Article

Role of Glucosinolates in Insect-Plant Relationships and Multitrophic Interactions

Department of Ecology, Swedish University of Agricultural Sciences, Uppsala S-750 07, Sweden.
Annual Review of Entomology (Impact Factor: 13.73). 10/2008; 54(1):57-83. DOI: 10.1146/annurev.ento.54.110807.090623
Source: PubMed

ABSTRACT

Glucosinolates present classical examples of plant compounds affecting insect-plant interactions. They are found mainly in the family Brassicaceae, which includes several important crops. More than 120 different glucosinolates are known. The enzyme myrosinase, which is stored in specialized plant cells, converts glucosinolates to the toxic isothiocyanates. Insect herbivores may reduce the toxicity of glucosinolates and their products by excretion, detoxification, or behavioral adaptations. Glucosinolates also affect higher trophic levels, via reduced host or prey quality or because specialist herbivores may sequester glucosinolates for their own defense. There is substantial quantitative and qualitative variation between plant genotypes, tissues, and ontogenetic stages, which poses specific challenges to insect herbivores. Even though glucosinolates are constitutive defenses, their levels are influenced by abiotic and biotic factors including insect damage. Plant breeders may use knowledge on glucosinolates to increase insect resistance in Brassica crops. State-of-the-art techniques, such as mutant analysis and metabolomics, are necessary to identify the exact role of glucosinolates.

Download full-text

Full-text

Available from: Richard James Hopkins
  • Source
    • "In contrast, drought can negatively affect herbivorous insects through decreases in plant growth, turgor pressure and water content, as well as through an increase of allelochemicals such as phenolics or glucosinolates (del Carmen Martínez-Ballesta et al., 2013; Inbar et al., 2001). Glucosinolates are the main defensive compounds in the Brassicaceae (Hopkins et al., 2009), and it has been proposed that they may have an important function in avoiding water loss by closing the stomata (Zhao et al., 2008). Interestingly, in recent years several herbivores have each been studied on a range of plant species from the Brassicaceae family (Table 1) (Gutbrodt et al., 2012, 2011; Khan et al., 2010, 2011; Mewis et al., 2012; Prill et al., 2014; Simpson et al., 2012; Tariq et al., 2013a, 2012; Vickers, 2011). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Plants are constantly exposed to multiple biotic and abiotic stresses, such as drought and herbivory. However, plant responses to these stresses have usually been studied in isolation. Here, we take a multidisciplinary approach addressing ecological and chemical aspects of plant responses to generalist herbivores and several intensities of drought. We hypothesize that in brassicaceous plants, the effects of drought stress on herbivores can be explained by an increase in indole glucosinolates. Four-week-old Arabidopsis thaliana plants were drought stressed for one week or watered as normal. Three types of drought stress were compared: (1) no watering for 1 week and then rewatered to saturation (low drought); (2) no watering for 1 week and then rewatered to 60% of soil water content (high drought); (3) watering every other day to 60% of soil water content (continuous drought). All three types of drought stress negatively affected both the larval mass of the leaf chewer Mamestra brassicae and the population growth of the phloem feeder Myzus persicae. This was associated with increased levels of herbivore-induced indole glucosinolates compared to infested control plants. Interestingly, the levels of total indole glucosinolates did not change in uninfested plants, except for the indole 4-methoxy-glucobrassicin that was induced by continuous drought. Two-choice experiments also showed that caterpillars of M. brassicae, but not aphids, avoided drought-stressed plants only after feeding on them, but not by visual/olfactory cues. However, on a knockout mutant blocked in the production of indole glucosinolates (cyp79B2 cyp79B3), the effect of drought on herbivore performance was similar to that on wild-type plants. The results of this study show that drought stress induced higher levels of indole glucosinolates; however, these levels were not responsible for higher resistance to generalist herbivores in drought-stressed plants.
    Full-text · Article · Mar 2016 · Environmental and Experimental Botany
    • "These contrasting results are probably due to differences in aphid genotypes studied and/or environmental conditions. Although glucosinolates are determining factors in Brassicaceae-insect interactions (Hopkins et al., 2009) and have defensive roles against herbivores (Kettles et al., 2013; Müller et al., 2010), other compounds may also affect ecological interactions between cruciferous plants and insects (Onkokesung et al., 2014). It is still an open question which mechanisms are responsible for the negative effect of drought on herbivore performance. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In nature, plants are exposed to biotic and abiotic stresses that often occur simultaneously. Therefore, plant responses to combinations of stresses are most representative of how plants respond to stresses. We used RNAseq to assess temporal changes in the transcriptome of Arabidopsis thaliana to herbivory by Pieris rapae caterpillars, either alone or in combination with prior exposure to drought or infection with the necrotrophic fungus Botrytis cinerea. Pre-exposure to drought stress or Botrytis infection resulted in a significantly different timing of the caterpillar-induced transcriptional changes. Additionally, the combination of drought and P. rapae induced an extensive downregulation of A. thaliana genes involved in defence against pathogens. Despite a more substantial growth reduction observed for plants exposed to drought plus P. rapae feeding compared with P. rapae feeding alone, this did not affect weight increase of this specialist caterpillar. Plants respond to combined stresses with phenotypic and transcriptional changes that differ from the single stress situation. The effect of a previous exposure to drought or B. cinerea infection on transcriptional changes to caterpillars is largely overridden by the stress imposed by caterpillars, indicating that plants shift their response to the most recent stress applied.
    No preview · Article · Feb 2016 · New Phytologist
  • Source
    • "Moreover, GLS and KRR levels after 4 d of caterpillar feeding were significantly higher in wild-type plants that had previously been exposed to caterpillar feeding (approximately 2-fold) than in previously unexposed wild-type plants (Fig. 5, A and C). Many studies on Arabidopsis showed that specialist herbivores such as P. brassicae caterpillars are highly adapted to GLS (Hopkins et al., 2009;Müller et al., 2010;Winde and Wittstock 2011). Therefore, plant resistance against specialist caterpillars is unlikely to depend on an individual group of defense metabolites such as GLS (Rasmann et al., 2015). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Plants respond to herbivory with the induction of resistance, mediated by distinct phytohormonal signaling pathways and their interactions. Phloem feeders are known to induce plant resistance via the salicylic acid (SA) pathway whereas biting-chewing herbivores induce plant resistance mainly via the jasmonate (JA) pathway. Here, we show that a specialist caterpillar (biting-chewing herbivore) and a specialist aphid (phloem feeder) differentially induce resistance against Pieris brassicae caterpillars in Arabidopsis thaliana plants. Caterpillar feeding induces resistance through the JA signaling pathway that is associated with the induction of kaempferol 3,7-dirhamnoside, whereas aphid feeding induces resistance via a novel mechanism involving sinapoyl malate. The role of sinapoyl malate is confirmed through the use of a mutant compromised in the biosynthesis of this compound. Caterpillar-induced resistance is associated with a lower cost in terms of plant growth reduction than aphid-induced resistance. A strong constitutive resistance against P. brassicae caterpillars in combination with a strong growth attenuation in plants of a T-DNA insertion mutant of WRKY70 (wrky70) suggest that the WRKY70 transcription factor, a regulator of downstream responses mediated by JA-SA signaling crosstalk, is involved in the negative regulation of caterpillar resistance and in trade-off between growth and defense. In conclusion, different mechanisms of herbivore-induced resistance come with different costs and a functional WRKY70 transcription factor is required for the induction of low-cost resistance.
    Full-text · Article · Jan 2016 · Plant physiology
Show more