44 research outputs found
Intraspecific variation for host immune activation by the spider mite Tetranychus evansi
Many parasites can interfere with their host’s defences tomaximize their fitness. Here, we investigated if there isheritable variation in the spider miteTetranychus evansifortraits associated with how they interact with their host plant.We also determined if this variation correlates with mitefecundity.Tetranychus evansican interfere with jasmonate (JA)defences which are the main determinant of anti-herbivoreimmunity in plants. We investigated (i) variation in fecundityin the presence and absence of JA defences, making use ofa wild-type tomato cultivar and a JA-deficient mutant(defenseless-1), and (ii) variation in the induction of JAdefences, in fourT. evansifield populations and 59 inbredlines created from an outbred population originating fromcontrolled crosses of the four field populations. We observed astrong positive genetic correlation between fecundity in thepresence (on wild-type) and the absence of JA defences (ondefenseless-1). However, fecundity did not correlate with themagnitude of induced JA defences in wild-type plants. Ourresults suggest that the performance of the specialistT. evansiis not related to their ability to manipulate plant defences,either because all lines can adequately reduce levels ofdefences, or because they are resistant to them.info:eu-repo/semantics/publishedVersio
Why do herbivorous mites suppress plant defenses?
Plants have evolved numerous defensive traits that enable them to resist herbivores. In turn, this resistance has selected for herbivores that can cope with defenses by either avoiding, resisting or suppressing them. Several species of herbivorous mites, such as the spider mites Tetranychus urticae and Tetranychus evansi, were found to maximize their performance by suppressing inducible plant defenses. At first glimpse it seems obvious why such a trait will be favored by natural selection. However, defense suppression appeared to readily backfire since mites that do so also make their host plant more suitable for competitors and their offspring more attractive for natural enemies. This, together with the fact that spider mites are infamous for their ability to resist (plant) toxins directly, justifies the question as to why traits that allow mites to suppress defenses nonetheless seem to be relatively common? We argue that this trait may facilitate generalist herbivores, like T. urticae, to colonize new host species. While specific detoxification mechanisms may, on average, be suitable only on a narrow range of similar hosts, defense suppression may be more broadly effective, provided it operates by targeting conserved plant signaling components. If so, resistance and suppression may be under frequency-dependent selection and be maintained as a polymorphism in generalist mite populations. In that case, the defense suppression trait may be under rapid positive selection in subpopulations that have recently colonized a new host but may erode in relatively isolated populations in which host-specific detoxification mechanisms emerge. Although there is empirical evidence to support these scenarios, it contradicts the observation that several of the mite species found to suppress plant defenses actually are relatively specialized. We argue that in these cases buffering traits may enable such mites to mitigate the negative side effects of suppression in natural communities and thus shield this trait from natural selection
Spotlight on the Roles of Whitefly Effectors in Insect–Plant Interactions
The Bemisia tabaci species complex (whitefly) causes enormous agricultural losses. These phloem-feeding insects induce feeding damage and transmit a wide range of dangerous plant viruses. Whiteflies colonize a broad range of plant species that appear to be poorly defended against these insects. Substantial research has begun to unravel how phloem feeders modulate plant processes, such as defense pathways, and the central roles of effector proteins, which are deposited into the plant along with the saliva during feeding. Here, we review the current literature on whitefly effectors in light of what is known about the effectors of phloem-feeding insects in general. Further analysis of these effectors may improve our understanding of how these insects establish compatible interactions with plants, whereas the subsequent identification of plant defense processes could lead to improved crop resistance to insects. We focus on the core concepts that define the effectors of phloem-feeding insects, such as the criteria used to identify candidate effectors in sequence-mining pipelines and screens used to analyze the potential roles of these effectors and their targets in planta. We discuss aspects of whitefly effector research that require further exploration, including where effectors localize when injected into plant tissues, whether the effectors target plant processes beyond defense pathways, and the properties of effectors in other insect excretions such as honeydew. Finally, we provide an overview of open issues and how they might be addressed
Genome streamlining in a minute herbivore that manipulates its host plant
The tomato russet mite, Aculops lycopersici, is among the smallest animals on earth. It
is a worldwide pest on tomato and can potently suppress the host’s natural resistance. We
sequenced its genome, the first of an eriophyoid, and explored whether there are genomic
features associated with the mite’s minute size and lifestyle. At only 32.5 Mb, the genome is the
smallest yet reported for any arthropod and, reminiscent of microbial eukaryotes, exceptionally
streamlined. It has few transposable elements, tiny intergenic regions, and is remarkably intronpoor, as more than 80% of coding genes are intronless. Furthermore, in accordance with ecological
specialization theory, this defense-suppressing herbivore has extremely reduced environmental
response gene families such as those involved in chemoreception and detoxification. Other losses
associate with this species’ highly derived body plan. Our findings accelerate the understanding of
evolutionary forces underpinning metazoan life at the limits of small physical and genome size.Netherlands Organisation for
Scientific ResearchNational Science FoundationHorizon 2020 - Research and Innovation Framework ProgrammeNational Institutes of HealthResearch Foundation Flandershttp://elifesciences.orgpm2021BiochemistryGeneticsMicrobiology and Plant Patholog
Defense suppression benefits herbivores that have a monopoly on their feeding site but can backfire within natural communities
Defense suppression benefits herbivores that have a monopoly on their feeding site but can backfire within natural communities
<p>Raw data including popution densities, mite fecundity, plant gene expression, phytohormone and bacterial growth data. November 2014.</p
Intraspecific variation in a generalist herbivore accounts for differential induction and impact of host plant defences
Plants and herbivores are thought to be engaged in a coevolutionary arms race: rising frequencies of plants with anti-herbivore defences exert pressure on herbivores to resist or circumvent these defences and vice versa. Owing to its frequency-dependent character, the arms race hypothesis predicts that herbivores exhibit genetic variation for traits that determine how they deal with the defences of a given host plant phenotype. Here, we show the existence of distinct variation within a single herbivore species, the spider mite Tetranychus urticae, in traits that lead to resistance or susceptibility to jasmonate (JA)-dependent defences of a host plant but also in traits responsible for induction or repression of JA defences. We characterized three distinct lines of T. urticae that differentially induced JA-related defence genes and metabolites while feeding on tomato plants (Solanum lycopersicum). These lines were also differently affected by induced JA defences. The first line, which induced JA-dependent tomato defences, was susceptible to those defences; the second line also induced JA defences but was resistant to them; and the third, although susceptible to JA defences, repressed induction. We hypothesize that such intraspecific variation is common among herbivores living in environments with a diversity of plants that impose diverse selection pressure