No abstract

The nucleotide-binding leucine-rich repeat (NLR) class of immune receptor, Sw-5b confers resistance to Tomato spotted wilt orthotospovirus (TSWV). Although Sw-5b is known to activate immunity upon recognition of the TSWV movement protein NSm, we know very little about the downstream events that lead to resistance. Here, we investigated the Sw-5b-mediated early transcriptomic changes that occur in response to mechanical and thrips-mediated inoculation of TSWV using near-isogenic tomato lines, CNPH-LAM 147 (Sw5b+/+) and Santa Clara (Sw-5b-/-). We observed earlier Sw-5b-mediated transcriptional changes in response to thrips-mediated inoculation compared to mechanical inoculation of TSWV. With thrips-mediated inoculation, differentially expressed genes (DEGs) were observed at 12, 24 and 72 hours post-inoculation (hpi). Whereas, with mechanical inoculation, DEGs were observed only at 72 hpi. Although some DEGs were shared between the two methods of inoculation, many DEGs were specific to either thrips-mediated or mechanical inoculation of TSWV. In response to thrips-mediated inoculation, an NLR immune receptor, cysteine-rich receptor-like kinase, G-type lectin S-receptor-like kinases, the ethylene response factor 1 and the calmodulin-binding protein 60 were induced. Fatty acid desaturase 2-9, cell death genes, DCL2b, RIPK/PBL14-like, ERF017 and WRKY75 were differentially expressed in response to mechanical inoculation. Our findings reveal Sw-5b responses specific to the method of TSWV inoculation. Although TSWV is transmitted in nature primarily by the thrips, Sw-5b responses to thrips inoculation have not been previously studied. Therefore, the DEGs we have identified in response to thrips-mediated inoculation provide a new foundation for understanding the mechanistic roles of these genes in the Sw-5b-mediated resistance.

The nucleotide-binding leucine-rich repeat (NLR) class of immune receptor, Sw-5b confers resistance to Tomato spotted wilt orthotospovirus (TSWV). Although Sw-5b is known to activate immunity upon recognition of the NSm of TSWV, we know very little about the downstream events that lead to resistance. Here, we investigated the early transcriptomic changes that occur in response to both mechanical and thrips-mediated inoculation of TSWV using near-isogenic resistant and susceptible tomato lines. Interestingly, Sw-5b induces earlier transcriptional changes in response to thrips-mediated inoculation compared to mechanical inoculation of TSWV. A subset of the differentially expressed genes (DEGs) observed at 12 and 24 hours post thrips-mediated inoculation of TSWV was only present at 72 hours post mechanical inoculation. Although some DEGs were shared between thrips and mechanical inoculation at 72 hours post-infection, many DEGs were specific to either thrips-mediated or mechanical inoculation of TSWV. In response to thrips-mediated inoculation, an NLR immune receptor, cysteine-rich receptor-like kinase, G-type lectin S-receptor-like kinases, and transcription factors such as the ethylene response factor 1 and the calmodulin-binding protein 60 were induced. Whereas, in response to mechanical inoculation, fatty acid desaturase 2-9, cell death genes, DCL2b, RIPK/PBL14-like, and transcription factors such as ERF017 and WRKY75 were differentially expressed. Our findings reveal novel insights into Sw-5b responses specific to the method of TSWV inoculation. Given that TSWV is transmitted in nature primarily by the thrips, the DEGs we have identified provide a foundation for understanding the mechanistic roles of these genes in the Sw-5b-mediated resistance.