Cymbidium mosaic virus (CymMV) and Odontoglossum ringspot virus (ORSV) are the two most prevalent viruses infecting orchids and causing economic losses worldwide. Upon virus infection, antiviral RNA silencing is activated to generate viral small-interfering RNAs (vsiRNAs). A research team led by Dr. Lin and Dr. Yao-Chien Chang (National Taiwan University) characterized the vsiRNAs from CymMV and ORSV singly or synergistically infecting Phalaenopsis amabilis. Regardless of early or late stage with single or double infection, CymMV and ORSV vsiRNAs were predominant in 21- and 22-nt sizes, with excess positive polarity and underrepresented 5’-guanine. Interestingly, most vsiRNA features remained unchanged with double inoculation, but additional ORSV vsiRNA hotspot peaks were prominent. The potential vsiRNA-mediated regulation of the novel targets in mixed infected tissues thereby provides a different view of CymMV and ORSV synergism. Hence, temporally profiled vsiRNAs from taxonomically distinct CymMV and ORSV illustrate active anti-viral RNA silencing in their natural host, Phalaenopsis, during both early and late stages of infection. Our findings provide insights into offense–defense interactions among CymMV, ORSV and orchids.

Link: https://doi.org/10.1111/mpp.12888