| 研究実績の概要 |
First year of the project was fully devoted to collection of large scale data for further analyses. Two large scale herbivory experiments have been completed in summer season of FY2021. Two herbivore types (chewing insect larvae and sucking insect adults) were used as proposed after implementing hydroponic rice plant cultivation system. Five tissues (young leaf, attacked leaf, old leaves, stem, and root) over time course of three days have been collected. Out of collected samples, all originally proposed analyses have been carried out; in particular, extensive mineral analysis from 440 rice samples by ICP-MS, phytohormones, and secondary metabolites by LC-MS/MS were performed at IPSR (Galis, Mitani). Sumigraph analysis of total nitrogen and carbon from 440 samples was performed at Yamagata University (Aboshi). Large scale RNA sequencing (RNAseq) of 110 pooled replicated samples was outsourced and analyzed data obtained in March 2022. In outcome, several mineral elements showed differential contents in herbivore attacked plants. Furthermore, large increases in nitrogen containing alkaloids (p-coumaroylputrescine, feruloylputrescine, isopentylamine) were found in the attacked leaves. Jasmonic acid was the main phytohormone elicited in locally attacked leaves. A large number of genes related to defense was elicited in locally attacked leaves but many genes for mineral transport have also been observed in the regulated gene set. Overall, a very large amount of data was obtained that clearly depict extensive changes in rice metabolism in response to herbivore attack.
|
| 今後の研究の推進方策 |
After completion of the first stage of the project, we have narrowed down the most important targets for further analysis. Using transciptome data, we will now focus on up-regulated genes involved in mineral transport. In particular, genes involved in nitrogen metabolism will be targeted as specific resources that supplement production of nitrogen containing alkaloids (p-coumaroylputrescine, feruloylputrescine, isopentylamine) observed in locally attacked leaves. Furthermore, we will analyze metabolism of urea as potential source of translocated ammonia in the rice plants. To extend our knowledge of metabolic changes, remaining plant tissues will be used to analyze sugar and acid contents in herbivore attacked plants, which is essential to monitor and understand energy resources in herbivore attacked rice. The importance of silicon and heavy metals in rice defense against herbivores will be further approached in FY2022. In particular, we will focus on nickel, cadmium and arsenic heavy metals as potential new defense tools in rice. Localization and distribution of silica during herbivore attack will be monitored in detail by microscopic and spectroscopic methods, taking the advantage of manipulation of silica content in rice hydroponic cultivation media. Direct toxicity of heavy metals to herbivores will be further examined in experiments with artificial diet supplemented with heavy metals.
We plan two presentations at international conference, reporting on silica role and systemic defense in rice to broader scientific community.
|
