Phosphoenolpyruvate carboxylase (PEPC) is a tightly regulated enzyme that controls carbohydrate partitioning to organic acid anions (malate, citrate) that are excreted in copious amounts by cluster (proteoid) roots of phosphate-deprived white lupin.
Shane et al. establish a novel mechanistic link between reversible, light-dependent activation of PEPC by in vivo phosphorylation, and the concentrations of sucrose, and its signalling metabolite trehalose-6-phosphate in lupin cluster roots. PEPC’s phosphorylation is correlated with enhanced rates of root organic anion exudation and phosphate uptake, and appears to be modulated by sucrose translocated from illuminated CO2-fixing leaves into the non-photosynthetic cluster roots.
This paper is part of the Root Biology Special Issue.