Dendrobium viroid, a new monocot-infecting apscaviroid

Area of Science:

• Plant pathology
• Virology
• Molecular biology

Background:

• Viroids are small, circular RNA pathogens infecting dicot species.
• Only two viroids were previously known to infect monocots, specifically coconut.

Purpose of the Study:

• To identify novel viroids using in silico data mining.
• To characterize a newly discovered viroid in Dendrobium officinale.

Main Methods:

• In silico screening of transcriptomic data.
• In vitro transcription and inoculation of plant tissues.
• 2D-PAGE and northern hybridization for detection.
• Phylogenetic analysis for classification.

Main Results:

• A novel viroid-like RNA, Dendrobium viroid (DVd), was identified in Dendrobium officinale.
• DVd is 324 nucleotides long, possesses characteristic viroid conserved regions (CCRs), and groups with Apscaviroid genus.
• Inoculation confirmed DVd infectivity in Dendrobium officinale plants.
• Field surveys indicated a low incidence (0.96%) of DVd in Chinese Dendrobium species.

Conclusions:

• DVd is the first viroid identified in orchids and the third in monocots.
• This discovery broadens the known host range of viroids.
• DVd represents a significant addition to the known diversity of plant-infecting RNA viruses.