A single point mutation in Tomato spotted wilt virus NSs protein is sufficient to overcome Tsw-gene-mediated resistance in pepper

Abstract

The nonstructural protein (NSs) of Tomato spotted wilt virus (TSWV) was previously identified as an avirulence determinant for Tsw-based resistance on pepper. The NSs of wild-type (WT) and resistance-breaking (RB) TSWV strains isolated in Hungary had only two amino acid substitutions (104, 461). We have analysed the ability of the NSs and their point mutant variants to trigger Tsw-mediated hypersensitive responses and RNA silencing suppressor (RSS) activity in patch assays. We identified a single amino acid change at position 104 (T-A) that was responsible for the necrosis induction or loss, while a significant difference was not detected in the RSS activity of the two parental strains. We have successfully complemented the infection of the WT strain on resistant pepper cultivar with the infectious S RNA transcript of the RB strain and the WT-T104A point mutant. Our work provides direct evidence that a single amino acid change can induce an RB phenotype.

Identification and characterization of a new class of Tomato spotted wilt virus isolates that break Tsw‐based resistance in a temperature‐dependent manner

“…Examples of virus resistance have been reported in which only one or two mutations within the Avr sequence have broken resistance (Bendahmane et al, 1995;Moffett, 2009 shown that the Tsw resistance gene positively selected for certain amino acids in the TSWV NSs sequence (Tentchev et al, 2011), specifically isoleucine (I) at position 79. Tentchev et al (2011) also proposed that the appearance of a resistance-breaking phenotype is probably the result of multiple independent evolutionary events, which is supported by the work of Almasi et al (2015Almasi et al ( , 2017. This is further supported by the present study, in which I79 was not the only amino acid that defined resistance-breaking phenotypes.…”

“…() also proposed that the appearance of a resistance‐breaking phenotype is probably the result of multiple independent evolutionary events, which is supported by the work of Almasi et al . (, ). This is further supported by the present study, in which I79 was not the only amino acid that defined resistance‐breaking phenotypes.…”

Impact of Host Resistance to Tomato Spotted Wilt Orthotospovirus in Peanut Cultivars on Virus Population Genetics and Thrips Fitness

“…An earlier study found no direct evidence to support the hypothesis that field resistance in peanut exerts selection pressure on TSWV, but that study was based on the evaluation of the TSWV N gene alone [40]. It is possible that alterations in other genes could also influence the virulence of isolates/strains [25,26,28]. The main objective of this study was to investigate if TSWV resistance in peanut exerts any selection pressure on any and/or all five genes of TSWV, namely N, NSs, Gn/Gc, NSm, and RdRp.…”

“…NSs was identified as RNA silencing suppressor during plant infection [38], and the N protein encapsidates the RNA segments to form ribonucleoprotein [39]. Heterogeneity in nucleotide sequences of NSs and NSm between wild type and RB strains of TSWV leading to positive selection was associated with resistance breakdown in pepper and tomato [25,26,28]. Sundaraj et al (2014) [40] did not find evidence of positive selection pressure on the N gene of TSWV isolates collected from TSWV-resistant peanut cultivars.…”

“…TSWV strains have overcome resistance conferred by single genes such as Tsw in pepper and Sw-5 in tomato in several places worldwide [14,[21][22][23][24]. Resistance-breaking (RB) TSWV strains originated from mutations leading to positive selection and/or reassortment [25][26][27][28]. While TSWV RB strains have not been reported in peanut, the potential threat of emergence of RB strains remains a concern.…”