A core function of EDS1 with PAD4 is to protect the salicylic acid defense sector in Arabidopsis immunity

Abstract

Plant defenses induced by salicylic acid (SA) are vital for resistance against biotrophic pathogens. In basal and receptor-triggered immunity, SA accumulation is promoted by Enhanced Disease Susceptibility1 with its co-regulator Phytoalexin Deficient4 (EDS1/PAD4). Current models position EDS1/PAD4 upstream of SA but their functional relationship remains unclear. In a genetic and transcriptomic analysis of Arabidopsis autoimmunity caused by constitutive or conditional EDS1/PAD4 overexpression, intrinsic EDS1/PAD4 signaling properties and their relation to SA were uncovered. A core EDS1/PAD4 pathway works in parallel with SA in basal and effector-triggered bacterial immunity. It protects against disabled SA-regulated gene expression and pathogen resistance, and is distinct from a known SA-compensatory route involving MAPK signaling. Results help to explain previously identified EDS1/PAD4 regulated SA-dependent and SA-independent gene expression sectors. Plants have evolved an alternative route for preserving SA-regulated defenses against pathogen or genetic perturbations. In a proposed signaling framework, EDS1 with PAD4, besides promoting SA biosynthesis, maintains important SA-related resistance programs, thereby increasing robustness of the innate immune system.

Convergent loss of an EDS1/PAD4 signalling pathway in several plant lineages predicts new components of plant immunity and drought response

“…This property highlights a possible intersection between the drought responsive ASTRAL genes and immunity. Both NDR1 and CCRPW8 mediated signalling converge in triggering increase in SA, which appears to be maintained in the aquatic species in our study (83).…”

A dominant‐interfering camta3 mutation compromises primary transcriptional outputs mediated by both cell surface and intracellular immune receptors in Arabidopsis thaliana

“…Previous studies have shown a differential requirement for defence phytohormones in CNL-mediated ETI in Arabidopsis (Tsuda et al, 2009;Maekawa et al, 2012;Cui et al, 2017). In quadruple mutant plants that simultaneously lack ET, jasmonic acid (JA) and SA signalling, designated deps (dde2 ein2 pad4 sid2), RPS2-mediated pathogen growth restriction was impaired by 80%, whereas RPM1-or MLA1-mediated immunity was largely retained (Tsuda et al, 2009;Maekawa et al, 2012).…”

The Arabidopsis thaliana N‐recognin E3 ligase PROTEOLYSIS1 influences the immune response

“…The fact that EDS1 solely controls the accumulation of a pool of proteins with antagonistic roles illustrates the need for a homeostatic mechanism to control the extent of SAR. Although signaling from the EDS1/PAD4 hub can work independently of SA, (Cui et al, ), its role in promoting SA‐mediated basal resistance has been extensively reported (Rietz et al, ). In line with the observed upregulation of SA‐associated proteins, prt1‐1 leaves infected with Pst DC3000 showed slightly increased levels of SA compared to WT (Figure a).…”