Small RNAs containing the pathogenic determinant of a chloroplast‐replicating viroid guide the degradation of a host mRNA as predicted by RNA silencing

Summary How viroids, tiny non‐protein‐coding RNAs (∼250–400 nt), incite disease is unclear. One hypothesis is that viroid‐derived small RNAs (vd‐sRNAs; 21–24 nt) resulting from the host defensive response, via RNA silencing, may target for cleavage cell mRNAs and trigger a signal cascade, eventually...

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Published in:	The Plant journal : for cell and molecular biology Vol. 70; no. 6; pp. 991 - 1003
Main Authors:	Navarro, Beatriz, Gisel, Andreas, Rodio, Maria Elena, Delgado, Sonia, Flores, Ricardo, Di Serio, Francesco
Format:	Journal Article
Language:	English
Published:	Oxford, UK Blackwell Publishing Ltd 01.06.2012 Blackwell
Subjects:	abnormal development albino Arabidopsis Base Sequence Biological and medical sciences cell cleavage Cell differentiation, maturation, development, hematopoiesis Cell physiology chloroplast development Chloroplasts Chloroplasts - virology Cloning complementary DNA Fruits Fundamental and applied biological sciences. Psychology Gene expression Gene Expression Regulation, Plant genes genetics Heat shock proteins heat‐shock protein 90 hosts leaves messenger RNA metabolism Molecular and cellular biology Molecular Sequence Data Mutagenesis, Insertional non‐coding RNAs Nucleic Acid Conformation Peach latent mosaic viroid peaches Plant Diseases Plant Diseases - genetics Plant Diseases - virology Plant pathology Plant physiology and development PLMVd prediction progeny proteins Prunus Prunus - genetics Prunus - virology Prunus persica rapid amplification of cDNA ends Ribonucleic acid RNA RNA Interference RNA silencing RNA Stability RNA, Messenger RNA, Messenger - genetics RNA, Messenger - metabolism RNA, Viral RNA, Viral - genetics Seedlings Sequence Analysis, RNA signal transduction transposons viroid pathogenesis viroids Viroids - genetics virology Pathogenesis viroid pathogenesis Host RNA silencing Virus Degradation Messenger RNA heat-shock protein 90 PLMVd Pathogenic Viroid non-coding RNAs Heat shock protein Non coding RNA Development Chloroplast chloroplast development
ISSN:	0960-7412, 1365-313X, 1365-313X
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Summary:	Summary How viroids, tiny non‐protein‐coding RNAs (∼250–400 nt), incite disease is unclear. One hypothesis is that viroid‐derived small RNAs (vd‐sRNAs; 21–24 nt) resulting from the host defensive response, via RNA silencing, may target for cleavage cell mRNAs and trigger a signal cascade, eventually leading to symptoms. Peach latent mosaic viroid (PLMVd), a chloroplast‐replicating viroid, is particularly appropriate to tackle this question because it induces an albinism (peach calico, PC) strictly associated with variants containing a specific 12–14‐nt hairpin insertion. By dissecting albino and green leaf sectors of Prunus persica (peach) seedlings inoculated with PLMVd natural and artificial variants, and cloning their progeny, we have established that the hairpin insertion sequence is involved in PC. Furthermore, using deep sequencing, semi‐quantitative RT‐PCR and RNA ligase‐mediated rapid amplification of cDNA ends (RACE), we have determined that two PLMVd‐sRNAs containing the PC‐associated insertion (PC‐sRNA8a and PC‐sRNA8b) target for cleavage the mRNA encoding the chloroplastic heat‐shock protein 90 (cHSP90), thus implicating RNA silencing in the modulation of host gene expression by a viroid. Chloroplast malformations previously reported in PC‐expressing tissues are consistent with the downregulation of cHSP90, which participates in chloroplast biogenesis and plastid‐to‐nucleus signal transduction in Arabidopsis. Besides PC‐sRNA8a and PC‐sRNA8b, both deriving from the less‐abundant PLMVd (−) strand, we have identified other PLMVd‐sRNAs potentially targeting peach mRNAs. These results also suggest that sRNAs derived from other PLMVd regions may downregulate additional peach genes, ultimately resulting in other symptoms or in a more favorable host environment for viroid infection.
Bibliography:	JN377825 – GenBank accession numbers for the nucleotide sequences reported . JN377892 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 14 ObjectType-Article-1 ObjectType-Feature-2 content type line 23
ISSN:	0960-7412 1365-313X 1365-313X
DOI:	10.1111/j.1365-313X.2012.04940.x