Dataset Information

Priming of jasmonate-mediated antiherbivore defense responses in rice by silicon.

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.

SUBMITTER: Ye M

PROVIDER: S-EPMC3780902 | biostudies-literature | 2013 Sep

REPOSITORIES: biostudies-literature

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Priming of jasmonate-mediated antiherbivore defense responses in rice by silicon.

Ye Mao M Song Yuanyuan Y Long Jun J Wang Ruilong R Baerson Scott R SR Pan Zhiqiang Z Zhu-Salzman Keyan K Xie Jiefen J Cai Kunzheng K Luo Shiming S Zeng Rensen R

Proceedings of the National Academy of Sciences of the United States of America 20130903 38

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-enhance ...[more]

PMID: 24003150

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Project description:Bacterial blight, caused by Xanthomonas oryzae pv. oryzae (Xoo), is the most destructive bacterial disease of rice. The cloned rice gene Xa21 confers resistance to a broad spectrum of Xoo races. To identify other genes involved in Xa21-mediated immunity, a whole-genome oligonucleotide microarray of rice was used to profile the expression of rice genes between incompatible interactions and mock treatments at 0, 4, 8, 24, 72 and 120 hours post inoculation (hpi) or between incompatible and compatible interactions at 4 hpi, respectively. A total of 441 differentially expressed genes, designated as XDGs (Xa21 mediated Differentially expressed Genes), were identified. Based on their functional annotations, the XDGs were assigned to 14 categories some of which encode resistance/defense related proteins and signaling regulators. Interestingly, most signaling-related genes were down-regulated at 4 and 8 hpi, suggesting that negative regulation of cellular signaling may play a role in the Xa21-mediated defense response. Moreover, a number of pathogenesis-related genes were induced at 72 and 120 hpi. Comparison of expression profiles mediated by other resistance genes revealed an interesting common responses in the plant immune system. Comparison analyses also suggest possible overlaps with hormone signaling pathways and with defense systems including basal defense and hypersensitive responses. We investigated the transcriptional characteristics of Xa21-mediated defense responses in rice using whole-genome oligonucleotide microarray, by comparing the expression profiles between incompatible interactions and mock treatments at five time-points and between incompatible and compatible interactions at 4 hours post inoculation. Microarray hybridization at each time point was carried out in three replications including two biological replications and one technological replication. To detect the genes that are significantly regulated and to eliminate those that have inconsistent expression data among replicated experiments, a cutoff of 1.5 fold change and 1.96 for intensity-dependent Z-scores were required in at least two experimental samples.

Project description:BACKGROUND:Bilberry (Vaccinium myrtillus L.) is one of the most abundant wild berries in the Northern European ecosystems. This species plays an important ecological role as a food source for many vertebrate and invertebrate herbivores. It is also well-recognized for its bioactive compounds, particularly substances involved in natural defenses against herbivory. These defenses are known to be initiated by leaf damage (e.g. chewing by insects) and mediated by activation of the jasmonic acid (JA) signaling pathway. This pathway can be activated by exogenous application of methyl jasmonate (MeJA), the volatile derivative of JA, which is often used to stimulate plant defense responses in studies of plant-herbivore interactions at ecological, biochemical, and molecular organismal levels. As a proxy for herbivore damage, wild V. myrtillus plants were treated in the field with MeJA and changes in gene expression were compared to untreated plants. RESULTS:The de novo transcriptome assembly consisted of 231,887 unigenes. Nearly 71% of the unigenes were annotated in at least one of the databases interrogated. Differentially expressed genes (DEGs), between MeJA-treated and untreated control bilberry plants were identified using DESeq. A total of 3590 DEGs were identified between the treated and control plants, with 2013 DEGs upregulated and 1577 downregulated. The majority of the DEGs identified were associated with primary and secondary metabolism pathways in plants. DEGs associated with growth (e.g. those encoding photosynthesis-related components) and reproduction (e.g. flowering control genes) were frequently down-regulated while those associated with defense (e.g. encoding enzymes involved in biosynthesis of flavonoids, lignin compounds, and deterrent/repellent volatile organic compounds) were up-regulated in the MeJA treated plants. CONCLUSIONS:Ecological studies are often limited by controlled conditions to reduce the impact of environmental effects. The results from this study support the hypothesis that bilberry plants, growing in natural conditions, shift resources from growth and reproduction to defenses while in a MeJA-induced state, as when under insect attack. This study highlights the occurrence of this trade-off at the transcriptional level in a realistic field scenario and supports published field observations wherein plant growth is retarded and defenses are upregulated.

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Priming of jasmonate-mediated antiherbivore defense responses in rice by silicon.

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Priming of jasmonate-mediated antiherbivore defense responses in rice by silicon.

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