Poster: Plant-pathogen interactions

Abs # 537: Breaking the silence in transgenic Phalaenopsis expressing a coat protein (CP) of Cymbidium mosaic virus (CymMV) reveals RNA-mediated resistance

Presenter:	Chan, Yuan-Li , sophia@gate.sinica.edu.tw
Authors	Chan, Yuan-Li  (A) (B)  Liao, Li-Jen  (C)   Pan, I-Chun  (B)   Hsu, Yau-Heiu  (D)   Chen, Wen-Huei  (E)   Chan, Ming-Tsair  (B)
Affiliations:	(A): Graduate Institute of Plant Biology, National Taiwan University (B): Institute of BioAgricultural Sciences, Academia Sinica (C): Institute of Life Science, National Kaohsiung Normal University (D): Graduate Institute of Agricultural Biotechnology, National Chung Hsing University (E): Agri-Business Department, Taiwan Sugar Corporation

Phalaenopsis orchid is one of the most sought after and its popularity has increased production tremendously in the last few years globally, both as potted plants and cut flowers. However, it is highly susceptible to the infection of Cymbidium mosaic virus (CymMV). To improve the ability of orchid plants against CymMV, an expression cassette harboring a maize ubiquitin promoter driven Cymbidium mosaic virus coat protein cDNA was transformed into protocorm-like bodies (PLBs) of Phalaenopsis orchid via particle bombardment. The stable transgene integration in transgenic orchid lines was confirmed by Southern blot analysis. Northern blot analysis revealed low signals of CP mRNA transcript, and no detectable CP was observed in a few transgenic orchid plants by western blot analysis. However, the transgenic plants exhibited enhanced resistance to CymMV infection via RT-PCR and ELISA analyses. To further identify the resistance of the transgenic plants, T0 progeny lines were assayed for resistance to CymMV as it occurs in the field and more than 50% of the progeny in five among the 13 tested lines showed CymMV protection. Results of nuclear run-on and small interfering RNA (siRNAs) analyses demonstrated that the virus resistance in the silenced transgenic orchid plants was RNA-mediated through a post-transcriptional gene silencing mechanism (PTGS). The molecular indicator of virus resistance to CymMV infection was proved to be siRNAs rather than CP mRNA. Results from the current study portray the attractive attributes of using CP gene for enhancing tolerance to CymMV in Phalaenopsis orchid, induced by RNA mediated.