Journal Article

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

Eamens, Andrew L., Wang, Ming-Bo, Smith, Neil A.

2011

Overview

The Cucumber mosaic virus (CMV) Y-satellite RNA (Y-Sat) has a small non-protein-coding RNA genome that induces yellowing symptoms in infected Nicotiana tabacum (tobacco). How this RNA pathogen induces such symptoms has been a longstanding question. We show that the yellowing symptoms are a result of small interfering RNA (siRNA)-directed RNA silencing of the chlorophyll biosynthetic gene, CHLI. The CHLI mRNA contains a 22-nucleotide (nt) complementary sequence to the Y-Sat genome, and in Y-Sat-infected plants, CHLI expression is dramatically down-regulated. Small RNA sequencing and 5' RACE analyses confirmed that this 22-nt sequence was targeted for mRNA cleavage by Y-Sat-derived siRNAs. Transformation of tobacco with a RNA interference (RNAi) vector targeting CHLI induced Y-Sat-like symptoms. In addition, the symptoms of Y-Sat infection can be completely prevented by transforming tobacco with a silencing-resistant variant of the CHLI gene. These results suggest that siRNA-directed silencing of CHLI is solely responsible for the Y-Sat-induced symptoms. Furthermore, we demonstrate that two Nicotiana species, which do not develop yellowing symptoms upon Y-Sat infection, contain a single nucleotide polymorphism within the siRNA-targeted CHLI sequence. This suggests that the previously observed species specificity of Y-Sat-induced symptoms is due to natural sequence variation in the CHLI gene, preventing CHLI silencing in species with a mismatch to the Y-Sat siRNA. Taken together, these findings provide the first demonstration of small RNA-mediated viral disease symptom production and offer an explanation of the species specificity of the viral disease.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Agrobacterium tumefaciens - genetics / Amino Acid Sequence / Biology / Chlorophyll / Cucumber mosaic virus / Cytomegalovirus / Disease / DNA methylation / Down-Regulation / Gene Silencing / Genes / Genetic aspects / Genetic engineering / Genomes / Health aspects / High-Throughput Nucleotide Sequencing / Host-Pathogen Interactions / Infections / Lyases - genetics / Molecular Sequence Data / Nicotiana - enzymology / Nicotiana - genetics / Nicotiana - virology / Nicotiana tabacum / Plant diseases / Plant Diseases - genetics / Plant Diseases - virology / Plant viruses / Plant Viruses - physiology / Plants, Genetically Modified - enzymology / Plants, Genetically Modified - genetics / Plants, Genetically Modified - virology / Plasmids / Proteins / Ribonucleic acid / RNA / RNA, Messenger - genetics / RNA, Messenger - metabolism / RNA, Satellite - genetics / RNA, Satellite - metabolism / RNA, Small Interfering - genetics / RNA, Small Interfering - metabolism / RNA, Viral - genetics / RNA, Viral - metabolism / Studies / Tobacco / Viral diseases / Viral infections / Virus diseases of plants / Virus Replication / Viruses