Biology subjects

Kopischke, M.

Publications and source records attributed to Kopischke, M..

3 recordsLinked to original sources

bioRxiv2021

A NET4-RabG3 couple mediate the link between actin and the tonoplast and is essential for normal actin cytoskeletal remodelling in stomatal closure to flg22

Members of the NETWORKED (NET) family are involved in actin-membrane interactions. They tether the cells plasma membrane (PM) to the actin network. Moreover, in a similar manner, they are also involved in the tethering of membrane bound organelles to the actin cytoskeleton; the endoplasmic reticulum (ER) and the ER to the PM. This raises the question as to whether NET proteins are involved in actin cytoskeletal remodelling. Here we show that two members of the NET family, NET4A and NET4B, are essential for normal guard cell actin reorganization, which is a process critical for stomatal closure in plant immunity. NET4 proteins interact with F-actin and with members of the Rab7 GTPase RABG3 family through two distinct domains, allowing for simultaneous localization to actin filaments and the tonoplast. NET4 proteins interact with GTP-bound, active RABG3 members, suggesting their function as downstream effectors. We also show that RABG3b is critical for stomatal closure induced by microbial patterns. Taken together, we conclude that the actin cytoskeletal remodelling during stomatal closure depends on a molecular link between actin filaments and the tonoplast, which is mediated by the NET4-RABG3b interaction. We propose that stomatal closure to microbial patterns involves the coordinated action of immune signalling events and proper actin cytoskeletal remodelling.

plant biology↗

bioRxiv2021

S-acylation is a positive regulator of FLS2-mediated plant immunity

Plant 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.

plant biology↗

bioRxiv2019

Barley RIC157 is involved in RACB-mediated susceptibility to powdery mildew

Successful obligate pathogens benefit from host cellular processes. For the biotrophic ascomycete fungus Blumeria graminis f.sp. hordei (Bgh) it has been shown that barley RACB, a small monomeric G-protein (ROP, RHO of plants), is required for full susceptibility to fungal penetration. The susceptibility function of RACB probably lies in its role in cell polarisation, which may be co-opted by the pathogen for invasive ingrowth of its haustorium. However, the actual mechanism of how RACB supports the fungal penetration success is little understood. RIC proteins (ROP-Interactive and CRIB-(Cdc42/Rac Interactive Binding) motif-containing) are considered scaffold proteins which can interact directly with ROPs via a conserved CRIB motif. Here we describe a yet uncharacterised RIC protein, RIC157, which can interact directly with RACB in planta. We show that RIC157 undergoes a recruitment from the cytoplasm to the cell periphery in the presence of activated RACB. During fungal infection, RIC157 and activated RACB colocalise at the penetration site, particularly at the haustorial neck. In a RACB-dependent manner, transiently overexpressed RIC157 renders barley epidermal cells more susceptible to fungal penetration. This suggests that RIC157 promotes fungal penetration into barley epidermal cells via its function downstream of RACB.

plant biology↗