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

• Published in: Plant physiology (Bethesda) 2015-09, Vol.169 (1), p.299-312
• Main Authors: Guan, Rongxia, Su, Jianbin, Meng, Xiangzong, Li, Sen, Liu, Yidong, Xu, Juan, Zhang, Shuqun
• Format: Article
• Language: English
• Subjects: Arabidopsis - drug effects; Arabidopsis - genetics; Arabidopsis - immunology; Arabidopsis - microbiology; Arabidopsis Proteins - metabolism; Bacterial Proteins - metabolism; Disease Resistance - drug effects; Disease Resistance - immunology; Enzyme Activation - drug effects; Ethylenes - biosynthesis; Ethylenes - metabolism; Gene Expression Regulation, Plant - drug effects; Mitogen-Activated Protein Kinases - metabolism; Models, Biological; Pathogen-Associated Molecular Pattern Molecules - metabolism; Plant Diseases - immunology; Plant Diseases - microbiology; Plant Immunity - drug effects; Protein Isoforms - metabolism; Pseudomonas syringae - drug effects; Pseudomonas syringae - physiology; Salicylic Acid - pharmacology; Signal Transduction - drug effects
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.15.00659

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 PAMP-triggered 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.