Manipulating PEPC levels in plants

This review examines the current understanding of the structural, functional and regulatory properties of C(4) and C(3) forms of higher plant phosphoenolpyruvate carboxylase. The emphasis is on the interactive metabolic and post-translational controls acting on the enzyme in the physiological context of C(4) photosynthesis and the anaplerotic pathway. A brief overview is given concerning the recent developments of PEPC-based genetic engineering of C(3) plants with the aim of improving photosynthetic performance in normal and limiting environmental conditions. So far, in spite of achieving a considerable increase in PEPC levels, more work needs to be done with respect to the correct dosage and location before that goal is reached. Some unpublished results on the transformation of maize with a sorghum C(4) PEPC cDNA are also presented. They show that it is possible to increase photosynthetic PEPC levels in this C(4) plant and that the modification in enzyme content has a pleiotropic physiological impact and, notably, an improved water use efficiency when water is limited.