Characterization of the Roles of SGT1/RAR1, EDS1/NDR1, NPR1, and NRC/ADR1/NRG1 in <i>Sw-5b</i>-Mediated Resistance to Tomato Spotted Wilt Virus

• Main Authors: Zhengqiang Chen, Qian Wu, Cong Tong, Hongyu Chen, Dan Miao, Xin Qian, Xiaohui Zhao, Lei Jiang, Xiaorong Tao
• Format: Article
• Language: English
• Published: MDPI AG 2021-07-01
• Series: Viruses
• Subjects: tomato spotted wilt virus; <i>Sw-5b</i>; NLR receptor; plant innate immunity; defense signaling
• Online Access: https://www.mdpi.com/1999-4915/13/8/1447

The tomato <i>Sw-5b</i> gene confers resistance to tomato spotted wilt virus (TSWV) and encodes a nucleotide-binding leucine-rich repeat (NLR) protein with an N-terminal Solanaceae-specific domain (SD). Although our understanding of how <i>Sw-5b</i> recognizes the viral NSm elicitor has increased significantly, the process by which <i>Sw-5b</i> activates downstream defense signaling remains to be elucidated. In this study, we used a tobacco rattle virus (TRV)-based virus-induced gene silencing (VIGS) system to investigate the roles of the SGT1/RAR1, EDS1/NDR1, NPR1, and NRC/ADR1/NRG1 genes in the <i>Sw-5b</i>-mediated signaling pathway. We found that chaperone SGT1 was required for <i>Sw-5b</i> function, but co-chaperone RAR1 was not. <i>Sw-5b</i>-mediated immune signaling was independent of both EDS1 and NDR1. Silencing <i>NPR1</i>, which is a central component in SA signaling, did not result in TSWV systemic infection in <i>Sw-5b</i>-transgenic <i>N. benthamiana</i> plants. Helper NLR NRCs (NLRs required for cell death) were required for <i>Sw-5b</i>-mediated systemic resistance to TSWV infection. Suppression of NRC2/3/4 compromised the <i>Sw-5b</i> resistance. However, the helper NLRs ADR1 and NRG1 may not participate in the <i>Sw-5b</i> signaling pathway. Silencing ADR1, NRG1, or both genes did not affect <i>Sw-5b</i>-mediated resistance to TSWV. Our findings provide new insight into the requirement for conserved key components in <i>Sw-5b</i>-mediated signaling pathways.