Вiological effects of viroids

Abstract

Possible potential microbial agents of a human which represent by ring highly complementary one-chained ribonucleic acid with an absent of protein coating, as for viruses containing a ribonucleic acid, are characterized. Pathogenic effects of viroids in comparison with viruses and defective viruses are considered. Intimate viroid’s mechanisms on a host cell are described. So viroids do not code any proteins, their action on a plant should be consequence of direct interaction of viroid’s ribonucleic acid and host cell’s contents. However the molecular mechanism by which viroids causes plants’ diseases still remains not completely determined. It is considered, that the first targets of viroid are the nucleic acids and proteins of the host cell. Genomes of some viroids contain areas complementary to some cellular RNA. In connection with it supposed, that disease begins because of inhibition of functions of these cellular ribonucleic acids or their cutting directed viroids by a ribonucleic acid. Pathogenicity of viroids can be also a result of mimicry at a molecular level. Because of features of structure or sequence nucleotides the viroid’s ribonucleic acid can replace by itself some cellular ribonucleic acids. In viroid’s pathogenesis also can be involved and an interference of ribonucleic acids. All this allows to assume, that viroids can become the reason of infectious diseases of the human.