Education

Institution Major/Area Degree Year

University Kaiserslautern, Germany Botany Diploma 2002

Research Interests

1. Characterization of the plastidic dicarboxylate transporter family in Arabidopsis thaliana and Spinacia oleracea:

The primary question of my research is to characterize the mRNA expression pattern of the plastidic dicarboxylate transporter (DiT) family in the plant model organisms Arabidopsis thaliana (At) and spinach (Spinacia oleracea, So). The gene family consist of three members in Arabidopsis (AtDiT 1, DiT 2.1, DiT 2.2) and two in spinach (SoDiT 1, SoDiT 2). The proteins catalyse the transport of dicarboxylates (malate, 2-oxoglutarate, glutamate, aspartate, and oxaloacetate) across the inner plastid envelope membrane. They provide the plastid with the precursor 2-oxoglutarate and facilitate the export of glutamate the end product of the nitrogen assimilation pathway (Figure 1).
A major way to regulate biological processes is at the level of transcription. I will monitor the steady-state level of the mRNA under certain circumstances. Besides the spatial and developmental mRNA abundance, I am also interested in the response to several environmental stimuli (light, nutrient availability, abiotic stress)

Figure 1: Overview of the plastidic dicarboxylate transporter family in higher plants. WEBER ET AL. (2004): Using mutants to probe the in vivo function of plastid envelope membrane metabolite transporters. Journal of Experimental Botany 55: 1231

2. Identification and characterization of plastidic phosphate transporter (pPT) homologues in the unicellular red algae Galdieria sulphuraria

The plastidic phosphate transporter family (pPT) is well studied in higher plants, especially in the model plant Arabidopsis thaliana. To date, 6 members are functional characterized in Arabidopsis. They facilitate the specific transport of triose-phosphate (TP), phosphoenylpyruvate (PEP), glucose-6-phosphate (Glc-6-P) and several pentose-phosphate molecules in a counter-exchange for orthophosphate over the inner membrane of plastids.
The purpose of my research is to identify and characterize homologues of the pPT family in the unicellular red algae Galdieria sulphuraria. An interesting feature of red algae is their carbon metabolism. In contrast to higher plants, they produce insoluble starch granules outside of their plastids. Therefore, a new situation occurs within the red algae. Galdieria cells have to organize the distribution of the fixed carbon for plastidic biosynthetic pathways and starch or floridoside (sucrose analogue) synthesis in the cytosol. A central role could play the plastidic translocator proteins which are involved in the transport of the most abundant sugar-phosphate molecules such as TP, PEP or Glc-6-P. A detailed characterization of their substrate specificity and expression pattern will certainly reveal differences to their counterparts in higher plants.
Based on primary sequence homology, I found 3 canditate ESTs from Galdieria which have a significant similarity to known pPT sequences from higher plants (Figure 2). Besides the data from the Galdieria-EST project, I could also include sequence information from the recent published genome draft of a closely related red alga Cyanidioschyzon merolae.

Figure 2: Phylogenetic analysis of the pPT family. The four main classes of the plastidic phosphate translocator family are highlighted. They provide the transport of glucose-6-phosphate (pGPT), PEP (pPPT), triose-phosphate (pTPT) and pentose-phosphate (pXPT) in higher plants. The first two letters indicate the species: Gs, Galdieria sulphuraria; CM, Cyanidioschyzon merolae; At, Arabidopsis thaliana; Nt, Nicotiana tabacum; Zm, Zea mays; Pm, Physcomitrella patens; Hs, Homo sapiens; Dm, Drosophila melanogaster; So, Spinacia oleracea; St, Solanum tuberosum; Ft, Flaveria trinervia; Ms, Mesembryanthemum crystallinum Sc, Saccharomyces cerevisiae; Nc, Neurospora crassa; Sp, Schizosaccharomyces pombe;

List of Publications

A.P.M. Weber, C. Oesterhelt, W. Gross, A. Bräutigam, L.A. Imboden, I. Krassovskaya, N. Linka, J. Truchina, J. Schneidereit, H. Voll, L.M. Voll, M. Zimmermann, A. Jamai, W.R. Riekhof, B. Yu, R.M. Garavito, C. Benning (2004) EST-analysis of the thermo-acidophilic red microalga Galdieria sulphuraria reveals potential for lipid A biosynthesis and unveils the pathway of carbon export from rhodoplasts. Plant Mol. Biol. In press