The RING E3 Ligase KEEP ON GOING Modulates JASMONATE ZIM-DOMAIN12 Stability

Abstract

Jasmonate (JA) signaling in plants is mediated by the JASMONATE ZIM-DOMAIN (JAZ) proteins that repress the activity of several transcription factors regulating JA-inducible gene expression. The hormone JA-isoleucine triggers the interaction of JAZ repressor proteins with the F-box protein CORONATINE INSENSITIVE1 (COI1), part of an S-phase kinase-associated protein1/Cullin1/F-box protein COI1 (SCF COI1 ) E3 ubiquitin ligase complex, and their degradation by the 26S proteasome. In Arabidopsis (Arabidopsis thaliana), the JAZ family consists of 13 members. The level of redundancy or specificity among these members is currently not well understood. Here, we characterized JAZ12, encoded by a highly expressed JAZ gene. JAZ12 interacted with the transcription factors MYC2, MYC3, and MYC4 in vivo and repressed MYC2 activity. Using tandem affinity purification, we found JAZ12 to interact with SCF COI1 components, matching with observed in vivo ubiquitination and with rapid degradation after treatment with JA. In contrast to the other JAZ proteins, JAZ12 also interacted directly with the E3 RING ligase KEEP ON GOING (KEG), a known repressor of the ABSCISIC ACID INSENSITIVE5 transcription factor in abscisic acid signaling. To study the functional role of this interaction, we circumvented the lethality of keg loss-of-function mutants by silencing KEG using an artificial microRNA approach. Abscisic acid treatment promoted JAZ12 degradation, and KEG knockdown led to a decrease in JAZ12 protein levels. Correspondingly, KEG overexpression was capable of partially inhibiting COI1-mediated JAZ12 degradation. Our results provide additional evidence for KEG as an important factor in plant hormone signaling and a positive regulator of JAZ12 stability.

Stomatal Defense a Decade Later

“…ABA concentration in the plant is known to be highly dependent on the air relative humidity (Okamoto et al, 2009). It is also possible that the recently proposed link between ABA and JA responses by the modulation of MYC2 transcriptional activity via PLY6 ABA receptor (Aleman et al, 2016) and the JASMONATE ZIM-DOMAIN12 (JAZ12) degradation via three RING ligase KEEP ON GOING in an ABA-dependent manner (Pauwels et al, 2015) may contribute to this issue. Nonetheless, conclusions drawn solely from pharmacological evidence can be confounded by the fact that the chemical applied (e.g.…”

The Kinase Activity of Calcineurin B-like Interacting Protein Kinase 26 (CIPK26) Influences Its Own Stability and that of the ABA-regulated Ubiquitin Ligase, Keep on Going (KEG)

“…KEG is a large protein consisting of two catalytic domains, RING and kinase domains, and two series of repeats, ankyrin and HERC2-like, used for protein-protein interaction. KEG’s role during plant development appears to be multifaceted as evidence suggests that KEG is a regulator of both abscisic acid (ABA) and jasmonate (JA) signaling (Stone et al, 2006; Liu and Stone, 2010, 2013; Chen et al, 2013; Lyzenga et al, 2013; Pauwels et al, 2015), in addition to regulation of post-golgi trafficking (Gu and Innes, 2012). …”

“…However, lack of a complete rescue suggests that KEG has other targets. A member of the CBL-Interacting Protein kinase (CIPK) family, CIPK26, was also identified as a KEG-interacting protein (Lyzenga et al, 2013; Pauwels et al, 2015). CIPK26 is an ubiquitination substrate and KEG targets both the kinase CIPK26 and downstream transcription factors (e.g., ABI5) for degradation by the 26S proteasome (Lyzenga et al, 2013).…”

Transcriptome Analysis of the Signalling Networks in Coronatine-Induced Secondary Laticifer Differentiation from Vascular Cambia in Rubber Trees

“…Available data indicated that AtJAZ1, AtJAZ3 and AtJAZ9 interacted with COI1414246 and AtJAZ1-6 and AtJAZ8-13 interacted with MYC2454647. These JAZ members mediated JA response204348. Although several JAZ homologues were isolated from the latex of rubber trees495051, little is known about their roles in secondary laticifer differentiation.…”