Redox regulation is a central principle of metabolism which controls enzyme activities and gene expression. At the Department of Plant Biochemistry and Physiology we work on both aspects:

A. Redox regulation of enzyme activity

In case of enzyme regulation, we are especially interested in redox regulation of plant peroxiredoxins and the V-type ATPase. The V-type ATPase is redox-regulated by thiol-disulfide-transition of regulatory cysteine residues in the subunits A and E (Tavakoli et al., 2001). In the alkyl hydroperoxide and H₂O₂ reducing peroxiredoxins a cysteine residue in the active site is oxidized during the reaction cycle (Fig. 1). Regeneration involves reductive difulfide cleavage by small redox proteins like thioredoxins (König et al., 2002). In case of 2-Cys peroxiredoxins additional redox regulation takes place by decamerization of the thiol (Cys-SH) and sulfinic acid (Cys-SOOH) form of the enzyme. As shown recently (König et al., 2003), decamerization leads to attachment of the 2-cys peroxiredoxin to the thylakoid membrane, while the intermittantly oxidized disulfide form is soluble in the chloroplast stroma. It is postulated that the 2-Cys peroxiredoxin is a structural redox sensor controlling photosynthetic activity.

Literature on redox regulation of the proteome:

Ströher E,  Dietz K-J (2001) RConcepts and approaches towards understanding the cellular redox proteome. Plant Biology 8, 407 - 418

Literature on redox regulation of cyclophilins:

Laxa M., König J., Dietz K.J., Kandlbinder A. (2006) Role of the cysteinyl residues in Arabidopsis thaliana cyclophilin CYP20-3 in peptidyl-prolyl cis-trans isomerase and redox-related functions. Biochemical Journal (in press)

Literature on redox regulation of the V-type ATPase:

Tavakoli N, Kluge C, Golldack D, Mimura T, Dietz K-J (2001) Reversible redox control of the plant vacuolar H+-ATPase activity is related to disulfide bridge formation not only in subunit A but also in subunit E. Plant J. 28 (1) 51-60

Kluge C, Lahr L, Hanitzsch L, Bolte S, Golldack D, Dietz K-J (2003) New insight into the structure and regulation of the plant vacuolar V-ATPase. J. Bioenerg. Biomemb. 35, 377-388.

Literature on the redox regulation of peroxiredoxins:

B. Redox regulation of gene expression

To study redox regulation of gene expression a set of cDNA arrays of nuclear, plastid and mitochondrial encoded genes (for details: cDNA-Arrays) is used to define regulation patterns in respect to environmental conditions. Thereby we are especially interested in photosynthetically controlled redox regulation. For specific promoters the signal transduction pathways are analysed using reporter gene approaches in wild-type and mutant backgrounds of Arabidopsis thaliana.

In addition, a forward genetic screen was set-up using transgenic Arabidopsis expressing luciferase under control of the 2-Cys peroxiredoxin A promoter, which is redox regulated by the photosynthetic electron transport and whose activity correlates with the acceptor availability at photosystem II. Aiming towards identification of signal transduction elements involved in the redox communication between chloroplasts and the nucleus, several mutants (rimb-mutants) were isolated, in which the reporter gene, the endogenous 2-Cys peroxiredoxin A gene and genes for other nuclear encoded chloroplast antioxidant enzymes are expressed at a lower level than in wild-type Arabidopsis. Mapping of the mutated genes is presently in progress.

Literature on redox regulation of gene expression and chloroplast-to-nucleus redox signalling:

Pena-Ahumada A, Kahmann U, Dietz K-J, Baier M (2006) Regulation of peroxiredoxin expression versus expression of Halliwell-Asada-Cycle enzymes during early seedling development of Arabidopsis thaliana. Photosynth. Res. (in press)

Wormuth D, Baier M, Kandlbinder A, Scheibe R, Hartung W, Dietz K-J (2006) Regulation of gene expression by photosynthetic signals triggered through modified CO2-availability. BMC Plant Biol. 6, 15

Baier M, Kandlbinder A, Dietz K-J, Golldack D (2006) New insights into abiotic stress signalling in plants. Progress in Botany 67, 248 - 274

Becker B, Holtgrefe S, Jung S, Wunrau C, Kandlbinder A, Baier M, Dietz K-J, Backhausen JE, Scheibe R (2006) Influence of the photoperiod on redox regulation and stress responses in Arabidopsis thaliana (Heynh.) plants under long- and short-day conditions. Planta 224, 380 - 393

Baier M, Kandlbinder A, Golldack D, Dietz K-J (2005) Oxidative stress and ozone: perception, signalling and response. Plant Cell environm. 28, 1012 - 1020

Baier M, Dietz K-J (2005) Chloroplasts as source and target of cellular redox regulation, a discussion on chloroplast redox signals in context of plant physiology. J. Exp. bot. 56, 1449 - 1462

Baier M, Ströher E, Dietz K-J (2004) The acceptor availability at photosystem I and ABA control nuclear expression of 2-Cys peroxiredoxin-A in Arabidopsis thaliana. Plant Cell Physiol. 45, 997 - 1006

Most of the work on redox-regulation of gene expression is funded by the German Research Foundation (DFG) within the collaboration network of Forschergruppe 387.