siRNAs Derived from Cymbidium Mosaic Virus and Odontoglossum Ringspot Virus Down-modulated the Expression Levels of Endogenous Genes in Phalaenopsis equestris

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

Interplay between CymMV/ORSV and Phalaenopsis equestris by sRNA-seq 509 (RNAi). In eukaryotes, upon viral infection RNAi employs Dicer and Dicer-like (DCL) enzymes to cleave viral RNAs into small interfering RNAs (siRNAs) with sizes about 21 nucleotides (nt), which are further amplified by RNAdependent RNA polymerases (RdRPs). These siRNAs are loaded into argonaute to form the RNA induced silencing complex to specifically silence target genes (Baulcombe, 2006; Ding, 2010) . Based on the mechanism, Kreuz et al., first proposed that high-throughput small RNA sequencing (sRNA-seq) can be used as a routine method to detect various DNA or RNA viruses (Kreuze et al., 2009) . Subsequently, to streamline this technology, Li et al. (2012 Li et al. ( , 2013 Li et al. ( , 2015 explored the VirusDetect, a bioinformatics pipeline that can efficiently analyze large scale small RNA (sRNA) datasets for both known and novel virus identification in plants and animals (Li et al., , 2013 Zheng et al., 2017) . Furthermore, Wu et al. (2010) also suggested a possibility of using sRNAs for viral genome assembly and virus discovery in invertebrate, such as fruit fly, mosquito and nematode. Recently, the method was used to detect the human viruses . In this study, we also identified and characterized the CymMV and ORSVderived siRNAs and predicted its host target genes from disease P. equestris plants through sRNA-seq to investigate the interaction between these two viruses and its host plant.