Arabidopsis Protein Phosphatase 2C ABI1 Interacts with Type I ACC Synthases and Is Involved in the Regulation of Ozone-Induced Ethylene Biosynthesis

Abstract

Ethylene plays a crucial role in various biological processes and therefore its biosynthesis is strictly regulated by multiple mechanisms. Posttranslational regulation, which is pivotal in controlling ethylene biosynthesis, impacts 1-aminocyclopropane 1-carboxylate synthase (ACS) protein stability via the complex interplay of specific factors. Here, we show that the Arabidopsis thaliana protein phosphatase type 2C, ABI1, a negative regulator of abscisic acid signaling, is involved in the regulation of ethylene biosynthesis under oxidative stress conditions. We found that ABI1 interacts with ACS6 and dephosphorylates its C-terminal fragment, a target of the stress-responsive mitogen-activated protein kinase, MPK6. In addition, ABI1 controls MPK6 activity directly and by this means also affects the ACS6 phosphorylation level. Consistently with this, ozone-induced ethylene production was significantly higher in an ABI1 knockout strain (abi1td) than in wild-type plants. Importantly, an increase in stress-induced ethylene production in the abi1td mutant was compensated by a higher ascorbate redox state and elevated antioxidant activities. Overall, the results of this study provide evidence that ABI1 restricts ethylene synthesis by affecting the activity of ACS6. The ABI1 contribution to stress phenotype underpins its role in the interplay between the abscisic acid (ABA) and ethylene signaling pathways.

Accumulation and Transport of 1-Aminocyclopropane-1-Carboxylic Acid (ACC) in Plants: Current Status, Considerations for Future Research and Agronomic Applications

“…Types I and II ACS proteins are phosphorylated by CDPKs, as in both groups CDPK phosphorylation motifs were identified in their C-termini (Tatsuki and Mori, 2001; Sebastia et al, 2004). Type I ACS proteins are dephosphorylated by protein phosphatase 2A (PP2A) and Protein phosphatase 2C (PP2C), decreasing their protein stability (Skottke et al, 2011; Ludwikow et al, 2014). Additionally, the activity of the type I ACSs can be increased by phosphorylation by the MAP kinases MPK3 and MPK6, which have been shown to be pathogen/stress-activated (Liu and Zhang, 2004; Joo et al, 2008; Han et al, 2010).…”

1-aminocyclopropane-1-carboxylic acid (ACC) in plants: more than just the precursor of ethylene!

“…Both in Arabidopsis (Chae et al, 2003; Kim et al, 2003; Liu and Zhang, 2004; Wang et al, 2004; Yoshida et al, 2005, 2006; Joo et al, 2008; Christians et al, 2009; Lyzenga et al, 2012) and in tomato (Tatsuki and Mori, 2001; Kamiyoshihara et al, 2010) it was shown that differential phosphorylation of certain ACS members directed the protein for proteasomal degradation. Protein stability of certain ACS members is further regulated by the protein phosphatase 2A (PP2A; Skottke et al, 2011) and PP2C (Ludwikow et al, 2014), demonstrating a complex balance between phosphorylation and dephosphorylation to secure protein activity and stability.…”

Effects of volatile organic compound ether on cell responses and gene expressions in Arabidopsis

“…These genes include MAP kinase phosphatase 1 (MKP1), protein phosphatase (PP) 2A1 (PP2A1), PP2A2, PP2A3&4, and PP2C-type phosphatase AP2C1 (AP2C1). These phosphatases are involved in modulating phytohormone biosynthesis in response to ozone or developmental cues (Ludwików et al 2014; Schweighofer et al 2007; Skottke et al 2011). The results in Fig.…”

“…Skottke et al (2011) showed that PP2A mediates a finely tuned regulation of overall ethylene production by differentially affecting the stability of specific classes of ACS enzymes. Ludwików et al (2014) showed that the Arabidopsis protein phosphatase type 2C is involved in the regulation of ethylene biosynthesis during ozone stress. In this study, the temporal expression patterns of MAP kinase and protein phosphatase genes were in good accordance with those of the hormone biosynthetic genes.…”