Viral Small Interfering RNAs Target Host Genes to Mediate Disease Symptoms in Plants

Autor: Jun ichi Inaba, Chikara Masuta, Takeaki Ishihara, Nobutoshi Myojo, Vitantonio Pantaleo, Kae Sueda, József Burgyán, Hanako Shimura
Jazyk: angličtina
Rok vydání: 2011
Předmět:
Zdroj: PLoS Pathogens, Vol 7, Iss 5, p e1002021 (2011)
PLoS Pathogens
PLOS pathogens 7 (2011). doi:10.1371/journal.ppat.1002021
info:cnr-pdr/source/autori:Shimura H., Pantaleo V., Ishihara T., Myojo N., Inaba J., Sueda K., Burgyan J., Masuta C./titolo:A Viral Satellite RNA Induces Yellow Symptoms on Tobacco by Targeting a Gene Involved in Chlorophyll Biosynthesis using the RNA Silencing Machinery/doi:10.1371%2Fjournal.ppat.1002021/rivista:PLOS pathogens/anno:2011/pagina_da:/pagina_a:/intervallo_pagine:/volume:7
ISSN: 1553-7374
1553-7366
DOI: 10.1371/journal.ppat.1002021
Popis: 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.
Author Summary Cucumber mosaic virus (CMV) Y satellite RNA (Y-sat) is an interesting subviral RNA because it changes the green mosaic induced by CMV into a bright yellow mosaic in Nicotiana tabacum. The molecular basis underlying the induction of symptoms by viruses is not well understood, and this Y-sat-mediated modification of symptoms has been a long-standing mystery. In this study, we discovered the molecular mechanism involved in the Y-sat-induced yellowing. First, we showed that transgenic N. benthamiana plants that expressed the inverted-repeat sequence of Y-sat also developed a yellow phenotype, similar to the Y-sat-infected plants. Then, we found that tobacco magnesium protoporphyrin chelatase subunit I gene (ChlI, the key gene involved in chlorophyll synthesis) was downregulated in the transgenic plants and in the Y-sat-infected plants. We then identified a 22-nt long sequence that is complementary to the Y-sat including four G-U pairs in the ChlI mRNA. Finally, we demonstrated that a short interfering RNA (siRNA) derived from Y-sat specifically targeted and downregulated the ChlI mRNA, thus impairing the chlorophyll biosynthesis pathway. This discovery of the molecular basis of the symptom modification induced by Y-sat is the first demonstration that a subviral RNA can induce disease symptoms by regulating host gene expression through the RNA silencing machinery.
Databáze: OpenAIRE
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