2014 年 26 巻 1 号 p. 59-63
Cells in clonally different lineages coordinate proliferation within a developing organ to ensure species-specific organ size and shape, and signaling between cells generally plays a pivotal role in this process. In the field of developmental biology, examining the molecular details and dynamics of the signaling remains a challenge. Previous studies have suggested that the size and shape of a leaf are determined through coordinated proliferation between epidermal and mesophyll cells, possibly through inter-celllayer signaling. However, the signaling mechanism remains largely unexplored because, until recently, little was known regarding the signaling molecules involved in this process. ANGUSTIFOLIA3 (AN3) in Arabidopsis thaliana encodes a transcriptional co-activator with homology to human synovial sarcoma translocation protein. Kawade et al. (2013) reported that AN3 is a signaling molecule that mediates inter-cell-layer signaling for the coordinated proliferation of leaf cells. AN3 is produced specifically in mesophyll cells and moves into epidermal cells, where it participates in transcriptional control for cell proliferation in destination cells. The identification of the signaling molecule involved in coordinated proliferation of leaf cells allows us to directly investigate the functional impact of inter-cell-layer signaling on leaf development. Interfering with AN3 movement across cell layers disrupts the coordinated proliferation of leaf cells. Leaf size and shape are also impaired in this situation, demonstrating that AN3 signaling itself is indispensable for normal leaf development. Based on these findings, Kawade et al. (2013) presented a novel model emphasizing the role of mesophyll cells as a signaling source for coordinated proliferation of leaf cells, as well as the regulation of leaf size and shape.
