Elucidation of the <i>ty-5</i> resistance network in tomato against tomato yellow leaf curl virus reveals the involvement of AP2/ERF gene

<h4>Introduction</h4>Tomato yellow leaf curl virus (TYLCV, <i>Begomovirus coheni</i>), a whitefly-transmitted begomovirus, causes serious economic losses to tomato crops globally. Over the past three decades, several genetic sources of TYLCV resistance have been identified and incorporated into tomato breeding. Among these is a recessive source of resistance known as <i>ty-5</i>.<h4>Methods</h4>In this study, we conducted a global transcriptome analysis to compare gene expression in a <i>ty-5</i> near isogenic tomato line and its susceptible recurrent parent at various stages of TYLCV infection.<h4>Results</h4>We identified 1,394 differentially expressed genes, including numerous defense-related genes and genes involved in RNA-mediated DNA methylation. In addition, the expression of key regulatory genes such as protein kinases (PKs) and transcription factors (TFs) was also significantly altered. To explore the function of one upregulated TF encoding an APETALA2/Ethylene Responsive Factor (AP2/ERF), tomato plants overexpressing this gene were generated and demonstrated to confer resistance to TYLCV.<h4>Discussion</h4>These results lead us to hypothesize that <i>ty-5</i>-mediated TYLCV resistance not only involves a <i>pelota</i> gene but is a product of two major pathways acting in concert: a typical host-disease resistance pathway and RNA-directed DNA methylation. Understanding the mechanism underlying <i>ty-5</i> resistance will facilitate the development of tomato germplasm with more durable TYLCV resistance.