The comparison of the cell-specific transcriptomes of bundle sheath (BS) and mesophyll (M) cells from successive developmental stages of maize leafs reveals that the number of genes preferentially transcribed in one cell type or the other varies considerably from the sink-source transition to mature photosynthetic stages. The number of differentially expressed (DE) genes is maximal at a stage well prior to full maturity, including those that encode key functions for C4 photosynthesis. The developmental dynamics of BS/M differential expression can be used to identify candidates for other C4-related functions and to simplify the identification of specific pathways members from otherwise complex gene families. The candidates for C4-related transcription factors identified with this developmental DE strategy overlap with those identified in studies using alternative strategies. Overall design: Nine day old third leaves of maize sections, located at -1 cm, +4 cm and +9 cm (leaf tip), relative to the sink-source transition, were collected. BS and M cells were captured from each section. There are two duplications for each section and each cell types. A total of 12 libraries were constructed for RNA-seq.