Pyruvate transport systems in organelles: future directions in C4 biology research

Pyruvate is a central metabolite that must be imported into organelles for specific metabolic processes, including C4 photosynthesis. Plastidial and mitochondrial pyruvate transporter molecules were recently identified: the former was found based on C4 photosynthesis transcriptome analysis and the latter using a bioinformatics approach in yeast. The transport activities of these molecules were recently investigated in heterologous expression systems: Escherichia coli and Lactococcus lactis, respectively. These studies demonstrated the important roles of the NHD1/Bass2-protein coupling function and the mitochondria pyruvate carrier protein complex in pyruvate uptake. Here, I summarize the approaches used to isolate these proteins and the issues that remain to be investigated.