Functional analysis of DAHP synthase isoforms in higher plants

• Applicant: Professorin Dr. Ingar Janzik
• Subject Area: Plant Biochemistry and Biophysics
• Term: from 2007 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 43741578

The 3-deoxy-D-arabino-heptulosonate-7-phosphate (DAHP) synthase [EC 2.5.1.54] catalyses the first step of the shikimate pathway, which is a key pathway for the synthesis of aromatic primary as well as secondary plant metabolites. This pathway plays a dual role in plant metabolic processes: On the one hand constitutive metabolites like aromatic amino acids for protein synthesis or cell wall components as lignin have to be synthesized, whereas on the other hand demands for secondary metabolites induced by diverse environmental impacts have to be served. This project aims to address the question, how far carbon flux into aromatic metabolism is adjusted already at the entry point into the shikimate pathway by modulation of DAHP synthase isoform gene expression and activity – especially during stress. In a first step the three identified DAHP synthases of Arabidopsis thaliana (L.) Heynh. and Nicotiana tabacum L. will be heterologously expressed in Escherichia coli. They will be characterized concerning their enzyme kinetics and putatively necessary posttranslational activation in vitro, which directly might reflect different functions. The in vitro characteristics will be complemented by analysis of the isoform specific expression in vivo. Therefore promoter-GUS-GFP reporter plants of Arabidopsis for each isoform will be generated and analysed under control and stress conditions. In parallel T-DNA knockout Arabidopsis plants for each of the three DAHP synthase isoform genes and double mutants as well as Nicotiana tabacum RNAi-knockout plants will be generated. To evaluate the control of the different isoforms on primary and secondary metabolism these plants will be analyzed under stress and non-stress conditions with respect to changes in primary and aromatic secondary metabolism and altered stress response.

• DFG Programme: Research Grants