Multilayered Regulation of Ethylene Induction Plays a Positive Role in Arabidopsis Resistance against Pseudomonas syringae

Abstract

Ethylene, a key phytohormone involved in plant-pathogen interaction, plays a positive role in plant resistance against fungal pathogens. However, its function in plant bacterial resistance remains unclear. Here, we report a detailed analysis of ethylene induction in Arabidopsis (Arabidopsis thaliana) in response to Pseudomonas syringae pv tomato DC3000 (Pst). Ethylene biosynthesis is highly induced in both pathogen/microbe-associated molecular pattern (PAMP)-triggered immunity and effector-triggered immunity (ETI), and the induction is potentiated by salicylic acid (SA) pretreatment. In addition, Pst actively suppresses PAMPtriggered ethylene induction in a type III secretion system-dependent manner. SA potentiation of ethylene induction is dependent mostly on MITOGEN-ACTIVATED PROTEIN KINASE6 (MPK6) and MPK3 and their downstream ACS2 and ACS6, two type I isoforms of 1-aminocyclopropane-1-carboxylic acid synthases (ACSs). ACS7, a type III ACS whose expression is enhanced by SA pretreatment, is also involved. Pst expressing the avrRpt2 effector gene (Pst-avrRpt2), which is capable of triggering ETI, induces a higher level of ethylene production, and the elevated portion is dependent on SALICYLIC ACID INDUCTION DEFICIENT2 and NONEXPRESSER OF PATHOGENESIS-RELATED GENE1, two key players in SA biosynthesis and signaling. High-order ACS mutants with reduced ethylene induction are more susceptible to both Pst and Pst-avrRpt2, demonstrating a positive role of ethylene in plant bacterial resistance mediated by both PAMP-triggered immunity and ETI.

Copper ions suppress abscisic acid biosynthesis to enhance defence against Phytophthora infestans in potato

“…It is induced by pathogen attack and environmental stimuli such as wounding, flooding, heavy metal stress, or ozone exposure (Moeder et al , ; Nie et al , ; Rao et al , ; Keunen et al , ). For example, ACS2 and ACS6 are required for ET induction by flg22 (Liu and Zhang, ; Guan et al , ) and the heavy metal chromium (Schellingen et al , ). In our previous study, Cu 2+ promoted the transcription of the AtACS8 gene to induce ET production (Zhang et al , ).…”

Pathogen-Responsive MPK3 and MPK6 Reprogram the Biosynthesis of Indole Glucosinolates and Their Derivatives in Arabidopsis Immunity

“…In search of the underlying mechanisms of MPK3/MPK6 in plant immunity, we found that MPK3/MPK6 regulate the biosynthesis of ethylene, an important plant stress hormone (Kim et al, 2003;Liu and Zhang, 2004;Joo et al, 2008;Han et al, 2010;Li et al, 2012;Guan et al, 2015), and camalexin, the major phytoalexin in Arabidopsis (Ren et al, 2008;Mao et al, 2011). Recently, a metabolomic analysis demonstrated that gain-of-function activation of MPK3/MPK6 reprograms defense metabolism, including camalexin and IGS (Lassowskat et al, 2014;Lee et al, 2015).…”

Tissue-specific synergistic bio-priming of pepper by two Streptomyces species against Phytophthora capsici

“…Altogether, ACC (the precursor of ET) and ET could act as the signaling molecules under stressful conditions and the high level of ERF gene expression could be efficient response led to decrease high levels of ACC and ET in leaf tissues. In the same way, Guan et al [53] revealed that Arabidopsis mutants in ACC Synthase (defect in ET production) showed greater susceptibility to P. syringae infection. The observations proposed that ERF gene in leaf tissue was more strongly up-regulated in IT20+SS14 than plants only inoculated with IT20.…”