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Schwarzländer, M.

Publications and source records attributed to Schwarzländer, M..

2 recordsLinked to original sources
bioRxiv2019

Arabidopsis glutathione reductase 2 is indispensable in plastids, while mitochondrial glutathione is safeguarded by additional reduction and transport systems

O_LIA highly negative glutathione redox potential (EGSH) is maintained in the cytosol, plastids and mitochondria of plant cells to support fundamental processes, including antioxidant defence, redox regulation and iron-sulfur cluster biogenesis. Out of two glutathione reductase (GR) proteins in Arabidopsis, GR2 is predicted to be dual-targeted to plastids and mitochondria, but its differential roles in these organelles remain unclear.\nC_LIO_LIWe dissected the role of GR2 in organelle glutathione redox homeostasis and plant development using a combination of genetic complementation and stacked mutants, biochemical activity studies, immunogold labelling and in vivo biosensing.\nC_LIO_LIOur data demonstrate that GR2 is dual-targeted to plastids and mitochondria, but embryo lethality of gr2 null mutants is caused specifically in plastids. Whereas lack of mitochondrial GR2 leads to a partially oxidised glutathione pool in the matrix, the ABC transporter ATM3 and the mitochondrial thioredoxin system provide functional backup and maintain plant viability.\nC_LIO_LIWe identify GR2 as essential in the plastid stroma, where it counters GSSG accumulation and developmental arrest. By contrast a functional triad of GR2, ATM3 and the thioredoxin system in the mitochondria provides resilience to excessive glutathione oxidation.\nC_LI

plant biology↗
bioRxiv2019

Chloroplasts Require Glutathione Reductase to Balance Reactive Oxygen Species and Maintain Efficient Photosynthesis

O_LIThiol-based redox-regulation is vital to coordinate chloroplast functions depending on illumination. Yet, how the redox-cascades of the thioredoxin and glutathione redox machineries integrate metabolic regulation and reactive oxygen species (ROS) detoxification remains largely unresolved. We investigate if maintaining a highly reducing stromal glutathione redox potential (EGSH) via glutathione reductase (GR) is necessary for functional photosynthesis and plant growth.\nC_LIO_LISince absence of the plastid/mitochondrial GR is embryo-lethal in Arabidopsis thaliana, we used the model moss Physcomitrella patens to create knock-out lines. We dissect the role of GR in chloroplasts by in vivo monitoring stromal EGSH dynamics, and reveal changes in protein abundances by metabolic labelling.\nC_LIO_LIWhereas stromal EGSH is highly reducing in wildtype and clearly responsive to light, the absence of GR leads to a partial oxidation, which is not rescued by light. Photosynthetic performance and plant growth are decreased with increasing light intensities, while ascorbate and zeaxanthin levels are elevated. An adjustment of chloroplast proteostasis is pinpointed by the induction of plastid protein repair and degradation machineries.\nC_LIO_LIOur results indicate that the plastid thioredoxin and glutathione redox systems operate largely independently. They reveal a critical role of GR in maintaining efficient photosynthesis.\nC_LI

plant biology↗