silicon and jasmonic-acid

Silicon (Si) fertilization alleviates biotic stresses in plants. Si enhances plant resistance against phytophagous insects through physical and biochemical mechanisms. In particular, Si modifies jasmonic acid levels and the emissions of herbivore-induced plant volatiles (HIPVs). Here, we investigated whether Si accumulation in the tissues of maize leaves modifies the emissions of constitutive and herbivore-induced plant volatiles, with cascade deterrent effects on oviposition site selection by Spodoptera exigua Hübner (Lepidoptera: Noctuidae). Maize plants were cultivated in a hydroponic system under three Si concentrations, resulting in three groups of plants expressing different Si concentrations in their tissues (0.31 ± 0.04, 4.69 ± 0.49, and 9.56 ± 0.30 g Si. Kg

Topics: Animals; Female; Herbivory; Larva; Oviposition; Silicon; Spodoptera; Zea mays

Root rot caused by Ilyonectria mors-panacis is a devastating fungal disease leading to defect in root quality and causes reduced yield during the perennial life cycle of Panax ginseng Meyer. This indicates the imperative need to understand the molecular basis of disease development and also to enhance tolerance against the fungus. With this idea, the protective effect of silicon (supplied as silica nanoparticles) in P. ginseng root rot pathosystem and its molecular mechanism was investigated in the current study. We have tested different concentrations of silicon (Si) to disease-infected ginseng and found that long term analysis (30 dpi) displayed a striking 50% reduction in disease severity index upon the treatment of Si. Expectedly, Si had no direct degradative effect against the pathogen. Instead, in infected roots it resulted in reduced expression of PgSWEET leading to regulated sugar efflux into apoplast and enhanced tolerance against I. mors-panacis. In addition, under diseased condition, both protopanaxadiol (PPD) and protopanaxatriol (PPT) type ginsenoside profile in roots were higher in Si treated plants. This is the first report indicating the protective role of Si in ginseng-root rot pathosystem, thereby uncovering novel features of ginseng mineral physiology and at the same time, enabling its usage to overcome root rot.

Topics: Cyclopentanes; Metabolic Networks and Pathways; Mevalonic Acid; Nanoparticles; Oxylipins; Panax; Phytosterols; Plant Diseases; Plant Roots; Silicon; Sugars; Triterpenes

The importance of magnesium (Mg) for plant growth is well-documented. Silicon (Si)-mediated alleviation of mineral deficiencies has been also reported in a number of plant species; however, there is no report on the relevance of Si nutrition in plants grown in Mg-deficient condition. Therefore, in the present work, an attempt was undertaken to study the role of Si nutrition in maize plants exposed to Mg deficiency. Plants were grown either under low (0.02 mM) or normal (0.5 mM) levels of Mg, with or without Si supplement. We have shown that Mg-deficient plants treated with Si maintained their growth and increased significantly the levels of chlorophyll and soluble sugars compared to those plants which did not receive Si. In addition, the concentrations of hexose-P, and glycolytic intermediate metabolites-mainly organic acids (isocitric and glutamic acids)-were increased in response to Si nutrition, which was associated with an increase in the levels of stress amino acids such as gamma-aminobutyric-acid (GABA), serine and glycine, as well as polyamines putrescine, which overall contributed to Mg stress tolerance. In addition, Si enhanced the levels of phytohormones cytokinin

Topics: Amino Acids; Biomass; Biosynthetic Pathways; Chlorophyll; Cyclopentanes; Gene Expression Regulation, Plant; Magnesium; Metabolome; Oxylipins; Plant Growth Regulators; Plant Proteins; Plant Roots; Plant Shoots; Silicon; Transcription, Genetic; Zea mays

Silicon (Si) has been known to regulate plant growth; however, the underlying mechanisms of short-term exogenous Si application on the regulation of calcium (Ca) and nitrogen (N), endogenous phytohormones, and expression of essential proteins have been little understood.. In conclusion, the current results suggest that short-term exogenous Si can significantly regulate rice plant physiology by influencing Ca, N, endogenous phytohormones, and proteins, and that 1.0 mM Si application is more beneficial to plants than higher concentrations.

Topics: Calcium; Cyclopentanes; Gene Expression Regulation, Plant; Gibberellins; Nitrogen; Oryza; Oxylipins; Plant Growth Regulators; Plant Proteins; Salicylic Acid; Silicon

Silicon (Si) application has been known to enhance the tolerance of plants against abiotic stresses. However, the protective mechanism of Si under heavy metals contamination is poorly understood. The aim of this study was to assess the role of Si in counteracting toxicity due to cadmium (Cd) and copper (Cu) in rice plants (Oryza sativa).. Si significantly improved the growth and biomass of rice plants and reduced the toxic effects of Cd/Cu after different stress periods. Si treatment ameliorated root function and structure compared with non-treated rice plants, which suffered severe root damage. In the presence of Si, the Cd/Cu concentration was significantly lower in rice plants, and there was also a reduction in lipid peroxidation and fatty acid desaturation in plant tissues. The reduced uptake of metals in the roots modulated the signaling of phytohormones involved in responses to stress and host defense, such as abscisic acid, jasmonic acid, and salicylic acid. Furthermore, the low concentration of metals significantly down regulated the mRNA expression of enzymes encoding heavy metal transporters (OsHMA2 and OsHMA3) in Si-metal-treated rice plants. Genes responsible for Si transport (OsLSi1 and OsLSi2), showed a significant up-regulation of mRNA expression with Si treatment in rice plants.. The present study supports the active role of Si in the regulation of stresses from heavy metal exposure through changes in root morphology.

Topics: Abscisic Acid; Adenosine Triphosphatases; Cadmium; Copper; Cyclopentanes; Metals, Heavy; Oryza; Oxylipins; Plant Proteins; Salicylic Acid; Silicon

We investigated the effects of silicon (Si) application on rice plants (Oryza sativa L.) and its responses in the regulation of jasmonic acid (JA) during wounding stress. Endogenous JA was significantly higher in wounded rice plants than in non-wounded. In contrast, Si treatment significantly reduced JA synthesis as compared to non-Si applications under wounding stress. mRNA expression of O. sativa genes showed down-regulation of lipoxygenase, allene oxide synthase 1, allene oxide synthase 2, 12-oxophytodienoate reductase 3, and allene oxide cyclase upon Si application and wounding stress as compared to non-Si-treated wounded rice plants. The physical injury-induced-oxidative stress was modulated by Si treatments, which resulted in higher catalase, peroxidase, and polyphenol oxidase activities as compared with non-Si-treated plants under wounding stress. The higher Si accumulation in rice plants also reduced the level of lipid peroxidation, which helped the rice plants to protect it from wounding stress. In conclusion, Si accumulation in rice plants mitigated the adverse effects of wounding through regulation of antioxidants and JA.

Topics: Cyclopentanes; Gene Expression Regulation; Oryza; Oxidative Stress; Oxylipins; Plant Proteins; Real-Time Polymerase Chain Reaction; Silicon

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.

Topics: Animals; Catechol Oxidase; Cyclopentanes; Gene Silencing; Heat-Shock Proteins; Herbivory; Intramolecular Oxidoreductases; Moths; Oryza; Oxylipins; Peroxidase; Signal Transduction; Silicon; Soil; Trypsin Inhibitors

The role of defence gene expression triggered by Cd toxicity in the plant's response to Botrytis cinerea was investigated in Arabidopsis thaliana Columbia 0. Silicon (0 or 1.5 mM) and Cd (0, 1 or 10 μM) were supplied to 3-month-old solution-cultured plants. After 3 days, half of the plants of each treatment were inoculated with Botrytis. Supplied Cd concentrations were below the toxicity threshold and did not cause shoot growth inhibition or evidence of oxidative stress, while Botrytis infection severely decreased plant growth in all treatments. The expression of marker genes PR1 and BGL2 for the salicylic acid (SA) and the PDF1.2 for the jasmonic acid-ethylene (JA-ET) signalling pathways was enhanced in 10 μM Cd-treated non-infected plants. Twenty hours after inoculation, PDF1.2 expression showed a strong increase in all treatments, while enhanced PR1, BGL2, and CHIB expression was only found 7 days after infection. A great synergistic effect of Cd and Botrytis on PDF1.2 expression was found in 10 μM Cd-treated plants. Silicon decreased PR1, BGL2, and CHIB, while increasing PDF1.2 expression, which indicates its role as a modulator of the signalling pathways involved in the plant's response to fungal infection. Botrytis growth decreased in 10 μM Cd-treated plants, which could be due to the combined effects of Cd and Botrytis activating the SA and JA-ET-mediated signalling pathways. Taken together, our results provide support for the view that Cd concentrations close to the toxicity threshold induce defence signalling pathways which potentiate the plant's response against fungal infection.

Topics: Arabidopsis; Arabidopsis Proteins; Botrytis; Cadmium; Cyclopentanes; Defensins; Disease Resistance; Dose-Response Relationship, Drug; Ethylenes; Gene Expression Regulation, Plant; Genes, Plant; Glucan Endo-1,3-beta-D-Glucosidase; Host-Pathogen Interactions; Oxylipins; Plant Diseases; Plant Leaves; Reverse Transcriptase Polymerase Chain Reaction; Salicylic Acid; Signal Transduction; Silicon; Time Factors