Dual-level regulation of ACC synthase activity by MPK3/MPK6 cascade and its downstream WRKY transcription factor during ethylene induction in Arabidopsis

• Published in: PLoS genetics Vol. 8; no. 6; p. e1002767
• Main Authors: Li, Guojing, Meng, Xiangzong, Wang, Ruigang, Mao, Guohong, Han, Ling, Liu, Yidong, Zhang, Shuqun
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01-06-2012; Public Library of Science (PLoS)
• Subjects: Arabidopsis; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis - physiology; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Biology; Biosynthesis; Botrytis - immunology; Botrytis - pathogenicity; Ethylenes - biosynthesis; Ethylenes - metabolism; Fruits; Gene expression; Gene Expression Regulation, Plant; Genetic aspects; Health aspects; Host-Pathogen Interactions - genetics; Host-Pathogen Interactions - immunology; Kinases; Lyases - genetics; Lyases - metabolism; Mitogen-Activated Protein Kinase Kinases - genetics; Mitogen-Activated Protein Kinase Kinases - metabolism; Mitogen-Activated Protein Kinases - genetics; Mitogen-Activated Protein Kinases - metabolism; Mutation; Phosphorylation; Physiological aspects; Plant defenses; Plant genetics; Plant Immunity - genetics; Plants, Genetically Modified; Protein Isoforms; Proteins; Regulation; Signal Transduction; Standard deviation; Transcription factors; Transcription Factors - genetics; Transcription Factors - metabolism; United States
• ISSN: 1553-7404; 1553-7390; 1553-7404
• DOI: 10.1371/journal.pgen.1002767

Plants under pathogen attack produce high levels of ethylene, which plays important roles in plant immunity. Previously, we reported the involvement of ACS2 and ACS6, two Type I ACS isoforms, in Botrytis cinerea-induced ethylene biosynthesis and their regulation at the protein stability level by MPK3 and MPK6, two Arabidopsis pathogen-responsive mitogen-activated protein kinases (MAPKs). The residual ethylene induction in the acs2/acs6 double mutant suggests the involvement of additional ACS isoforms. It is also known that a subset of ACS genes, including ACS6, is transcriptionally induced in plants under stress or pathogen attack. However, the importance of ACS gene activation and the regulatory mechanism(s) are not clear. In this report, we demonstrate using genetic analysis that ACS7 and ACS11, two Type III ACS isoforms, and ACS8, a Type II ACS isoform, also contribute to the B. cinerea-induced ethylene production. In addition to post-translational regulation, transcriptional activation of the ACS genes also plays a critical role in sustaining high levels of ethylene induction. Interestingly, MPK3 and MPK6 not only control the stability of ACS2 and ACS6 proteins via direct protein phosphorylation but also regulate the expression of ACS2 and ACS6 genes. WRKY33, another MPK3/MPK6 substrate, is involved in the MPK3/MPK6-induced ACS2/ACS6 gene expression based on genetic analyses. Furthermore, chromatin-immunoprecipitation assay reveals the direct binding of WRKY33 to the W-boxes in the promoters of ACS2 and ACS6 genes in vivo, suggesting that WRKY33 is directly involved in the activation of ACS2 and ACS6 expression downstream of MPK3/MPK6 cascade in response to pathogen invasion. Regulation of ACS activity by MPK3/MPK6 at both transcriptional and protein stability levels plays a key role in determining the kinetics and magnitude of ethylene induction.