PHOSPH-UBIQ-IMMUN · Dynamic interplay between phosphorylation and ubiquitination during plant receptor kinase-mediated immunity

Dynamic interplay between phosphorylation and ubiquitination during plant receptor kinase-mediated immunity

The growing population and changing climate challenge the quest for food security. Plant pathogens lead to annual global food production yield losses up to 16-20%. Our travel systems enable pathogens to rapidly spread globally, allowing new diseases to emerge, as shown by the 2016 wheat blast epidemy in Bangladesh, a global food security threat. Thus, plant biologists urgently need to find solutions for existing and emerging diseases. To help plants better protect themselves, we need to know the nature of plant-pathogen interactions and underlying mechanisms of plant immunity by studying how plants respond to pathogen attack, from the moment of recognition of pathogen-associated molecular patterns (PAMPs) to well-orchestrated defense responses. Many PAMPs and their corresponding pattern recognition receptors (PRRs) have been identified, and common principles in activation of PTI have arisen. PAMP-driven interaction of receptor and co-receptor leads to transphosphorylation events resulting in complex activation and phosphorylation of downstream cytoplasmic kinases. The last ones emerged as integrative points of signal transduction, with BIK1 being a key convergent point in signaling triggered by different PAMPs. BIK1 is genetically involved in most PTI outputs, however, many of its downstream targets are still unknown. Prof. Zipfel’s lab recently identified a potential BIK1 phosphorylation motif. A search for this motif in proteins known from the literature to be phosphorylated in response to PAMP treatment, led to the identification of candidate BIK1 substrates. These candidates were verified in a preliminary screen based on the ability of BIK1 to phosphorylate its targets in in vitro kinase assays and to interact with them in planta. Among them, an E3 ubiquitin ligase, which we named BIK1 PHOSPHORYLATION SUBSTRATE 1 (BPS1), was found; as well as two ubiquitin-specific proteases, which we called BPS2 and BPS3. PHOSPH-UBIQ-IMMUN aimed to understand how BIK1 regulates PTI via the characterization of its substrates, thus revealing a dynamic interplay between phosphorylation and ubiquitination events in plant immune signalling. Characterization of key components of immune signalling will ultimately lead to our ability to manipulate them to strengthen plant defense.

Data: CORDIS, © European Union