore attack rates is not well understood. Here, we evaluated seasonal changes in defensive root latex chemistry of Taraxacum officinale plants in the field and correlated the changes with seasonal fluctuations in abiotic factors and damage potential by Melolontha melolontha, a major natural enemy of T. officinale. We then explored the causality and consequences of these relationships under controlled conditions. The concentration of the defensive sesquiterpene lactone taraxinic acid ß-D glucopyranosyl ester (TA-G) varied substantially over the year and was most strongly correlated to mean monthly temperature. Both temperature and TA-G levels were correlated with annual fluctuations in potential M. melolontha damage. Under controlled conditions, plants grown under high temperature produced more TA-G and were less attractive for M. melolontha. However, temperature-dependent M. melolontha feeding preferences were not significantly altered in TA-G deficient transgenic lines. Our results suggest that fluctuations in temperature leads to variation in the production of a root defensive metabolites that co-varies with expected attack of a major root herbivore. Temperature-dependent herbivore preference, however, is likely to be modulated by other phenotypic alterations.


Assuntos
Besouros/fisiologia , Glucosídeos/metabolismo , Lactonas/metabolismo , Sesquiterpenos/metabolismo , Taraxacum/química , Animais , Biomassa , Besouros/crescimento & desenvolvimento , Glucosídeos/química , Glucosídeos/farmacologia , Herbivoria/efeitos dos fármacos , Lactonas/química , Lactonas/farmacologia , Larva/efeitos dos fármacos , Larva/fisiologia , Raízes de Plantas/química , Raízes de Plantas/metabolismo , Raízes de Plantas/parasitologia , Plantas Geneticamente Modificadas/metabolismo , Plantas Geneticamente Modificadas/parasitologia , Estações do Ano , Sesquiterpenos/química , Sesquiterpenos/farmacologia , Taraxacum/metabolismo , Taraxacum/parasitologia , Temperatura
14.
Proc Natl Acad Sci U S A ; 116(46): 23174-23181, 2019 11 12.
Artigo em Inglês | MEDLINE | ID: mdl-31659056

RESUMO

Plants defend themselves against herbivores through the production of toxic and deterrent metabolites. Adapted herbivores can tolerate and sometimes sequester these metabolites, allowing them to feed on defended plants and become toxic to their own enemies. Can herbivore natural enemies overcome sequestered plant defense metabolites to prey on adapted herbivores? To address this question, we studied how entomopathogenic nematodes cope with benzoxazinoid defense metabolites that are produced by grasses and sequestered by a specialist maize herbivore, the western corn rootworm. We find that nematodes from US maize fields in regions in which the western corn rootworm was present over the last 50 y are behaviorally and metabolically resistant to sequestered benzoxazinoids and more infective toward the western corn rootworm than nematodes from other parts of the world. Exposure of a benzoxazinoid-susceptible nematode strain to the western corn rootworm for 5 generations results in higher behavioral and metabolic resistance and benzoxazinoid-dependent infectivity toward the western corn rootworm. Thus, herbivores that are exposed to a plant defense sequestering herbivore can evolve both behavioral and metabolic resistance to plant defense metabolites, and these traits are associated with higher infectivity toward a defense sequestering herbivore. We conclude that plant defense metabolites that are transferred through adapted herbivores may result in the evolution of resistance in herbivore natural enemies. Our study also identifies plant defense resistance as a potential target for the improvement of biological control agents.


Assuntos
Benzoxazinas/metabolismo , Besouros/parasitologia , Herbivoria , Interações Hospedeiro-Parasita , Rabditídios/fisiologia , Animais , Besouros/metabolismo , Cadeia Alimentar , Zea mays
15.
J Chem Ecol ; 45(7): 638-648, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31227972

RESUMO

Although the production of phytohormones has been commonly associated with production of plant defence and stress-related traits, few studies have simultaneously investigated this phenomenon across several plant species that grow along large-scale ecological gradients. To address these knowledge gaps, we performed a common garden experiment with six Cardamine species, which collectively encompass an elevational gradient of 2000 m. We quantified constitutive and Pieris brassicae caterpillars-induced phytohormones and chemical defences in leaves. We found a correlated expression of phytohormone production and the subsequent induction of chemical defences, and this correlated expression reduced herbivore performance. Furthermore, we found that abiotic conditions associated with the optimal elevation range of each species influenced the production of phytohormones and chemical defences, as well as plant growth and productivity. In particular, we found that plant species adapted to milder abiotic conditions at low elevations grew faster, were more productive and produced greater levels of chemical defences. In contrast, plant species adapted to harsher abiotic conditions at high elevations tended to produce greater levels of defence-related oxylipins. Overall, these findings highlight the importance of disentangling the role of phytohormones in mediating plant adaptations to shifting biotic and abiotic conditions.


Assuntos
Cardamine/química , Glucosinolatos/química , Himenópteros/fisiologia , Reguladores de Crescimento de Plantas/química , Animais , Cardamine/metabolismo , Cromatografia Líquida de Alta Pressão , Glucosinolatos/farmacologia , Herbivoria , Interações Hospedeiro-Parasita/efeitos dos fármacos , Himenópteros/crescimento & desenvolvimento , Larva/efeitos dos fármacos , Larva/fisiologia , Reguladores de Crescimento de Plantas/farmacologia , Folhas de Planta/química , Folhas de Planta/metabolismo , Espectrometria de Massas em Tandem
16.
New Phytol ; 221(2): 976-987, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30178602

RESUMO

Wall-associated kinases (WAKs) have recently been identified as major components of fungal and bacterial disease resistance in several cereal crop species. However, the molecular mechanisms of WAK-mediated resistance remain largely unknown. Here, we investigated the function of the maize gene ZmWAK-RLK1 (Htn1) that confers quantitative resistance to northern corn leaf blight (NCLB) caused by the hemibiotrophic fungal pathogen Exserohilum turcicum. ZmWAK-RLK1 was found to localize to the plasma membrane and its presence resulted in a modification of the infection process by reducing pathogen penetration into host tissues. A large-scale transcriptome analysis of near-isogenic lines (NILs) differing for ZmWAK-RLK1 revealed that several differentially expressed genes are involved in the biosynthesis of the secondary metabolites benzoxazinoids (BXs). The contents of several BXs including DIM2 BOA-Glc were significantly lower when ZmWAK-RLK1 is present. DIM2 BOA-Glc concentration was significantly elevated in ZmWAK-RLK1 mutants with compromised NCLB resistance. Maize mutants that were affected in overall BXs biosynthesis or content of DIM2 BOA-Glc showed increased NCLB resistance. We conclude that Htn1-mediated NCLB resistance is associated with a reduction of BX secondary metabolites. These findings suggest a link between WAK-mediated quantitative disease resistance and changes in biochemical fluxes starting with indole-3-glycerol phosphate.


Assuntos
Ascomicetos/fisiologia , Benzoxazinas/metabolismo , Resistência à Doença , Doenças das Plantas/imunologia , Zea mays/enzimologia , Doenças das Plantas/microbiologia , Zea mays/genética , Zea mays/imunologia , Zea mays/microbiologia
17.
Ecol Evol ; 8(13): 6756-6765, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30038772

RESUMO

Climate change is predicted to increase the risk of drought in many temperate agroecosystems. While the impact of drought on aboveground plant-herbivore-natural enemy interactions has been studied, little is known about its effects on belowground tritrophic interactions and root defense chemistry. We investigated the effects of low soil moisture on the interaction between maize, the western corn rootworm (WCR, Diabrotica virgifera), and soil-borne natural enemies of WCR. In a manipulative field experiment, reduced soil moisture and WCR attack reduced plant performance and increased benzoxazinoid levels. The negative effects of WCR on cob dry weight and silk emergence were strongest at low moisture levels. Inoculation with entomopathogenic nematodes (EPNs, Heterorhabditis bacteriophora) was ineffective in controlling WCR, and the EPNs died rapidly in the warm and dry soil. However, ants of the species Solenopsis molesta invaded the experiment, were more abundant in WCR-infested pots and predated WCR independently of soil moisture. Ant presence increased root and shoot biomass and was associated with attenuated moisture-dependent effects of WCR on maize cob weight. Our study suggests that apart from directly reducing plant performance, drought can also increase the negative effects of root herbivores such as WCR. It furthermore identifies S. molesta as a natural enemy of WCR that can protect maize plants from the negative impact of herbivory under drought stress. Robust herbivore natural enemies may play an important role in buffering the impact of climate change on plant-herbivore interactions.

18.
Nat Commun ; 9(1): 2738, 2018 07 16.
Artigo em Inglês | MEDLINE | ID: mdl-30013066

RESUMO

By changing soil properties, plants can modify their growth environment. Although the soil microbiota is known to play a key role in the resulting plant-soil feedbacks, the proximal mechanisms underlying this phenomenon remain unknown. We found that benzoxazinoids, a class of defensive secondary metabolites that are released by roots of cereals such as wheat and maize, alter root-associated fungal and bacterial communities, decrease plant growth, increase jasmonate signaling and plant defenses, and suppress herbivore performance in the next plant generation. Complementation experiments demonstrate that the benzoxazinoid breakdown product 6-methoxy-benzoxazolin-2-one (MBOA), which accumulates in the soil during the conditioning phase, is both sufficient and necessary to trigger the observed phenotypic changes. Sterilization, fungal and bacterial profiling and complementation experiments reveal that MBOA acts indirectly by altering root-associated microbiota. Our results reveal a mechanism by which plants determine the composition of rhizosphere microbiota, plant performance and plant-herbivore interactions of the next generation.


Assuntos
Benzoxazóis/farmacologia , Folhas de Planta/imunologia , Raízes de Plantas/metabolismo , Microbiologia do Solo , Zea mays/imunologia , Animais , Bactérias/crescimento & desenvolvimento , Benzoxazóis/metabolismo , Óxidos N-Cíclicos/farmacologia , Flavonoides/farmacologia , Fungos/fisiologia , Glucosídeos/farmacologia , Herbivoria/efeitos dos fármacos , Larva/efeitos dos fármacos , Larva/fisiologia , Folhas de Planta/metabolismo , Folhas de Planta/parasitologia , Raízes de Plantas/microbiologia , Pirróis/farmacologia , Rizosfera , Solo/química , Spodoptera/efeitos dos fármacos , Spodoptera/fisiologia , Zea mays/metabolismo , Zea mays/microbiologia , Zea mays/parasitologia
19.
Int J Syst Evol Microbiol ; 68(8): 2664-2681, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29877789

RESUMO

Bacterial symbionts are crucial for the infectivity and success of entomopathogenic nematodes as biological control agents. The current understanding of the symbiotic relationships is limited by taxonomic uncertainties. Here, we used whole-genome sequencing and traditional techniques to reconstruct the phylogenetic relationships between all described Photorhabdus species and subspecies as well as 11 newly isolated symbiotic bacteria of Heterorhabditis nematodes, including the unreported bacterial partner of H. beicherriana. In silico DNA-DNA hybridization, orthologous average nucleotide identity and nucleotide sequence identity of concatenated housekeeping genes scores were calculated and set into relation with current cut-off values for species delimitation in bacteria. Sequence data were complemented with biochemical and chemotaxonomic markers, and ribosomal protein fingerprinting profiles. This polyphasic approach resolves the ambiguous taxonomy of Photorhabdusand lead to the proposal for the elevation of most of them into a higher taxon and the creation of several new taxa: 15 new species, one of which is newly described: Photorhabdus bodei sp. nov. (type strain LJ24-63T=DSM 105690T=CCOS 1159T) and the other 14 arise through the proposal of elevating already described subspecies to species, and are proposed to be renamed as follows: Photorhabdus asymbioticasubsp. australis as Photorhabdus australis sp. nov., Photorhabdus luminescenssubsp. akhurstii as Photorhabdus akhurstii sp. nov., Photorhabdus luminescenssubsp. caribbeanensis as Photorhabdus caribbeanensis sp. nov., Photorhabdus luminescenssubsp. hainanensis as Photorhabdus hainanensis sp. nov., Photorhabdus luminescenssubsp. kayaii as Photorhabdus kayaii sp. nov., Photorhabdus luminescenssubsp. kleinii as Photorhabdus kleinii sp. nov., Photorhabdus luminescenssubsp. namnaonensis as Photorhabdus namnaonensis sp. nov., Photorhabdus luminescenssubsp. noenieputensis as Photorhabdus noenieputensis sp. nov., Photorhabdus luminescenssubsp.laumondii as Photorhabdus laumondii sp. nov., Photorhabdus temperatasubsp. cinerea as Photorhabdus cinerea sp. nov., Photorhabdus temperatasubsp. khanii as Photorhabdus khanii sp. nov., Photorhabdus temperatasubsp. stackebrandtii as Photorhabdus stackebrandtii sp. nov., Photorhabdus temperatasubsp. tasmaniensis as Photorhabdus tasmaniensis sp. nov., and Photorhabdus temperatasubsp. thracensis as Photorhabdus thracensis sp. nov. In addition, we propose the creation of two new subspecies, one of which arises through the reduction of rank: Photorhabdus laumondii subsp. laumondii comb. nov. (basonym: P. luminescenssubsp. laumondii) and the second one is newly described: Photorhabdus laumondii subsp. clarkei subsp. nov. (type strain BOJ-47T=DSM 105531T=CCOS 1160T). Finally, we propose to emend the description of three species, which results from the proposal of elevating three subspecies to the species status: Photorhabdus asymbiotica, Photorhabdus temperata and Photorhabdus luminescens, formerly classified as Photorhabdus asymbioticasubsp. asymbiotica, Photorhabdus temperatasubsp.temperata and Photorhabdus luminescenssubsp. luminescens, respectively.


Assuntos
Genoma Bacteriano , Photorhabdus/classificação , Filogenia , Rhabditoidea/microbiologia , Animais , Técnicas de Tipagem Bacteriana , DNA Bacteriano/genética , Hibridização de Ácido Nucleico , Photorhabdus/genética , Análise de Sequência de DNA , Simbiose
20.
New Phytol ; 217(1): 355-366, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-28877341

RESUMO

Domesticated plants are assumed to have weakened chemical defenses. We argue, however, that artificial selection will have maintained defense traits against specialized herbivores that have coexisted with the crops throughout their domestication. We assessed the performance of eight species of insect herbivores from three feeding guilds on six European maize lines and six populations of their wild ancestor, teosinte. A metabolomics approach was used in an attempt to identify compounds responsible for observed differences in insect performance. Insects consistently performed better on maize than on teosinte. As hypothesized, this difference was greater for generalist herbivores that are normally not found on teosinte. We also found clear differences in defense metabolites among the different genotypes, but none that consistently correlated with differences in performance. Concentrations of benzoxazinoids, the main chemical defense in maize, tended to be higher in leaves of teosinte, but the reverse was true for the roots. It appears that chemical defenses that target specialized insects are still present at higher concentrations in cultivated maize than compounds that are more effective against generalists. These weakened broad-spectrum defenses in crops may explain the successes of novel pests.


Assuntos
Benzoxazinas/metabolismo , Insetos/fisiologia , Plantas/imunologia , Animais , Produtos Agrícolas/química , Produtos Agrícolas/genética , Produtos Agrícolas/imunologia , Produtos Agrícolas/parasitologia , Domesticação , Herbivoria , Folhas de Planta/genética , Folhas de Planta/imunologia , Folhas de Planta/parasitologia , Raízes de Plantas/genética , Raízes de Plantas/imunologia , Raízes de Plantas/parasitologia , Plantas/química , Plantas/genética , Plantas/parasitologia , Zea mays/química , Zea mays/genética , Zea mays/imunologia , Zea mays/parasitologia
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