EDS1 in tomato is required for resistance mediated by TIR‐class R genes and the receptor‐like R gene Ve

Abstract

Summary In tobacco and other Solanaceae species, the tobacco N gene confers resistance to tobacco mosaic virus (TMV), and leads to induction of standard defense and resistance responses. Here, we report the use of N‐transgenic tomato to identify a fast‐neutron mutant, sun1‐1 (suppressor of N), that is defective in N‐mediated resistance. Induction of salicylic acid (SA) and expression of pathogenesis‐related (PR) genes, each signatures of systemic acquired resistance, are both dramatically suppressed in sun1‐1 plants after TMV treatment compared to wild‐type plants. Application of exogenous SA restores PR gene expression, indicating that SUN1 acts upstream of SA. Upon challenge with additional pathogens, we found that the sun1‐1 mutation impairs resistance mediated by certain resistance (R) genes, (Bs4, I, and Ve), but not others (Mi‐1). In addition, sun1‐1 plants exhibit enhanced susceptibility to TMV, as well as to virulent pathogens. sun1‐1 has been identified as an EDS1 homolog present on chromosome 6 of tomato. The discovery of enhanced susceptibility in the sun1‐1 (Le_eds1‐1) mutant plant, which contrasts to reports in Nicotiana benthamiana using virus‐induced gene silencing, provides evidence that the intersection of R gene‐mediated pathways with general resistance pathways is conserved in a Solanaceous species. In tomato, EDS1 is important for mediating resistance to a broad range of pathogens (viral, bacterial, and fungal pathogens), yet shows specificity in the class of R genes that it affects (TIR‐NBS‐LRR as opposed to CC‐NBS‐LRR). In addition, a requirement for EDS1 for Ve‐mediated resistance in tomato exposes that the receptor‐like R gene class may also require EDS1.

Genetic Dissection ofVerticilliumWilt Resistance Mediated by Tomato Ve1

“…4A; Table II), indicated by stunting (reduced plant height, leaf length, and stem diameter), confirming the previously described involvement of Eds1 in Ve-mediated signaling (Hu et al, 2005). Clear and consistent loss of Verticillium resistance in Motelle plants also was observed upon treatments with recombinant viruses targeting Mek2, Nrc1, Acif1, and Ndr1 ( Fig.…”

“…The only gene implicated in downstream signaling is the tomato homolog of Arabidopsis Eds1 (for Enhanced Disease Susceptibility1; Aarts et al, 1998;Hu et al, 2005). To further identify genes required for Ve-mediated resistance, a set of candidate genes was selected, some of which have previously been implicated in RLP signaling mediated by the tomato Cf genes against C. fulvum.…”

Diversity, Pathogenicity, and Management of Verticillium Species

“…By analogy, the Ve proteins may bind a Verticillium spp.-associated effector, and subsequently transmit a signal via endocytosis. Downstream signaling of both Ve1 and Ve2-mediated resistance in tomato is apparently mediated in part by SUN1, a homolog of the Arabidopsis gene for enhanced disease susceptibility (EDS1), although the functions of EDS and SUN1 are not characterized (67).…”

R proteins as fundamentals of plant innate immunity

“…2) [87]. EDS1 (Enhanced Disease Susceptibility 1) protein shows homology to eukaryotic lipases and is a mediator in the signaling pathway initiated by most proteins of the TIR-NBS-LRR family, playing a key role in the regulation of the plant response to abiotic and biotic stress [88][89][90]. Furthermore, EDS1 and PAD4 can regulate the level of salicylate accumulation, and their activity is regulated through FMO1 monooxygenase and NUD7 hydrolase [91].…”