Heavy metal stress can prime for herbivore-induced plant volatile emission.
ABSTRACT Heavy metals are important pollutants that can severely impact ecological foodwebs. In addition to direct toxic effects, these contaminants have been suggested to disrupt chemical communication channels between plants and insects that rely on volatile organic compounds (VOCs). We investigated how different concentrations of copper (Cu) and cadmium (Cd) stress affect the capacity of Zea mays to synthesize VOCs in the presence and absence of herbivorous insects. Hydroponically grown maize exposed to a high and low concentration of either Cu or Cd showed stunted growth and lower photosynthetic capacities. Herbivores feeding on stressed plants also had attenuated growth rates. Heavy metal treatment alone did not induce VOC emission in maize plants; however, the higher Cu dose was found to prime for enhanced volatile production that can be triggered by caterpillar feeding. Cu stress correlated with increased levels of reactive oxygen species in roots and priming of herbivore-induced jasmonic acid in leaves. Plants challenged with Cd and herbivory did not differ in responses compared with herbivore-damaged controls with no heavy metals added to the substrate. For Cu stress, our results support the 'single biochemical mechanism for multiple stressors' model which predicts overlapping signalling and responses to abiotic and biotic stress factors.
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ABSTRACT: Although the function of silicon (Si) in plant physiology has long been debated, its beneficial effects on plant resistance against abiotic and biotic stresses, including insect herbivory, have been well documented. In addition, the jasmonate (JA) signaling pathway plays a crucial role in mediating antiherbivore defense responses in plants. However, potential interactions between JA and Si in response to insect attack have not been examined directly. To explore the role JA may play in Si-enhanced resistance, we silenced the expression of allene oxide synthase (OsAOS; active in JA biosynthesis) and CORONATINE INSENSITIVE1 (OsCOI1; active in JA perception) genes in transgenic rice plants via RNAi and examined resulting changes in Si accumulation and defense responses against caterpillar Cnaphalocrocis medinalis (rice leaffolder, LF) infestation. Si pretreatment increased rice resistance against LF larvae in wild-type plants but not in OsAOS and OsCOI1 RNAi lines. Upon LF attack, wild-type plants subjected to Si pretreatment exhibited enhanced defense responses relative to untreated controls, including higher levels of JA accumulation; increased levels of transcripts encoding defense marker genes; and elevated activities of peroxidase, polyphenol oxidase, and trypsin protease inhibitor. Additionally, reduced Si deposition and Si cell expansion were observed in leaves of OsAOS and OsCOI1 RNAi plants in comparison with wild-type plants, and reduced steady-state transcript levels of the Si transporters OsLsi1, OsLsi2, and OsLsi6 were observed in Si-pretreated plants after LF attack. These results suggest a strong interaction between Si and JA in defense against insect herbivores involving priming of JA-mediated defense responses by Si and the promotion of Si accumulation by JA.Proceedings of the National Academy of Sciences 09/2013; · 9.81 Impact Factor
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ABSTRACT: Rare earth elements (REEs) at proper concentrations were observed to alleviate heavy metal stress. However, the potential mechanisms are not clear. Thus, the present work focused on the mechanisms of lanthanum (La) ions on the generation and elimination of reactive oxygen species (ROS) production in leaves of rice seedlings hydroponically cultivated in 30 µM cadmium chloride (CdCl2) for two days. Results showed that the decline of O2 · - or H2O2 was attributed not only to the decreased expressions of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases-related gene, protein synthesis, and isozymes, but also to the decrease of xanthine oxidase (XOD), diamine oxidase (DAO), and guaiacol peroxidases (POD) isozymes and activities. Superoxide dismutase (SOD)-, catalase (CAT)- and ascorbate peroxidase (APX)-related genes and isozymes were also differentially upregulated to control ROS accumulation when proper concentrations of La were combined with 30 µM Cd. Based on the results, it may be concluded that La at proper concentrations not only limited the generation of O2 · - and H2O2 from the enzymatic sources, but also promoted the elimination of O2 · - and H2O2 via the up-regulating expressions of antioxidant enzymes-related genes and activities in the rice seedling's leaves under Cd stress. Environ Toxicol Chem © 2014 SETACEnvironmental Toxicology and Chemistry 04/2014; 33(7). · 2.83 Impact Factor
- Arthropod-Plant Interactions 01/2014; · 1.57 Impact Factor