The siRNAs targeting the left or right terminal region of chrysanthemum stunt viroid (CSVd) sequence suppress the development of disease symptoms caused by CSVd infection of chrysanthemum, but do not suppress viroid propagation

Abstract

ABSTRACTTransgenic chrysanthemum plants harbouring the genes producing small interfering RNAs (siRNAs) whose sequence was designed based on the chrysanthemum stunt viroid (CSVd) genome were established. The siRNAs are expected to target and decompose CSVd RNA through a silencing mechanism. The CSVd-infected plants were grafted as scions onto the stocks of either non-transgenic or transgenic plants, and axial shoots that elongated from the stocks were rooted and grown to investigate if the plants are resistant to CSVd under greenhouse conditions. The non-transgenic plants infected with CSVd showed severe disease symptoms, i.e. stunted growth and spotty chlorotic lesions on leaves, but no such symptoms were observed in the transgenic plants. The real-time quantitative reverse transcription PCR for monitoring the amounts of CSVd indicated that CSVd equally accumulated in both non-transgenic and transgenic plants. The present results suggest that the resistant feature of the transgenic plants to CSVd was due to interference with the pathway of symptom development, and not the inhibition of CSVd replication.