94 research outputs found
Genetic variation and trait plasticity in plant defence suppression
No full textAs plantas evoluíram um conjunto complexo de defesas, algumas delas induzíveis por herbivoria. Por sua vez, os herbívoros evoluíram para lidar com tais defesas, sendo que alguns conseguem suprimir as defesas do hospedeiro, geralmente através de efetores salivares. Apesar de crucial para a otimização do controlo de pragas, a variação genética e plasticidade da supressão de defesas é ainda pouco estudada. Assim sendo, esta tese teve como objetivo ampliar o conhecimento sobre a variabilidade genética e o impacto do ambiente na supressão de defesas. Para isso, estudei as pragas de tomateiros Tetranychus urticae e T. evansi, nas quais algumas populações conseguem suprimir defesas. Primeiro, estudei se a supressão de defesas é variável e como é que se correlaciona com a fecundidade de T. evansi. Observei que, apesar da supressão ser variável, a fecundidade não está correlacionada com os seus diferentes níveis. De seguida, avaliei se a supressão é comum em populações naturais de T. urticae obtidas de tomateiros. Descobri que esse era o caso, e que o gene effector 84 é altamente variável nesta espécie. De seguida, demonstrei que a supressão é mantida a uma temperatura elevada, apesar da expressão do effector 84 diminuir, sugerindo plasticidade. Para além disso, modelos de dinâmica populacional revelaram que uma temperatura elevada favorece ácaros T. urticae que suprimem defesas, excluindo ácaros que induzem defesas. Finalmente, observei que plantas infestadas com supressores não conseguem estabelecer defesas contra uma densidade alta de herbívoros, ao contrário de quando infestadas com indutores. Os meus resultados mostram que ambas as espécies têm variabilidade genética para a supressão de defesas e que a expressão do effector 84 é plástica com a temperatura. Esta tese oferece informações relevantes sobre como a supressão de defesas pode evoluir e ser mantida na natureza, uma vez que sugere que a adaptação ao hospedeiro e alterações na temperatura podem ser fatores importantes para a sua seleção, com implicações na gestão de pragas.Whereas many herbivores induce plant defences, many others can suppress them. Defence suppression promotes herbivore performance, and it is mediated via herbivore-derived compounds called effectors, often peptides produced in the salivary glands of herbivores. be Although crucial for optimizing pest control, the genetic variation and plasticity of defence suppression in herbivore communities is poorly understood. As such, this thesis aimed to increase knowledge on these. In this thesis, I studied the destructive pests Tetranychus urticae and T. evansi species, in which some populations can suppress tomato plant defences. First, I investigated if traits related to defence suppression in T. evansi are genetically variable and how this variation correlates with mite fecundity. I found that fecundity is a genetic variable for T. evansi but it is not affected by varying degrees of tomato JA defences. Then, we evaluated if defence suppression is a common trait among field T. urticae mites collected from tomato plants. I found this to be true and that the salivary effector 84 is highly variable in this species. Next, I showed that defence suppression is maintained at a high temperature, although the expression of effector 84 decreases, suggesting plasticity. Also, population dynamics models revealed that a high temperature may favour T. urticae mites that suppress defences, possibly displacing T. urticae inducer mites. Finally, I revealed plants infested with suppressor mites are compromised in mounting defences in a density-dependent manner, as opposed to inducer mites. My findings show that both mite species have genetic variation for defence suppression and that effector expression is plastic with temperature. This thesis also offers powerful insights into how defence suppression can evolve and be maintained in nature, as it suggests that host adaptation and high temperatures could be drivers for the selection of such a trait, with implications for crop pests management.Dutch Research Council através dos projetos ALWOP.283, NWO-VICI 1939
Genetic variation and trait plasticity in plant defence suppression
No full textAs plantas evoluíram um conjunto complexo de defesas, algumas delas induzíveis por herbivoria. Por sua vez, os herbívoros evoluíram para lidar com tais defesas, sendo que alguns conseguem suprimir as defesas do hospedeiro, geralmente através de efetores salivares. Apesar de crucial para a otimização do controlo de pragas, a variação genética e plasticidade da supressão de defesas é ainda pouco estudada. Assim sendo, esta tese teve como objetivo ampliar o conhecimento sobre a variabilidade genética e o impacto do ambiente na supressão de defesas. Para isso, estudei as pragas de tomateiros Tetranychus urticae e T. evansi, nas quais algumas populações conseguem suprimir defesas. Primeiro, estudei se a supressão de defesas é variável e como é que se correlaciona com a fecundidade de T. evansi. Observei que, apesar da supressão ser variável, a fecundidade não está correlacionada com os seus diferentes níveis. De seguida, avaliei se a supressão é comum em populações naturais de T. urticae obtidas de tomateiros. Descobri que esse era o caso, e que o gene effector 84 é altamente variável nesta espécie. De seguida, demonstrei que a supressão é mantida a uma temperatura elevada, apesar da expressão do effector 84 diminuir, sugerindo plasticidade. Para além disso, modelos de dinâmica populacional revelaram que uma temperatura elevada favorece ácaros T. urticae que suprimem defesas, excluindo ácaros que induzem defesas. Finalmente, observei que plantas infestadas com supressores não conseguem estabelecer defesas contra uma densidade alta de herbívoros, ao contrário de quando infestadas com indutores. Os meus resultados mostram que ambas as espécies têm variabilidade genética para a supressão de defesas e que a expressão do effector 84 é plástica com a temperatura. Esta tese oferece informações relevantes sobre como a supressão de defesas pode evoluir e ser mantida na natureza, uma vez que sugere que a adaptação ao hospedeiro e alterações na temperatura podem ser fatores importantes para a sua seleção, com implicações na gestão de pragas.Whereas many herbivores induce plant defences, many others can suppress them. Defence suppression promotes herbivore performance, and it is mediated via herbivore-derived compounds called effectors, often peptides produced in the salivary glands of herbivores. be Although crucial for optimizing pest control, the genetic variation and plasticity of defence suppression in herbivore communities is poorly understood. As such, this thesis aimed to increase knowledge on these. In this thesis, I studied the destructive pests Tetranychus urticae and T. evansi species, in which some populations can suppress tomato plant defences. First, I investigated if traits related to defence suppression in T. evansi are genetically variable and how this variation correlates with mite fecundity. I found that fecundity is a genetic variable for T. evansi but it is not affected by varying degrees of tomato JA defences. Then, we evaluated if defence suppression is a common trait among field T. urticae mites collected from tomato plants. I found this to be true and that the salivary effector 84 is highly variable in this species. Next, I showed that defence suppression is maintained at a high temperature, although the expression of effector 84 decreases, suggesting plasticity. Also, population dynamics models revealed that a high temperature may favour T. urticae mites that suppress defences, possibly displacing T. urticae inducer mites. Finally, I revealed plants infested with suppressor mites are compromised in mounting defences in a density-dependent manner, as opposed to inducer mites. My findings show that both mite species have genetic variation for defence suppression and that effector expression is plastic with temperature. This thesis also offers powerful insights into how defence suppression can evolve and be maintained in nature, as it suggests that host adaptation and high temperatures could be drivers for the selection of such a trait, with implications for crop pests management.Dutch Research Council através dos projetos ALWOP.283, NWO-VICI 1939
Plant Responses to Phytophagous Mites/Thrips and Search for Resistance
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Exploring The Potential Of Synthetic Fuels From CO2 And H2
No full textThe world needs to decarbonize, and that includes the transport sector, which accounts for almost a quarter of the GHG emissions. Electrification and hydrogen-powered transport are increasing significantly. But, a new category of hydrogen-based fuels (synthetic fuels) could be part of the solution as well. Synthetic fuels are fuels that are made from CO2 and low-carbon hydrogen. Their use would reduce GHG emissions and mitigate the negative effects we have on climate change. Also, they are compatible with existing infrastructure, which increases the possibility of becoming part of the energy mix in the short term. Despite the increasing attention, there is a lack of literature that combines qualitative research with quantitative insights and a lack of research on the macro-environment of the synthetic fuel system.This study aims to provide an extensive overview of the critical internal and external uncertainties that influence the synthetic fuel supply chain. Additionally, the study wants to look at the impact of the identified factors by using scenarios to model future developments. Scholars are highlighting the potential of synthetic fuels, and the International Energy Agency expects them to play a role in the future energy mix. However, high costs and regulatory uncertainty might prove to be significant barriers to their development. The synthetic fuel system is complex, and their are a lot of factors with that impact each other and a lot of uncertainty in terms of how key factors will develop in the future. The research question focuses on the potential of synthetic fuels in the future. This research uses an integrated approach to look at the system, as the important factors are highly dependent of each other. A PESTEL-analysis was done to highlight the different categories of factors influencing the synthetic fuel supply chain. The Political, Economic, Social, Technological, Environmental and Legal factors together form the driving forces and uncertainties surrounding synthetic fuels. After an extensive literature study to create thorough understanding of the synthetic fuel system, relevant literature was reviewed and discussed to identify the most important factors and uncertainties. These factors are elaborately discussed and then summarized and categorized. The factors with high impact were done reviewed and discussed further with quantitative experiments. The critical uncertainties were quantified by analyzing scenarios in a Mixed-Integer Linear Programming (MILP) model using the program Linny-R. The mix of qualitative and quantitative research makes it possible to understand the synthetic fuel system better. Using Linny-R, the system was modelled in a simplified way by linking the relevant feedstocks, processes and products. The advantage of Linny-R is that it is very suited for looking at integrated systems. The identified factors have a lot of interdependencies and that makes it interesting to look at the impact of uncertainties on multiple factors at the same time. The results showed the major impact the energy price and the electrolyzer Capex have on the hydrogen and subsequent synthetic fuel prices, as they are at least twice as expensive as fossil fuels on the short term. The high current prices for renewable energy weigh heavily on the hydrogen costs, which in turn has a major impact on the costs for synthetic fuels. The results also show the importance of renewable energy availability, as the average price increases significantly due to the intermittency of renewable energy sources. This intermittency leads to lower capacity factors for the electrolyzer, which increases the electrolysis costs per tonne hydrogen. These two factors are the main cost drivers of hydrogen and finding the right balance between the capacity factor and cheap energy is key for reaching an optimal synthetic fuel price. Technological developments and efficiency gains will decrease the price significantly in the future. However, it will definitely remain challenging to become competitive in the short term. In the longer term, there is potential if adequate regulatory support is provided and hydrogen prices continue to decrease due to innovation and scalability. Hydrogen production, and even more so, synthetic fuel production in countries with favourable conditions for renewable energy could lead to lower prices than local production. A potential disadvantage is more competition and geopolitical tensions making the supply chain riskier, requiring a higher rate of return. Because the model also incorporated the fossil fuel production and the carbon emissions, the impact of policy could also be taken into account. While the results show that the impact of policy measures like carbon pricing is definitely lower than the impact of significant hydrogen cost reductions, it is clear that this policy does make synthetic fuel production more attractive. The integrated approach of the system shows that multiple developments are needed for the ambition of cost-parity for synthetic and fossil fuels. While this cost-parity may never be reached, under the right circumstances the synthetic fuel price can become very close. Additional policy measures like blend-in quota and higher subsidies could further increase the demand. The results highlight the challenges but also the potential of synthetic fuels. In order to make them part of the inevitable transition to sustainable alternatives for the transport sector, governments, policymakers, international organisations and customers need to align their efforts to collectively (partly) shift towards synthetic fuels. This is a big opportunity to reduce GHG emissions and reach the climate targets from the Paris Agreement.Complex Systems Engineering and Management (CoSEM
Tomato Reproductive Success Is Equally Affected by Herbivores That Induce or That Suppress Defenses
No full textHerbivory induces plant defenses. These responses are often costly, yet enable plants under attack to reach a higher fitness than they would have reached without these defenses. Spider mites (Tetranychus ssp.) are polyphagous plant-pests. While most strains of the species Tetranychus urticae induce defenses at the expense of their performance, the species Tetranychus evansi suppresses plant defenses and thereby maintains a high performance. Most data indicate that suppression is a mite-adaptive trait. Suppression is characterized by a massive down-regulation of plant gene-expression compared to plants infested with defense-inducing mites as well as compared to control plants, albeit to a lesser extent. Therefore, we hypothesized that suppression may also benefit a plant since the resources saved during down-regulation could be used to increase reproduction. To test this hypothesis, we compared fruit and viable seed production of uninfested tomato plants with that of plants infested with defense-inducing or defense-suppressing mites. Mite-infested plants produced fruits faster than control plants albeit in lower total amounts. The T. evansi-infested plants produced the lowest number of fruits. However, the number of viable seeds was equal across treatments at the end of the experiment. Nonetheless, at this stage control plants were still alive and productive and therefore reach a higher lifetime fitness than mite-infested plants. Our results indicate that plants have plastic control over reproduction and can speed up fruit- and seed production when conditions are unfavorable. Moreover, we showed that although suppressed plants are less productive in terms of fruit production than induced plants, their lifetime fitness was equal under laboratory conditions. However, under natural conditions the fitness of plants such as tomato will also depend on the efficiency of seed dispersal by animals. Hence, we argue that the fitness of induced plants in the field may be promoted more by their higher fruit production relative to that of their suppressed counterparts
Distinct Signatures of Host Defense Suppression by Plant-Feeding Mites
No full textTomato plants are attacked by diverse herbivorous arthropods, including by cell-content-feeding mites, such as the extreme generalist Tetranychus urticae and specialists like Tetranychus evansi and Aculops lycopersici. Mite feeding induces plant defense responses that reduce mite performance. However, T. evansi and A. lycopersici suppress plant defenses via poorly understood mechanisms and, consequently, maintain a high performance on tomato. On a shared host, T. urticae can be facilitated by either of the specialist mites, likely due to the suppression of plant defenses. To better understand defense suppression and indirect plant-mediated interactions between herbivorous mites, we used gene-expression microarrays to analyze the transcriptomic changes in tomato after attack by either a single mite species (T. urticae, T. evansi, A. lycopersici) or two species simultaneously (T. urticae plus T. evansi or T. urticae plus A. lycopersici). Additionally, we assessed mite-induced changes in defense-associated phytohormones using LC-MS/MS. Compared to non-infested controls, jasmonates (JAs) and salicylate (SA) accumulated to higher amounts upon all mite-infestation treatments, but the response was attenuated after single infestations with defense-suppressors. Strikingly, whereas 8 to 10% of tomato genes were differentially expressed upon single infestations with T. urticae or A. lycopersici, respectively, only 0.1% was altered in T. evansi-infested plants. Transcriptome analysis of dual-infested leaves revealed that A. lycopersici primarily suppressed T. urticae-induced JA defenses, while T. evansi dampened T. urticae-triggered host responses on a transcriptome-wide scale. The latter suggests that T. evansi not solely down-regulates plant gene expression, but rather directs it back towards housekeeping levels. Our results provide valuable new insights into the mechanisms underlying host defense suppression and the plant-mediated facilitation of competing herbivore
Intraspecific variation for host immune activation by the spider mite Tetranychus evansi
No full textInternational audienceMany parasites can interfere with their host's defences to maximize their fitness. Here, we investigated if there is heritable variation in the spider mite Tetranychus evansi for traits associated with how they interact with their host plant. We also determined if this variation correlates with mite fecundity. Tetranychus evansi can interfere with jasmonate (JA) defences which are the main determinant of anti-herbivore immunity in plants. We investigated (i) variation in fecundity in the presence and absence of JA defences, making use of a wild-type tomato cultivar and a JA-deficient mutant ( defenseless-1 ), and (ii) variation in the induction of JA defences, in four T. evansi field populations and 59 inbred lines created from an outbred population originating from controlled crosses of the four field populations. We observed a strong positive genetic correlation between fecundity in the presence (on wild-type) and the absence of JA defences (on defenseless-1 ). However, fecundity did not correlate with the magnitude of induced JA defences in wild-type plants. Our results suggest that the performance of the specialist T. evansi is not related to their ability to manipulate plant defences, either because all lines can adequately reduce levels of defences, or because they are resistant to them
A Jasmonate-Inducible Defense Trait Transferred from Wild into Cultivated Tomato Establishes Increased Whitefly Resistance and Reduced Viral Disease Incidence
No full textWhiteflies damage tomatoes mostly via the viruses they transmit. Cultivated tomatoes lack many of the resistances of their wild relatives. In order to increase protection to its major pest, the whitefly Bemisia tabaci and its transmitted Tomato Yellow Leaf Curl Virus (TYLCV), we introgressed a trichome-based resistance trait from the wild tomato Solanum pimpinellifolium into cultivated tomato, Solanum lycopersicum. The tomato backcross line BC5S2 contains acylsucrose-producing type-IV trichomes, unlike cultivated tomatoes, and exhibits increased, yet limited protection to whiteflies at early development stages. Treatment of young plants with methyl jasmonate (MeJA) resulted in a 60% increase in type-IV trichome density, acylsucrose production, and enhanced resistance to whiteflies, leading to 50% decrease in the virus disease incidence compared to cultivated tomato. Using transcriptomics, metabolite analysis, and insect bioassays we established the basis of this inducible resistance. We found that MeJA activated the expression of the genes involved in the biosynthesis of the defensive acylsugars in young BC5S2 plants leading to enhanced chemical defenses in their acquired type-IV trichomes. Our results show that not only constitutive but also these inducible defenses can be transferred from wild into cultivated crops to aid sustainable protection, suggesting that conventional breeding strategies provide a feasible alternative to increase pest resistance in tomato.This work was funded by grants AGL2013-48913-C2-01-R/AGR (Spanish MICINN, co-financed by EU FEDER) and P10-AGR-6516 (Consejería de Economía, Innovación y Ciencia, Junta de Andalucía, Spain). RE-B was recipient of a FPI grant by MICINN. JA was supported by the Netherlands Organization for Scientific Research NWO (Earth and Life Sciences ALW/TOP 854.11.005). MK was supported by Netherlands Organization for Scientific Research NWO (Technology Foundation STW/VIDI 13492). EM and RF-M are members of AGR-214 and AGR-129 research groups, respectively, partially funded by the Consejería de Economía, Innovación y Ciencia, Junta de Andalucía, Spain (co-financed by EU FEDER-FSE). AG was funded by TRADITOM (634561) under the H2020 SFS-07a-2014 EU Program, the Spanish Ministry BIO2013-42193-R, and the EU COST-FA1106.Peer reviewedPeer Reviewe
Social robots as eating companions
No full textPrevious research shows that eating together (i.e., commensality) impacts food choice, time spent eating, and enjoyment. Conversely, eating alone is considered a possible cause of unhappiness. In this paper, we conceptually explore how interactive technology might allow for the creation of artificial commensal companions: embodied agents providing company to humans during meals (e.g., a person living in isolation due to health reasons). We operationalize this with the design of our commensal companion: a system based on the MyKeepon robot, paired with a Kinect sensor, able to track the human commensal's activity (i.e., food picking and intake) and able to perform predefined nonverbal behavior in response. In this preliminary study with 10 participants, we investigate whether this autonomous social robot-based system can positively establish an interaction that humans perceive and whether it can influence their food choices. In this study, the participants are asked to taste some chocolates with and without the presence of an artificial commensal companion. The participants are made to believe that the study targets the food experience, whilst the presence of a robot is accidental. Next, we analyze their food choices and feedback regarding the role and social presence of the artificial commensal during the task performance. We conclude the paper by discussing the lessons we learned about the first interactions we observed between a human and a social robot in a commensality setting and by proposing future steps and more complex applications for this novel kind of technology.Human Information Communication Desig
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