The impact of PEPC phosphorylation on growth and development of Arabidopsis thaliana: Molecular and physiological characterization of PEPC kinase mutants

Two phosphoenolpyruvate carboxylase (PEPC) kinase genes (PPCk1 and PPCk2) are present in the Arabidopsis genome; only PPCk1 is expressed in rosette leaves. Homozygous lines of two independent PPCk1 T-DNA-insertional mutants showed very little (dln1), or no (csi8) light-induced PEPC phosphorylation and a clear retard in growth under our greenhouse conditions. A mass-spectrometry-based analysis revealed significant changes in metabolite profiles. However, the anaplerotic pathway initiated by PEPC was only moderately altered. These data establish the PPCk1 gene product as responsible for leaf PEPC phosphorylation in planta and show that the absence of PEPC phosphorylation has pleiotropic consequences on plant metabolism. (C) 2009 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved

Variation of the Polypeptide Composition of Mitochondria Isolated from Different Potato Tissues

The protein contents of mitochondria from different potato (Solanum tuberosum L.) tissues (tubers, dark-grown shoots, and green leaves) grown in a greenhouse or in vitro were compared by two-dimensional polyacrylamide gel electrophoresis. Two different methods were used: using the method that gave the highest resolution, an average number of 360 polypeptides was revealed on the mitochondrial patterns after silver staining. The mitochondrial protein patterns of etiolated tissues (tubers, dark-grown shoots) are roughly similar but distinct from those of green leaves. The four subunits of the glycine decarboxylase complex (involved in photorespiration) and a few other polypeptides are very abundant in green tissues, compared with nonphotosynthetic tissues. Conversely, some other polypeptides that are abundant in tubers and dark-grown shoots are hardly detectable in green leaf mitochondria. A rabbit antiserum was raised against a 40 kilodalton polypeptide that is among the most characteristic of these nonphotosynthetic tissue-specific polypeptides, and the N-terminal sequence of this polypeptide was determined. No effect of in vitro culture was observed on the protein composition of mitochondria isolated from differentiated tissues. However, the protein patterns of callus and cell suspension mitochondria are distinct from those of any differentiated tissues, although their basic pattern is clearly mitochondrial