Host‐induced gene silencing compromises Verticillium wilt in tomato and Arabidopsis

Abstract

SUMMARYVerticillium wilt, caused by soil-borne fungi of the genus Verticillium, is an economically important disease that affects a wide range of host plants. Unfortunately, host resistance against Verticillium wilts is not available for many plant species, and the disease is notoriously difficult to combat. Host-induced gene silencing (HIGS) is an RNA interference (RNAi)-based process in which small RNAs are produced by the host plant to target parasite transcripts. HIGS has emerged as a promising strategy for the improvement of plant resistance against pathogens by silencing genes that are essential for these pathogens. Here, we assessed whether HIGS can be utilized to suppress Verticillium wilt disease by silencing three previously identified virulence genes of V. dahliae (encoding Ave1, Sge1 and NLP1) through the host plants tomato and Arabidopsis. In transient assays, tomato plants were agroinfiltrated with Tobacco rattle virus (TRV) constructs to target V. dahliae transcripts. Subsequent V. dahliae inoculation revealed the suppression of Verticillium wilt disease on treatment with only one of the three TRV constructs. Next, expression of RNAi constructs targeting transcripts of the same three V. dahliae virulence genes was pursued in stable transgenic Arabidopsis thaliana plants. In this host, V. dahliae inoculation revealed reduced Verticillium wilt disease in two of the three targets. Thus, our study suggests that, depending on the target gene chosen, HIGS against V. dahliae is operational in tomato and A. thaliana plants and may be exploited to engineer resistance in Verticillium wilt-susceptible crops.

Recognition of Verticillium effector Ave1 by tomato immune receptor Ve1 mediates Verticillium resistance in diverse plant species

“…At ten days after TRV treatment, plants were challenged with either the V. dahliae race 1 strain JR2 , or an Ave1 deletion mutant (V. dahliae JR2△Ave1;, and inspected for Verticillium wilt symptoms (stunting and wilting) up to 14 days post inoculation (dpi). As expected, no significant disease symptoms were observed on TRV::GUStreated plants that were inoculated with the wild-type race 1 V. dahliae strain (Song et al, 2016 It was recently demonstrated that Tobacco mosaic virus (TMV) may infect fungi in addition to plants, remaining for up to six subcultures, and also persisted in plants infected by the virus-infected fungus (Mascia et al, 2014 Figure S1A). Furthermore, the fungal isolates were used to infect Ve1 tomato plants and tomato plants that lack…”

“…Constructs for the constitutive expression of VdAve1, SlPNP, VvPNP, FoAve1, CbAve1, ChAve1 and XacPNP have been described previously Song et al, 2016). VnAve1 was amplified from V.…”

“…Verticillium disease assay on A. thaliana, as well as fungal biomass quantification in 6 infected A. thaliana plants were performed as previously described Song et al, 2016). The fungus-specific primer ITS1-F, based on the internal transcribed spacer (ITS) region of the ribosomal DNA, in combination with the V. dahliae-specific reverse primer ST-Ve1-R ) were used to measure fungal colonization.…”

“…The fungus-specific primer ITS1-F, based on the internal transcribed spacer (ITS) region of the ribosomal DNA, in combination with the V. dahliae-specific reverse primer ST-Ve1-R ) were used to measure fungal colonization. Primers for tomato actin and A. thaliana RuBisCo (Table S1) were used as endogenous plant control as described earlier Song et al, 2016).…”

“…More recently, homologs of tomato Ve1 acting as immune receptors that govern 6 resistance against V. dahliae race 1 strains through recognition of the Ave1 effector have been characterized in other plant species including tobacco, potato, wild eggplant and hop, suggesting an ancient origin of the immune receptor Ve1 (Song et al, 2016).…”