Many aphids are major agricultural pests because of their unparalleled reproductive capacity and their ability to manipulate host plant physiology. Aphid population growth and its impact on plant ...fitness are strongly influenced by interactions with other organisms, including plant pathogens, endophytes, aphid endosymbionts, predators, parasitoids, ants, and other herbivores. Numerous molecular and genomic resources have recently been developed to identify sources of aphid resistance in plants, as well as potentially novel targets for control in aphids. Moreover, the same model systems that are used to explore direct molecular interactions between plants and aphids can be utilized to study the ecological context in which they occur.
Reactive oxygen species (ROS) such as hydrogen peroxide and superoxide are produced in plants in response to many biotic and abiotic stressors, and they can enhance stress adaptation in certain ...circumstances or mediate symptom development in others. The roles of ROS in plant-pathogen interactions have been extensively studied, but far less is known about their involvement in plant-insect interactions. A growing body of evidence, however, indicates that ROS accumulate in response to aphids, an economically damaging group of phloem-feeding insects. This review will cover the current state of knowledge about when, where, and how ROS accumulate in response to aphids, which salivary effectors modify ROS levels in plants, and how microbial associates influence ROS induction by aphids. We will also explore the potential adaptive significance of intra- and extracellular oxidative responses to aphid infestation in compatible and incompatible interactions and highlight knowledge gaps that deserve further exploration.
The conversion of oleic acid (C18:1) to linoleic acid (C18:2) in the endoplasmic reticulum is critical to the accumulation of polyunsaturated fatty acids in seeds and other tissues, and this reaction ...is catalyzed by a Δ12-desaturase, FATTY ACID DESATURASE2 (FAD2). Here, we report that the tomato (
) genome harbors two genes,
and
, which encode proteins with in vitro Δ12-desaturase activity. In addition, tomato has seven divergent FAD2 members that lack Δ12-desaturase activity and differ from canonical FAD2 enzymes at multiple amino acid positions important to enzyme function. Whereas
and
are downregulated by biotic stress, the majority of divergent
genes in tomato are upregulated by one or more stresses. In particular,
is induced by the potato aphid (
) and has elevated constitutive expression levels in
(
), a tomato mutant with enhanced aphid resistance and altered fatty acid profiles. Virus-induced gene silencing of
in
results in significant increases in aphid population growth, indicating that a divergent
gene contributes to aphid resistance in this genotype. Thus, the
gene family in tomato is important both to primary fatty acid metabolism and to responses to biotic stress.
Fatty acid desaturases (FADs) in plants influence levels of susceptibility to multiple stresses, including insect infestations. In this study, infestations of the greAtFABen peach aphid (
) on
were ...reduced by mutations in three desaturases:
, which encodes a chloroplastic stearoyl-acyl-carrier-protein 9-desaturase, and
or
, which encode ω-3 FADs in the chloroplast and endoplasmic reticulum (ER) respectively. These data indicate that certain FADs promote susceptibility to aphids, and that aphids are impacted by desaturases in both the chloroplast and ER. Aphid resistance in
,
, and/or
might involve altered signaling between these subcellular compartments. C18:1 levels are depleted in
, whereas C18:2 accumulation is enhanced in
and
. In contrast,
has higher than normal C18:2 levels but also high C18:1 and low C18:0, and does not impact aphid numbers. Potentially, aphids may be influenced by the balance of multiple fatty acids (FAs) rather than by a single species, with C18:2 promoting aphid resistance and C18:1 promoting susceptibility. Although the
mutant also accumulates higher-than-normal levels of C16:2, this FA does not contribute to aphid resistance because a triple mutant line that lacks detectable levels of C16:2 (
) retains comparable levels of aphid resistance as fad7. In addition, aphid numbers are unaffected by the
mutation that inhibits C16:1 synthesis. Together, these results demonstrate that certain FADs are important susceptibility factors in plant-aphid interactions, and that aphid resistance is more strongly associated with differences in C18 abundance than C16 abundance.
The relationship between phloem-feeding insects (PFIs) and plants offers an intriguing example of a highly specialized biotic interaction. These insects have evolved to survive on a nutritionally ...imbalanced diet of phloem sap, and to minimize wound responses in their host plants. As a consequence, plant perception of and responses to PFIs differ from plant interactions with other insect-feeding guilds. Transcriptome-wide analyses of gene expression are currently being applied to characterize plant responses to PFIs in crop plants with race-specific innate resistance, as well as in compatible interactions with susceptible hosts. Recent studies indicate that PFIs induce transcriptional reprogramming in their host plants, and that plant responses to PFIs appear to be quantitatively and qualitatively different from responses to other insects or pathogens. Transcript profiling studies also suggest that PFIs induce cell wall modifications, reduce photosynthetic activity, manipulate source–sink relations, and modify secondary metabolism in their hosts, and many of these responses appear to occur within the phloem tissue. Plant responses to these insects appear to be regulated in part by the salicylate, jasmonate, and ethylene signalling pathways. As additional transcript profiling data become available, forward and reverse genetic approaches will be necessary to determine which changes in gene expression influence resistance or susceptibility to PFIs.
Prenatal alcohol exposure (PAE) has been shown to impair learning, memory and executive functioning in children. Perseveration, or the failure to respond adaptively to changing contingencies, is a ...hallmark on neurobehavioral assessment tasks for human fetal alcohol spectrum disorder (FASD). Adaptive responding is predominantly a product of the medial prefrontal cortex (mPFC) and is regulated by corticosteroids. In our mouse model of PAE we recently reported deficits in hippocampal formation-dependent learning and memory and a dysregulation of hippocampal formation glucocorticoid receptor (GR) subcellular distribution. Here, we examined the effect of PAE on frontal cortical-dependent behavior, as well as mPFC GR subcellular distribution and the levels of regulators of intracellular GR transport. PAE mice displayed significantly reduced response flexibility in a Y-maze reversal learning task. While the levels of total nuclear GR were reduced in PAE mPFC, levels of GR phosphorylated at serines 203, 211 and 226 were not significantly changed. Cytosolic, but not nuclear, MR levels were elevated in the PAE mPFC. The levels of critical GR trafficking proteins, FKBP51, Hsp90, cyclophilin 40, dynamitin and dynein intermediate chain, were altered in PAE mice, in favor of the exclusion of GR from the nucleus, indicating dysregulation of GR trafficking. Our findings suggest that there may be a link between a deficit in GR nuclear localization and frontal cortical learning deficits in prenatal alcohol-exposed mice.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Plant α-dioxygenases (α-DOX) are fatty acid-hydroperoxidases that contribute to the synthesis of oxylipins, a diverse group of compounds primarily generated through oxidation of linoleic (LA) and ...linolenic acid (LNA). Oxylipins are implicated in plant signaling against biotic and abiotic stresses. We report here that the potato aphid (Macrosiphum euphorbiae) induces Slα-DOX1 but not Slα-DOX2 expression in tomato (Solanum lycopersicum). Slα-DOX1 upregulation by aphids does not require either jasmonic acid (JA) or salicylic acid (SA) accumulation, since tomato mutants deficient in JA (spr2, acx1) or SA accumulation (NahG) still show Slα-DOX1 induction. Virus-induced gene silencing of Slα-DOX1 enhanced aphid population growth in wild-type (WT) plants, revealing that Slα-DOX1 contributes to basal resistance to aphids. Moreover, an even higher percent increase in aphid numbers occurred when Slα-DOX1 was silenced in spr2, a mutant line characterized by elevated LA levels, decreased LNA, and enhanced aphid resistance as compared with WT. These results suggest that aphid reproduction is influenced by oxylipins synthesized from LA by Slα-DOX1. In agreement with our experiments in tomato, two independent α-dox1 T-DNA insertion mutant lines in Arabidopsis thaliana also showed increased susceptibility to the green peach aphid (Myzus persicae), indicating that the role α-DOX is conserved in other plant-aphid interactions.
•HTP systems automate image analysis of large numbers of samples in order to:-objectively quantify continuously variable traits like insect damage.-enable nondestructive repeated measures over the ...course of infestation.-quantify traits like water status that cannot be seen in the visible spectrum.•Characterize multiple dimensions of the plant ‘phenome’ within a single experiment.
Through automated image collection and analysis, high-throughput phenotyping (HTP) systems non-destructively quantify a diversity of traits in large plant populations. Some platforms collect data in greenhouses or growth chambers while others are field-based. Platforms also vary in the number and type of sensors, including visible, fluorescence, infrared, hyperspectral, and three-dimensional cameras that can detect traits within and beyond the visible spectrum. These systems could be applied to quantify the impact of herbivores on plant health, to monitor herbivores in choice or no-choice bioassays, or to estimate plant properties such as defensive allelochemicals. By increasing the throughput, precision, and dimensionality of these measures, HTP has the potential to revolutionize the field of plant–insect interactions, including breeding programs for resistance and tolerance.
We report here that disruption of function of the ω-3 FATTY ACID DESATURASE7 (FAD7) enhances plant defenses against aphids. The suppressor of prosystemin-mediated responses! (sprl) mutation in tomato ...(Solatium lycopersicum), which eliminates function of FAD7, reduces the settling behavior, survival, and fecundity of the potato aphid (Macrosiphum euphorbiae). Likewise, the antisense suppression of LeFAD7 expression in wild-type tomato plants reduces aphid infestations. Aphid resistance in the sprl mutant is associated with enhanced levels of salicylic acid (SA) and mRNA encoding the pathogenesis-related protein P4. Introduction of the Naphthalene/salicylate hydroxylase transgene, which suppresses SA accumulation, restores wild-type levels aphid susceptibility to sprl. Resistance in sprl is also lost when we utilize virus-induced gene silencing to suppress the expression of NONEXPRESSOR OF PATHOGENESIS-RELATED PROTEINS1 (NPR1), a positive regulator of many SA-dependent defenses. These results indicate that FAD7 suppresses defenses against aphids that are mediated through SA and NPR1. Although loss of function of FAD7 also inhibits the synthesis of jasmonate (JA), the effects of this desaturase on aphid resistance are not dependent on JA; other mutants impaired in JA synthesis (acx1) or perception (jail-1) show wild-type levels of aphid susceptibility, and sprl retains aphid resistance when treated with methyl jasmonate. Thus, FAD7 may influence JA-dependent defenses against chewing insects and SA-dependent defenses against aphids through independent effects on JA synthesis and SA signaling. The Arabidopsis (Arabidopsis thaliana) mutants Atfad7-2 and Atfad7-1fad8 also show enhanced resistance to the green peach aphid (Myzus persicae) compared with wild-type controls, indicating that FAD7 influences plantaphid interactions in at least two plant families.
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