A Viral Satellite RNA Induces Yellow Symptoms on Tobacco by Targeting a Gene Involved in Chlorophyll Biosynthesis using the RNA Silencing Machinery
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Symptoms on virus-infected plants are often very specific to the given virus. The molecular mechanisms involved in viral symptom induction have been extensively studied, but are still poorly understood. Cucumber mosaic virus (CMV) Y satellite RNA (Y-sat) is a non-coding subviral RNA and modifies the typical symptom induced by CMV in specific hosts; Y-sat causes a bright yellow mosaic on its natural host Nicotiana tabacum. The Y-sat-induced yellow mosaic failed to develop in the infected Arabidopsis and tomato plants suggesting a very specific interaction between Y-sat and its host. In this study, we revealed that Y-sat produces specific short interfering RNAs (siRNAs), which interfere with a host gene, thus inducing the specific symptom. We found that the mRNA of tobacco magnesium protoporphyrin chelatase subunit I (ChlI, the key gene involved in chlorophyll synthesis) had a 22-nt sequence that was complementary to the Y-sat sequence, including four G-U pairs, and that the Y-sat-derived siRNAs in the virus-infected plant downregulate the mRNA of ChlI by targeting the complementary sequence. ChlI mRNA was also downregulated in the transgenic lines that express Y-sat inverted repeats. Strikingly, modifying the Y-sat sequence in order to restore the 22-nt complementarity to Arabidopsis and tomato ChlI mRNA resulted in yellowing symptoms in Y-sat-infected Arabidopsis and tomato, respectively. In 5'-RACE experiments, the ChlI transcript was cleaved at the expected middle position of the 22-nt complementary sequence. In GFP sensor experiments using agroinfiltration, we further demonstrated that Y-sat specifically targeted the sensor mRNA containing the 22-nt complementary sequence of ChlI. Our findings provide direct evidence that the identified siRNAs derived from viral satellite RNA directly modulate the viral disease symptom by RNA silencing-based regulation of a host gene.
- 2011-05-05
論文 | ランダム
- 現代中国の政治社会的アポリア (特集 世界のなかの中国--強権体制・経済発展・地域格差・社会不安の先は)
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- 応答から来たるべき正義へ--デリダの責任と正義をめぐる思考
- 「ケア」をめぐるアポリア : 「ケア」の理論的系譜
- 書評 小田中直樹『歴史学のアポリア--ヨーロッパ近代社会史再読』