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

摘要

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 (). Ethylene biosynthesis is highly induced in both pathogen/microbe-associated molecular pattern ()-triggered immunity and effector-triggered immunity (), and the induction is potentiated by salicylic acid () pretreatment. In addition, actively suppresses -triggered ethylene induction in a type III secretion system-dependent manner. 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 pretreatment, is also involved. expressing the avrRpt2 effector gene (), which is capable of triggering , 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 biosynthesis and signaling. High-order ACS mutants with reduced ethylene induction are more susceptible to both and -avrRpt2, demonstrating a positive role of ethylene in plant bacterial resistance mediated by both -triggered immunity and .