The phosphoenolpyruvate/phosphate translocator is required for phenolic metabolism, palisade cell development, and plastid-dependent nuclear gene expression

The Arabidopsis chlorophyll a/b binding protein (CAB) gene underexpressed I (cue1) mutant underexpresses light-regulated nuclear genes encoding chloro plast-localized proteins, cue1 also exhibits mesophyll-specific chloroplast and cellular defects, resulting in reticulate leaves. Both the gene undere xpression and the leaf cell morphology phenotypes are dependent on light in tensity. In this study, we determine that CUE1 encodes the plastid inner en velope phosphoenolpyruvate/phosphate translocator (PPT) and define amino ac id residues that are critical for translocator function. The biosynthesis o f aromatics is compromised in cue1, and the reticulate phenotype can be res cued by feeding aromatic amino acids. Determining that CUE1 encodes PPT ind icates the in vivo role of the translocator in metabolic partitioning and r eveals a mesophyll cell-specific requirement for the translocator in Arabid opsis leaves, The nuclear gene expression defects in cue1 suggest that a li ght intensity-dependent interorganellar signal is modulated through metabol ites dependent on a plastid supply of phosphoenolpyruvate.