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siRNAs Derived from Cymbidium Mosaic Virus and Odontoglossum Ringspot Virus Down-modulated the Expression Levels of Endogenous Genes in Phalaenopsis equestris
Plant Pathol. J. 2019;35:508-520
Published online October 1, 2019
© 2019 The Korean Society of Plant Pathology.

Han-hong Lan*, Cui-mei Wang, Shuang-shuang Chen, and Jian-ying Zheng

School of Biological Sciences and Biotechnology, Minnan Normal University, Zhangzhou 363000, China
Correspondence to: Phone) +86-596-2528735, FAX) +86-591-2528735

Handling Editor : Yoon, Ju-Yeon
Received March 15, 2019; Revised June 10, 2019; Accepted July 9, 2019.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Interplay between Cymbidium mosaic virus (CymMV)/Odontoglossum ringspot virus (ORSV) and its host plant Phalaenopsis equestris remain largely unknown, which led to deficiency of effective measures to control disease of P. equestris caused by infecting viruses. In this study, for the first time, we characterized viral small interfering RNAs (vsiRNAs) profiles in P. equestris co-infected with CymMV and ORSV through small RNA sequencing technology. CymMV and ORSV small interfering RNAs (siRNAs) demonstrated several general and specific/new characteristics. vsiRNAs, with A/U bias at the first nucleotide, were predominantly 21-nt long and they were derived predominantly (90%) from viral positive-strand RNA. 21-nt siRNA duplexes with 0-nt overhangs were the most abundant 21-nt duplexes, followed by 2-nt overhangs and then 1-nt overhangs 21-nt duplexes in infected P. equestris. Continuous but heterogeneous distribution and secondary structures prediction implied that vsiRNAs originate predominantly by direct Dicer-like enzymes cleavage of imperfect duplexes in the most folded regions of the positive strand of both viruses RNA molecular. Furthermore, we totally predicted 54 target genes by vsiRNAs with psRNATarget server, including disease/stress response–related genes, RNA interference core components, cytoskeleton-related genes, photosynthesis or energy supply related genes. Gene Ontology classification showed that a majority of the predicted targets were related to cellular components and cellular processes and performed a certain function. All target genes were down-regulated with different degree by vsiRNAs as shown by realtime reverse transcription polymerase chain reaction. Taken together, CymMV and ORSV siRNAs played important roles in interplay with P. equestris by down modulating the expression levels of endogenous genes in host plant.
Keywords : CymMV, ORSV, Phalaenopsis equestris, siRNAs, sRNA-seq

October 2019, 35 (5)
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