Viroids; pathogenicity and changes in the host proteome and transcriptome

Because of the small size of viroids (~246- 436 nucleotides), lack of protein-coding capacity, and causing some sever diseases, the virulence mechanism of viroids in host is being one of the interesting aspects of their study. Direct and indirect interaction between viroids and host factors in various studies has been proved; resulting to change in proteome and host transcripts and finally disease in plants. Latest presented model for these changes is the RNA silencing mechanism that has been proved for both viroid families. This review highlights the latest finding on pathogenicity mechanisms of viroids.