Strategies for Engineering of Virus-Resistant Plants: Focus on RNases.

Currently, there are approximately 6500 species of viruses known in the world, among which more than 1500 are plant viruses. Most of them are capable of causing epiphytoties, which lead to decreased yields, reduced product quality, and sometimes put valuable commercial varieties or even entire plant species at risk of extinction. The global spread of viruses leads to the need to strengthen phytosanitary and quarantine restrictions, which requires additional financial costs. Understanding of viral biology and the principles of its propagation is a key factor in the formation of strategies and methods for combating these pathogens. Among the newest approaches are the genetic engineering technologies. Their use made it possible to create a number of plant varieties with increased resistance to viruses. However, the problem of creating virus-resistant plants still remains one of the most urgent since viruses acquire the ability to bypass defense mechanisms with time and there is a need to obtain new resistant varieties. There are several main approaches for obtaining of transgenic plants with increased resistance to viruses. They are based on RNA interference, resistance associated with viral capsid proteins, RNA-satellites, antisense RNAs, replicases, RNA-dependent RNA polymerase, the action of ribonucleases, ribosome-inactivating proteins, hammerhead ribozymes, miRNAs, plant antibodies, etc. One of the approaches to creating virus-resistant plants is the use of ribonuclease genes. The genes encoding ribonucleases have different origin and belong to a wide range of hosts: bacteria, fungi, plants, and animals. In particular, extracellular ribonucleases are able to cut nonspecifically molecules of viral RNA in apoplast that allows for creating plants with increased resistance to various plant viruses. This review is focused on the study of various genetic engineering approaches and the prospects of their use for the creation of virus-resistant plants. Emphasis is placed on the study of heterologous ribonuclease genes influence. [ABSTRACT FROM AUTHOR]