PUB4, a CERK1-Interacting Ubiquitin Ligase, Positively Regulates MAMP-Triggered Immunity in Arabidopsis

Abstract

Lysin motif (LysM) receptor-like kinase CERK1 is a co-receptor essential for plant immune responses against carbohydrate microbe-associated molecular patterns (MAMPs). Concerning the immediate downstream signaling components of CERK1, receptor-like cytoplasmic kinases such as PBL27 and other RLCK VII members have been reported to regulate immune responses positively. In this study, we report that a novel CERK1-interacting E3 ubiquitin ligase, PUB4, is also involved in the regulation of MAMP-triggered immune responses. Knockout of PUB4 resulted in the alteration of chitin-induced defense responses, indicating that PUB4 positively regulates reactive oxygen species generation and callose deposition but negatively regulates MAPK activation and defense gene expression. On the other hand, detailed analyses of a double knockout mutant of pub4 and sid2, a mutant of salicylic acid (SA) synthesis pathway, showed that the contradictory phenotype of the pub4 mutant was actually caused by abnormal accumulation of SA in this mutant and that PUB4 is a positive regulator of immune responses. The present and recent findings on the role of PUB4 indicate that PUB4 is a unique E3 ubiquitin ligase involved in the regulation of both plant immunity and growth/development.

Ubiquitin signalling: controlling the message of surface immune receptors

“…UBC35 and its close homologue UBC36 are the main sources of the Lys63 chain in Arabidopsis (Romero-Barrios et al, 2020), which play a key role in vesicle trafficking (Leitner et al, 2012;Martins et al, 2015;Moulinier-Anzola et al, 2020). Pairing of PUB22, its closely related homologue PUB24, and PUB4 with UBC35, supports a role in regulating vesicular traffic (Turek et al, 2018;Desaki et al, 2019;Derkacheva et al, 2020). PUB13, however, which mediates endocytosis of BRI1 (Zhou et al, 2018) and most likely that of FLS2 (Lu et al, 2011), interacted with a different subset of E2s.…”

“…1b,c). Similarly, the E3 PUB4 associates and supports responses to chitin by the receptor CERK1 (Desaki et al, 2019). More recently, PUB4 was proposed to play a dual role in BIK1 stability by promoting the degradation of nonactivated BIK1, while preserving activated BIK1 from degradation (Derkacheva et al, 2020) (Fig.…”

Lysin Motif (LysM) Proteins: Interlinking Manipulation of Plant Immunity and Fungi

“…RLCK VII-4 was specifically shown to be important for chitin signaling through its role in activation of the MAPK cascade upon perception of chitin thus connecting a PRR to MAPK signaling [31]. Taken together, these results indicate that the CERK1-RLCK signaling module plays a conserved role in the production of ROS in Arabidopsis and rice during a chitin-triggered immune response [21][22][23][24][25][26][27][28][29][30][31]. Rice chitin receptor OsCERK1 matures in the endoplasmic reticulum from where it is transported to the ectoplasmic reticulum through the Golgi apparatus.…”

“…Plant U-box protein 4 (PUB4) is a ubiquitin ligase that interacts with CERK1. It is a positive regulator of chitin signaling through its role in ROS production and callose deposition upon perception of chitin oligosaccharide [30]. Arabidopsis receptor-like cytoplasmic kinase VII members including RLCK VII-4, RLCK VII-5, RLCK VII-7, and RLCK VII-8 function downstream of the PRRs involved in flagellin and chitin signaling, contributing to the callose deposition and ROS generation.…”

Understanding and Exploiting Post-Translational Modifications for Plant Disease Resistance

“…Ub E3 ligase PUB25/26 targets nonactivated immune kinase BIK1 for degradation to modulate BIK1 levels (Figure 1) [89]. PUB4 interacts with CERK1 and is a positive regulator of chitin-induced immune responses [90].…”