a viral satellite rna induces yellow symptoms on tobacco by targeting a gene involved in chlorophyll biosynthesis using the rna silencing machinery卫星rna病毒诱导黄色烟草出现症状通过瞄准一个基因参与叶绿素生物合成使用rna沉默机制.pdfVIP

A Viral Satellite RNA Induces Yellow Symptoms on Tobacco by Targeting a Gene Involved in Chlorophyll Biosynthesis using the RNA Silencing Machinery 1 2 1 1 1 Hanako Shimura , Vitantonio Pantaleo , Takeaki Ishihara , Nobutoshi Myojo , Jun-ichi Inaba , Kae 1 ´ ´ 2 1 Sueda , Jozsef Burgyan , Chikara Masuta * 1 Research Faculty of Agriculture, Hokkaido University, Kita-ku, Sapporo, Japan, 2 Istituto di Virologia Vegetale, CNR, Torino, Italy Abstract 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