S-acylation stabilizes ligand-induced receptor kinase complex formation during plant pattern-triggered immune signalling

SummaryPlant receptor kinases are key transducers of extracellular stimuli, such as the presence of beneficial or pathogenic microbes or secreted signalling molecules. Receptor kinases are regulated by numerous post-translational modifications. Here, using the immune receptor kinases FLS2 and EFR, we show that S-acylation at a cysteine conserved in all plant receptor kinases is crucial for function. S-acylation involves the addition of long-chain fatty acids to cysteine residues within proteins, altering their biophysical properties and behaviour within the membrane environment. We observe S-acylation of FLS2 at C-terminal kinase domain cysteine residues within minutes following perception of its ligand flg22, in a BAK1 co-receptor dependent manner. We demonstrate that S-acylation is essential for FLS2-mediated immune signalling and resistance to bacterial infection. Similarly, mutating the corresponding conserved cysteine residue in EFR supressed elf18 triggered signalling. Analysis of unstimulated and activated FLS2-containing complexes using microscopy, detergents and native membrane DIBMA nanodiscs indicates that S-acylation stabilises and promotes retention of activated receptor kinase complexes at the plasma membrane to increase signalling efficiency

S-acylation stabilizes ligand-induced receptor kinase complex formation during plant pattern-triggered immune signaling

Plant receptor kinases are key transducers of extracellular stimuli, such as the presence of beneficial or pathogenic microbes or secreted signaling molecules. Receptor kinases are regulated by numerous post-translational modifications.1,2,3 Here, using the immune receptor kinases FLS24 and EFR,5 we show that S-acylation at a cysteine conserved in all plant receptor kinases is crucial for function. S-acylation involves the addition of long-chain fatty acids to cysteine residues within proteins, altering their biochemical properties and behavior within the membrane environment.6 We observe S-acylation of FLS2 at C-terminal kinase domain cysteine residues within minutes following the perception of its ligand, flg22, in a BAK1 co-receptor and PUB12/13 ubiquitin ligase-dependent manner. We demonstrate that S-acylation is essential for FLS2-mediated immune signaling and resistance to bacterial infection. Similarly, mutating the corresponding conserved cysteine residue in EFR suppressed elf18-triggered signaling. Analysis of unstimulated and activated FLS2-containing complexes using microscopy, detergents, and native membrane DIBMA nanodiscs indicates that S-acylation stabilizes, and promotes retention of, activated receptor kinase complexes at the plasma membrane to increase signaling efficiency

In pursuit of RAFT-functional polyethylene : exploration of a novel class of Sn-RAFT agents and the preparation and application of RAFT-functional polyethylene-like poly(ω-pentadecalactone)

This work explores the preparation of Reversible Addition-Fragmentation chain-Transfer (RAFT)-functional polyethylene (PE). Challenges in developing methods to control the polymerization of primary radicals and prepare functional polyethylene are significant. Modest control over ethylene polymerization demonstrated via F-RAFT polymerization inspired our interest in RAFT agent design and we envisaged that metallo-RAFT agents could present different reactivities towards primary radicals. Considering the challenge of attempting to develop chemistry for the controlled radical polymerization of primary radicals, preparation of RAFT-functional polyethylene-like poly(ω-pentadecalactone) (PPDL) was also investigated. We envisaged the preparation of RAFT-functional PPDL to be more convenient than reported strategies to prepare functional polyethylene all whilst being a “green” alternative to PE that may be suitable for some applications. Chapter 1 discusses challenges in preparing functional polyethylene via controlled radical polymerization techniques. Furthermore, metallo-RAFT chemistry and the ring-opening polymerization of macrocyclic esters are reviewed. Chapter 2 describes the synthesis of PPDL via enzymatic ring-opening polymerization (eROP). Using a bifunctional initiator appropriate for the RAFT polymerization of acrylic and styrenic monomers, RAFT-functional poly(ω-pentadecalactone) was prepared. Furthermore, chain extension of the macro-chain-transfer agent was utilized to prepare acrylic and styrenic block copolymers of PPDL. To our knowledge, this is the first preparation of block copolymers of poly(ω-pentadecalactone) via a combination of eROP and RAFT polymerization techniques. Chapter 3 describes the large scale synthesis and characterization of a selection of acrylic block copolymers of PPDL suitable for fuels applications. Furthermore, the fuels testing of these copolymers for cold flow applications is described. In general, all block copolymers of PPDL, in particular poly(ω-pentadecalactone)-b-poly(isodecyl acrylate) improved the cold flow performance of various diesel fuels. Chapter 4 reports the synthesis of Sn-RAFT agents and their subsequent use in the controlled radical polymerization of several vinylic monomers. Chapter 5 summarizes the findings in chapters 2 – 4 and Chapter 6 communicates the associated experimental data

Polymers from macrolactones: from pheromones to functional materials.

Recent advances in the ring-opening polymerization (ROP) of macrolactones (MLs) have afforded access to novel, potentially degradable polymeric materials featuring long aliphatic chains. These developments extend the synthetic robustness and versatility of ROP to a greater range of interesting monomers, many of which can be derived from sustainable or renewable feedstocks, to access polymeric materials boasting a diversity of properties and potential applications. This review discusses current strategies to catalyse the ROP of MLs, comparing and contrasting them with those known for the ROP of small and medium sized lactones, and highlights recent developments in the preparation, functionalization, and application of materials featuring poly(macrolactone)s (PMLs)