Biology subjects

König, K.

Publications and source records attributed to König, K..

3 recordsLinked to original sources

bioRxiv2024

Complexome profiling of the Chlamydomonas psb28 mutant reveals THYLAKOID ENRICHED FRACTION 5 as an early photosystem II assembly factor

Several auxiliary factors are required for the assembly of photosystem (PS) II, one of which is Psb28. While the absence of Psb28 in cyanobacteria has little effect on PSII assembly, we show here that the Chlamydomonas psb28-null mutant is severely impaired in PSII assembly, showing drastically reduced PSII supercomplexes, dimers and monomers, while overaccumulating RCII, CP43mod and D1mod. The mutant had less PSI and more Cytb6f and showed fewer thylakoid stacks and distorted chloroplast morphology. Complexome profiling of the psb28 mutant revealed that TEF5, the homolog of Arabidopsis PSB33/LIL8, co-migrated particularly with RCII. TEF5 also interacted with PSI. A Chlamydomonas tef5 null mutant is also severely impaired in PSII assembly and overaccumulates RCII and CP43mod. RC47 was not detectable in the light-grown tef5 mutant. Our data suggest a possible role for TEF5 in facilitating the assembly of CP47mod into RCII. Both the psb28 and tef5 mutants exhibited decreased synthesis of CP47 and PsbH, suggesting negative feedback regulation possibly exerted by the accumulation of RCII and/or CP43mod in both mutants. The strong effects of missing auxiliary factors on PSII assembly in Chlamydomonas suggest a more effective protein quality control system in this alga than in land plants and cyanobacteria. One-sentence summaryThe Chlamydomonas psb28 mutant is severely impaired in PSII assembly which via complexome profiling allowed identifying TEF5 as a novel PSII assembly factor that likely facilitates CP47 assembly. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (https://academic.oup.com/plcell/pages/General-Instructions) is: Michael Schroda (m.schroda@rptu.de).

plant biology↗

bioRxiv2022

TurboID reveals the proxiomes of CGE1, VIPP1, and VIPP2 in Chlamydomonas reinhardtii

In Chlamydomonas reinhardtii, VIPP1 and VIPP2 play a role in the sensing and coping with membrane stress and in thylakoid membrane biogenesis. To gain more insight into these processes, we aimed to identify proteins interacting with VIPP1/2 in the chloroplast and chose proximity labeling (PL) for this purpose. We used the transient interaction between the nucleotide exchange factor CGE1 and stromal HSP70B as test system. While PL with APEX2 and BioID proved to be inefficient, TurboID resulted in significant biotinylation in vivo. TurboID-mediated PL with VIPP1/2 as baits under ambient and H2O2 stress conditions confirmed known interactions of VIPP1 with VIPP2, HSP70B and CDJ2. Novel proteins in the VIPP1/2 interaction network can be grouped into proteins involved in the biogenesis of thylakoid membrane complexes and the regulation of photosynthetic electron transport. A third group comprises 11 proteins of unknown function whose genes are upregulated under chloroplast stress conditions. We named them VIPP PROXIMITY LABELING (VPL1-11). and confirmed the proximity of VIPP1 and VPL2 in a reciprocal experiment. Our results demonstrate the robustness of TurboID-mediated PL for studying protein interaction networks in the chloroplast of Chlamydomonas and pave the way for analyzing functions of VIPPs in thylakoid biogenesis and stress responses.

plant biology↗

bioRxiv2019

Ischaemic preconditioning and pharmacological preconditioning with dexmedetomidine in an equine model of small intestinal ischaemia-reperfusion

Small intestinal strangulation associated with ischaemia-reperfusion injury (IRI) is common in horses. In laboratory animals IRI can be ameliorated by ischaemic preconditioning (IPC) and pharmacological preconditioning (PPC) with dexmedetomidine. The aim of this study was to determine the effect of PPC with dexmedetomidine or IPC in an equine model of small intestinal ischaemia-reperfusion (IR).\n\nIn a randomized controlled experimental trial, 15 horses were assigned to three groups: control (C), IPC, and PPC with dexmedetomidine (DEX). All horses were placed under general anaesthesia and 90% jejunal ischaemia was induced for 90 minutes, followed 30 minutes of reperfusion. In group IPC, three short bouts of ischaemia and reperfusion were implemented, and group DEX received a continuous rate infusion of dexmedetomidine prior to the main ischaemia. Jejunal biopsies were collected before ischaemia (P), and at the end of ischaemia (I) and reperfusion (R). Mucosal injury was assessed by the Chiu-Score, inflammatory cells were stained by cytosolic calprotectin. The degree of apoptosis and cell necrosis was assessed by cleaved-caspase-3 and TUNEL.\n\nParametric data were analyzed by two-way ANOVA for repeated measurements followed by Dunnetts t-test. Non parametric data were compared between groups at the different time points by a Kruskal-Wallis-Test and a Wilcoxon-2-Sample-test.\n\nThe mucosal injury score increased during I in all groups. After reperfusion, IRI further progressed in group C, but not in IPC and DEX. In all groups the number of cleaved caspase-3 and TUNEL positive cells increased from P to I. The number of TUNEL positive cells were lower in group DEX compared to group C after I and R. Infiltration with calprotectin positive cells was less pronounced in group DEX compared to group C, whereas in group IPC more calprotectin positive cells were seen.\n\nIn conclusion, IPC and DEX exert protective effects in experimental small intestinal ischaemia in horses.

physiology↗