In plants, the regular pattern of trichomes (leaf hairs) is thought to be generated during development through intercellular communication. That is,trichome inhibitors, which are activated by self-enhanced trichome activators,move between cells to determine the trichome pattern. On , Zhao and colleagues refine this model, which is largely based on data obtained from the root hair system, through a detailed analysis of the TTG1-bHLH-MYB complex,which activates trichome initiation and patterning in Arabidopsis. By co-precipitation, they confirm that the WD40 repeat protein TTG1 associates with the bHLH protein GL3 and the R2R3-MYB protein GL1 in vivo. They identify the trichome activators GL2 and TTG2, and repressors CPC and ETC1 as being transcriptional targets of this complex by showing that GL1 and TTG1 bind to their promoters in vivo. Finally,they provide the first direct evidence that the trichome repressor CPC moves between cells in developing leaves. Thus, they conclude, the TTG1-bHLH-MYB complex affects trichome patterning by directly regulating downstream targets and the movement of trichome repressors.
