Modulation of Polyamine Biosynthesis in Transformed Tobacco Plants by Targeting Ornithine Decarboxylase to an Atypical Subcellular Compartment

G Nölke,J Drossard,S Agdour,B Schneider,S Schillberg,R Fischer

doi:10.2174/1874070700802010183

Abstract

Ornithine decarboxylase (ODC) is a cytosolic enzyme that catalyses the direct decarboxylation of L-ornithine to putrescine, one of the rate-limiting steps of polyamine biosynthesis in plants. We targeted recombinant human ODC to the cytosol and apoplast of transformed tobacco (Nicotiana tabacum) plants, and evaluated the impact of subcellular compartmentalization on the accumulation of the enzyme and its corresponding metabolic product. Immunoblot analysis showed that human ODC accumulated to high levels in both the cytosol and apoplast of transiently transformed tobacco leaves. In stably transformed tobacco plants with ODC targeted to the apoplast, enzyme activity increased by up to 32- fold (P < 0.001) and putrescine levels increased by up to 8.5-fold (P < 0.05) compared to wild type plants. These results demonstrate that the subcellular targeting of polyamine pathway enzymes may provide a useful strategy to enhance the accumulation and activity of enzymes involved in polyamine biosynthesis and may increase metabolic flux toward desired end products.

Highlights

Polyamines are ubiquitous, low-molecular-weight, polycationic compounds involved in crucial developmental, physiological and metabolic processes [1]
The odc cDNA sequence was amplified from a human prostate cDNA library and introduced into two expression cassettes that directed the recombinant protein to the cytosol and apoplast, respectively (Fig. 1)
Total RNA extracted from tobacco leaves transformed with the pODC-cyt or pODC-apo constructs was analysed by Northern blot to confirm the presence of corresponding transcripts

Summary

Introduction

Polyamines are ubiquitous, low-molecular-weight, polycationic compounds involved in crucial developmental, physiological and metabolic processes [1]. We demonstrated that targeting of recombinant ODC to a different and atypical subcellular compartment resulted in significant increased enzyme activity and putrescine levels.

Objectives

Results

Conclusion