RLP AgroScience GmbH, 67435 Neustadt an der Weinstrasse, Germany.
Centre for Organismal Studies Heidelberg, University of Heidelberg, 69117 Heidelberg, Germany.
Cells. 2021 May 13;10(5):1187. doi: 10.3390/cells10051187.
Viroids are plant pathogenic, circular, non-coding, single-stranded RNAs (ssRNAs). Members of the family replicate in the nucleus of plant cells through double-stranded RNA (dsRNA) intermediates, thus triggering the host's RNA interference (RNAi) machinery. In plants, the two RNAi pillars are Post-Transcriptional Gene Silencing (PTGS) and RNA-directed DNA Methylation (RdDM), and the latter has the potential to trigger Transcriptional Gene Silencing (TGS). Over the last three decades, the employment of viroid-based systems has immensely contributed to our understanding of both of these RNAi facets. In this review, we highlight the role of in the discovery of RdDM, expound the gradual elucidation through the years of the diverse array of RdDM's mechanistic details and propose a revised RdDM model based on the cumulative amount of evidence from viroid and non-viroid systems.
类病毒是植物病原、环状、非编码、单链 RNA（ssRNA）。该科的成员通过双链 RNA（dsRNA）中间体在植物细胞的细胞核中复制，从而触发宿主的 RNA 干扰（RNAi）机制。在植物中，RNAi 的两个主要支柱是转录后基因沉默（PTGS）和 RNA 指导的 DNA 甲基化（RdDM），后者有可能触发转录基因沉默（TGS）。在过去的三十年中，基于类病毒的系统的应用极大地促进了我们对这两种 RNAi 方面的理解。在这篇综述中，我们强调了 在 RdDM 发现中的作用，阐述了多年来通过各种 RdDM 机制细节的逐步阐明，并基于来自类病毒和非类病毒系统的累积证据提出了一个修正后的 RdDM 模型。
