Light‐driven uptake of pyruvate into mesophyll chloroplasts from maize

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Abstract
(i) Photosynthesis in maize, a C4 species, involves a movement of pyruvate from the bundle sheath to the mesophyll, which has been suggested to occur by symplastic diffusion. (ii) Measurement ofmetabolite distribution in maize leaves revealed that the bulk of the pyruvate in the mesophyll was not in diffusion equilibrium with pyruvate in the bundle sheath, indicating that most of the mesophyll pyruvate was not located in the cytosol but accummulated in a subcellular compartment. (iii) In concurrence with these results, transport measurements revealed a light‐dependent active transport of pyruvate into maize mesophyll chloroplasts, probably driven by a proton gradient. This active transport of pyruvate may be regarded as an important factor in driving a malate‐pyruvate shuttle in C4 photosynthesis.