Ruprecht-Karls-Universität Heidelberg
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Dr. Steffen Greiner

Dr. Steffen Greiner
Dr. Steffen Greiner
Im Neuenheimer Feld 360
69120 Heidelberg
Fon +49 6221 54-5786
Fax +49 6221 54-5859
steffen.greiner AET
(deputy business manager)

PMEI-related inhibitor proteins: Their roles in the regulation of sugar and pectin metabolism

Sucrose-hydrolyzing invertases in the cell wall and the vacuole, and cell wall-localized pectin methylesterases are post-translationally regulated by inhibitory proteins belonging to the same protein family: pectin methylesterase inhibitor-related proteins (PMEI-RP). PMEI-RPs are predicted to serve multiple functions in sugar and cell wall metabolism during plant development and in response to stress exposure. This project aims at unraveling the roles of different PMEI-RPs in different plant species, plant organs and cell types. Furthermore, the biotechnological potential of up- or down-regulation of certain PMEI-RP isoforms in selected crop species is explored. 

Inulin metabolism in Chicory

Inulin is used as carbohydrate storage compound in plants but may also be involved in several stress responses. The economically most important source is chicory, which accumulates inulin in its taproots. Biotechnological goals are to increase inulin yield and its degree of polymerization (DP). Enzymes responsible for inulin biosynthesis in chicory are sucrose:sucrose 1-fructosyltransferase (1-SST) and fructan:fructan 1-fructosyltransferase (1-FFT), inulin degradation is catalyzed by fructan 1-exohydrolases (1-FEHs). We are investigating the possibility of post-translational control of FAZYs via proteinaceous inhibitors, as found for acid invertases, enzymes evolutionarily and structurally related to FAZYs. We are pursuing 3 different strategies in order to isolate FAZY specific inhibitors: a) affinity chromatography with recombinant FAZY proteins as bait; b) Deep Sequencing of chicory cDNAs; c) Invertase inhibitor engineering.

Additionally, we have established the chicory hairy root culture (CiHRC) as a model system to explore regulatory mechanisms impacting on inulin metabolism in planta. We are currently studying aspects of hormonal regulation of FAZYs in CiHRC.


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