中央研究院 資訊科學研究所

Kranz anatomy, an evolved plant structure essential for high efficicency of carbon fixation for C4 photosynthesis, means that the vein is wrapped around by one layer of bundle sheath (BS) cells and one layer of mesophyll (M) cells. Whereas only M cells are involved in C3 photosynthesis, both BS and M cells are involved in C4 photosynthesis. To understand the regulatory and functional differentiation between BS and M cells, we studied their transcriptomes in newly matured maize second leaves.  Surprisingly, many more genes were expressed in BS cells than in M cells, indicating many functional shifts to BS cells. Pathway analyses reveal that the M cells play important roles in light reaction and essential cellular and biochemical functions, while the BS cells specialize in transport, signalling, and BS cell wall development, etc.
To dissect the regulation of kranz development, we studied the transcriptome dynamics of maize embryonic leaves from dry seed up to 72hr post imbibition. During the time course, ∼13,900 genes, including 590 TF genes, are differentially expressed, with the top 1% expressed genes changed drastically between 30h and 54h. Clusters of genes involved in hormone metabolism, signalling, and responses are differentially expressed at various time points, and TF gene expression is also modular and stage specific. We predicted TF-binding sites from clusters of co-expressed genes.